Positive feedbacks from the carbon cycle
Two papers appeared in Geophysical Research Letters today claiming that the warming forecast for the coming century may be underestimated, because of positive feedbacks in the carbon cycle. One comes from Torn and Harte, and the other from Scheffer, Brovkin, and Cox. Both papers conclude that warming in the coming century could be increased by carbon cycle feedbacks, by 25-75% or so. Do we think it's time to push the big red Stop the Press button down at IPCC?
The approaches of both papers are similar. The covariation of temperature versus CO2 (and methane in Torn and Harte) is tabulated for a record in the past. For the Torn and Harte paper, the time frame chosen is the last 360,000 years, while Scheffer et al. focus on the Little Ice Age, from 1500-1600 A.D. In both cases it is assumed that the climate shift is driven by some external thermal driver. As the temperature warms (in the case of the deglaciation) or cools (the LIA), the CO2 concentration of the atmosphere changes in the sense of a positive feedback, rising associated with warming or falling in response to cooling. The changing CO2 drives a further change in temperature.
In general, it is clear that eventually the sense of these articles could be correct. The response of the terrestrial biosphere to rising CO2 could go either way; toward an increase in uptake because of CO2 fertilization or a longer growing season (as we see today) versus an increase in soil carbon respiration in warmer conditions (the reason why tropical soils contain so little carbon). Uncertainties in the response of the terrestrial biosphere to rising CO2 is a major source of uncertainty for the climate change forecast (Cox et al., 2000).
The oceans are presently taking up about 2 Gton C per year, a significant dent in our emissions of 7 Gton C per year. This could slow in the future, as overturning becomes inhibited by stratification, as the buffer loses its capacity due to acidification. Eventually, the fluxes could reverse as with a decrease in CO2 solubility due to ocean warming.
The biggest question, however, before pushing the Stop the Press button at IPCC, is timing. The CO2 transition through the deglaciation took 10,000 years. (Actually this helps to constrain the cause of the CO2 transition, because the air/sea equilibration time scale for CO2 would be considerably shorter than that.) The timescale that seems intrinsic to IPCC is a century or so, during which we should be able to reap only a small fraction of any harvest that takes 10,000 years to grow. The Scheffer et al paper avoids this issue by restricting its attention to a time period of just a century.
Scheffer et al illustrate the potential feedback for the coming century in a figure which looks something like Figure A.
Temperature depends on CO2 concentration via radiative equilibrium in the blue curves, and CO2 concentration in the air is affected by temperature according to the red lines. A rise in CO2 concentration from an external source changes the equilibrium CO2 as a function of T relation toward higher CO2, to the right, labeled "forcing". The stable final equilibrium is where the two relations cross, with further CO2 degassing from the land or the ocean, so that more CO2 ends up in the atmosphere than would have if there were no feedback (a vertical red line). A climate sensitivity calculated from the coupled system is higher than one that ignores any carbon cycle feedbacks.
The situation today is complicated somewhat by a carbon spike transient. Atmospheric CO2 is rising so quickly that the terrestrial biosphere and the ocean carbon reservoirs find themselves far out of equilibrium. In attempting to keep up, the other reservoirs are taking up massive amounts of CO2. If emissions were to stop today, it would take a few centuries for the atmosphere to equilibrate, and it would contain something like 25% of our emitted CO2.
I would draw our current situation as in Figure B, with CO2 concentration wildly higher than the equilibrium red line, poised to relax toward lower concentrations if emissions stopped. The effect of the carbon cycle feedback is to change the equilibrium atmospheric CO2 that we are relaxing toward. It seems to me that the most important part of the equation for our immediate future is the decay rate of that carbon spike, rather than the equilibrium value that CO2 will relax to in hundreds of years.
27 May 2006 at 10:24 AM
This page (http://www.realclimate.org/index.php?p=311) does not render properly, either in Firefox or Safari, on a mac running OS 10.3.9. The “B” graph is about 1/2 covered by the brown list on the right side of the page. I could test from a windows machine, but I’ll bet some of the readers of this site are running macs!
