RealClimate

1. On the other hand this assumes no positive feedbacks are already in play, no?

Comment by cervantes — 3 Mar 2010 @ 8:56 AM

2. The authors’ very brief summary of the letter (access to the letter is limited to subscribers), at the link you provided, doesn’t seem to match your discussion above.

“Committed climate warming” H. Damon Matthews & Andrew J. Weaver

Abstract
The perception that future climate warming is inevitable stands at the centre of current climate-policy discussions. We argue that the notion of unavoidable warming owing to inertia in the climate system is based on an incorrect interpretation of climate science.

What gives?

Comment by Angelo Lamana — 3 Mar 2010 @ 9:10 AM

3. How can you discuss the topic of future warming commitment
based on AR4 models which totally neglect the real driver
of future warming, namely ice-sheet responses?
The Hansen et al study (2004) on target atmospheric CO2
and climate sensitivity is quite clear on this topic:
equilibrium responses would double the GCM-based estimates,
with very little to be said about transient effects.

Comment by Nonlinear Guy — 3 Mar 2010 @ 9:25 AM

4. I think this framing is still arbitrary, in that the CO2 emissions are set to zero, but aerosol emissions are (presumably) allowed to continue. It is thus the climate commitment of only CO2, not considering other anthropogenic climate forcings.

The warming commitment if we stop all human emissions (GHG and aerosol) is probably very substantial: The cooling effect of the aerosol will very quickly disappear, thereby ‘unmasking’ the greenhouse warming, approximately half of which has been canceled by aerosol cooling up to now.

Not considering the change in net uptake of carbon by the ocean, you can put the following numbers on that (based on Ramanathan and Feng, 2009):

Global average surface temperatures have increased by about 0.75 degrees Celsius since the beginning of the industrial revolution, of which ~0.6 °C is attributable to human activities. The total radiative forcing by greenhouse gases is around 3 W/m2, with which we have ‘committed’ the planet to warm up by 2.4 °C (1.6-3.6 °C), according to a climate sensitivity of 3 °C (2-4.5 °C) for a doubling of CO2. The observed amount of warming thus far has been less than this, because part of the excess energy is stored in the oceans (amounting to ~0.5 °C), and the remainder (~1.3 °C) has been masked by the cooling effect of anthropogenic aerosols.

This simple analysis shows that the ‘2 degree target’ of ‘dangerous anthropogenic interference’ is looming on the horizon, as the climate equilibrates and aerosol pollution is cleaned up. An increased uptake of carbon by the oceans (in the hypothetical situation of stopping all emissions immediately) is not likely to cancel the ‘unmasked’ greenhouse warming in addition to canceling the ‘committed’ ocean warming.

Comment by Bart Verheggen — 3 Mar 2010 @ 9:27 AM

5. I agree with @cervantes. This should be taken with a grain of salt, given that our understanding of the small scale processes such as clouds and aerosols as feedbacks are fairly poor. I’d like the physical argument for why cutting back emissions to zero will affect these processes so quickly.

Comment by Sean — 3 Mar 2010 @ 9:51 AM

6. One could also argue that the stratosphere isn’t being loaded with all sorts of aerosols right now because of “social interia” and that the “correct interpretation of climate science” is therefore that there’s a strong cooling commitment. As gavin euphemistically puts it, the practical implications of such reframing would be “small”. Yet another culture vs. nature quasi-theological debate which amounts to nothing…

Until such time as meaningful mitigation is seriously considered and planned for, the real-world scenario remains BAU and the debate which actually matters remains the one about the size of the fossil fuel reserves.

Comment by Anonymous Coward — 3 Mar 2010 @ 9:54 AM

7. Am I right in thinking that, what this paper is saying is that it is incorrect to say that even if there were zero emissions from today the earth would still warm for a bit? That instead, going cold turkey to net zero emissions, the surface would continue to absorb CO2 and the temperature would in fact fall or at least stay the same?

And the reason for continued warming is simply because it is impractical or more properly not possible for us to stop emitting CO2 suddenly and totally, therefore CO2 will continue to rise and the temperature will rise.

And that provided we significantly curb emissions over the next couple of decades, a new equilibrium will be reached.

I’ve been assuming we will have to virtually stop CO2 emissions at some stage, but doubt even that is possible to the nth degree given the need to grow food, build houses etc., at least not without sequestration, afforestation or other offsets of some kind. Is there a level worked out that we can emit some and reach a new radiation balance? Or do we have to go to net zero, or even negative?

Comment by Sou — 3 Mar 2010 @ 9:58 AM

8. Angelo Lamana,
I don’t see the inconsistency. All Gavin has done is spell out the “why” behind the brief statement in the abstract.

Comment by Ray Ladbury — 3 Mar 2010 @ 10:02 AM

9. It seems that Matthews and Weaver ignore sulfates. If we stop emissions today, there will be warming of about 0.5C as the atmosphere clears out. I don’t understand how temperatures will not rise if we clean out the troposphere and remove the aerosols which are now cooling.

Comment by Alan Robock — 3 Mar 2010 @ 10:09 AM

10. @ 2 Angelo Lamana says “The authors’ very brief summary of the letter (access to the letter is limited to subscribers), at the link you provided, doesn’t seem to match your discussion above.”

Seems to match it perfectly to me. What are you talking about?

Comment by Josie — 3 Mar 2010 @ 10:16 AM

11. 2: Angelo wrote “what gives?”

I don’t see any contradiction between Gavin’s summary and the abstract. I don’t have access to the article right now either but the abstract certainly is not in obvious contradiction with Gavin’s summary. As Gavin clearly stated the meaning of “committed climate change” is ambiguous. Both the constant composition assumption and the zero CO2 emissions seem like entirely reasonable definitions to me. The constant composition assumption results in another quarter degree of warming while the zero CO2 emissions results in no further warming.

Comment by John E. Pearson — 3 Mar 2010 @ 10:21 AM

12. “Climate scientists are paid to do climate science,” said Gavin A. Schmidt, a senior climatologist with the National Aeronautics and Space Administration’s Goddard Institute of Space Studies. “Their job is not persuading the public.”

Hey Gavin, if your job is to do ‘climate science’ and not ‘persuade’ the public, why do you spend so much time and effort with RealClimate.Org?

[Response: Because I think it is worthwhile even if I don't get paid for it. - gavin]

Comment by Paul — 3 Mar 2010 @ 10:22 AM

13. Angelo Lamana-

Mathews and Weaver address “inertia in the climate system”. Gavin addresses “societal inertia” – the likelihood that the strict criteria of “immediate zero CO2 emissions” will actually be met (as opposed to the easier but also unlikely possibility that we could hold current atmospheric CO2 concentrations steady through immediate 60-70+% emission reduction).

If I understand correctly, Gavin makes 2 points with regards to this paper:

- Realistically, continued warming is inevitable.

- If however, the (almost inconceivable) abrupt global total cessation of (fossil) C emissions were to occur, then we could expect warming to stop without further need for mitigation.

Comment by arch stanton — 3 Mar 2010 @ 10:26 AM

14. The first paragraph seems to go against what we know about Convection and Evaporation does it not?

While an increase in the amount of radiation the Earth receives by trapping outgoing IR would increase surface temps, would the increased surface temp not increase the convection and evaporation rates introducing a negative feedback?

We observe that the troposphere increases in altitude going from the poles to the tropics, and this behavior shows that as energy pressure (temperature) increases, the volume of the atmosphere also increases since it is elastic in nature. Without this elastic property of the atmosphere, the temperatures in tropical regions would be higher than we observe since the volume of the atmosphere would would be less as described by PV=nRT.

If convection and evaporation were not present, I could see the argument being made that a slight increase in Radiation having some warming effect, however convection and evaporation do exist within the Troposphere and the rate of cooling the two exhibit increases as surface temps increase.

We must also take into consideration that there are three ways to cool the planet within the Troposphere and account for them all. The Earth is only heated via Radiation, and cools via Radiation, Convection, and Evaporation in order of increasing magnitude.

Am I missing something?

Comment by Steve A Morris — 3 Mar 2010 @ 10:32 AM

15. Angelo, the summary refers to what the authors see as a common misunderstanding (in their words, “an incorrect interpretation of climate science”): that we are committed to further warming from past emissions. Warming to this point is presumably from past emissions, but their results suggest that it’s future emissions, not past, that commit us to warm more from this point forward. Further down in the letter they say

“Constant-composition commitment is often misinterpreted as the unavoidable warming that is yet to manifest in response to past greenhouse-gas emissions. However, the climate warming commitment from past greenhouse-gas emissions is more correctly defined as a ‘zero-emissions commitment’ — that is, the future climate change that would occur, should greenhouse-gas emissions be eliminated entirely.” (As in their Fig 1 that Gavin inlined above.)

“…From this we conclude that the elimination of carbon dioxide emissions leads to little or no further climate warming; that is, future warming is defined by the extent of future emissions, rather than by past emissions.”

Their results do NOT imply that we can continue emitting at current levels without experiencing warming – but that sure is easy to read into the abstract. Also, I would expect that their findings will not always hold – if we end up with a concentration too great for the biosphere to handle, say, then past emissions alone will commit us to future warming.

Comment by Ian — 3 Mar 2010 @ 10:34 AM

16. The point they make is that future climate change due to inertia has been assessed by keeping CO2 concentrations at some predetermined level, that is, that there will be no future increase in human input of CO2 into the atmosphere. That, they argue however, is somewhat arbitrary and actual climate inertia should be measured by assuming that human emissions are cut to zero. Basically, they say that let’s see what the climate will do when we remove humans entirely, whereas other studies have asked: what will the climate do if we continue to pollute as usual, but without increased emissions.

As far as I can tell.

Comment by Silver R. — 3 Mar 2010 @ 10:43 AM

17. The last paragraph of this post is poorly written/argued.

As a practical matter for what? As written it only makes sense to be read “as a practical matter for predicting the future”.

The charter of climate science (and especially this subtopic) has always been contingent prediction. Since this kind of teasing out does seem relevant to discussions along those lines, you are undermining yourself in a muddy way. At the very least your language is confusing as to what you think the “practical” matter is.

[Response: The practical matter is whether we need to be working on adaptation to further warming. And we do. - gavin]

Comment by Tom — 3 Mar 2010 @ 10:53 AM

18. I don’t have access to the original, but it seems odd that M&W would suggest that socioeconomic inertia matters, then reframe emissions commitment in a way that ignores that. From a human perspective, commitment (of resources) occurs at the time of construction of GHG-emitting capital. A more policy-relevant test of commitment might be a scenario with emissions decaying with some lifetime that reflects natural capital turnover (15 to 50 years). That path (no new emitting capital, but no abandonment) is a better reflection of what’s possible with great effort than the zero-emissions-now path suggested.

Comment by Tom Fiddaman — 3 Mar 2010 @ 10:57 AM

19. I don’t understand their figure. The IPCC AR4 scenario A1B(21) calls for warming between approx. 2-5 deg C by 2100. This is a “middle of the road” scenario which would look outrageous on their figure. It also is beginning to look outrageous to systemic eyes.
I want an answer to this, please: In order for the AR4 scneraio I mention to come true, the decedal increase in temp observed from 2000-2010 would need to jump 100% to 700% per decade to reach the modeled change. Is this outrageous to a physicist at this point????????

[Response: The AR4 results in the figure are from constant-2000 composition, not any of the scenarios, which of course warm up significantly more. - gavin]

Comment by thomas hine — 3 Mar 2010 @ 10:57 AM

20. Did they really consider all human emissions? As I understand it (from the IPCC report and from Ramanathan en Feng, Sept 23 2008 in PNAS) stopping all emissions suddenly would cause about 1.6 degree Celsius of extra warming, because short-lived pollution would quickly be removed from the atmosphere. No more global cooling, while the greenhouse gases would stay.
Did I misunderstand something?

[Response: This is a very good point - and I'm pretty sure they did not assess this. - gavin]

And indeed, what about positive feedbacks?

Comment by Elmar Veerman — 3 Mar 2010 @ 11:11 AM

21. Sorry, it looks like I didn’t realize there figure was the “constant” model ensembles. But my second question still remains, as you’ve conceded to the reality of the issue towards the end of the post.

Comment by thomas hine — 3 Mar 2010 @ 11:12 AM

22. Wait, that doesn’t sound right at all. If emissions dropped to zero immediately, the concentrations would start to fall, but relatively slowly (given what we know about the half-life of carbon in the atmosphere) – i.e. over decades. Throughout this time, the concentrations will be elevated over pre-industrial levels, meaning a stronger greenhouse effect, and hence give a continued warming effect. I don’t see how the blue line could be flat.

Ramanathan and Feng gave a figure greater than 2 degrees for this zero emissions scenario, but they also zeroed out aerosol pollution too. Schellenhuber’s editorial on the R&F paper attempts to compare what happens if don’t zero out the aerosols (and gets something closer to 1 degree). But both of them show continued warming for decades.

Comment by Steve Easterbrook — 3 Mar 2010 @ 11:19 AM

23. Angelo Lamana:

I think you’re missing something.

The letter notes that “Stable atmospheric concentrations of greenhouse gases would lead to continued warming, but if carbon dioxide emissions could be eliminated entirely, temperatures would quickly stabilize or even decrease over time. Future warming is therefore driven by socio-economic inertia, and is only as inevitable as future emissions.”

This isn’t in contrast to the discussion above, which notes that Matthew and Weaver make an interesting point – if we want to talk about ‘true’ climate inertia, we should set our future emissions to zero and see how the system responds. “From this we conclude that the elimination of carbon dioxide emissions leads to little or no further climate warming; that is, future warming is defined by the extent of future emissions, rather than by past emissions.” This notes that we aren’t really “committed” to future warming if we stop all GHG emissions now.

But we know that isn’t realistic – there is a societal inertia to such a radical change in emissions. We know we won’t cut all emissions tomorrow, and as noted above, even cutting emissions by 60-70% and keeping atmospheric levels constant has considerable inertia.

The point made above is that while the authors of the letter do point out something that is indeed true, it simply isn’t realistic – there may be little climate inertia, but there is a mountain of socio-economic inertia.

Comment by Nick — 3 Mar 2010 @ 11:20 AM

24. Angelo #2 – Perhaps you could explain why the Matthews-Weaver’s abstract and Gavin’s discussion don’t match…? Because I don’t see any contradiction at all.

Comment by Paul Levy — 3 Mar 2010 @ 11:27 AM

25. “….adaptation (over and above what is necessary to reduce vulnerabilities to current climate conditions)…”

Adaptation is what we humans do best. Are the “vulnerabilities to current climate conditions” unusual? (other than the recent record snowfalls)

I’m ready to adapt to a couple of extra degrees in the near future.

Comment by Anne — 3 Mar 2010 @ 11:29 AM

26. Angelo @2: No, it does match, actually. The idea of climate inertia is that when you increase the CO2 concentration in the atmosphere it takes the climate system a good deal of time for all its components to fully adjust and reach a new equilibrium temperature. Glacial melt and ocean warming, etc., result from, but take longer than, the warming in the atmosphere caused by the increased CO2. There’s the additional fact that while some parts of the climate system can adjust on a timescale of a few decades, others adjust so slowly that they will still be out of equilibrium several centuries from now.

The question is, how great is the inertia in the short-term, say, through the end of this century? What will the short-term adjustment look like, how much warming are we already committed to, based on the CO2 we’ve already emitted?

To answer that we need to define what “based on the CO2 we’ve already emitted” means. Does it mean the level of CO2 in the atmosphere currently? If it does, then that level could be held constant if, hypothetically, we were to cut our emissions by 60-70%, to levels that that no longer exceed what the oceans and the biosphere can simultaneously absorb.

But if we take “based on the CO2 we’ve already emitted” literally, then the relevant thing to ask is how would the climate system adjust, how would global temperature behave, if we immediately cut our emissions back to zero? COThat’s apparently what they’re doing here. But it’s really a question about how the climate system responds to what we’ve been doing to it, rather than what our policies should be.

Comment by Mukei — 3 Mar 2010 @ 11:36 AM

27. Angelo @2: No, it does match, actually. The idea of climate inertia is that when you increase the CO2 concentration in the atmosphere it takes the climate system a good deal of time for all its components to fully adjust and reach a new equilibrium temperature. Glacial melt and ocean warming, etc., result from, but take longer than, the warming in the atmosphere caused by the increased CO2. There’s the additional fact that while some parts of the climate system can adjust on a timescale of a few decades, others adjust so slowly that they will still be out of equilibrium several centuries from now.

The question is, how great is the inertia in the short-term, say, through the end of this century? What will the short-term adjustment look like, how much warming are we already committed to, based on the CO2 we’ve already emitted?

To answer that we need to define what “based on the CO2 we’ve already emitted” means. Does it mean the level of CO2 in the atmosphere currently? If it does, then that level would be held constant if, hypothetically, we were to cut our emissions by 60-70%, to levels that that no longer exceed what the oceans and the biosphere can simultaneously absorb.

But if we take “based on the CO2 we’ve already emitted” literally, then the relevant thing to ask is how would the climate system adjust, how would global temperature behave, if we immediately cut our emissions back to zero, so that CO2 concentration in the atmosphere can begin to fall. What’s the effect of that on temperature? That’s apparently what they’re asking here. But it’s really a question regarding how the climate system responds to what we’ve been doing to it, rather than what our policies should be.

Comment by Mukei — 3 Mar 2010 @ 11:42 AM

28. Since temperatures are already raised and there is more warming in the pipeline, who is to say that CO2 will adjust downwards as opposed to temperatures adjusting upwards. CO2 has been much higher in the past. There is nothing magical about pre-industrial CO2 levels.

Comment by RichardC — 3 Mar 2010 @ 11:51 AM

29. Cervantes #1. That’s what worries me – Arctic ice is a positive feedback already happening.

February’s Arctic Sea Ice News & Analysis, (http://nsidc.org/arcticseaicenews) says:

A recent paper by Thorsten Markus at NASA Goddard Space Flight Center suggests that the later freeze-up is the dominant factor lengthening the melt season. The analysis shows that, on average, autumn freeze-up starts nearly four days later each decade. Extensive open water at the end of the summer melt season, combined with warmer autumns, delay the autumn freeze-up. The larger expanses of open water absorb more solar energy, and before ice can form again, that heat must be released back to the atmosphere.

Comment by Geoff Beacon — 3 Mar 2010 @ 11:51 AM

30. Once again, the scientific study referenced, certainly paid by tax payers, is not available to the general public.

If I cannot have access to the information, I cannot communicate around me, because I don’t know.

We therefore cannot assess the claims and should not expect the general public to be well informed and make rational voting decisions.

When will they get it?

Comment by Jean — 3 Mar 2010 @ 11:54 AM

31. The paper took me a few reads, think I’m still confused. This sounds contradictory:

“Climate change commitment is defined as the future warming to which we have committed ourselves by virtue of past human activities. Because of the slow response time of the climate system, the equilibrium climate consistent with current levels of greenhouse gases will not be reached for many centuries. This so-called constant-composition commitment results as temperatures gradually equilibrate with the current atmospheric radiation imbalance, and has been estimated at between 0.3 °C and 0.9 °C warming over the next century.”

vs

“Constant-composition commitment is often misinterpreted as the unavoidable warming that is yet to manifest in response to past greenhouse-gas emissions. However, the climate warming commitment from past greenhouse-gas emissions is more correctly defined as a ‘zero-emissions commitment’ — that is, the future climate change that would occur, should greenhouse-gas emissions be eliminated entirely”

Eh? In that 1st para, they say past human activity has committed us to 0.3 to 0.9 degrees in the next century, as the climate system has a lag. They call this the constant-composition commitment… but then go on to say that it *isn’t* unavoidable warming yet to manifest. Am I being daft or is that contradictory?

