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Climate change commitments

Filed under: — gavin @ 3 March 2010 - (Español)

There is an interesting letter in Nature Geoscience this month on what climate changes we have actually already committed ourselves to. The letter, by Mathews and Weaver (sub. reqd.), makes the valid point that there are both climatic and societal inertias to consider.

Their figure neatly demonstrates the different issues:

The upper line is often what is referred to as the ‘climate change commitment’ (for instance Wigley, 2005). This is the warming you get if we keep CO2 (and other GHG and pollutant levels) constant at today’s values. (Technically, the figure shows the case staying at year 2000 values). In such a scenario, the planet still has a radiative imbalance, and the 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. Thus the conclusion has been that because of climate inertia, further warming is inevitable.

However, constant concentrations of CO2 imply a change in emissions – specifically an immediate cut of around 60 to 70% globally and continued further cuts over time. 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. With this definition then, there is no climate change commitment because of climate inertia. Instead, the reason for the likely continuation of the warming is that we can’t get to zero emissions any time soon because of societal, economic or technological inertia.

That is an interesting reframing of an issue that comes up all the time in discussions of adaptation and mitigation. This is because it demonstrates that adaptation (over and above what is necessary to reduce vulnerabilities to current climate conditions) is unnecessary if mitigation is dramatic enough.

However, the practical implication of this reframing is small. We are clearly not going to get to zero emissions any time soon, and even the 60-70% cuts required to stabilise concentrations initially seem a long way off. Thus as a practical matter, it doesn’t really matter whether the inertia is climatic or societal or technological or economic because the globe will continue to warm under all realistic scenarios (what we do have a possible control over is the magnitude of that warming). Thus further adaptation measures will still be needed.

212 Responses to “Climate change commitments”

  1. 151
    Ron Taylor says:

    What about this quote from the press release:

    “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]

  2. 152
    KSW says:

    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).

  3. 153
    SecularAnimist says:

    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.

  4. 154
    Brian Dodge says:

    @ Ron Taylor — 5 March 2010 @ 10:05 AM
    “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).

  5. 155
    Steve Fish says:

    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.


  6. 156
    Septic Matthew says:

    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.

  7. 157
    Greg says:

    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.

    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?

  8. 158
    Rod B says:

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

  9. 159
    Walt The Physicist says:

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

  10. 160
    Earl Killian says:

    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?

  11. 161
    Rod B says:

    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]

  12. 162
    Completely Fed Up says:

    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.

  13. 163
    Hank Roberts says:

    > 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.

  14. 164
    Jerry Steffens says:

    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.

  15. 165
    Garrett says:

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

  16. 166
    flxible says:

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

  17. 167
    RiHo08 says:

    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.

  18. 168
    dennis baker says:

    And yet you still support inaction?

  19. 169
    Richard Brenne says:

    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
    off-the-top-of-my-head guesses, not including dandruff.

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

  20. 170

    And climate skeptic Roy Spencer keeps running into record global temps: Feb 2010 2nd hottest in UAH satellite measurements

  21. 171
    flxible says:

    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.

  22. 172
    Sebastian says:

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

    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]

  23. 173
    Brian Dodge says:

    Shakarova et al in the Supplementary Online Material – – 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.”

  24. 174
    Len Ornstein says:

    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]

  25. 175
    Septic Matthew says:

    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.

  26. 176
    sidd says:

    Re:Shakhova methane article:

    I was directed to

    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.


  27. 177
    Clark Lampson says:

    #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.

  28. 178
    Chris S. says:

    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.”

  29. 179
    flxible says:

    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.

  30. 180
    Ray Ladbury says:

    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.

  31. 181
    Ray Ladbury says:

    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.

  32. 182
    GFW says:

    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?

  33. 183
    Lawrence Coleman says:

    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.

  34. 184
    john McCormick says:

    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

  35. 185
    Len Ornstein says:

    Gavin: Re your answer in 174

    “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]

  36. 186
    Septic Matthew says:

    178, Chris S and 179, flxible,

    thank you.

  37. 187
    Mike Morgan says:

    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).

  38. 188
    Gilles says:

    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 .. ?

  39. 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.

  40. 190
    Gilles says:

    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.

  41. 191
    Lawrence Coleman says:

    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.

  42. 192
    Gilles says:

    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]

  43. 193
    Clark Lampson says:

    #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.

  44. 194
    Gilles says:

    “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….

  45. 195
    Ray Ladbury says:

    Gilles, read the link from Tamino.

    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.

  46. 196
    Sekerob says:

    @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.

  47. 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)
    “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)
    “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)
    “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.”

    TC Johns et al., Climate Dynamics, 2003 (free, full download)
    “In this study we examine the anthropogenically forced climate response over the historical period, 1860
    to present, and projected response to 2100…”

    Oreskes, Science, 2004 (free, full download)
    “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.”

    Nature, CD Thomas, 2004 (free, full download)
    “Anthropogenic climate change seems set to generate very large numbers of species level

    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

    “…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

    “…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”.

    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.


    Karl, Trenberth, Science, 2003 (free, full download)
    “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)

    “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.”

    PM Vitouseket al., Science, 1997 (free, full download)
    “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.”

    V Ramanathan – science, 2001 (free, full download)
    “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)
    “…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.”

    RB Alley et al., Science, 2003 (free, full download)
    “…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.”

    PJ Beggs – Clinical & Experimental Allergy, 2004 (free, full download)
    “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.”

    FS Chapin et al., Nature, 2000 (free, full download)
    “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

    P Schwartz, D Randall, Department of Defense, 2003 (free, full download)
    “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.”

    J Zalasiewicz et al., GSA Today, 2008 (free, full download)
    “There is now scientific consensus that anthropogenic carbon emissions are the cause.”

    King, Science, 2004 (free, full download) or
    “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

    “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.)

    PJ Crutzen, Nature, 2002 (free, full download)”
    …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)
    “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.”

    JA Patz et al., Nature, 2005 (free, full download)
    “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.”

    JE Hansen, M Sato – … National Academy of Sciences, 2001 (free, full download)
    “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)
    “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…”

    Timothy M. Lenton et al., PNAS, 2007 (free, full download)
    “Our synthesis of present knowledge suggests that a variety of tipping elements could reach their critical point within this century under anthropogenic climate change.”

    Ramanathan V, Feng Y, Proc Natl Acad Sci, 2008 (free, full download)
    “The committed warming is inferred from the most recent Intergovernmental Panel on Climate Change (IPCC) estimates of the greenhouse forcing and climate sensitivity.”

  48. 198
    Herbert says:

    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,

  49. 199
    Gilles says:

    Ray :illes, read the link from Tamino.

    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.

  50. 200
    Ray Ladbury says:

    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.