[Response:thanks! fixed now. David]
27 May 2006 at 11:00 AM
Is there any hope for gaining insight into the interaction between a “carbon spike transient” and the kinds of feedbacks these slower processes bring by examining the PETM event?
[Response: The timing is father fuzzy from this event. There may be an initial 13-c change in planktonic forams (surface ocean) before the benthic ones (deep ocean), but it’s impossible to tell if the invasion took 100 years or 500, which is the information that would relevant to this question. ]
Re Torn et al. It seems problematic to draw too many parallels between a process that took 10K yrs and one that is playing out over one century, especially if it involves the biosphere which will undoubtably react very differently to such a sudden warming. And what about the multi-century lag between T and CO2 in deglaciation? Why do they expect to see effects in this century?
Do either paper’s conclusions depend on specific mechanisms or is it more based on observation of past correlations?
[Response:Not really. I think they’d be stronger if the mechanisms were well-known and quantifiable, more than they are. David]
27 May 2006 at 11:27 AM
Why didn’t this huge CO2 feedback not occur in the Eemian?
[Response:Warmer temperature, but not higher CO2? Good question. David]
I can only see a response of 10 ppm/K.
27 May 2006 at 11:38 AM
You are all missing the point. Water vapour is the main greenhouse gas not carbon dioxide. When the Artic ice melts (due to the increase CO2 levels)then the increase in water vapour due to a warmer and wetter ocean surface will have a runaway effect caused by the positive feedback from the saturated vapour pressure which increases exponetially. This will be compounded by the loss of albedo from the sea ice. The time to press the big red Stop button has long passed.
It is well known that carbon dioxide did not drive the recent deglaciation, nor did it (or methane) drive the rapid warming at the end of the Younger Dryas. It is not the main player in the climate stakes, but by moving the snow line it can alter the planetary albedo and so trigger a rapid warming.
[Response: This isn’t a correct statement. The amplifying effect of water vapor feedback is already incorporated in the “radiative” temperature vs. CO2 curves in Figs (a) and (b). The detailed shape of those curves is affected by the specific assumptions made about water vapor feedback (specifically the way in which relative humidity in the mid to upper troposphere changes with temperature). –raypierre]
27 May 2006 at 11:45 AM
As I read the article, the positive feed back, is either a potosynthesis or respiration.
This paper, using carbon isotope measurements concludes a net transfer to land of some 600 Gt: Estimate of deglaciation carbon transfer
Woods Hole puts the amount of upper ocean carbon (first 100 meters?) at less than 800 gigatons while land holds a little less than 2,000 gigatons, and deep ocean has someting like 40,000 gigaton. Prior to fossil fuel use the atmosphere held something less than 600 gigaton. I hope my conversion from petagram to gigaton is correct.
So, the mind boggles with the various scenarios. It seems that the land response to deglaciation is more complex then a simple scenario favoring respiration early and photosynthesis later, which was my guess. The tropics have less carbon and nothern tundra is suspected to be a net carbon source as it warms, yet the northern tundra gained carbon during deglaciation.
[Response:You are correct that the 13-C seems to tell us that there was net uptake of organic carbon during the deglaciation, which makes explaining the atmospheric CO2 rise more difficult to explain. Truly the mind boggles. David]
Given the length of the Holocene, the land carbon, worldwide, must have reached eqilibrium, all things being equal. If I compare inter-glacial time periods and holocene plant growth rates of the northern hemispere I suspect that the net introduction of nothern carbon continued well into the holocene. A simple transfer of tropical carbon north does not explain the additional 600gt total, unless the paper cited is wrong; or the net transfer occured early during deglaciation.
The deep oceans might have been net producer of carbon until the introduction of fossil carbon and deep upwelling stopped as the fossil carbon atmospheric pressure grew.
Is there something in the science of ocean carbon that could cause increasing ocean carbon on the surface to push back on the release of deep carbon, a change in circulation, or am I just wrong about upwelling of deep carbon?