Or are they saying the “so-called constant composition” commitment shouldn’t be labelled thus, and should instead be called the “zero-emissions commitment?”

So – they’re concluding that if we magically turned off all carbon emissions tomorrow, we’d almost immediately cease temperature increase?

Comment by Dan Olner — 3 Mar 2010 @ 12:02 PM

32. Angelo,

The first two sentences don’t give enough context to the letter. Here’s the first paragraph:

The perception that future climate warming is inevitable stands at the centre of current climate-policy discussions. We argue that the notion of unavoidable warming owing to inertia in the climate system is based on an incorrect interpretation of climate science. Stable atmospheric concentrations of greenhouse gases would lead to continued warming, but if carbon dioxide emissions could be eliminated entirely, temperatures would quickly stabilize or even decrease over time. Future warming is therefore driven by socio-economic inertia, and is only as inevitable as future emissions. As a consequence, mitigation efforts to minimize future greenhouse-gas emissions can successfully restrict future warming to a level that may avoid dangerous anthropogenic interference with the climate system. The challenge of climate mitigation, although daunting, is fully within the scope of human control.

Comment by davey — 3 Mar 2010 @ 12:11 PM

33. 2 Angelo Lamana says:

Angelo, that’s exactly what Gavin says?

‘ … subsequent temperatures (depending slightly on the model you are using) would either be flat or slightly decreasing. With this definition then, there is no climate change commitment because of climate inertia.’

Comment by HotRod — 3 Mar 2010 @ 12:16 PM

34. After reading the full letter I’m curious about one thing. They claim that if human emissions were stopped tomorrow that CO2 would fall at a “rate similar to the mixing of heat into the deep ocean.” There ought to be pretty large error bars on the uptake of CO2. As of a few years ago the “missing sink” (where roughly 3 gigatons of carbon go every year) was still not fully understood. These guys discuss it. http://www.whrc.org/carbon/missingc.htm It is also worth noting that zeroing out CO2 emissions requires not only cessation of fossil fuel burning it also requires cessation of changes in land use which I believe account for about 20% of CO2 emissions (at least that’s my reading of the Woods Hole page).

Comment by John E. Pearson — 3 Mar 2010 @ 12:19 PM

35. re #2 Angelo Lamana says:
3 March 2010 at 9:10 AM
“”"”The authors’ very brief summary of the letter (access to the letter is limited to subscribers), at the link you provided, doesn’t seem to match your discussion above.

“Committed climate warming” H. Damon Matthews & Andrew J. Weaver

Abstract
The perception that future climate warming is inevitable stands at the centre of current climate-policy discussions. We argue that the notion of unavoidable warming owing to inertia in the climate system is based on an incorrect interpretation of climate science.

What gives?”"”"

Angelo, It sounds like you are cherry picking, purposefully trying to confuse people and putting up a straw man. Use science and not politics.

I saw at the place I used to be, a certain shift when climate commitment was published by at least two of the senior scientists there. After that, I saw for the first time a certain feeling of quiet desperation emerge.

One of the senior scientists there (extremely conservative senior scientist who got after me occasionally about being too bold), publicly used the phrase, “this [human caused climate change evidence] is alarming to me.”

For an almost reactionary conservative senior scientist to say this was a paradigm shift to say the least.

Comment by Richard Ordway — 3 Mar 2010 @ 12:22 PM

36. Angelo, read Gavin’s post again: “Matthews and Weaver make the point that this is a little arbitrary and that the true impact of climate inertia would be seen only with emissions cut to zero. That is, if we define the commitment as the consequence only of past emissions, then you should set future emissions to zero before you calculate it. This is a valid point, and the consequence of that is seen in the lower lines in the figure.”

“CO2 concentrations would start to fall immediately since the ocean and terrestrial biosphere would continue to absorb more carbon than they release as long as the CO2 level in the atmosphere is higher than pre-industrial levels (approximately). And subsequent temperatures (depending slightly on the model you are using) would either be flat or slightly decreasing.”

Gavin has simply expanded the summary based on the full contents of the letter.

Sko sswhere

Comment by Ron Taylor — 3 Mar 2010 @ 12:23 PM

37. Is this referring to Charney or longterm climate response?
I think of Charney factors as changing over decades, and longterm as changing over a few thousand years. This chart is for a couple hundred years.

Comment by Hank Roberts — 3 Mar 2010 @ 12:25 PM

38. If the radiative forcing due to GHGs were stabilized, you say the planet would still have a radiative imbalance, and “warming will continue until the oceans have warmed sufficiently to equalise the situation – giving an additional 0.3 to 0.8ºC warming over the 21st Century”. However, isn’t it true that most energy is removed from the earth’s surface by convection and evaporation, not radiation (because the lower troposphere contains so much GHGs, especially water vapor)? Isn’t net radiative equilibrium for the whole planet therefore restored when the upper troposphere, not the ocean, warms? Can this happen in a short period of time (weeks?) rather than decades because there is relatively little mass that needs to warm?

After radiative cooling, air subsiding from a warmer upper troposphere may eventually slowly warm the oceans. However, this probably shouldn’t be characterized as a return to an equilibrium situation, since the earth’s atmosphere and oceans are far from equilibrium at all times. As can be seen your graph, our climate models make a wide range of predictions (perhaps 0.5-5 degC, a 10-fold uncertainty) about how much “committed warming” will occur in the future under any stabilization scenario, so we don’t seem to have a decent understanding of these processes.

[Response: The issue is the balance at the top of the atmosphere, not the surface. - gavin]

Comment by Frank — 3 Mar 2010 @ 12:41 PM

39. “On the other hand this assumes no positive feedbacks are already in play, no?”

No, just no runaway positive feedback – which we pretty clearly don’t have yet.

Comment by NoPreview NoName — 3 Mar 2010 @ 12:48 PM

40. “…terrestrial biosphere would continue to absorb more carbon than they release…”

I would imagine this is a false assumption. The terrestrial biosphere is shrinking. Trees and the understory shrubs are in decline, thus they must be emitting more carbon than they absorb. They are dying, not growing.

Comment by Gail — 3 Mar 2010 @ 1:06 PM

41. It would have been nice to see scenarios on the other side of the “social inertia” parameter included, too, given that emissions are likely to (continue to) increase in the short term as the recession ends.

And absent meaningful agreements on mitigation, of course.

Comment by Kevin McKinney — 3 Mar 2010 @ 1:28 PM

42. Well, if we’re really committed to not mitigating and to spending $$kazillions on adaptation, which is looks like we are, then where’s the money going to come from? I have an idea, we could save perhaps even in the$$kazillions from mitigating global warming and reducing GHGs down by 80% (at least down to 70% without any sacrifice or lowering of productivity or living standards), and use that for adaptation :)

Comment by Lynn Vincentnathan — 3 Mar 2010 @ 1:33 PM

43. Your point that it does not matter depends on what we call mitigation. If we embark on a path that is equivalent to setting emissions to zero now (say by having a period of negative emissions in the 2035 to 2050 time frame), and call the sequestration we accomplish mitigation then mitigation can arrest climate change, make adaptation unneeded and bring us to a safe concentration of carbon dioxide in the atmosphere as Hansen has pointed out. If we instead consider our clean up efforts to be a form of adaptation to prior mess making, then we have a choice between effective adaptation in the clean up and panicked and unseemly adaptation in the response to sea level rise etc….

Comment by Chris Dudley — 3 Mar 2010 @ 1:33 PM

44. This does not correlate with Dr. Dan Lunt’s observations at Bristol University that 3 million years ago, the CO2 was 340 – 400 ppm and the temperature was 2 – 3 deg warmer. Why?

[Response: In the paper we discuss the impact of longer term processes - particularly vegetation change and ice sheet change. These are both amplifying factors . - gavin]

Comment by Lee Norton — 3 Mar 2010 @ 1:43 PM

45. Slightly OT question.

My understanding of climate sensitivity is that it is dynamic in nature. In other words, the present day climate system with its current configuration of ice sheets, biota, contents, etc. has an S value of about 2.5 degrees. How does this value compare with what what we think S was in earlier periods in Earth’s history (e.g. do we think it was closer to 1 when there was little ice and/or carbon locked up in vegetation)?

Thanks,

Bruce M.

Comment by Bruce M. — 3 Mar 2010 @ 1:55 PM

46. Well, I even hate to bring up some minor disprecancy among climate scientists. You know where the denialists would go with it, and that’s what would REALLY be damaging to science. A chilling effect on even scientists’ usual disagreements that lead to better and better science, because they’re always having to look over their shoulders at the blood-dripping fangs of the denialists close on their heels, looking for some climate scientist to break from the pack so they can attack.

But, what about the suggestion by Ramanathan and Feng (2008) that even if we go down to zero GHG emissions, we are committed to 2.4 C warming. What accounts for the difference between the Wigley figure of .3 to .8 C (which would mean ? up to 1.6 C warming) and the 2.4 C figure. And which one seems closer to reality, as perceived by today’s science? See:

Ramanathan, V., and Y. Feng. 2008. “On Avoiding Dangerous Anthropogenic Interference with the Climate System: Formidable Challenges Ahead.” Proceedings of the National Academy of Sciences 105.38: 14245-14250.

Comment by Lynn Vincentnathan — 3 Mar 2010 @ 1:57 PM

47. The authors’ very brief summary of the letter (access to the letter is limited to subscribers), at the link you provided, doesn’t seem to match your discussion above.

It seems consistent to me. What about it seems inconsistent to you?

Comment by dhogaza — 3 Mar 2010 @ 2:02 PM

48. Angelo:

The summary seems to me like a very good match to the discussion. The point being that it isn’t inertia in the climate system that makes warming inevitable — it is inertia in the social system.

Comment by Black — 3 Mar 2010 @ 2:07 PM

49. Gavin:

You state:

“the planet still has a radiative imbalance, and the warming will continue until the oceans have warmed sufficiently to equalise the situation”.

Isn’t the main problem that, even if we stopped adding any fossil-fuel-derived CO2 to the atmosphere, the ocean circulations haven’t yet reached ‘steady state’ – i.e., a stable thermocline and deep ocean temperature – and therefore THAT is the source of the Hansen et al. “heat in the pipeline”? That only after the atmosphere has ‘equilibrated’ with THAT ocean, will the atmospheric temperature have peaked?

And (because of the unavailability of the full text of their paper), from their abstract:

“We argue that the notion of unavoidable warming owing to inertia in the climate system is based on an incorrect interpretation of climate science.”

Comment by Len Ornstein — 3 Mar 2010 @ 2:15 PM

50. A Previous article: “David Frank and his Swiss coworkers at WSL have just published an interesting new approach to answering it. They empirically estimate the distribution of gamma, the temperature-induced carbon dioxide feedback” appears to directly contradict the above. “Climate change commitments” also contradicts the other things I have read and the fact that we have already crossed some thresholds such as Arctic ocean ice melting, tundra peat bog thawing and clathrate melting.

An additional 0.8 degrees C of warming is a doubling of the present warming.

Since I don’t have access to Nature Geoscience either, please explain the incorrect interpretation and tell us who really got it wrong. If Mathews and Weaver are correct, that is a little less bad news. I find it hard to believe, but even if correct not a reason for celebration. No doubt the denialists will find reason to celebrate. The Republicans will also find reason to further reduce the Climate Bill and the Clean Air Act. They will read only the “60% cut” and say that President Obama’s goals are too “severe.”

I hope Mathews and Weaver are correct. I am awaiting further research and clarification.

Comment by Edward Greisch — 3 Mar 2010 @ 2:18 PM

51. Solomon et al. (2009) did essentially the same, didn’t they? They ran various scenarios with abrupt transitions to zero emissions, albeit all peaking at at higher CO2 concentrations later in the 21st century.

Their glass seemed to be half empty, and was widely misreported to say our goose was cooked no matter what we did to mitigate. Matthews and Weaver find the glass half full and use it to reframe the debate in favor of strong mitigation. Full marks to M&W for grasping the psychology of communicating climate change.

But how much sea-level rise would we still be committed to if we quit carbon cold turkey now? That’s one adaptation cost they don’t seem to discuss.

Zero emissions, now, is not realistic, of course. But just think where we could have been already if we hadn’t wasted two decades. Sigh. Better not waste any more.

Wonder how the deniers are going to spin this graph. I mean, damn the context, they cannot not abuse graph that shows some temperatures going down while the IPCC says they’ll go up! All they need is a name for the IPCC’s latest “mistake” … hm … “Realismgate”?

Solomon, Susan et al. (2009). “Irreversible climate change due to carbon dioxide emissions,” PNAS, online January 28, 2009, doi:10.1073/pnas.0812721106.

Comment by CM — 3 Mar 2010 @ 2:23 PM

52. I am very puzzled by the Figure that you provide with the text, because it suggests that the mean value for the IPCC models during the 21st century almost coincides with the “constant composition” scenario. It is stated that the latter scenario would yield a 0.3 to 0.8ºC warming over the 21st century. As far as I understand, the IPCC predictions have always been much higher. Can you perhaps explain this, before we get endless debates based on misunderstandings?

[Response: The diagram is only for the constant-2000 concentrations. The business-as-usual scenarios that people talk about have steadily increasing concentrations. - gavin]

Comment by wilt — 3 Mar 2010 @ 2:28 PM

53. Angelo: Future warming is not necessarily inevitable, if we drastically cut emissions now. Since immediate and drastic cuts are not very likely, we will see further warming. Not due to climatic inertia, but to social inertia. Seems pretty simple to me. Or are you being deliberately obtuse?

Comment by Sean A — 3 Mar 2010 @ 2:33 PM

54. I may be misreading the graph, but doesn’t it imply that there is no “warming in the pipeline”? I would consider that good news.

Thanks,
tim

Comment by Tim G — 3 Mar 2010 @ 3:04 PM

55. I’ve always interpreted the “we will simply adapt” meme as an implied appeal to techno-triumphalism … the idea that technology will bail us out. The abstract idea then becomes the concrete excuse; we don’t have to do anything about this because “someone” will come up with an “idea” that will change everything. This for all values of “someone” not equal to me and all values of “idea” that don’t overlap with the set of solutions that entail life style changes.

Technology is the final balm for the weak minded because it really is indistinguishable from magic. We will happily go into a dark place and then wait for someone to invent light.

Comment by cougar_w — 3 Mar 2010 @ 3:28 PM

56. I’d be very interested in seeing a projection that mirrors what is actually likely to happen. That is, an apathetic “show me the money” style public combined with “we like things as they are” power bases will combine to obstruct any mitigation whatsoever until perceptible climate changes are more apparent and so more difficult to refute. The two scenarios outlined here, both constant composition and zero emissions, are very, very unlikely to happen even within a decade.

For example:

Phase I, Apathy: Two more decades of warming and accompanying side effects (ice melt, etc.) equivalent to the 1990-2010 increase will probably be enough (necessary and sufficient?) to start to make people question their own hesitation to act.

Phase II, Reluctant Concern: After that, mitigation efforts will be slow, taking another decade or so before people really get scared, and get serious.

Phase III, Action-with-Friction: After that, it will take another decade (at least) for the politics, cold warfare, technology and other social aspects to catch up and start to make a truly noticeable dent in where CO2 goes (i.e. get it to start declining).

Phase IV, Concerted Action: Finally, 40 years from now, things will be in place to begin to actually either level off or possibly reduce atmospheric CO2 levels.

This is all a hypothetical, of course, with rule-of-thumb time periods thrown in. Other people could put other time frames on these four phases of climate change reaction (20 more years of apathy, 10 years of reluctant concern, 10 years of action-with-friction, an eventual future of concerted action). Sorry if my own time frames are depressingly pessimistic. It would actually make an interesting sociology study.

But however this is framed… what do future temperatures look like if this pattern is followed?

Comment by Bob — 3 Mar 2010 @ 3:47 PM

57. Angelo –

Matthews and Weaver were making the point that the issue of climate inertia has been overstated/conflated with a different issue. The climate inertia issue is whether the CO2 that we have already dumped into the atmosphere is going to keep the warming going even IF we ended all emissions. If there was a significant amount of climatic inertia, the Earth would continue to warm despite zero future emissions.

Matthews and Weaver’s conclusion is that with a zero emission policy, global temperatures would remain constant or even begin to decrease (which makes some amount of sense – trees and other biota would start to remove the CO2 and store it). That means that there is no climatic inertia in the system.

The constant CO2 scenario means that we have to continue emitting CO2, but at the same rate as the Earth can store it, which would require a 60-70% cut, as Gavin points out. Even in this scenario, the Earth would continue to warm.

I think Matthews and Weaver were pointing out that continued warming with constant CO2 is associated with climate inertia, which is incorrect. It is the inertia in society, our dependence on fossil fuels for example, which will drive the continued warming – NOT the inertia in the climate system.

So the short summary abstract from Matthews and Weaver, which you have access to, is true – that unavoidable warming due to climatic inertia is incorrect. From my read, Gavin agrees with this. However, Gavin very correctly points out that zero emissions is a bit of a pipe dream, and that 60-70% cuts are also unlikely. Therefore, even if the climatic inertia will have little to no effect on future warming, the significant societal inertia essentially guarantees it.

From my viewpoint, Matthews and Weaver point out that we have much more control over our own climatic future than some people realize. Or, and to quote a favorite cartoon character from my youth (and now I’m dating myself and pointing out my geek-hood):

“The Power is yours!”
-Captain Planet (from Captain Planet and the Planeteers)

Comment by Dan Sinnett — 3 Mar 2010 @ 4:02 PM

58. Feddback indeed – how can you ‘set future emissions to zero’ with the forcing of natural emmissions of carbon dioxide and methane – surely this ensures ‘unavoidable warming owing to inertia in the climate system’?

Comment by Tony Lowes — 3 Mar 2010 @ 4:03 PM

59. I wonder if in calculating the zero emission scenario, they take into account the drop in aerosols that result from fossil fuel burning. As these have a cooling effect that cancels out much of greenhouse gas warming, the removal of the cooling effect would also have a warming impact.

Comment by John Cook — 3 Mar 2010 @ 4:04 PM

60. P.S. To those lacking a subscription or university access, some (most?) public libraries have subscriptions to scientific magazines. If you really care enough about this subject, or truly want to be educated on it, take advantage of these resources. Further, there are motions towards making publicly funded research more available to the public after a period of time. Lastly, reports by the national academies and other government agencies are often freely available.

Comment by Dan Sinnett — 3 Mar 2010 @ 4:09 PM

61. Interesting discussion, but perhaps we should now guess and adapt to the way this paper is likely to be misrepresented.

Comment by Geoff Wexler — 3 Mar 2010 @ 4:52 PM

62. It’s nice to see discussion of an actual science paper again, rather than yet more media analysis.

The question about “what would happen with zero emissions” is an interesting one, albeit hypothetical. We could imagine it happening if a sudden plague wiped out our civilization, for instance.

As far as I can understand it, reading across several papers (references below), there might well be a number of stages.

Stage 1: CO2 levels in the atmosphere start declining straight away (while the oceans continue to acidify).

The radiative imbalance due to CO2 forcing starts to fall, counteracting the “warming in the pipeline”.
Global temperature stays approximately at today’s level or falls a little.

Stage 2: CO2 stops falling, because there is a portion (20-25%) of our emissions which is persistent for thousands of years. The airborne fraction of our emissions has been 40-50%, which means about half the extra CO2 in the atmosphere will stay there long-term i.e. CO2 bottoms out at around 335ppm. Temperature rises owing to fast-feedbacks (Charney sensitivity) for that level are around 0.75 degrees C above pre-industrial, roughly where we are today.

Stage 3: However, this is high enough to cause melting on all our land ice-sheets, and so slow albedo feedbacks will kick in too (Earth System Sensitivity). A slow warming resumes, leading to an additional 0.75 degrees or so over the next few centuries. But at the same time, we see the full temperature-dependent CO2 response, with CO2 levels slowly rising again, likely about 16-20ppm per degree C judging by the change between LGM and Holocene. This increased CO2 causes a bit more warming, which causes a bit more CO2, and so on, but in a convergent series.

Stage 4: CO2 levels converge back up to around today’s levels (370-400ppm), and the temperature to around
2.5 to 3 degrees above pre-industrial levels. The Greenland and West Antarctic ice-sheets have gone. Part
of the East Antarctic ice-sheet has gone too. Earth resembles the Pliocene.

Stage 5: Our persistent CO2 finally drops out of the atmosphere after maybe 100,000 years. Milankovich cycles resume, and eventually there is a new stade allowing ice sheets to grow again. A climate like the
Holocene is not restored until the next interglacial after that.

That seems to be what we’re committed to: “Hell and high water” for thousands of years plus a probable mass extinction whose effects will last for millions of years. Given that (or even a fraction of that), it’s not enough to reduce emissions to zero: somehow we must make them NEGATIVE (i.e. suck CO2 out of the atmosphere again). It’s a long away from current policy discussions.

References: Stage 1 is described in the above paper.

For persistent fraction of CO2, see e.g. <a href="http://www.pik-potsdam.de/~victor/archer.subm.clim.change.pdf&quot; Archer, <a href="http://melts.uchicago.edu/~archer/reprints/montenegro.2007.fate_CO2.pdf&quot; Montenegro et al,
<a href="http://geosci.uchicago.edu/~archer/reprints/archer.2009.ann_rev_tail.pdf&quot; Archer et al.

For evidence on Charney sensitivity, see Annan and Hargreaves.

On Earth System Sensitivity, see Hansen et al and the Pliocene papers below.

For CO2 response to temperature, see Cox and Jones and the discussion of Frank et al here .

A number of recent papers on the mid-Pliocene indicate that CO2 levels were similar to today’s
including Pagani et al, Lunt et al and Schneider and Schneider . Whereas Tripati et al reconstruct them even lower than today.

For a discussion why it takes 100,000 years or more to undo the damage, see How Long will global warming last?

Comment by Dr Nick Bone — 3 Mar 2010 @ 5:03 PM

63. Just to track this question:

5, 6, 9, 20 (implicitly), 22, and 59 mention the need to consider the result of aerosols (sulfates) falling rapidly once fossil fuel burning ceases. Gavin affirms that as a good question, inline in 20.

Comment by Hank Roberts — 3 Mar 2010 @ 5:07 PM

64. We can easily get to a 50% cut without changing peoples’ lives – replace coal power with nuclear.

Comment by Foobear — 3 Mar 2010 @ 5:09 PM

65. I’d like to give a second response in order to clarify the absurdity of the Figure
above which “neatly demonstrates the different issues”. If you add a carbon cycle
model to demonstrate that actually there is no future warming commitment, then
you should also add ice-sheet responses, for which you don’t even need the fancy
super computer GCMs. Paleo data (Hansen et al, 2008) provide sufficient information
to see that the long-term equilibrium warming would amount to 2 x 1 = 2 degrees in
the zero emissions case (based on the plm 1 degrees oceans-only induced equilibrium value presented in the figure).

Comment by Nonlinear Guy — 3 Mar 2010 @ 5:20 PM

66. Okay, we’ve been over the carbon cycle responses about a thousand times now – your shallow Arctic seabeds & permafrost regions, which are going to continue outgassing by all estimates, both modeled and real-time measurements.

This was also a problem with a previous paper on this subject:

http://www.realclimate.org/index.php/archives/2010/02/good-news-for-the-earths-climate-system/

Here’s the problematic statement:

CO2 concentrations would start to fall immediately since the ocean and terrestrial biosphere would continue to absorb more carbon than they release as long as the CO2 level in the atmosphere is higher than pre-industrial levels (approximately).

I’m sure gavin would admit that his expertise is not in the area of biogeochemical cycling – but aren’t there several huge questions here? What’s the basis of this argument when we know quite clearly that terrestrial environment is NOT absorbing more carbon than it is releasing?

Look at the land use change estimates – deforestation has played a large role. Permafrost outgassing is similarly a major issue – and what about all the studies on the Southern Ocean sink saturation – they don’t matter either? Canadian pine forests – they were going to be a source of “carbon credits” for Canada to exchange for tar sand emissions, but they’ve lost so much mass that they now count as an emission debt, not a credit – which shows how unscientific the carbon trading schemes are, by the way.

Consider the natural uptake of CO2 during the slow progression into a glacial maximum – what is the range? 280 ppm to 190 ppm – a 110 ppm drop over tens of thousands of years. Why on earth would you expect the atmospheric CO2 to start declining rapidly, even if we halted emissions?

The real question here is the extent to which we’ve enlarged the circulating carbon pools – and also changed the global ocean circulation. There are plenty of reasons to wonder about a slowed ocean circulation, and spreading hypoxia and anoxic conditions in deep waters, as well.

Finally, it seems that Wigley did indeed fix conditions:

The Climate Change Commitment
T. M. L. Wigley

Even if atmospheric composition were fixed today, global-mean temperature and sea level rise would continue due to oceanic thermal inertia.

Wigley also neglects carbon cycle feedbacks, but step by step is the way science is done.

So, are we saying that CO2 levels would start dropping by what, a ppm every few years? if we suddenly stopped burning fossil fuels?

That seems highly unlikely – what if the permafrost starts outgassing at higher rates?

Comment by Ike Solem — 3 Mar 2010 @ 5:21 PM

67. Gavin well put. This is somewhat along the lines of what I have been saying, but better put in the terms of climate inertia. Of course we should do what we can to reduce future emissions, but we also have to accept a growing population will still need technology which emits GHG.

Oh and on a side note I liked the recent commentary you wrote on Gilbert N. Plass on pp. 64-65 of the Jan-Feb 2010 issue of American Scientist.

Plass was certainly very accurate considering the technology he had to work with… for those who have not done so, I suggest you grab that issue of AS.

Comment by Jacob Mack — 3 Mar 2010 @ 5:23 PM

68. “Dr Nick Bone says:
3 March 2010 at 5:03 PM

It’s nice to see discussion of an actual science paper again, rather than yet more media analysis.

The question about “what would happen with zero emissions” is an interesting one, albeit hypothetical. We could imagine it happening if a sudden plague wiped out our civilization, for instance.”

It’s an interesting thought experiment…I’m not a scientist, but I think in the absence of man Mother Nature might recover more quickly than we might think. For example, a lot of new vegetation would soon appear in areas man currently keeps in closely manicured lawns or even in roads and such. And sites subjected to heavy grazing by farm animals would start to recover as those farm animals died down to a more natural population. How much and how fast that would affect CO2 uptake, I couldn’t begin to guess, but I’d think it could be noticeable within a decade or two.

Comment by Witgren — 3 Mar 2010 @ 5:43 PM

69. From the abstract: “… mitigation efforts to minimize future greenhouse-gas emissions can successfully restrict future warming to a level that may avoid dangerous anthropogenic interference with the climate system.”

But the warming that has already occurred from the excess GHGs that we have already emitted is already causing “dangerous anthropogenic interference with the climate system”.

Comment by SecularAnimist — 3 Mar 2010 @ 5:46 PM

70. Dr. Bone: Thanx for a cogent analysis.

But what if the trajectory you outline destabilizes a)the permafrost or b)mathane clathrates ?

Comment by sidd — 3 Mar 2010 @ 5:47 PM

71. Gavin:

Hansen et al (2005) (Gavin is one of the “et al”)

http://pubs.giss.nasa.gov/docs/2005/2005_Hansen_etal_1.pdf

talks about “warming in the pipeline”.

Isn’t that most of the ‘further’ warming (climatic inertia?) that would be realized if all burning of fossil fuel and all deforestation came suddenly to an end?

Wouldn’t that warming continue for a number of years?

Isn’t that mainly due to the time it takes for the heat, previously absorbed near the surface of the oceans, to mix to a steady-state distribution in the oceans and with the atmosphere?

[Response: No. The heat that goes into the ocean generally stays there. The upper ocean will only warm to the equilibrium level if it stops losing heat to the deep ocean. At equilibrium, the ocean will have a significantly larger heat content than originally (which is why there is sea level rise via thermal expansion). - gavin]

Comment by Len Ornstein — 3 Mar 2010 @ 5:48 PM

72. “On the other hand this assumes no positive feedbacks are already in play, no?”

No, just no runaway positive feedback – which we pretty clearly don’t have yet.

Comment by NoPreview NoName — 3 March 2010 @ 12:48 PM

Um…albedo effect? permafrost releasing methane? melting polar ice? forests turning from carbon sinks to carbon emitters? If those aren’t runaway positive feedbacks, what would be? Does anyone have any clue how to stop them?

Thought not.

Comment by Gail — 3 Mar 2010 @ 6:07 PM

73. I agree with Bob (56). His scenario strikes me as more realistic, if politically incorrect. Remember, even though it was killing tens of thousands each year, it took forty years to get something done about tobacco. Big money carries a big stick.

If we started analyzing such scenarios, maybe it would help get the attention of the policy makers.

Comment by Ron Taylor — 3 Mar 2010 @ 6:47 PM

74. David (65) — On the Whatevergate thread I posted a prediction for GISTEMP global decadal averge for the 2010s; warmer. That used just the Arrhenius approximation for CO2. I’m working up a slighter better predictor program, a slightly more complex conceptual model of the global climate, so watch for it.

But I don’t know how to make regional predictions although I have seen papers which attempt this. Generally drier and hotter in southern Europe over the rest of the century as I recall.

Comment by David B. Benson — 3 Mar 2010 @ 6:55 PM

75. Jean,Once again, the scientific study referenced, certainly paid by tax payers, is not available to the general public.

I presume you mean that you have to pay Nature to read what they publish? I would like to know what you think would be both better and practical. Is the US taxpayer going to fund Nature? If all research is made available free, then journals disappear. How do you ensure archive, referencing, and more importantly manage the peer-review process? Do you as tax payer want to stump up for that? Are you going to increase research funding to cover that cost? At the moment, the system is “user-pays” which I understood to be the American way. (I am not a US citizen. I would be very happy for you, the tax payers of US, to pay for my journal subscriptions).

Comment by Phil Scadden — 3 Mar 2010 @ 7:07 PM

76. For those like me who don’t have a subscription and haven’t gotten out of the house and down to the library yet, abstracts of a few possibly related articles can be found. Looks like there’s a lot of teaching possible here, if the paywall can be gotten around somehow.

Too bad there’s no millionaires’ tip jar for scientists wondering about buying out the publisher so their work could be made available right away.

http://www.ncbi.nlm.nih.gov/pubmed/19516338?itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum&ordinalpos=2

Nature. 2009 Jun 11;459(7248):829-32.
The proportionality of global warming to cumulative carbon emissions.

Matthews HD, Gillett NP, Stott PA, Zickfeld K.

Department of Geography, Planning and Environment, Concordia University, 1455 de Maisonneuve Blvd W., Montreal, Quebec, H3G 1M8, Canada. dmatthew@alcor.concordia.ca

The global temperature response to increasing atmospheric CO(2) is often quantified by metrics such as equilibrium climate sensitivity and transient climate response. These approaches, however, do not account for carbon cycle feedbacks and therefore do not fully represent the net response of the Earth system to anthropogenic CO(2) emissions. ….

——
Proc Natl Acad Sci U S A. 2007 Jun 12;104(24):9949-54. Epub 2007 Jun 4.
Transient climate-carbon simulations of planetary geoengineering.
Matthews HD, Caldeira K.
Comment in:
* Proc Natl Acad Sci U S A. 2007 Jun 12;104(24):9915-6.
Geoengineering … there may be little cost to delaying the deployment of geoengineering strategies until such a time as “dangerous” climate change is imminent.

——–
Proc Natl Acad Sci U S A. 2009 Sep 22;106(38):16129-34. Epub 2009 Aug 17.
Setting cumulative emissions targets to reduce the risk of dangerous climate change.
Zickfeld K, Eby M, Matthews HD, Weaver AJ.
Comment in:
* Proc Natl Acad Sci U S A. 2009 Sep 29;106(39):16539-40.

Comment by Hank Roberts — 3 Mar 2010 @ 7:13 PM

77. re 30 Jean says:

“”Once again, the scientific study referenced, certainly paid by tax payers, is not available to the general public.

If I cannot have access to the information, I cannot communicate around me, because I don’t know.

We therefore cannot assess the claims and should not expect the general public to be well informed and make rational voting decisions.

When will they get it?”"”
_________________________________________________________________________

Jean, one study does not the body make since 1824…and it sure did not when I was at the place I was for 11 years. The synthesis of published climate science since 1824 is the IPCC 2007 AR4 which is freely available.

That is why political people say, “OMFG!!! this one study that just came out disproves human caused global warming.”…again. again. again and yet again (absolutely none of which stands up over time. This is deceiptful to say this. It is really a body of evidence of thousands of studies since 1824 that you need to concern yourself with…not just one study.Only politicans say this.

Remember, this study is available at most libraries if you are so desperate to make a voting policy decision based on only one study out of thousands that have the same general conclusions.

A small sample of freely available (downloadable to the public) studies stating that anthropogenic climate change is happening.

Remember, to use only the latest studies from reputable scientific journals that have been vetted over about two years because science moves on too.

One magazine for instance, Energy and Environment is not a scientific journal and prints at best pseudo science that does not stand up over time and sometimes seems to act like a scientific journal. Any real scientist whose climate science work holds up over time would know this…not the public or the pseudo scientists. This is the way it has been done since the 1600s.

TC Johns et al., Climate Dynamics, 2003
http://xweb.geos.ed.ac.uk/~dstevens/publications/johns_cd03.pdf

Oreskes, 2004, Science
http://www.sciencemag.org/cgi/content/full/306/5702/1686?paged=78

Nature, CD Thomas, 2004
http://eprints.whiterose.ac.uk/117/1/thomascd2.pdf

JT Houghton, Intergovernmental Panel on Climate Change, 2001

JT Houghton, Intergovernmental Panel on Climate Change, 1995

Karl, Trenberth, Science, 2003
http://kfrserver.natur.cuni.cz/global/pdf/2003_climate%20change.pdf

Comment by Richard Ordway — 3 Mar 2010 @ 7:21 PM

78. Jean@30,
Look into how much it costs to publish an article in a journal like Nature. Now, look at your contribution to this study (about \$0.05). Do you see why you have to pay for the subscription now?

Comment by Ray Ladbury — 3 Mar 2010 @ 7:55 PM

79. Hank (#63),
I’m 6. I did not mention that. Read my post again. What I mentionned is the need to consider not only the cooling commitment from the mitigation which ain’t happening but also the cooling commitment from geoengineering which ain’t happening as well. Surely all counterfactuals deserve equal consideration.

Alert readers might have picked up the modest proposal between the lines. Recall that the only reliable way to neutralize “social inertia” would also stop emissions and send a whole lot of aerosols up there in one fell swoop. Let it not be said there are no alternatives to adaptation!

Comment by Anonymous Coward — 3 Mar 2010 @ 8:02 PM

80. The comment here by Bart Verheggen using work by Ramanathan and Feng, coupled with the comment by Elmar Veerman about the greenhouse gases remaining long after shorter lived masking aerosols are removed, identify a flaw in the argument and they seem to effectively rebut the argument that ending carbon dioxide emissions would lead quickly to global temperature stabilizing.

On the question of positive feedbacks I am reminded of the study “Abrupt Climate Change: Inevitable Surprises” (2002) National Academy of Sciences, which identified potential positive feedback loops that could result in rapid and harmful climate shifts. Now recent work shows carbon dioxide and methane feedback loops are initiating [1-4]. The question is as a practical matter can we do anything effective to limit greenhouse emissions before we pass critical tipping points? Tipping points after which mitigation will not work because release of carbon stores now sequestered due to being frozen in permafrost takes over the system. It seems clear we do not have sufficient understanding and data to say where the tipping points may be, nor even to know if we have already passed a point of no return.

Meanwhile reading the US Energy Information Agency global forecasts for coal mining and petroleum production makes it quite clear that Business As Usual is the global reality. As Copenhagen clearly showed there is no political will to force massive economic changes and there will not be, not until there are immense and clear cut catastrophic changes that obviously are the result of global warming. I think that is almost certain to be too late. We are committed to the Hot World and adaptation is the way of the future for my children and grandchildren, much as I wish it were not so.

1. Ping, C.-L., et al., High stocks of soil organic carbon in the North American Arctic region. Nature Geosci, 2008. 1(9): p. 615-619.
2. Lawrence, D.M., et al., Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss. Geophys. Res. Lett., 2008. 35.
3. Walter, K.M., L.C. Smith, and F.S. Chapin, 3rd, Methane bubbling from northern lakes: present and future contributions to the global methane budget. Philos Transact A Math Phys Eng Sci, 2007. 365(1856): p. 1657-76.
4. Walter, K.M., et al., Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming. Nature, 2006. 443(7107): p. 71-75.

Comment by Don Condliffe — 3 Mar 2010 @ 8:27 PM

81. How would you assess the state of “societal inertia” right now?

Even without ratifying the Kyoto treaty the US embarked under Bush on a faster development of non-hydro renewables and CC&S, increased the investment still more, and yet again still more under Obama. The UN, EU, and China have massive reforestation projects, and nearly every industrial nation is expanding its non-hydro renewable energy supplies and nuclear power generation.

The strongest motivator (except for CC&S) is the worry over declining or unreliable oil supplies, but the impact on AGW is substantial.

Comment by Septic Matthew — 3 Mar 2010 @ 9:38 PM

82. Jean@30 says:
Once again, the scientific study referenced, certainly paid by tax payers, is not available to the general public.
If I cannot have access to the information, I cannot communicate around me, because I don’t know.
We therefore cannot assess the claims and should not expect the general public to be well informed and make rational voting decisions.

When will they get it?

Jean – For starters, it’s not a “scientific study”, it’s a letter to the editor of a scientific journal, definitely available to the public, with payment of the magazine cost, same as anything else on your news stand – Gavin choosing to discuss it here makes it available to the public.

Next off, it’s likely the authors were not paid with any tax money for thinking about climate inertia vs social inertia and writing a letter to an editor about it, and if they were, it would only be your tax money if you are Canadian, in which case you might try emailing either author, both professors at Canadian Universities and both amenable to public outreach, and largely paid by their respective provinces and student fees. You might even be able to audit a course with one of them, but of course that would cost you!
As for assessing “the claims”, Gavin gave us a good leg up on that, although many of the “general public” might not be interested in thinking about what he had to say, prefering to immediateely decide it’s easier to claim something is being hidden, which just goes to show Gavin got it right. :)

Comment by flxible — 3 Mar 2010 @ 10:21 PM

83. re: Steve A Morris (#14)
“The Earth is only heated via Radiation, and cools via Radiation, Convection, and Evaporation in order of increasing magnitude.”
In fact, I believe that the Earth is only cooled by radiation. Convection and Evaporation will move energy between the Earth Surface and the atmosphere but the energy still remains in the Earth system, only when this results in increased radiation from the Earth will the Earth system cool–but of course, this is exactly what the climate models are modelling.

Comment by Dave E — 3 Mar 2010 @ 10:26 PM

84. RE: Steve A Morris — 3 March 2010 @ 10:32 AM and Frank — 3 March 2010 @ 12:41 PM:

Evaporation and convection move heat about, but it can only be transferred to the vacuum “thermos bottle” of space via radiation.

Steve

Comment by Steve Fish — 3 Mar 2010 @ 10:35 PM

85. At the current setting of the climate “thermostat”, the Greenland Ice sheet is melting and losing mass by calving icebergs faster than snow is accumulating at high elevations. The rate of loss is accelerating, partly because we keep turning up the thermostat with more CO2, and partly because the lost mass moves more surface into the melt zone and out of the accumulation zone. It’s obvious to me that unless we turn down the thermostat (eliminate CO2 emissions, maybe act to restore some of the natural sinks we’ve upset), Greenland will continue to melt. Only the Bern2.5CC model scenario shows declining Temperatures, but I don’t know when Greenland will stop melting even under that (unlikely) trajectory. I wonder how much sea level rise we have in the pipeline.

Comment by Brian Dodge — 3 Mar 2010 @ 10:56 PM

86. Does a return to pre-industrial mean global temperature necessarily mean no adaptation? Or could you get the same mean with large regional differences?

Comment by Lab Lemming — 3 Mar 2010 @ 11:42 PM

87. I really question whether the (zero emissions) scenario really makes sense. Without resorting to GCMs, we can probably answer some questions. The most salient issues I think would be:
(1) Rapid reversal of the aerosol effect (or should we assume deliberate “geoengineering” to counteract it).
(2) The evolution of CO2 level with time.
(3) Thermal inertia of the climate system.
(4) Vegetation and ice feedbacks that over time change the albedo as a function of temperature.
Factor 2, clearly is a cooling effect. Last time I had seen results for CO2 retention the results were expressed as a prony series (a weighted sum of decaying exponentials). IIRC the first couple of terms had pretty low time constants, so the concentration decay forcing might give a significant cooling effect in early years. The first factor is likely pretty substantial. The third one is what roughly twenty years for near surface ocean heating? The fourth could be important over decadal and longer time scales.

I’m guessing W&W essentially did 2, and 3, and they had them roughly cancelling out. But aren’t (1) and (4) both warming effects? (1) should be pretty fast acting, and probably not that hard to estimate. (4) Contains both short (vegetation, sea ice) and long (ice sheets) time scales.

Comment by Thomas — 4 Mar 2010 @ 12:14 AM

88. Despite several people mentioning it, and Hank R doing a round-up of who has mentioned it, I’m not sure most of the commentariat have understood the crucial importance of Bart V’s critique right there at comment #4. The idea of testing zero CO2 emission with constant (current) sulfate emission is unphysical (unless we’re geoengineering the sulfates). So anyone who thinks this paper means there’s no warming in the pipeline is wrong. I would suggest to Gavin that he amend the original post to reflect what Bart said.

On an entirely separate, and off topic issue, can anyone tell me what the typical spatial and temporal resolution of a full-scale GCM run is? For example, how about the GISS-E runs in the IPCC AR4. Thanks in advance.

Comment by GFW — 4 Mar 2010 @ 1:26 AM

89. I tried a simple modeling of the temperature curve by assuming a (linear) relaxation equation towards the equilibrium temperature Teq with a time constant tr (representing the climatic inertia) : dT/dt = – (T-Teq)/tr . With an increasing forcing F(t), Teq is itself a function of time , which can be in the same spirit approximated by a linear relationship Teq(t) = To + A F(t) where A is the sensitivity to forcing.
F(t) can be further approximated. If we take a logarithmic sensitivity to GHG concentration, and an exponential growth of this concentration, it is something like ln(1+Aexp(kt)) which is close to 0 as long as exp(kt) << 1/A and then grows asymptotically linearly with time. So it seems a good approximation to take a linear forcing after some date Tbeg (around 1970 in the models) F = F0.t

finally we get dT/dt =- (T-T0-A.F0.t)/tr after Tbeg, and 0 before.
this is a very simple linear differential equation whose solution is analytic and reads
T(t) = T0 + A.F0.tr (t/tr-(1-exp(-t/tr))

This has the right behaviour : for small times t<>tr it grows linearly with the forcing but with some shift due to the accumulated delay (and the shift is necessary for the small imbalance to produce the warming). I think that most of the climate solutions can be reproduced by this two-parameters (forcing+relaxation time) solutions.
Problem : with a linearly increasing forcing, the slope should also increase linearly because of the quadratic behavior as long as t<<tr. If the warming trend has increased indeed since 1970, it doesn't seem to be true anymore since 2000. If it were the saturation of relaxation time, it would indicate a small time (30 years) and a small sensitivity. Or the curve is messed up by natural fluctuations but it means than the 1970-2000 warming was also partly due to fluctuations. In any case, the absence of acceleration of the trend points towards a low climate sensitivity.
T(t) =

[Response: Gilles, posting under different names in the same thread is a strict no-no. Please do not do it again. - gavin]

Comment by ary — 4 Mar 2010 @ 2:24 AM

90. Hi Gavin

In the constant CO2 scenario (about 370ppm) how are accounted, if they are, the others radiative species : aerosols, GES (other than CO2,…?

[Response: Not included at all. - gavin]

Comment by meteor — 4 Mar 2010 @ 3:17 AM

91. CM #51

But how much sea-level rise would we still be committed to if we quit carbon cold turkey now?

Our a href=”http://www.pnas.org/content/early/2009/12/04/0907765106.full.pdf”>PNAS formula says

dH/dt = a T + b dT/dt.

Believing that, with dT/dt = 0, T = 1 degree constant (assumed from the graph to be over pre-industrial?) and a = 0.56 cm/degree/year, we get a total sea level rise 2010-2100 of 50 cm. And going on at 56 cm/century after that.

Comment by Martin Vermeer — 4 Mar 2010 @ 3:42 AM

92. Wow! I composed my 5-stage scenario when there were only 2 comments, and we’re already up to 70. (My own came in at comment 62.) Quite a lot of other posters have also mentioned positive feedbacks, including albedo and carbon feedbacks.

On aerosols (comments 5,6,9,20,22,59,63); so it looks like “Stage 1″ would be a bit of a bumpy ride after all. Total human pollution consists of CO2 (+ve forcing), other GHGs (+ve forcing), areosols (-ve forcing) and a few others, netting out to roughly the same effect as CO2. See Section 2.9.2 of AR4 WG1 report. If human civilization stopped suddenly, then the aerosols would flush out fastest, so radiative imbalance increases. But most of the other GHGs start going down pretty fast too (< century), and CO2 starts going down straight away too, especially given regrowth in cities, agricultural land etc. (See comment 68). So we probably get a sudden bump up in temperature, followed by a decline to the "Stage 2" temperature and CO2 level (with other forcings back to pre-industrial).

On comment 70, I hadn't considered a sudden "belch" of methane from clathrates and permafrost: I didn't think the temperature would get hot enough, fast enough in the zero-emissions scenario. (Though it might do if we continue emitting through the 21st century.) The effect of "slow leak" methane could be added: roughly the same effect as the CO2 response to temperature, but amplifying it somewhat. (Hansen et al's paleo data suggest the amplification is by about 25% when CH4 and N2O move in synch with CO2). The point is that CH4 is oxidized over ~decade timescales, so the "slow leak" is balanced at a new methane equilibrium. Maybe it adds another half degree at Stage 4, but it's swamped by the error margins of the CO2 response anyway.

The real issue is that residual ~20% of industrial CO2. It is like a stubborn stain which just won't go away and eventually causes most of the long-term damage (Stages 3 and 4). Even when the carbon cycle is in our favour, draw-down gets buffered by the oceans putting CO2 back again. I'm mostly interested in feasible suggestions for how to get rid of that residual stain, and estimates of how long they'd take.

Comment by Dr Nick Bone — 4 Mar 2010 @ 3:50 AM

93. Ike Solem (#66) said:

we know quite clearly that terrestrial environment is NOT absorbing more carbon than it is releasing

Huh? Despite deforestation dominating over regrowth, there’s been a net carbon uptake by the terrestrial biosphere over the past decades (AR4 carbon budget: fig. 7.3, table 7.1, discussion). What we don’t clearly know is where, or why, or for how long.

Comment by CM — 4 Mar 2010 @ 3:52 AM

94. 2001-2010 was the Snowiest Decade on Record
http://climate.rutgers.edu/snowcover/files/moncov.nhland.txt

I know it’s just weather not climate.

As for Al Gore my question is he right about moisture in the atmosphere? Do I believe the scientists or Al Gore? The choice is yours!
http://www.nypost.com/p/news/opinion/opedcolumnists/al_latest_global_warming_whopper_TolFbG2ccT5XPtKtXoOx0L

[Response: If you believe the New York Post over the IPCC report, you are far more foolish than you appear. There is more moisture in the air and that does lead to observed and predicted increases in precipitation intensity (section 3.8.2.2 in AR4 WG1). - gavin]

Comment by Jimbo — 4 Mar 2010 @ 4:49 AM

95. What are the implications for world food production of reducing CO2 emissions below the current annual incremental 57% uptake thereof by the world’s biota (ie from c.57% of 10 GtC in 2009 to c57% of 2 GtC as proposed by Hansen and at Copenhagen)?

Comment by Tim Curtin — 4 Mar 2010 @ 5:00 AM

96. Steve A. Morris (14),

You have the order wrong. The Earth cools by 389 watts per square meter by radiation, 80 by evapotranspiration and 17 by conduction and convection. And evaporation, while cooling the surface, also puts more water vapor in the air, and water vapor is a greenhouse gas.

What makes you think climate models ignore surface cooling other than radiative? Manabe and Strickler introduced a convective adjustment into their RCM in 1964.

Comment by Barton Paul Levenson — 4 Mar 2010 @ 5:30 AM

97. Richard C (28): There is nothing magical about pre-industrial CO2 levels.

BPL: They’re the levels our entire civilization developed in.

Comment by Barton Paul Levenson — 4 Mar 2010 @ 5:34 AM

98. Frank (38): isn’t it true that most energy is removed from the earth’s surface by convection and evaporation, not radiation

BPL: NO. It is not even remotely true. Surface cooling is as follows:

Latent heat*: 80 W m^-2
Sensible heat**: 17 W m^-2

*Evapotranspiration
**Conduction and convection

How the hell did this denier meme get started? I think I saw it advanced first by a crackpot on a blog, possibly the engineer who signs himself Ali Tekhassi. But it is measurably, verifiably WRONG. And misleading. Which I suppose is the idea.

Comment by Barton Paul Levenson — 4 Mar 2010 @ 5:38 AM

99. @cervantes [1]
“On the other hand this assumes no positive feedbacks are already in play, no?”

Note that one of the models on the figure is HadCM3LC. I *think* the “LC” stands for “Land Carbon”, in which case there has been an attempt to use a model that would include some of the possible carbon-cycle positive feedbacks.

As I understand it, the contributions for carbon-cycle feedbacks aren’t expected to kick in until later in the century, depending on the scenario, so this isn’t too surprising.

I think the paper makes a very good point – which is that, essentially, how much the climate warms is up to us. Whilst a certain amount of economic inertia is inevitable [eg think of the carbon emissions necessary to manufacture wind turbines, until there are enough wind turbines to power their own manufacture] we still have the discretion to choose a rapid or slow transition.

Comment by Timothy — 4 Mar 2010 @ 5:55 AM

100. Some of the energy going into the oceans gets converted to potential energy due to the higher surface level, i.e. “work” is being done to push up the surface against gravity. Does anybody have a sense of how much this reduces the surface temperature?

[Response: Completely negligible. Work out the average movement up of the centre of mass of the ocean due to thermal expansion- maybe 0.5/mm per year. Calculate the increase in potential energy m*g*delta h per m2, and you get roughly 6x10^-5 W/m2. Roughly 4 orders of magnitude smaller than the heating rate. - gavin]

Comment by Mark S — 4 Mar 2010 @ 7:23 AM

101. BPL: “How the hell did this denier meme get started?”

The same way as the one about volcanoes produce more in one year than humans have done in their history.

Someone lied to them and they unquestioningly accepted it.

Comment by Completely Fed Up — 4 Mar 2010 @ 7:29 AM

102. Phil Scadden #75: Jean is obviously an old-school social-ist, who believes everything of social value should be free.

I admire the idealism, impractical though it is in the real world.

Comment by Philip Machanick — 4 Mar 2010 @ 7:37 AM

103. “[Response: Gilles, posting under different names in the same thread is a strict no-no. Please do not do it again. - gavin]”
Sorry Gavin, it was totally unwanted. I just posted that in a hurry before going to work, and I assume I misclicked somewhere and edited the field with my name without noticing that I types strange characters. I am not Ary, I’m Gilles, and I have no intention of hiding anything. BTW part of my post was messed up by a unidentified bug (actually I guess the misuse of “>” and “<" in the wrong order, confusing with HTML flags) , and is partly not understable . I meant that for t much smaller than tr, the evolution is quadratic in time (developing the exponential), but it grows then linearly with time when t larger than tr. Sorry for the inconvenience.

Comment by Gilles — 4 Mar 2010 @ 7:58 AM

104. “54
Tim G says:
3 March 2010 at 3:04 PM

I may be misreading the graph, but doesn’t it imply that there is no “warming in the pipeline”?”

I’d have to see the methodology, but it could be that the period over which they consider a useful integral the pipeline empties quickly and any effervescing of CO2 from oceans countered by biological takeup.

But even if it’s taking things far too optimistically, this is no different from those who look at the sensitivity ranges from the models and assume that 1.5-2C per doubling is right and therefore we have another hundred years to work on something else.

Comment by Completely Fed Up — 4 Mar 2010 @ 8:14 AM

105. I was a little surprised by this post too – my understanding was that, if humans suddenly disappeared from the planet and all our CO2-producing activities ceased, atmospheric CO2 would still only decline slowly as there is no great natural capacity for absorbing CO2 on short timescales over and above the annual ‘breathing’ of around 6ppm. This post suggests that atmospheric CO2 would almost instantly decline by tens of ppm so that the current radiative imbalance would disappear almost immediately, and global mean temperature would stabilise (all other natural factors being equal). Is that correct?

I think the key to resolving my confusion, and perhaps that of others, would be if we could see how the CO2 levels are projected to change in this scenario, rather than just temperature. I can see that atmospheric CO2 would stop increasing straight away, but I’d like to see how quickly it *declined* to levels that would cancel out the current radiative imbalance. I think that would help people understand the argument put forward here. Is such a graph presented in the paper? Could Gavin or someone run one off, or would that involve a lot of work? I don’t understand how global temperature would stop rising unless and until the radiative imbalance disappeared.

Cheers…

Comment by Icarus — 4 Mar 2010 @ 8:20 AM

106. Gilles, I guess that since you made a mistake there, everything you’ve ever posted is wrong, as is all the stuff you’ve cited.

Just like happened in “*gate”.

Comment by Completely Fed Up — 4 Mar 2010 @ 8:42 AM

107. #100 My estimates are little bit different from Mr. Gavin’s. Linear thermal expansion coefficient for water at 20 C is A=6.910^-5, 1/K (taken from Wikipedia, of course). Let’s assume that only L= 1 m of water is heated up, and the increase of temperature is DT = 10C. Then, linear thermal expansion DL = A*L *DT= 6.910^-5*1*10 = 6.910^-4, m. The center of gravity raises half of that and then the increase of the potential energy per unit area is DE_p=ro*L*g*DL/2 =ro*L^2*g*A*DT, where water density is ro=10^3 kg/m^3, and g=10m/s^2. Then for the case of 1 m thickness of the heated water layer and temperature increase of 10C the increase of potential energy per square meter is DE=3.4 W/m^2. This is 5 orders of magnitude higher that estimated by Mr. Gavin. However, it could be that he assumed that only top10 millimeters of water is heated and the average increase of temperature is only 1 degree C. Or may be, just may be he assumed that the increase of potential energy is DE=ro*DL*g*DL/2?

[Response: I assumed a sea-level rise of about 0.5 mm/yr due to thermal expansion over the whole ocean. You have calculated the Joules/m2, not W/m2 since you do not have any time scale in your calculation. That might make a significant difference. - gavin]

Comment by Walt The Physicist — 4 Mar 2010 @ 9:05 AM

108. Hi again Gavin

In the graph you show, I don’t understand the blue curve who shows a constant temperature
In the case of zero emissions the temperature must decrease, because the concentration and subsequent radiative forcing of CO2 decrease.
It’s showed in the Bern 2.5CC curve.
So what about the blue curve?

[Response: Different carbon cycle model. - gavin]

Comment by meteor — 4 Mar 2010 @ 9:10 AM

109. Gavin’s inline to Jimbo: “Response: If you believe the New York Post over the IPCC report, you are far more foolish than you appear.”

Based on Jimbo’s previous posts, can I register a dissenting opinion here?

Comment by Ray Ladbury — 4 Mar 2010 @ 9:28 AM

110. Gavin,
May be I assumed too fast heating rate. If the rate is a day it does give about 10^-5 W/m^2. However, you assumed the average motion of the center of gravity of the ocean. This assumes total depth involved. Let’s assume depth of 1000m and heating by 10C over period of 100 days. Then the formula DE_p/Time=ro*L*g*DL/2 =ro*L^2*g*A*DT/Time will again give about 1W/m^2. I think that in general, such oversimplified estimates never give accurate picture. The outcome depends on too many parameters that are not known with sufficient accuracy.

[Response: Huh? 10C over 1000m in 100 days? What planet are you living on? Sea level rise is about 3 mm/yr - say half is due to thermal expansion (which is the only bit that counts for this calculation). Do the math and stop making excuses. - gavin]

Comment by Walt The Physicist — 4 Mar 2010 @ 10:09 AM

111. Philip (#102),
You just wrote a pithy anti-freedom comment on a free CMS running on a free web server. How impractical is the free exchange of information again?

The global public is already footing much of the bill for Nature through institutional subscribtions and such. I used to be able to check out this stuff through my U’s web proxy with my own student login. Now I need to use someone else’s login. What could this hurdle possibly achieve?

Comment by Anonymous Coward — 4 Mar 2010 @ 10:21 AM

112. Re: my#61

I think that I have seen more than one contrarian argument which uses a non-stated assumption that the climate response to a change in greenhouse gases should be instantaneous. As I see it this was and still is an error.

It is introduced whenever the effect is to favour the author’s goal of reducing the estimated warming. I have not got the details here, but Lindzen’s non peer reviewed letter to his mayor and Monckton’s pseudo-paper in the Sunday Telegraph
come to mind, except that the latter contained additional errors. That is one reason why the implications of this paper need to be expressed very carefully.

Comment by Geoff Wexler — 4 Mar 2010 @ 10:26 AM

113. May be wea re talking about different things. Lets estimate the work per unit area done on the water column due to thermal expansion during seasonal temperature variations. The work is proportional to the second power of length of the water column, i.e. DE_p/Time= =ro*L^2*g*A*DT/Time. Thus the estimate depends strongly on the assumed depth of the column of water that expands. Assuming that the water column is 1m deep, the increase of temperature is 10C, and the time that of this temperature increase is about two months, the power density that is consumed for increase of potential energy of water column is ~10-6 W/m^2. If the length of the water column is assumed as 10 m. the power density consumed for expansion is 0.01 W/m^2. And if L is 100m the power density consumed for expansion is 1 W/m^2. And this is something that should be taken into account if one is trying to achieve accuracy of modeling ~ 0.1 C. I thought that this is what post#100 was asking for.

[Response: But then the fluxes of heat on a seasonal time scales are much much larger. For your example, the heat flux for the 1m/10 C change is 4000*10*1000*1 = 4x10^7 J/m2, or 7 W/m2 (for two months), for 10m/10C, 70W/m2 and for 100m/10C, 700 W/2 - and so the heat fluxes are always almost three orders of magnitude larger. Potential energy changes are therefore negligible. - gavin]

Comment by Walt The Physicist — 4 Mar 2010 @ 10:57 AM

114. An FYI:

To view an archived video of a March 2, 2010, lecture by Dr. Naomi Oreskes at the University of Rhode Island’s 2010 Vetlesen Lecture Series entitled: “Merchants of Doubt: How a Handful of Scientists Obscure the Truth about Climate Change,” please visit:

http://www.uri.edu/vetlesen

Comment by Sloop — 4 Mar 2010 @ 11:01 AM

115. Jimbo (94), I gavee a quick read to your New York Post reference. It is a typical misuse of valid information to make a point. For example, Gore’s statement about additional moisture in the atmosphere contributing to more extreme precipitation events was countered with references to reductions in stratospheric water vapor. That is totally irrelevant, since weather events are generated in the troposphere, not the stratosphere. And as Gavin noted, there is definitely more water vapor in the troposphere. Also, as predicted by AGW, the stratosphere is cooling, which should lead to reduced water vapor there.

See how perfectly valid scientific information can be misused to turn scientific logic on its head? Dunning-Kruger (or calculated dishonesty) strikes again.

Comment by Ron Taylor — 4 Mar 2010 @ 11:16 AM

116. BPL (98), but shouldn’t the cooling from IR radiation be netted out with the 330 or so IR back radiation? (I don’t know if this would alter your main thought though.)

Comment by Rod B — 4 Mar 2010 @ 11:52 AM

117. More about societal inertia: Barton Paul Levenson has generously supplied the following figures for the fraction of new electricity generation in the US from new wind installations:

2004 4%
2005 12%
2006 19%
2007 35%
2008 42%

I think that total figures for 2009 have not yet been compiled, but the absolute amount for 2009 was substantially more than in 2008. This is in a nation that is occasionally portrayed as one of the most societally intert in response to the AGW challenge. Figures like this for the US and EU are somewhat misleading because we have exported so much manufacturing capacity to China, which has increased its fossil-fuel burning capacity greatly. But now even China is expanding its non-fossil fuel energy supply faster than its fossil fuel energy supply (albeit from a small base), and building some of the largest CC&S plants in the world. China even has massive reforestation projects underway (can my favorites — the salt-tolerant mangroves — be far behind?) What is being called BAU is in fact a tremendous shift in investment toward renewables, mostly prompted by the limited supply of fossil fuels.

This does not affect the science of AGW, but it ought to inform the prognostications and policy recommendations.

Comment by Septic Matthew — 4 Mar 2010 @ 12:30 PM

118. Mark S says: 4 March 2010 at 7:23 AM

(work done raising sea level)

Negligible as Gavin said, but still a cool question.

Comment by Doug Bostrom — 4 Mar 2010 @ 12:56 PM

119. I don’t know. Isn’t all this essentially a matter of semantics ?
To me the notion of “unavoidable warming in the pipeline” or “inertia” clearly refers to the constant-forcing commitment.
If you further cut emissions to zero, then CO2 begins to be withdrawn from the atmosphere (BTW it would be interesting to see the corresponding atmospheric CO2 concentrations on their figure, for the UVIC, HadCM3 and Bern models), so I guess a negative radiative forcing is applied, right ? so it is like releasing the accelerator pedal but also hitting the brakes (so you’re not truly measuring ‘inertia’). I guess that you are talking about something else, then (maybe, the fact that the combined carbon cycle/climate system has no inertia in terms of T° with respects to CO2 emissions).

Comment by ICE — 4 Mar 2010 @ 1:51 PM

120. Gavin,
True, relatively to the absorbed sun irradiance and radiative heat loss the work spent for potential energy change of ocian water is small; however, how smal is small. If one tries to compute temeprature change due to very small optical absorption in atmosphere with accuracy much better than 0.1 degree (let’s say 0.01 degree) than such “cool question”, as Doug Boston said in #118, becomes important. Your resistance to even consider it as a posibility reinforces my feeling that simulation accuracy of 0.01 degree in temperature predictions wasn’t actually achieved.

[Response: I have no idea to what you are referring. Someone asked me a question about potential energy and I did the math and showed it to be a negligible effect.. How does that get translated into a refusal to consider the possibility. And who has ever claimed an accuracy of 0.01 degree C in temperature predictions? Please stay focussed. - gavin]

Comment by Walt The Physicist — 4 Mar 2010 @ 2:22 PM

121. further on the issue of “societal inertia”, here are two tables documenting the recent reductions in the use of coal and natural gas in the production of electricity in the US:

http://www.eia.doe.gov/cneaf/electricity/epm/table2_1_a.html

http://www.eia.doe.gov/cneaf/electricity/epm/table2_4_a.html

Obviously, some of this reduction is caused by the financial panic and recession, but combined with the increased deployment of wind and solar generation the reduction will probably be sustained, and increased. Recently, with the discovery and extraction of more natural gas, these tables include conversion of some coal-fired plants to gas-fired. Decreasing the consumption of coal is costly, but not catastrophically so, if not done too rapidly.

We don’t know the future, but I’d bet on a 75% reduction in coal use in the US in 2 decades before I’d bet on the devastation of US agriculture in 2 decades, just with programs already in place. Unless, of course, CC&S proves out. Capturing CO2 to grow algae looks like a good bet, but I don’t know how good.

Comment by Septic Matthew — 4 Mar 2010 @ 3:05 PM

122. Gavin,
I’d like to ascertain your idea of requred accuracy of numerical model prediction of temperature increase due to CO2 concentration increase. If the temeprature raise measured is in the order of few tens of a degree, isn`t it reasonable to expect accuracy of 0.01 degree from modeling?

[Response: What you expect has nothing to do without what is possible. But I have no idea what you are talking about - accuracy in what metric over what time based on what assumptions? Where did you see such a claim in the first place? - gavin]

Comment by Walt The Physicist — 4 Mar 2010 @ 3:12 PM

123. Gavin:

With respect to your response to 71 (and 49?), I just don’t see how your answer is a response to my questions ;-)

In Hansen et al (2005) you state:

“The lag in the climate response to a forcing is a sensitive function of equilibrium climate
sensitivity, varying approximately as the square of the sensitivity (1), AND IT DEPENDS ON THE RATE OF HEAT EXCHANGE BETWEEN THE OCEAN’S SURFACE MIXED LAYER AND THE DEEPER OCEAN (2–4).
The lag could be as short as a decade, if climate sensitivity is as small as 0.25ºC per
W/m2 of forcing, but it is a century or longer if climate sensitivity is 1ºC perW/m2 or larger
(1, 3). Evidence from Earth’s history (3–6) and climate models (7) suggests that climate
sensitivity is 0.75º ± 0.25ºC perW/m2, implying that 25 to 50 years are needed for Earth’s
surface temperature to reach 60% of its equilibrium response (1).”

So why isn’t THAT lag the same as the “inertia in the climate system” to which M & W are referring?

Doesn’t M & W’s blue and grey lines in their figure ‘deny’ this lag/inertia?

Isn’t their:

“We argue that the notion of unavoidable warming owing to inertia in the climate system is based on an incorrect interpretation of climate science.”

saying that the Hansen et al (2005) “additional global warming of 0.85×0.67 ~0.6ºC is ‘in the pipeline’ ” is “an incorrect interpretation”?

[Response: No. But the translation of a radiative imbalance into a temperature rise implies the continuation of the that drivers of that imbalance. Thus it is equivalent to the constant-concentration commitment. - gavin]

Comment by Len Ornstein — 4 Mar 2010 @ 3:17 PM

124. Lab Lemming (86) — There is certainly hysteresis in the climate system so return to the exact regional conditions of, say, the first quarter of the 20th century is not possible. On the other hand, there is always the necessity of continual adapation to the pink noise of climate.

Comment by David B. Benson — 4 Mar 2010 @ 3:26 PM

125. Walt The Physicist says: 4 March 2010 at 3:12 PM

“I’d like to ascertain your idea of required accuracy of numerical model prediction of temperature increase due to CO2 concentration increase. ”

Whats your notion of that, Walt? I may be wrong but I smell a rhetorical question. If I’m not wrong, why not say what’s on your mind?

Comment by Doug Bostrom — 4 Mar 2010 @ 4:00 PM

126. The more I think about the issue and the discussion, the more I don’t understand the article or its implications at all.

My primitive understanding of climate inertia is that it needs to be fairly sizable for the issue of AGW to matter at all. Otherwise, every night when the sun goes down the threat from AGW would go away.

Comment by Jeffrey Davis — 4 Mar 2010 @ 4:03 PM

127. Gavin:

In Hansen et al (2005) you state

“Our climate model, driven mainly by increasing human-made greenhouse
gases and aerosols, among other forcings, calculates that Earth is now absorbing
0.85 ± 0.15 watts per square meter more energy from the Sun than it
is emitting to space. This imbalance is confirmed by precise measurements of
increasing ocean heat content over the past 10 years. Implications include (i) the
of atmospheric composition”.

How can “without further change of atmospheric composition” mean anything other than essentially complete cessation of the burning of fossil fuels together with the end of deforestation?

[Response: No. It means that atmospheric composition stays the same. Same CO2 concentration, same aerosol concentration, same ozone concentration. - gavin]

So the 0.6ºC is a “temperature rise” WITHOUT “the continuation of the drivers of that imbalance”!

This would be a ‘sort of’ “constant-concentration commitment” (leading SLOWLY to the probable ensuing oceanic and biospheric drawdown towards pre-industrial atmospheric ~280 ppm).

M & W state:

“Stable atmospheric concentrations of greenhouse gases would lead to continued warming, but if carbon
dioxide emissions could be eliminated entirely, temperatures would quickly stabilize or even decrease
over time.”

So by “Stable atmospheric concentrations of greenhouse gases” they mean holding the level constant by continuing to burn enough fossil fuel to stay near (for example) 390 ppm. By “if carbon dioxide emissions could be eliminated entirely” they PROBABLY mean my “essentially complete cessation of the burning of fossil fuels together with the end of deforestation”.

Therefore, if Hansen et al (2005) is essentially ‘correct’, M & W are wrong on about “quickly stabilize” – so long as “quickly means more rapidly than ~80 years – as is certainly implied by there 2 lower plots!

You really need to restate your interpretation of their letter to make clear what you mean visa vis Hansen et al (2005) and what you’ve said above that could easily be interpreted as a reversal of your 2005 position ;-)

Comment by Len Ornstein — 4 Mar 2010 @ 4:22 PM

128. Gavin,
As I understood from your appearance on CNN, you know from computer simulations that the CO2 emission that started in 1800s with some estimated variable in time rate causes the observed increase of average temperature during past 200 years. This observed increase of temperature is several tenths of a degree C. Then, simulation accuracy higher than 0.1C is required to model such increase. Is such accuracy achievable and do you guys know all the heat sources and sinks with sufficient accuracy?

[Response: For the long term global trends, the signal clearly comes out of the noise. - gavin]

Comment by Walt The Physicist — 4 Mar 2010 @ 4:28 PM

129. re. 126Jeffrey Davis says:

“”"”The more I think about the issue and the discussion, the more I don’t understand the article or its implications at all.

My primitive understanding of climate inertia is that it needs to be fairly sizable for the issue of AGW to matter at all. Otherwise, every night when the sun goes down the threat from AGW would go away.”"”

Think of one watt per square meter extra energy not being allowed to escape back to space from the Sun. That is a lot of energy. It can warm up the land reasonably quickly…but the oceans are so huge that it takes about 30-50 years to warm them up. This slows up global warming for 30-50 years, but once the oceans have warmed up to a point (caught up), the extra 1 W/M2 can now show itself and warm up the land surface and create climate changes.

IPCC- 2007, 2001, 1995, 1990.
http://www.ipcc-wg1.unibe.ch/publications/wg1-ar4/ar4-wg1-spm.pdf

Comment by Richard Ordway — 4 Mar 2010 @ 4:34 PM

130. Walt The Physicist (122 & 128) — I have posted a simple conceptual model of climate which explains the instrumental record surprisingly well. You’ll find it in a recent comment of the Whatevergate thread.

Comment by David B. Benson — 4 Mar 2010 @ 5:00 PM

131. Just to elaborate for anyone who doesn’t recognize the chart that Gavin points in 128 to Fig. 9-3 (IPCC AR4 WG1, Summary for Policymakers)

It’s a two-part picture. The black line in both is the observed temperature change.

The upper chart shows how models do match temperature when the models run include the forcings caused by human activity.

The lower chart shows how models run without including human-caused CO2 etc. don’t match the temperature)

If you need the caption and full discussion see the chapter:
http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter9.pdf

(I’m sure I posted a html link to the same information a few weeks ago when that same figure was posted — but darned if I can find it now).

Comment by Hank Roberts — 4 Mar 2010 @ 5:20 PM

132. Anonymous Coward #111. Curious that you interpreted my comment as “anti-freedom”. I was merely commenting on the state of the world, and the demise of idealism.

But your logic is interesting. Nature is a private enterprise as far as I know (if it’s not, pick another journal to correct the argument: there are many that are run for profit). By your logic, a privately-owned journal when selling subscriptions to a publicly funded institution must also be selling such a subscription to the general public. Take this a step further. If NASA or your publicly funded alma mater buys a car, does this mean every member of the public is entitled to drive that car?

Don’t get me wrong. I would much prefer that all information was free and accessible. I just find it very odd that this argument is coming from a direction that is usually blindly pro-business.

Comment by Philip Machanick — 4 Mar 2010 @ 5:37 PM

133. Gavin – I think, given the comments on this thread, which reflect my own confusion, that you need to have another go at summarising the implications of this research. If this is overturning the concept of “temperature rise already in the system” then it needs much more explanation. If it is saying that instantly turning off the CO2 tap leaves global temperatures constant, then it also needs explanation. If it is saying that turning the tap off gives an immediate rapid decline in temperatures, even more explanation is needed. Or am I being particularly stupid today?

[Response: The point Matthews and Weaver are making is partly a matter of semantics, but I think it's an improved way of thinking about warming commitment. There is absolutely nothing incorrect about the old notion of warming that remains "in the pipeline" if you hold the atmospheric CO2 concentration fixed. What Matthews and Weaver are pointing out is that using fixed CO2 concentration as your standard is kind of ridiculous. To maintain the concentration fixed, you would need to have continuing emissions, in small but ever decreasing amounts. If you could reduce the emissions that much and calibrate them so closely, why not just reduce them to zero? If you do reduce them to zero, then CO2 goes down very slowly, and that's enough to cancel out the warming that was "in the pipeline" leading to a flat temperature (or perhaps a declining temperature, depending on how rapidly the carbon cycle model makes things go down. So, properly viewed, the "commitment" to future warming in the old way of thinking is just a commitment because you've made a commitment to continue emitting. It's your choice, not wired into the climate system. Now, the sad fact of the matter is that even if emissions go all the way down to 1 Gt carbon per year, that still isn't enough to keep CO2 from growing; it does slow things down considerably, but that last gigatonne still gives you a gradually rising (rather than stabilized) CO2 concentration. This is probably the most realistic optimistic scenario that is likely to occur, unless air capture methods come along that can take care of that last gigatonne. So, I agree with Gavin that Matthews and Weaver are right, but the point is probably moot. --raypierre]

Comment by David Horton — 4 Mar 2010 @ 5:40 PM

134. For the chart Gavin links to above as
the signal clearly comes out of the noise
–> the final figures and captions are also available separately in this PowerPoint:

IPCC Working Group I Technical Summary FINAL FIGURES
To view the caption, select “Notes Page” from the “View” Menu….
www1.ipcc.ch/graphics/graphics/ar4-wg1/ppt/figure09.ppt

For Walt, below is a brief excerpt from the full caption; you can look it up
(I admit it’s hard to find!)

“Figure 9.5. Comparison between global mean surface temperature anomalies (°C) from observations (black) and AOGCM simulations forced with (a) both anthropogenic and natural forcings and (b) natural forcings only. …

… in (a) as obtained from 58 simulations produced by 14 models with both anthropogenic and natural forcings. The multi-model ensemble mean is shown as a thick red curve and individual simulations are shown as thin yellow curves. Vertical grey lines indicate the timing of major volcanic events….

… The simulated global mean temperature anomalies in (b) are from 19 simulations produced by five models with natural forcings only….

Further details of the models included and the methodology for producing this figure are given in the Supplementary Material, Appendix 9.C. After Stott et al. (2006b).”

Comment by Hank Roberts — 4 Mar 2010 @ 5:41 PM

135. What would help to reduce a lot of the confusion would be if the graph included lines indicating the projected CO_2 level, not just the projected temperature.

If we could literally turn off the taps today (including stopping land clearing etc.) the CO_2 level would drop reasonably fast by about 50% of recent emissions that had not yet had time to be absorbed by natural processes. However the increase that’s there from the longer term has already had the opportunity to be absorbed and hasn’t, and so will be there longer-term.

Also, it’s not clear to me that the various carbon cycle models that quantify the fast, medium and slow absorption processes will still work the same way if the increase stops. Increased ocean solubility of CO_2 with increasing atmospheric partial pressure for example would stop fairly quickly if you stop adding CO_2 to the atmosphere (much of the 50% “fast” absorption), and we would switch over to the competing effect of warming oceans having lower CO_2 solubility (Henry’s law) being the major effect on the oceans.

On the other hand, temperature change for constant CO_2 takes time to bed down because of slow feedbacks. The confusion here looks to me to be over the extent to which these two effects (slow down of absorption, longer-term feedbacks) interact.

Comment by Philip Machanick — 4 Mar 2010 @ 6:36 PM

136. Philip (#132),
Idealism isn’t dead. One of the places where it lives today is in the software you’re using right now. You may be surprised but idealism has become a big business. Red Hat’s market cap is quite practical at over 5 billion dollars for instance but its main product is free software. You can basically download it, use it, modify it and resell it as your own without owing them a penny.

As a practical matter, people don’t need subscriptions to share the contents of Nature. So I would hope that Nature will wake up to the 21st century and make its content freely available to the public. It’s in their interest not to wait too long.

The ennemies of the free exchange of ideas have long stretched analogies between information and physical objects beyond any usefulness. I’m not interested in going over this argument again, least of all here.

Comment by Anonymous Coward — 4 Mar 2010 @ 7:10 PM

137. Bob #56 I think this is a realistic time-frame. At the same time the phrase “We’re utterly r@@ted” keeps on drifting through my mind when I think about that scenario.

Comment by calyptorhynchus — 4 Mar 2010 @ 7:45 PM

138. “What would help to reduce a lot of the confusion would be if the graph included lines indicating the projected CO_2 level, not just the projected temperature.”
The Solomon et al PNAS paper assumed different scenario – growth of emissions @2% to various levels, then immediate transition to zero emmissions, but it is a similar set of curves – decreasing CO2 & temperatures with multiple time constant long tails. see http://www.pnas.org/content/106/6/1704/F1.large.jpg
“Eyeball extrapolation” to a peak of 400ppm followed by zero emissions would lead one to the conclusion that temperature would stay above preindustrial for at least the next thousand years, although there would be a short term decline; CO2 shows a larger drop, but still remains above preindustrial levels for millenia.

Comment by Brian Dodge — 4 Mar 2010 @ 7:56 PM

139. Gavin, why is there never any mention of what I consider to be the most realistic scenario where pretty much immediately after mankind goes CO2 neutral, it goes CO2 negative, and possibly aggressively so?

Given that to become CO2 neutral there will have been massive exponential increases in non-fossil fuel energy (as is already happening with wind as has been pointed out earlier) it seems completely realistic to expect this not to just stop the exact instant there is enough energy to supply our needs, but to continue and produce energy that exceeds our needs. The extra energy could obviously then be used to suck the CO2 out of the air. There are already prototype machines that do this, of course in 50 years time they will be much better, and probably used to get CO2 as feedstock to make liquid fuels also.

Is this not talked about because it is considered “moral hazard”?

Honesty isn’t the most likely scenario the one where we “red line” the CO2 level, then try to fix it up, rather than just let CO2 stabilize, and do nothing about the fact that it will cause sea level rises large enough to flood many cities etc in the following hundred years.

Comment by Russell — 4 Mar 2010 @ 10:59 PM

140. I’m not convinced that warming could stop as major emissions
cease. Climate inertia is one aspect, but there are others to
calculate.

Assuming emissions means primarily emissions from coal
fired power plants and transportation, wouldn’t the sudden
loss of the reflective contribution of atmospheric aerosols
allow slowly dissipating concentrations of ghgs to trap more
IR radiation? As long as even the slight warming we have
persists there will also be natural emissions we can’t stop.

I’d suggest a graph that included warming as CO2 emissions
stopped but taking into consideration that aerosols also
stopped combined with potential natural outgassing of ghgs
from permafrost and subsea formations. Do we have any
idea of what that is?

For insight see:

“Methane Releases from Arctic Shelf May Be Much Larger
and Faster Than Anticipated”
ScienceDaily
Mar. 5, 2010
“A section of the Arctic Ocean seafloor that holds vast stores
of frozen methane is showing signs of instability and
widespread venting of the powerful greenhouse gas, according
to the findings of an international research team led by
University of Alaska Fairbanks scientists Natalia Shakhova
and Igor Semiletov.

The research results, published in the March 5 edition of the
journal Science, show that the permafrost under the East
Siberian Arctic Shelf, long thought to be an impermeable
barrier sealing in methane, is perforated and is leaking
large amounts of methane into the atmosphere. Release
of even a fraction of the methane stored in the shelf
could trigger abrupt climate warming.

“The amount of methane currently coming out of the East Siberian Arctic Shelf is comparable to the amount coming out of the entire world’s oceans,” said Shakhova, a researcher at UAF’s International Arctic Research Center. “Subsea permafrost is losing its ability to be an impermeable cap.”

[...]

Comment by Tim Jones — 4 Mar 2010 @ 11:02 PM

141. Using my (“Ary” ‘s one indeed :) ) simple linear approximation, the evolution of temperature would be given by

dT/dt = – (T-To-A.F(t))/tr

where A is the sensitivity to the forcing F(t) and To the preindustrial temperature

The old “commitment” corresponds to a constant concentration, so a constant forcing Fc after some time, giving a simple exponential terminal rise towards the equilibrium temperature To+A.Fc

The new “commitment” corresponds to the complete cut off of any emission, giving a gradual decrease of F(t). The general solution of the equation for any F(t) is reads:

T = To + A.\int^t_to F(t) exp[(t-t')/tr]dt’ (sorry for the latex style, int means integral)

so you can play with any forcing you want. However, my equation can not describe a constant solution since it would mean that dT /dt = 0 so A.F(t) = T-To, which is contradictory if T is constant and F(t) varies. A constant temperature is ONLY possible for the exact solution T=Teq with a constant forcing, which is NEVER reached (mathematically) if there has been any variation in the past (which is obvious in the general exact solution above). This is NOT a feature of carbon cycle absorption model but a feature of the linear relaxation model of the temperature, what ever the forcing is and so whatever the carbon cycle used. So i understand the “Bern model” curve, describing a decreasing F(t) and and a decreasing temperature , but I’m surprised by the “constant temperature ” curve which is possible only if the linear relaxation towards equilibrium temperature is plainly wrong. But why is it wrong ?

Comment by Gilles — 5 Mar 2010 @ 2:10 AM

142. So this chart says if we are able to cut emissions by 2/3rds the CO2 concentration will remain constant at ~400 ppm and global average temperatures will rise to an asymptote of 1.3 degC above 1800, only 0.3 degC higher than today.

The chart suggests that 66% cuts will really stop GW for all practical purposes.

Is the intent to this defuse the argument that we are already too late to stop catatrophic global warming? What about 350.org?

Comment by anony — 5 Mar 2010 @ 2:16 AM

143. Future International Court Fantasy.

Class action of victims of global warming vs UK government and Nigel Lawson’s Instititute.

Nigel Lawson’s Institute.
Yes we admit that we closed down the UEA , and the IPCC and blocked all action to reduce CO2 emissions after the year 2011, but that does not mean that we were responsible for such a high proportion of the damage. You should be looking at the UK government’s responsibility. How about the National Coal Board and the state controlled British Petroleum? and what about the actions of the owners of the coal mines before 1945?

UK government.
No ; these industries were recently privatised so it is the Lawson Institute which is more to blame ; we refer the jury to Mathews and Weaver. You are using the wrong definition of committed warming. If we had not followed the Lawson Institute’s advice we might have been able to reduce CO2 emissions to zero in 2011 and follow the horizontal line in the MW graph. The Lawson Institute should pay a higher proportion of the total damages.

Comment by Geoff Wexler — 5 Mar 2010 @ 5:29 AM

144. Tim Curtin (95),

None whatsoever. My time series analysis of cereal production against CO2, fertilizer consumption, and dT for 1961-2002 indicate that the correlation with CO2 is spurious and that fertilizer consumption has been the only relevant factor.

Comment by Barton Paul Levenson — 5 Mar 2010 @ 5:38 AM

145. Rod B (116),

No. If you want to net out ALL the cooling with ALL the warming, you get rough stability. But there is no reason to “net out” just the radiative cooling.

Sunlight and atmospheric back-radiation HEAT the Earth.
Longwave radiation, latent heat, and sensible heat COOL the Earth.
Most of the cooling is radiative. Period.

Comment by Barton Paul Levenson — 5 Mar 2010 @ 5:44 AM

146. Any comments on the new Science study? Is any of this new information on methane release incorporated into the current models? I’m unsettled.
http://www.sciencemag.org/cgi/content/abstract/327/5970/1246

Comment by Mike Ern — 5 Mar 2010 @ 8:14 AM

147. Raypierre, thanks for your clear explanation, but like some others here, I still do not understand why positive feedbacks like methane release, continued loss of sea ice albedo, and ocean saturation would not contribute additional warming for at least decades, independently of the direct CO2 effect. Perhaps that energy is taken up in the continuing warming of the ocean?

Comment by Ron Taylor — 5 Mar 2010 @ 9:54 AM

148. According to quotes from the lead scientist on the Science Magazine report, atmospheric methane levels in the Arctic are about 1.85 ppm, which is roughly three times the worldwide level.

[Response: That's not right. There is a north-south gradient, but it is small - mean CH4 levels globally are around 1800 ppb (=1.8 ppm). - gavin]

I calculate that as roughly an additional 30ppm CO2 equivalent over the Arctic. That would seem to make a significant difference in the greenhouse effect there, and not good news, since there is reason to expect that the difference will continue to increase. It is a local positive feedback with global consequences.

Comment by Ron Taylor — 5 Mar 2010 @ 10:05 AM

149. Oops! Thanks Gavin, lesson learned. Check quotes like this, even if they come from a good scientist. I had your number right at my fingertips, but did not check.

Comment by Ron Taylor — 5 Mar 2010 @ 10:37 AM

150. 123 Len Ornstein wrote:

“So why isn’t THAT lag the same as the “inertia in the climate system” to which M & W are referring?”

Len, here’s a naive calculation that I went through recently. Assume that a change in forcing results in a change in the equilibrium temperature. As a base line you can assume that a 1W/m^2 change in forcing results in a change of 1K. Ask yourself how long that will take if the forcing first heats the atmosphere plus the top couple meters of ocean, then next the top 200 meters of ocean, then next the rest of the ocean. In other words, ignore transport issues which can only slow things down in any event. The answers are: yearish for the atmosphere, 3 decades for the top 200 meters of ocean, and 500 years for the rest of the ocean. I haven’t read Hansen 2005 but elementary physics says there is no possible way for there to be no lag at all. The reason that the paper that started this thread says “there is no warming in the pipeline” is because they are considering a substantially different forcing scenario than the one that results from constant CO2.

Comment by John E. Pearson — 5 Mar 2010 @ 10:40 AM

“The release to the atmosphere of only one percent of the methane assumed to be stored in shallow hydrate deposits might alter the current atmospheric burden of methane up to three to four times,” Shakhova said. “The climatic consequences of this are hard to predict.”

Since there is so little methane in the atmosphere, I assume the radiative forcing would be roughly proportional to the concentration. If that is true, then tripling the concentration with all else fixed would increase the net radiation forcing from about 1.6w/m2 now to about 2.6w/m2, plus additional positive feedbacks. Is this correct?

[Response: Actually it goes like sqrt(CH4/CH4_0). Tripling current CH4 would be a forcing of just under 1W/m2, and would decay relatively rapidly if the extra emissions were not sustained. - gavin]

Comment by Ron Taylor — 5 Mar 2010 @ 10:47 AM

152. This statement, under a zero future emisions scenario, seems to be a major assumption of the paper:

“CO2 concentrations would start to fall immediately since the ocean and terrestrial biosphere would continue to absorb more carbon than they release as long as the CO2 level in the atmosphere is higher than pre-industrial levels”

What is the basis of this statement? How are the thresholds mentioned by Edward Greish (Arctic ocean ice melting, tundra peat bog thawing and clathrate melting) accounted for?

I suspect that even if all anthropogenic sources of CO2 were immediately stopped that radiative imbalance that already exists will result in continued increases in greenhouse gases and further warming for sometime before the biosphere adapts. Convince me I’m wrong (please).

Comment by KSW — 5 Mar 2010 @ 11:11 AM

153. I hope that RealClimate will devote a post to the new study on Siberian methane emissions. On the face of it, it is … dare I say … alarming.

And it would seem to go right to the point of this current discussion, with regard to what sort of “change” we are already committed to.

Comment by SecularAnimist — 5 Mar 2010 @ 12:23 PM

154. @ Ron Taylor — 5 March 2010 @ 10:05 AM
from http://www.sciencemag.org/cgi/content/full/327/5970/1246
“From values averaging 2.10 ± 0.02 parts per million (ppm) (1 SD) through the Kara Sea, the CH4 mixing ratio increased markedly after passage through the Vilkitskyi Strait and entering the ESAS, averaging 2.97 ± 0.15 ppm in the Laptev Sea and 2.66 ± 0.09 ppm in the East Siberian Sea, with spikes in the 6.4 to 8.2 ppm range.”
“The median summertime supersaturation was 880% in background areas and 8300% in hotspot areas…” (CH4 dissolved in the water column)
Large areas can average 30%, not three times, higher CH4 concentrations. The heterogeneity – “hotspots” in the water column and “spikes” in the atmospheric mixing ratio – imply release mechanisms with large nonlinearities. According to a whole lot of crappy bloggers that don’t bother to provide links to the original source(what a surprise!) the lead author on the study, Natalia Shakhova, may have said “Our concern is that the subsea permafrost has been showing signs of destabilization already”. (It may originate in a copyrighted Asian News International story, or Dr Shakhova may say “I never said that” – YMMV; wading through all the blog hits in google to find an original reliable source has been frustrating).

Comment by Brian Dodge — 5 Mar 2010 @ 12:33 PM

155. RE– Comment by Hank Roberts — 4 March 2010 @ 7:59 PM:

Hank, I was just confused by your hand-warming thought experiment because ones hand can’t tell the difference between warming due to visible and infrared wavelengths when both are present and both are significant. On the other hand this issue caused me to take my physics text in hand to learn more, so your efforts were a handy teaching exercise for me.

Steve

Comment by Steve Fish — 5 Mar 2010 @ 12:44 PM

156. 144, Barton Paul Levenson: My time series analysis of cereal production against CO2, fertilizer consumption, and dT for 1961-2002 indicate that the correlation with CO2 is spurious and that fertilizer consumption has been the only relevant factor.

Controlled experiments show that increased CO2 increases productivity of food crops, increases drought resistance of food crops, or both. Natural observations of temperate and Boreal forests shows increased growth rates as CO2 has increased (even where not fertilized by sulfur and nitrogen oxides.)

Which brings up a question: how much more energy is removed from the atmosphere by the increased storage of energy in the carbon bonds of cellulose? (Even if it is mostly caused by increased use of fertilizer, and by higher-yielding varieties.) Just curious.

Comment by Septic Matthew — 5 Mar 2010 @ 1:07 PM

157. The clathrate gun hypothesis has always worried me, since it’s one feedback loop that would rapidly grow out of control and that we generally have no real response to.

http://www.sciencemag.org/cgi/content/abstract/327/5970/1246

Is this cause for great concern? I’ve read that atmospheric methane concentrations have been changing at a much slower pace since the 90′s, so what conclusions can we draw from observations such as this?

Comment by Greg — 5 Mar 2010 @ 1:21 PM

158. BPL (145), I’ll go along with that as defined.

Comment by Rod B — 5 Mar 2010 @ 1:54 PM

159. David B. Benson #130:
Thanks, I’ll check.

Comment by Walt The Physicist — 5 Mar 2010 @ 2:01 PM

160. I was going to make a comment about Ramanathan and Feng’s 2008 PNAS paper, but I see others have already done so. I would appreciate if you did a post on this topic some day. Is their assertion generally accepted, or disputed in the climate science community?

Comment by Earl Killian — 5 Mar 2010 @ 2:14 PM

161. Gavin (151), as SQRT(3) = 1.732, did you mean slightly less than 2 W/m2, not 1 W/m2? Or am I missing some underlying operations?

[Response: 'Goes like' just indicates the pattern of the rate of increase, it is qualitative, not quantitative. The formula are given in Table 6.2 in IPCC TAR. - gavin]

Comment by Rod B — 5 Mar 2010 @ 2:24 PM

162. SM: “Controlled experiments show that increased CO2 increases productivity of food crops, increases drought resistance of food crops, or both.”

Controlled experiments have shown that increased CO2 does not increase productivity and has shown that pest animals are more readily able to eat the food crop.*

*please note neither of us have said that ALL crops are covered by the studies reported.

Comment by Completely Fed Up — 5 Mar 2010 @ 2:36 PM

163. > ones hand can’t tell the difference between warming due to visible and
> infrared wavelengths when both are present

Put your hand in the sunbeam, notice how much warmth you’re feeling.
Take your hand out of the sunbeam; do you notice an immediate change?

To the extent your hand actually changed temperature from absorbing light, it will still feel warmer.

To the extent you’re feeling infrared, you’ll feel the change immediately.

Yes, the hand is an approximate instrument; thermometers were a great improvement, and as you say, there’s more in the physics texts.

But don’t forget, when someone tells you the CO2 in the atmosphere is blocking all the infrared — you can test it quite simply and know they’re wrong.

Comment by Hank Roberts — 5 Mar 2010 @ 2:53 PM

164. Re: Gavin’s response to #133

While we’re talking about implausible scenarios (reducing emissions to zero immediately), why not include the possibility of actually removing CO2 from the atmosphere and consider a scenario in which CO2 concentrations are immediately reduced to pre-industrial levels? Then, cooling would begin immediately.

Comment by Jerry Steffens — 5 Mar 2010 @ 3:06 PM

165. #157 Greg, it means game over. It’s starting, the undoing of the Azolla event:

Comment by Garrett — 5 Mar 2010 @ 3:14 PM

166. Brian Dodge@154 – Might find something from where Dr Shakhova works

Comment by flxible — 5 Mar 2010 @ 3:19 PM

167. Making an assumption of zero emissions to calculate the momentum for continued warming seems to me to be analogous to determining how many angels can dance on the head of a pin. Climate sensitivity is the unkown, or is it? Two recent global experiments, one cooling, Mt Pinatubo, and one warming El Nino both “poked” the atmosphere in different directions. Did global temperatures return to their pre-eruption and pre-tropical warming baselines? Yes they did. So, for the levels of greenhouse gases at that time, there was no “runaway” reaction. We can speculate that the Medieval Warming Period also did not result in a runaway climate change. Climate, as opposed to weather, seems to be rather insensitive to perturbations. Current climate models containing low sensitivity estimations are more believable. We know that we are not going to get to zero emission in the near future, so don’t incorporate such an assumption in a model. We have a lot to learn and a measured approach using the data we have, including the above observations, is more likely to be believable and carry the day. The anthropogenic signal may still be lost in the noise, that is alright in the long run. We have time.

Comment by RiHo08 — 5 Mar 2010 @ 3:19 PM

168. And yet you still support inaction?

Comment by dennis baker — 5 Mar 2010 @ 3:23 PM

169. This might be slightly off-topic but it’s about how much is in the pipeline in the Earth’s crust.

If we’ve added about 110 CO2 ppm by burning fossil fuels, how much more is in the pipeline (keeping in mind that sometime within the last three decades I believe we will have burned more than in all human history before that combined)?

From oil – another 40 ppm due to being so close to peak oil?

From natural gas – another 50 ppm because even though its cleaner, there’s more of it?

From coal – another 100 ppm in part because we’ve burned much of the cleanest coal first?

From tar sands – Another 100 ppm if we’re that stupid?

From oil shale – The least likely of the five, but 100 ppm if we’re insanely stupid enough to burn it (something I questioned previous U.S. Secretary of Energy under Bush Samuel Bodman about after he recommended using oil shale, tar sands and coal-to-liquids)?

That totals 390 CO2 ppm, a doubling not from pre-industrial but from current levels. These are just my

I’d enjoy hearing more educated guesses than mine. I feel educated guesses are better than no guesses at
all.

Comment by Richard Brenne — 5 Mar 2010 @ 3:25 PM

170. And climate skeptic Roy Spencer keeps running into record global temps: Feb 2010 2nd hottest in UAH satellite measurements http://bit.ly/RoySp

Comment by Kees van der Leun — 5 Mar 2010 @ 3:30 PM

171. Septic Matthew@156 – Some results don’t seem quite as optimistic even when CO2 is the only variable – there are a lot of other influences on food crop productivity, we don’t eat just biomass – also one of the factors that needs to be considered is how long lasting any effect is.

Comment by flxible — 5 Mar 2010 @ 3:36 PM

172. Slightly off topic, but could somebody address this gem in the American Spectator?

http://spectator.org/archives/2010/03/02/climategate-this-time-its-nasa

Looks like another WUWT style attempt to suggest that reporting stations have been jockeyed to get the desired result. Nice to see guys like McIntyre don’t have to worry about being unemployed–the spin machine really eats that stuff up.

[Response: More lies, but this time they are harking back to an older piece of misrepresentation regarding the 2007 corrections to some US data that did not affect the global numbers at all. Note the sleight of hand switch from Hansen discussing global temperatures to the comment about 1934 in the US temperatures. See our post "1934 and all that" and the official GISS 2007 report for more details. - gavin]

Comment by Sebastian — 5 Mar 2010 @ 3:44 PM

173. Shakarova et al in the Supplementary Online Material – http://www.sciencemag.org/cgi/data/327/5970/1246/DC1/1 – say “We consider our estimates very conservative because they do not include non-gradual ebullition component, which is crucial when it comes to CH4 release from decaying seabed deposits.”

Comment by Brian Dodge — 5 Mar 2010 @ 4:21 PM

174. John 150:

I’m sorry for being dense, but from my reading of Hansen et al (2005), their warming “in the pipeline” is that which will be transferred to the atmosphere and land surface in the future as a result of forcings up to date (2003 for their forcings). This has to be about equal about to, or less than, any increase that would occur if CO2 levels were suddenly clamped to the 2003 value. But M & W’s middle plot, in the Figure Gavin provides, (their zero emissions) shows no sign of such increase!

[Response: No. This is a fundamental misunderstanding. The net imbalance at the TOA implies that the planet is absorbing heat. This is going into the ocean. This will stop once the ocean has warmed up sufficiently that the outgoing long wave again matches the incoming short wave. The current temperatures are not sufficient to do this (since there is a TOA imbalance) and so there is further warming 'in the pipeline' as long as the the forcings stay the same. The 'in the pipeline' statement is exactly equivalent to the current-concentration commitment discussed above. If you changed the concentrations, the imbalance would change also and the calculation would no longer work. - gavin]

Comment by Len Ornstein — 5 Mar 2010 @ 4:49 PM

175. 171, flxible, here is a quote from that web page that you cited: Because of these problems large scale free air or outdoor experiments were developed. These experiments are typically referred to as FACE or Free Air CO2 Enrichment. These experiments show a much smaller boost to production than chamber experiments. Woody plants such as trees and cotton still showed a significant increase in biomass production. However, crop plants such as grains showed a much lower boost in production. While wheat and rice showed some increases in yield, the increases were so small that they “were not statistically significant”. Sorghum yield was not affect by growth at elevated CO2. Rising temperatures combined with decreasing soil moisture, which are side effects of increased greenhouse gases, will work to retard plant growth. Recent review papers state that there is “serious doubt …. that rising [CO2] will fully offset losses due to climate change.” A list of review papers can be found here. Real time data as well as archive data can be found here.

Decreasing soil moisture is not expected to be a universal concomitant of AGW, according to the IPCC AR4, nor even the dominant concomitant. As far as I can tell (even from the peer-reviewed articles cited by that web page), the predominant response to increased CO2 is net increased primary productivity.

162, completely fed up: *please note neither of us have said that ALL crops are covered by the studies reported.

That’s a good point. Also: not every microclimate has been studied: at high altitudes in the Rockies, increased CO2 and decreased soil moisture work against each other, at different times of the year. What the net is has not yet been studied, afaik, and the moisture study was a simulation, not an empirical manipulation.

Comment by Septic Matthew — 5 Mar 2010 @ 5:18 PM

176. Re:Shakhova methane article:

I was directed to

http://www.global-chance.org/IMG/pdf/CH4march2008.pdf

by Mr. Lou Grinzo at climateprogress. In Figure 4 and table 2, a comparison is made between relative global warming potential of sustained releases of CH4 as compared to CO2 at different time horizons. The effect of a sustained release of CH4 has the same GWP as that of a sustained release of 81 times the amount of CO2 over a time of 20 years.The factors for 50,100,250 and 500 years are 57,39,21,and 13.

The authors make the case that using the 21 multiplier appropriate for century timescales is not appropriate, especially in the early decades where GWP would be underestimated by a factor of 80.

I see an estimate of 3.8 teragram/yr CH4 release from North Siberian Lakes in Zimov, Nature, v443, pp71-75, 2006. This has increased by 58% since 1974. Shakhova has 8 Tg/yr from the seabed.

Only including these we have 8 Tg from the seabed, 4 from the lakes, for 12 Tg annual CH4 out. 12Tg of CH4 for twenty years has a GWP over that period of 0.72 Pg sustained CO2 release. I believe that by comparison, annual human fossil and land use CO2 emission is around 30 petagram, so thats round 2% extra in terms of GWP over 20 years.

Not huge, but definitely significant.

If these CH4 releases rise quickly, say by a factor of 10, we cook much quicker. Of course I might have done the math wrong.

sidd

Comment by sidd — 5 Mar 2010 @ 5:42 PM

177. #170: Roy did use the opportunity to report Feb 2010 under V5.3 rather than last months V5.2, which had the delightful effect of making the last two months more to his liking. I’m waiting with baited breath for the denialsphere to scream about this.

Comment by Clark Lampson — 5 Mar 2010 @ 5:56 PM

178. Re: #171 & #175: (FACE experiments) a good review can be found here:

Elevated CO2 effects on plant carbon, nitrogen, and water relations: six important lessons from FACE. Leakey et al. (2009) Journal of Experimental Botany 60(10)

(available from all good libraries)

The six lessons are: “First, elevated CO2 stimulates photosynthetic carbon gain and net primary production over the long term despite down-regulation of Rubisco activity. Second, elevated CO2 improves nitrogen use efficiency and, third, decreases water use at both the leaf and canopy scale. Fourth, elevated CO2 stimulates dark respiration via a transcriptional reprogramming of metabolism. Fifth, elevated CO2 does not directly stimulate C4 photosynthesis, but can indirectly stimulate carbon gain in times and places of drought. Finally, the stimulation of yield by elevated CO2 in crop species is much smaller than expected.”

Comment by Chris S. — 5 Mar 2010 @ 6:35 PM

179. Mathew@175 – Don’t expect soil moisture to remain favorable in all the major grain producing areas, some of which are regularly subject to wipeout levels [too much or not enough] already, and the reports on that page indicate “Rising temperatures combined with decreasing soil moisture, which are side effects of increased greenhouse gases, will work to retard plant growth” – As I said, we don’t eat “primary productivity”, biomass, we eat the “fruit”, secondary production – see the line “wheat and rice showed some increases in yield, the increases were so small that they “were not statistically significant”. Sorghum yield was not affect[ed] by growth at elevated CO2″. The increased biomass production in trees and non-food grasses may have an effect on the sequestration question, but I don’t eat trees much. :)

I do grow a lot of my own food, and I can tell you that there are many veg varieties that simply do not bloom with temperature, nitrogen or carbon above their “prefered value” or way beyond a certain balance, regardless of soil moisture. While certainly plant breeding can develop varieties that do better under different conditions once we see just what the conditions are ….. dinner can’t wait.

Comment by flxible — 5 Mar 2010 @ 6:52 PM

180. Richard Brenne, When I looked at this a couple of months ago, I could see reaching 1000 ppmv, but just barely, and that assumed that ~60% went into the atmosphere and 40% into the oceans and biosphere on average. There’s a lot more natural gas than we thought, and there’s still a lot of coal. Granted, economics might limit the fraction we can burn, but 800-1000 ppmv is probably not a bad upper limit.

Comment by Ray Ladbury — 5 Mar 2010 @ 7:58 PM

181. RiHo08@167
Huh? Volcanic perturbation favors a sensitivity of around 3 degrees per doubling–just like all the other independent data sources. Somehow, I don’t find it comforting when somebody who doesn’t know what he’s talking about tells me that we have time.

Comment by Ray Ladbury — 5 Mar 2010 @ 8:01 PM

182. Re Clark Lampson’s comment at 177. I’m rather confused by Roy Spencer’s 5.2 -> 5.3 adjustment. It *appears* to be a simple change to each month with Dec-Mar being negative adjustments, and Apr-Nov being positive (but smaller) so the average change is zero. It also appears (by comparing his January graph with February’s that he’s adjusted many of the previous years. For example in 2003 January and February get pushed down while May and September are pulled up, in accordance with his adjustment. But oddly enough January and February of 1998 don’t budge (neither does May, and Sept just twitches up a bit). Is his adjustment something that phases in from late 1998 to some time in the early 2000s?

Comment by GFW — 5 Mar 2010 @ 8:10 PM

183. Hate to throw another spanner in the works of the climate modellers but a new study shows that widespread methane emissions are occuring under the east siberian arctic shelf at a depth of only 50m at a rate of about 1 Tg/yr..eqv 1Mil Tonnes. That’s the equivalent to all the CH4 emissions over the world’s oceans at present.

[Response: Stay tuned--there will be a post on that paper/topic coming soon. It's not as significant as it might at first appear--Jim]

Climate modelling is only as good as the raw data..but the raw data is changing so quickly in regard to # of variables and quality and quantity.
This CH4 release is only going to greatly intensify over the short/medium term and probably turn into the principal climate forcer before we know it. This is not including the methane release from the tundra.
The long and short of it is that we cannot stabilise the world’s climate in time to prevent this new catastophic tipping point from being breached.

Comment by Lawrence Coleman — 5 Mar 2010 @ 8:34 PM

184. RE #9

Did we not learn something about the effect of Mt., Pinatubo’s aerosol emissions on global temperature? Of Course, Dr. Robock is correct.

The additional 0.5 degree C increase awaits as South Asian and China clear their air of the Asian Brown cloud.

John McCormick

Comment by john McCormick — 5 Mar 2010 @ 9:19 PM

“If the CO2 levels were suddenly clamped” (=current-concentration commitment?), it seems to me that’s ‘initially close to’ stopping all further burning of fossil fuels plus stopping deforestation.

So at THAT moment, the imbalance between the TOA and the surface (mainly ocean) would be unchanged. Until that imbalance is dissipated by further radiative and convective redistribution of heat within and between the ocean, land and troposphere, the lower troposphere and ocean will continue to warm, to establish a ‘new’ average lapse rate, and this will take at least decades, would raise the surface temperature about 0.6ºC – and this is what’s “in the pipeline”.

So why am I wrong when I complain that M & W’s “zero emissions” plot fails to show this?

Surely by “zero emissions”, they didn’t mean all respiration on the planet and all bio-sequestration also ceases! Even that wouldn’t completely suppress a delayed peaking.

[Response: "zero emissions" is not the same as constant concentration. For CO2, there is currently net uptake by the biosphere and ocean, and so absent any human emissions, there would be a net decrease of CO2. - gavin]

Comment by Len Ornstein — 5 Mar 2010 @ 9:33 PM

186. 178, Chris S and 179, flxible,

thank you.

Comment by Septic Matthew — 5 Mar 2010 @ 10:12 PM

187. I am just a concerned citizen. What always seems to be missing in all of this is a SIMPLE 1-page summary that can lay out irrefutable proof of AGW. Should be something WIDELY circulated that connects the dots from very basic fundamental data: c02 at 270 provided a warming of x degrees, proven in 1790. The volume of the atmosphere is y. Of that, there is z cubic miles of c02 at 270. We have burned up ‘a’ cubic miles of c02. b% has been absorbed into the oceans. Therefore we can account for 97% of the increase from human sources. Etc. There is a fundamental lack of understanding of what I outlined above in the general population. The attack monsters deny everything, because wherever this is layed out, it is overly complicated. Keep it simple. Challenge Fox news to have people come on to refute it and crucify them. PS: I did the math above myself and came very close, but I didn’t have all the accurate numbers. But I did this, because I was starting to have doubts and I needed to convince myself that the good guys really are the good guys. Lots of doubt out there. Pay attention.

[Response:Your post is a little confusing because on the one hand you're arguing for sound bite level explanations, which are impossible for a complex science topic, and on the other hand you're asking people to do math--which is anathema to most. There are lots of easily available, simplified explanations out there if one looks, for example, here, and here, among many others. The evidence has been presented in a wide variety of formats and level of detail, all of which can be found with a simple Google search. The problem is that people are not spending the time to educate themselves--Jim]

PPS: I don’t think people yet understand how a 2 degree F warming can melt so much arctic ice. (I don’t understand it in any level of detail, so there are people who think you guys are off your rockers).

Comment by Mike Morgan — 6 Mar 2010 @ 12:12 AM

188. BPL:”None whatsoever. My time series analysis of cereal production against CO2, fertilizer consumption, and dT for 1961-2002 indicate that the correlation with CO2 is spurious and that fertilizer consumption has been the only relevant factor.”
And a geographical analysis of countries GDP against temperature and use of fossil fuels would show generally that the correlation with temperature is spurious and that the use of fossil fuel is the only relevant factor. Be logical please : you can’t use this argument as a proof of causality in one case, and not in the other. Any serious analysis shows that use of fossil fuel is the first cause of richness, and temperature is mainly immaterial : if you have fossil fuels, you can adapt to any extreme conditions. And if you think than fossil fuel are by no way necessary and that we have plenty of possibilities of producing cheap and abundant energy, this energy should be as efficient as fossil fuels to counteract any change in temperature : what not using the enormous potential of Sun to irrigate, produce fertilizers (you basically need only hydrogen) , clean water, grow food on artificial and climatised greenhouses, and so on .. ?

Comment by Gilles — 6 Mar 2010 @ 2:52 AM

189. Anonymous Coward: #136: you’d have to be part of a pretty select band to know a lot more than I do about the free software movement, and I am very interested in extending the ideas of not only free software development but also internet standards development to academic publication, but:

(a) this is seriously OT
(b) it’s unfair to attack the climate science community for a systemic problem in academic publication.

If you want to talk constructively, email me at the address on my petition.

Comment by Philip Machanick — 6 Mar 2010 @ 5:24 AM

190. Ray “Huh? Volcanic perturbation favors a sensitivity of around 3 degrees per doubling–just like all the other independent data sources. ”
What the relevance of calibrating long range sensitivity, which could imply a number of different rearrangements, to impulsive events that have only short term responses? if climate inertia is not well know, I don’t see how it is really useful. BTW i have the impression that the curves published in AR4 overestimate systematically the effect of volcanoes, in temperature, troposphere overpressure, and smoothed forcings. They almost exactly cancel the high solar activity in the “naturel without anthropogenic” models, but I doubt that volcanoes have been much more active thoughout the XXth century. They were probably only much better KNOWN.

Comment by Gilles — 6 Mar 2010 @ 5:52 AM

191. Thanks Jim..noted. As one of the preliminary studies I still find the rate disturbing. We are at just the tip of the iceberg at present(pun not intended)dont forget. With the arctic ice melting at an unprecedented rate ‘ice albedo’ the warming of the arctic ocean will and is has to be significant. Say the arctic surface waters down to 100m warm by another 0.5-1.5C over the coming decades that will in turn no doubt release massive amounts of CH4 not just from the ocean but the tundra as well. The figures at present may not look overly alarming but the rate of CH4 release will grow in all likelihood exponentially from now on.

Comment by Lawrence Coleman — 6 Mar 2010 @ 6:26 AM

192. L Coleman “With the arctic ice melting at an unprecedented rate”

over which period do you estimate this rate, and what is the comparison period over which you state it is “unprecedented” ?

[Response: You're missing his point, which is, that the loss of ice in the arctic not only decreases the global albedo, it leads to direct heating of the Arctic ocean, and this could well affect methane release from clathrates. How the ice melt rate compares to other times is beside the point--Jim]

Comment by Gilles — 6 Mar 2010 @ 7:09 AM

193. #182: I noticed the same thing, and looked up NOAA-15 launch date: 5/13/98. So indeed the peak months that are adjusted down now, were before the AMSU sensors came into play in 98. Interestingly, he claims the need for the adjustment was because V5.2 relied more heavily on the older MSU data rather than the newer AMSU. In that case would not data prior to AMSU need adjustment also? The implication is no, its related to merging the old and new. I’m generally happy to assume the adjustment has been carefully done. What I find interesting is the month used to switch over. He even stated that February would see the largest adjustment, hence was a good month to make the switch on, as people would notice it most. My immediate thought was why he didn’t choose to do the switch on a month when the adjustment would be the maximum upward instead of the maximum downward. I’m pretty sure that would have caused a good deal more notice, with lots of claims from the denialsphere that he must surely be cooking the books! Or he could have made the adjustment on a month when it had no effect.

Comment by Clark Lampson — 6 Mar 2010 @ 7:31 AM

194. “How the ice melt rate compares to other times is beside the point–Jim”

so why say “unprecedented” if it is not ?

now concerning the retroaction loop warming-> melt -> warming ocean -> release of methane clathrate-> warming, I think we are still very far from a catastrophic runaway : I understood that methane release from the arctic is only a few percent of the total, and methane in itself is only a minor part of the global GHG effect. Before the arctic methane contribution triggers a much larger GHG effect, overwhelming the main (CO2) component to trigger a non linear feedback, it should be first be multiplied by 100 or more !!

and before seeing that, we should first observe a hint of acceleration of methane concentration increase… but quite on the opposite, methane has stagnated during the period when Arctic has experienced the largest warming, and when Arctic ice melt has also been the largest (in the 2000-2010 decade). So something must be rotten in the loop….

Comment by Gilles — 6 Mar 2010 @ 8:04 AM

http://tamino.wordpress.com/2008/10/19/volcanic-lull/

There is both a short-term and a long-term response due to the inertia in the oceans.

And given your track record here, I hope it’s OK with you that I don’t consider your “impression” to have much bearing on the science.

Comment by Ray Ladbury — 6 Mar 2010 @ 8:27 AM

196. @Lawrence Coleman, 183. Maybe this larger image from Atmos expresses it already visibly. I don’t know, but remember from my youth skating on bubble rich moats and ditches and the ice being crap, brittle, frothy cake.

http://arctic.atmos.uiuc.edu/cryosphere/NEWIMAGES/arctic.seaice.color.000.png

Comment by Sekerob — 6 Mar 2010 @ 8:54 AM

197. “”"”I am just a concerned citizen. What always seems to be missing in all of this is a SIMPLE 1-page summary that can lay out irrefutable proof of AGW.”"”"

I propose the following as evidence…although perhaps too simplistic…I propose that the following is a smoking gun that human-caused global warming is happening and will continue.

The below published peer-reviewed studies, which hold up over time in reputable science journals/panels, by author’s whose work has held up over time of which the articles have held up over time, is a sort of smoking gun (the premise that humans are causing the global warming/climate changes has not been even slightly sucessfully rebutted over time in the world wide peer review system…although researchers are constantly trying).

The following studies conclude that human-caused global warming is happening and/or that the human-caused global warming science is factual. The basic premise of human-caused climate change and/or its mechanisms, which these articles state as fact, have not come even close to being countered in the juried, refereed, world-wide peer-reviewed literature over the years.

All of the following publications have had more than enough time to be rebutted in the world-wide juried, refereed literature and come from reputatable scientific journals/sources. I did not list any publications more recent than 2008 in order for them to be given time to be rebutted.

V Ramanathan – Science, 1988 (abstract says it)
http://www.sciencemag.org/cgi/content/abstract/240/4850/293
“Since the dawn of the industrial era, the atmospheric concentrations of several radiatively active gases have been increasing as a result of human activities. The radiative heating from this inadvertent experiment has driven the climate system out of equilibrium with the incoming solar energy.” [THIS NEATLY SUMMARIZES HUMAN-CAUSED CLIMATE CHANGE/GLOBAL WARMING AS FIRST WRITTEN IN 1824- FOURIER]

KP Shine, PMF Forster – Global and Planetary Change, 1999 (free, full download)
http://www.dvgu.ru/meteo/library/19990087.pdf
“Human activity has perturbed the Earth’s energy balance by altering the properties of the atmosphere and the surface.”

PR Epstein et al., Bulletin of the American Meteorological Society, 1998 (free, full download)
http://www.decvar.org/documents/epstein.pdf
“The Intergovernmental Panel on Climate Change concluded that there is “discernible evidence” that humans—through accelerating changes in multiple forcing factors—have begun to alter the earth’s climate regime.”

http://xweb.geos.ed.ac.uk/~dstevens/publications/johns_cd03.pdf
“In this study we examine the anthropogenically forced climate response over the historical period, 1860
to present, and projected response to 2100…”

http://www.sciencemag.org/cgi/content/full/306/5702/1686?paged=78
“Such statements suggest that there might be substantive disagreement in the scientific community about the reality of anthropogenic climate change. This is not the case…”

“The scientific consensus is clearly expressed in the reports of the Intergovernmental Panel on Climate Change (IPCC)… In its most recent assessment, IPCC states unequivocally that the consensus of scientific opinion is that Earth’s climate is being affected by human activities: “Human activities … are modifying the concentration of atmospheric constituents … that absorb or scatter radiant energy. … [M]ost of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.”

“The IPCC is not alone in its conclusions. In recent years, all major scientific bodies in the United States whose members’ expertise bears directly on the matter have issued similar statements.”

http://eprints.whiterose.ac.uk/117/1/thomascd2.pdf
“Anthropogenic climate change seems set to generate very large numbers of species level
extinctions.”

JT Houghton, Intergovernmental Panel on Climate Change (IPCC), 2001 (free, full download)
“Anthropogenic climate change will persist for many centuries.”

“The warming over the last 50 years due to anthropogenic greenhouse gases can be identified.”

“Concentrations of atmospheric greenhouse gases and their radiative forcing have continued to increase as a result of human
activities.”

“…global average water vapour concentration and precipitation are projected to increase during the 21st
century. By the second half of the 21st century, it is likely that precipitation will have increased over northern mid- to
high latitudes and Antarctica in winter. At low latitudes there are both regional increases and decreases over land
areas.”

“…it is very likely that the 20th century warming has contributed significantly to the observed sea level rise,
through thermal expansion of sea water and widespread loss of land ice.”

“The balance of evidence suggests a discernible human influence on global climate”.
(NOTE HOW CONSERVATIVE THE IPCC IS- ALL 130 COUNTRIES HAVE TO UNANOMOUSLY VOTE ON EVERY SINGLE WORD ON THE ABOVE SUMMARY FOR POLICY MAKERS).

JT Houghton, Intergovernmental Panel on Climate Change, 1995 (free, relevant parts viewable)
“The first IPCC Assessment Report of 1990 concluded that continued accumulation of anthropogenic greenhouse gases in the atmosphere would lead to climate change whose rate and magnitude were likely to have important impacts on natural and human systems.”

“The balance of evidence suggests a discernible human influence on global climate”.

“Increases in greenhouse gas concentrations since preindustrial times) ie. Since about 1750) have lead to a positive radiative forcing of climate, tending to warm the surface and to produce other changes of climate.”

“Many greenhouse gases remain in the atmosphere for a long time) for CO2 and N2O, many decades to centuries)…”

“Future unexpected, large and rapid climate system changes (as have occurred in the past) are, by their nature, difficult to predict. This implies that future climate changes may also involve “surprises”. In particular these arise from the non-linear nature of the climate system. When rapidly forces, non-linear systems are especially subject to unexpected behavior.

(NOTE-THE IPCC IS NOTORIOUSLY ON THE CONSERVATIVE SIDE BECAUSE ABOUT 130 COUNTRIES HAVE TO UNANAMOUSLY VOTE ON THE ALREADY PUBLISHED PEER-REVIEWED SCIENCE).

http://kfrserver.natur.cuni.cz/global/pdf/2003_climate%20change.pdf
“Modern climate change is dominated by human influences, which are now large enough to exceed the bounds of natural variability.”

“The main source of global climate change is human-induced changes in atmospheric composition.”

A Haines, RS Kovats, D Campbell-Lendrum, C, The Lancet, 2006 (free, full download)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1294362/pdf/jrsocmed00091-0029.pdf

“The concern now is about the enhanced green-house effect
which is occurring as a result of anthropogenic emissions of greenhouse gases.”
“There are a number of feedback mechanisms which
may play a role… in determining the response of climate to increases in
greenhouse gases.”

“Dramatic reductions in fossil fuel use will be necessary in developed countries in order to stabilize greenhouse
gases at the same time as permitting some developing countries to increase their energy use.”

http://people.oregonstate.edu/~lintzh/Vitousek%20et%20al_%201997.pdf
“Increased CO2 represents the most important human enhancement to the greenhouse effect; the
consensus of the climate research community is that it probably already affects climate
detectably and will drive substantial climate change in the next century…”

“the carbon dioxide concentration in the atmosphere has increased by nearly 30 percent since the beginning of
the Industrial Revolution;”

“Humanity adds CO2 to the atmosphere by mining and burning fossil fuels, the residue of life from
the distant past…”

“Conflicts arising from the global use of water will be exacerbated in the years ahead, with a growing human population
and with the stresses that global changes will impose on water quality and availability.”

http://www-cas.ucsd.edu/personnel/vram/publications/Ram_etal_Sci_2001.pdf
“The role of GHGs in global warming will increase because of their accumulation in the atmosphere.”

“It is important to differentiate the decadal to centennial time scales involved in GHG warming from the time scale of aerosol lifetimes, which is only several days.”

“Greenhouse gases absorb upwelling infrared (IR, also referred to as longwave) radiation and reduce the outgoing
long-wave (.4 mm) radiation at the top-of-the atmosphere (TOA). The TOA radiative forcing (that is,
the change in the outgoing longwave radiation), due to the observed increase in GHGs since the early
20th century, is about 2.4 W m22”

PA Stott, DA Stone, MR Allen, Nature, 2004 (abstract says it)
http://www.nature.com/nature/journal/v432/n7017/abs/nature03089.html
“…we estimate it is very likely (confidence level >90%) that human influence has at least doubled the risk of a heat wave exceeding this threshold magnitude.”

http://pubs.giss.nasa.gov/docs/2003/2003_Alley_etal.pdf
“…it is conceivable that human forcing of climate change is increasing the probability of large, abrupt events… Amplifiers are abundant in the climate system and can produce large changes with minimal forcing.”

http://www.ncbi.nlm.nih.gov/pubmed/15479264
“Human activities are resulting in increases in atmospheric greenhouse gases, such as carbon dioxide, and changes in global climate. These, in turn, are likely to have had, and will continue to have, impacts on human health. …Despite this, a number of studies have revealed potential impacts of climate change on aeroallergens that may have enormous clinical and public health significance.”

http://fiesta.bren.ucsb.edu/~gsd/resources/courses/bio-chapin.pdf
“We have more than doubled the concentration of methane and increased concentrations of other gases that contribute to
climate warming. In the next century these greenhouse gases are likely to cause the most rapid climate change that
the Earth has experienced since the end of the last glaciation 18,000 years ago and perhaps a much longer
time.”

http://famguardian.org/Subjects/Environment/Articles/ClimateChange-20090131.pdf
“Warming of the climate system has been detected in changes of surface and atmospheric temperatures,
temperatures in the upper several hundred metres of the ocean and in contributions to sea level rise.
Attribution studies have established anthropogenic contributions to all of these changes. The observed pattern
of tropospheric warming and stratospheric cooling is very likely due to the combined influences of greenhouse
gas increases and stratospheric ozone depletion.”

“Anthropogenic forcing is likely to have contributed to changes in wind patterns, affecting extra-tropical
storm tracks and temperature patterns in both hemispheres. However, the observed changes in the Northern
Hemisphere circulation are larger than simulated in response to 20th century forcing change.”

http://www.ftsnet.it/documenti/260/Antropocene.pdf
“There is now scientific consensus that anthropogenic carbon emissions are the cause.”

http://www.sciencemag.org/cgi/content/summary/303/5655/176 or
http://www.heatisonline.org/contentserver/objecthandlers/index.cfm?id=4566&method=full
“Global warming due to increased greenhouse gas emissions poses the most severe problem for governments today.”

“Climate change is real, and the causal link to increased greenhouse emissions is now well
established.”

“In less than 200 years, human activity has increased the atmospheric concentration of greenhouse gases by some 50% relative to preindustrial levels.”

“Moreover, it’s a myth that reducing carbon emissions necessarily makes us poorer. Taking action to tackle climate change can create economic opportunities and higher living standards.”
“But we already know enough about the problem to agree on the urgent need to address it.”(REMEMBER,THE ABOVE PUBLICATION HAS HELD UP UNDER OPEN, REFEREED, JURIED WORLD-WIDE PEER REVIEW SINCE 2004…THIS IS HOW SCIENCE HAS BEEN DONE SINCE THE 1600s.)

…substantial increases in the concentrations of ‘greenhouse’ gases — carbon
dioxide by 30% and methane by more than 100% — reaching their highest levels over
the past 400 millennia, with more to follow. So far, these effects have largely been
caused by only 25% of the world population. The consequences are, among others,
acid precipitation, photochemical ‘smog’ and climate warming.”

Bradley, The Holocene, 1993 (abstract says it)
http://hol.sagepub.com/cgi/content/abstract/3/4/367
“Climatic changes resulting from greenhouse gases will be superimposed on natural climatic variations.”

WR Emanuel, HH Shugart, MP Stevenson – Climatic Change, 1985 (abstract says it)
“…can be altered by climatic change due to natural causes or due to human activities such as those leading to increasing atmospheric CO2 concentration.”

http://summits.ncat.org/docs/patz_nature_2005.pdf
“The World Health Organization estimates that the warming and precipitation trends due to anthropogenic climate change of the past 30 years already claim over 150,000 lives annually.”

http://www.pnas.org/content/98/26/14778.long
“This warming is, at least in part, a result of anthropogenic climate forcing agents.”

J Hansen, M Sato, P Kharecha,- Phil. Trans. R. Soc. A, 2007 (abstract says it)
http://rsta.royalsocietypublishing.org/content/365/1856/1925.abstract
“Recent greenhouse gas (GHG) emissions place the Earth perilously close to dramatic climate change that could run out of our control, with great dangers for humans and other creatures. Carbon dioxide (CO2) is the largest human-made climate forcing…”

http://www.pnas.org/content/105/6/1786.full
“Our synthesis of present knowledge suggests that a variety of tipping elements could reach their critical point within this century under anthropogenic climate change.”

http://climatechangepsychology.blogspot.com/2008/09/v-ramanathan-and-y-feng-on-avoiding.html
“The committed warming is inferred from the most recent Intergovernmental Panel on Climate Change (IPCC) estimates of the greenhouse forcing and climate sensitivity.”

Comment by Richard Ordway — 6 Mar 2010 @ 9:15 AM

198. The blue line is my favorit.

A constant climate over 300 years, great.

Did something like that ever happen in real climate nature?

No way, but why do you show us fictions like that?

Greetings from Austria,
Herbi

Comment by Herbert — 6 Mar 2010 @ 9:27 AM

http://tamino.wordpress.com/2008/10/19/volcanic-lull/

Ray, being a professional scientist, I consider that my reflexions as scientific as, or even more than, the average level on this forum, including yours. But I’m not particularly interested in this kind of rhetorics. Tamino’s post is a nice example of the confusion (that he apparently often makes) between “I can fit data with some assumptions” and “My model is proved to be right”. If you look at his “fits” (and similar curves shown with climate models), you can see that although the overall model curve superimposes correctly to the observed ones, the characteristic features associated with the presence of eruptions don’t. The slope at the beginning of century is underestimated. The rising part stops well before the big eruption of Agung in 1963. The drop in temperature after each eruptions is not really observed, just “within error bars”. So I don’t see in his post any strong validation of sensitivity against data – probably we could fit also data with an influence of major wars as well.

Comment by Gilles — 6 Mar 2010 @ 11:36 AM

200. Gilles, if you were in fact a scientist, you would know the difference between doing a fit to an arbitrary putative forcing and a KNOWN forcing like volacnism.
Tamino isn’t trying to fit the short-term response. You should understand that by the fact that he is doing a 30-year smooth. He’s interested in the response of the oceans to the mean level of volcanism. That seems to me to be a very reasonable question AND it gives what is actually quite a good match.

Comment by Ray Ladbury — 6 Mar 2010 @ 11:51 AM

201. Gilles – “(…) probably we could fit also data with an influence of major wars as well.”
Or maybe to fossil fuel production?

I’m amazed at the improvement in your grasp of english latley, but your “debate” continues to hover at the same level of simple contrarianism.

Comment by flxible — 6 Mar 2010 @ 12:24 PM

At the moment of a switch to “zero emissions” (“at THAT moment”) there would be about 0.6ºC of ‘surface warming’ still in the pipeline”.

Do you mean to imply that the subsequent decrease of CO2 in (“so absent any human emissions, there would be a net decrease of CO2″) would cancel the temperature rise that would otherwise result from the warming still in the pipeline so that M & W’s “zero emission” plot would immediately go flat?

That’s very hard to believe – and if so, certainly should have required explication by M & W – or you!

Comment by Len Ornstein — 6 Mar 2010 @ 1:40 PM

203. Gilles (199) — Tamino’s to box model follows from the known physics. Read Gavin Schmidt (with co-authors) about ModelE and also
http://www.iac.ethz.ch/people/knuttir/papers/knutti08jgr.pdf

I have an even simplier conceptual model based on the known physics:
http://www.realclimate.org/index.php/archives/2010/02/whatevergate/comment-page-23/#comment-164509

Comment by David B. Benson — 6 Mar 2010 @ 2:23 PM

204. Ray : “Gilles, if you were in fact a scientist”

thais only proves your low capability of discerning the truth, at least as far as I am concerned.

, you would know the difference between doing a fit to an arbitrary putative forcing and a KNOWN forcing like volacnism.
Tamino isn’t trying to fit the short-term response. You should understand that by the fact that he is doing a 30-year smooth. He’s interested in the response of the oceans to the mean level of volcanism. That seems to me to be a very reasonable question AND it gives what is actually quite a good match.

KNOWN forcing ? let’s read the AR4, chapter 6.6.3.2 :

“The considerable difficulties in calculating hemispheric and regional volcanic forcing changes (Robock and Free, 1995; Robertson et al., 2001; Crowley et al., 2003) result from sensitivity to the choice of which ice cores are considered,
assumptions as to the extent of stratosphere penetration by eruption products, and the radiative properties of different volcanic aerosols and their residence time in the stratosphere. Even after producing some record of volcanic activity, there are major differences in the way models implement this. Some use a direct reduction in global radiative forcing with no spatial discrimination (von Storch et al., 2004), while other models prescribe geographical changes in radiative forcing (Crowley et al., 2003; Goosse et al., 2005a; Stendel et al., 2006). Models with more sophisticated radiative schemes are able to incorporate prescribed aerosol optical depth changes, and interactively calculate the perturbed (longwave and shortwave) radiation budgets (Tett et al., 2007). The effective level of (prescribed or diagnosed) volcanic forcing therefore varies considerably between the simulations (Figure 6.13a).”

and look at the Figure 6.13a before concluding that the physics is well known. There is obviously considerable uncertainty in the effect of volcanic (and all types of as well ) aerosols.And again the match with data is not that good, because no characteristic feature of volcano eruptions is really visible in the instrumental curve, besides the very short term (which goes hardly out of the natural fluctuations anyway) : the date of the break doesn’t match, the instantaneous slopes don’t match, the amplitude of the sharp decreases don’t match either.

Comment by Gilles — 6 Mar 2010 @ 7:10 PM

205. Re: Gilles, the information you are clingling to seems to me a little out of date, sure there was a temporary slowing of the CH4 curve a few years back but as we speak its on the upward move again.
Also as CH4 released becomes oxidised in the atmosphere in about 7 years (7 years is the tip of the bell curve for CH4 transformation rates) it turns into CO2..even more CO2. So another way of thnking about all the clathrates beneath the ocean is as potential CO2!
If you say ” I think we are still very far from a catastrophic runaway” it shows how unimaginative you must be..can’t you visualise anything at all? If you happen to know the solution to prevent the oceans warming any further..then and only then can you smugly rest on your laurels.

Comment by Lawrence Coleman — 7 Mar 2010 @ 12:11 AM

206. “Re: Gilles, the information you are clingling to seems to me a little out of date, sure there was a temporary slowing of the CH4 curve a few years back but as we speak its on the upward move again.”

The “upward move” is less significant than the flat temperature curve since 2000, but I didn’t claim that CH4 wasn’t to rise anymore in the future, I said that there is no hint of non linear acceleration due to retroaction. The fact that more methane is released when temperature rises is a normal linear response, probably associated with a growing number of warm days in Arctic (which is probably partly due to a high AMO oscillation) , but I see no sign of a feedback on methane curve.

Comment by Gilles — 7 Mar 2010 @ 3:33 AM

207. Gilles:”The “upward move” is less significant than the flat temperature curve since 2000,”

1) a curve is not flat.
2) the temperature graph since 2000 is increasing
3) it is far too short to ascribe it to any climate trend

Comment by Completely Fed Up — 8 Mar 2010 @ 9:52 AM

208. http://tamino.wordpress.com/2009/08/24/methane-north-and-south/

Comment by Hank Roberts — 8 Mar 2010 @ 11:06 AM

209. For info. I’ve done some updates to my little spreadsheet here showing the combined impact of Earth system sensitivity (ESS) and CO2 response to temperature (gamma).

I originally put this sheet together after the article “Good news for the Earth’s climate system?”: see

The latest sheet and table look at the case of a drop to zero emissions immediately after a peak level of CO2 is reached. The “Residual (persistent) CO2″ row is the level of CO2 at Stage 2 of my 5-stage scenario, as detailed in comment 62 above. The rows “Ultimate CO2″ and “Ultimate warming” indicate the situation reached at Stage 4 after all the slow feedbacks have played out.

There are columns for peak CO2 of 4 x pre-industrial, 2 x pre-industrial, 1.5 x pre-industrial and present levels. The final column indicates what might have happened if we’d stopped emitting back in the 1980s when Global Warming first became a political issue.

The sheet only considers CO2 and CO2 feedbacks: to add in other greenhouse feedbacks (from methane etc.), a rough approximation is just to scale up “gamma” slightly e.g move to the 20ppm column.

There isn’t a lot of “good news” anywhere in this analysis. However, it is important to keep up hope and keep civilization going. If our civilization collapses this century, it will only limit the short-term problem (Stages 1 and 2) while the long-term outlook (Stages 3 and 4) still looks bleak. It seems our descendants will need to try and clear up our mess, i.e. mop up the residual CO2 somehow, and I doubt they’ll be able to manage that if they’re back living in caves.

Comment by Dr Nick Bone — 8 Mar 2010 @ 4:17 PM

210. Having a beer with a group of retired Engineers, one of the guys was holding forth on a solution he had just developed for some arcane world problem. The guy who had gone for the round, returned and said, “You have to first determine if it’s an engineering problem or a political problem. It it’s a political problem, engineers will never solve it.”

Comment by Ken Peterson — 9 Mar 2010 @ 1:31 PM

211. Gilles,
That is why, looking at the average effect smoothed over time is a better way to do it.

Afraid of uncertainties, Gilles?

Comment by Ray Ladbury — 9 Mar 2010 @ 2:11 PM

212. hi gavin,
they’re talking about you over at Capital Weather Gang:
http://voices.washingtonpost.com/capitalweathergang/2010/03/scientists_hit_the_blogosphere.html

and from a commenter,

“Finally, scientists need to…provide hard scientifc and verifiable proof that this consensus indeed exists. I’ve heard tons of claims, but have been able to find precious little evidence to support this…”

PROJECT JIM, anyone?

Comment by walter crain — 10 Mar 2010 @ 8:15 AM

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