[Response:CO2 invades the ocean in some places, where it’s cold or where CO2 has been stripped out by phytoplankton, and it invades in other places. I don’t think of the deep sea as being a huge source of carbon waiting to get out, I think of it as being in equilibrium with the atmosphere. Of course, if you stirred up the ocean more quickly than biology could keep up, or if you killed the biology, then the deep sea would be a source of carbon to the air. David]
27 May 2006 at 11:52 AM
First of all, when do we start heading for that alleged “equilibrium” CO2 level?” We’re doing a dynamic process here, not a static one, and the warming we get will come from the CO2 we have, not the amount we ought to eventually expect with the current temperature. That leftward arrow is a fiction until people get alarmed in a constructive way, which is not yet a general reaction. For now, diagram A is our actual condition, and we need a serious change in behavior to make B apply (which may not occur until a shortage of fuel-burning humans sets in.)
[Response:Situation B is where we are, insofar as the CO2 is still invading the oceans and the land. You are right that the equilibration arrow is a fiction because we’re adding CO2 faster than it goes away. If we cut emission by about half, uptake would balance release and atmospheric CO2 would stabilize. David ]
The immediate effect of these positive feedback processes is not simply an increase in the eventual equilibrium temperature, but an increase in the amount of CO2 entering the atmosphere and increasing the current temperature. Perhaps not a large enough increase to dominate our own contributions, but working to bring us closer to whatever other potentially destabilizing thresholds may lie ahead.
27 May 2006 at 1:32 PM
Re #2 The question about the 10ka+ spikes of Carbon dioxide is whether it is cause or effect of something. We have several things to take into account. First, the CO2 contents of the oceans is double digits compared to the atmosphere; next, atmospheric pCO2 is very sensitive to changes in surface curents (eg El Nino), changing sink areas and CO2 venting areas and there is clear evidence for oceanic CO2 exchange . Furthermore, the Thermohaline ocean current underwent strong and quick changes around the end of the ice age (Younger Dryas).
Therefore, it cannot be excluded that those CO2 spikes were the direct and exclusive result of those oceanic changes (Hodell et al 2001), rather than that it was primarily temperature cause - effect related.
Moreover, the initial warming is assumed to have started about 19ka ago (Clark et al 2004), whereas the start of the CO2 spike is dated not before 17ka (Monnin et al 2004). Hence maintaining the claim of interaction between the two appears to require some revisiting of the evidence.
Refs
Clark et al (2004), Rapid Rise of Sea Level 19,000 Years Ago and Its Global Implications. Science 21 May 2004: 1141-1144
Hodell D.A et al (2001) Late Pleistocene evolution of the ocean’s carbonate system, Earth and Planetary Science Letters 192 (2001) 109-124
Monnin, E., et al 2004. EPICA Dome C Ice Core High Resolution Holocene and Transition CO2 Data. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2004-055.
27 May 2006 at 2:11 PM
Does that big red button happen to say ‘Do Not Press This Button’?
27 May 2006 at 2:18 PM
Question: Lakes with CO2 at the bottom sometimes turn over and the CO2 kills a whole village. Can the ocean do that too, killing the whole planet? How high above sea level do I have to live to be safe from ocean CO2 overturn?
[Response: You’re thinking of Lake Nyos, I imagine. The uptake of atmospheric CO2 at the ocean surface could not conceivably create the kind of CO2 profile that lead to the lake-type catastrophic release; CO2 enters through the surface of the ocean, and only gradually is brought to the deep ocean. One of the proposed schemes for CO2 sequestration, however, is to inject liquified CO2 directly to the bottom of the ocean, and here it’s not as immediately obvious that a catastrophic release can be ruled out. This was discussed in the IPCC carbon sequestration report that just came out, and a Lake Nyos type catastrophic release seems to be essentially impossible, because of the greater depths and pressures involved in the ocean, and the greater stratification that is working to inhibit vertical mixing. The ecological effects of ocean floor CO2 disposal provide lots of cause for worry, but catastrophic release is one thing you can probably breathe easy about. –raypierre]
27 May 2006 at 2:34 PM
I was thinking along the lines of comment 6. To continue with the thought it seems to me that identified positive feedbacks to increase the effect of higher CO2 levels operate in the near term. Examples include: albedo change from north pole sea ice melt and northern forest albedo decrease. Other identified positive feedback loops include methane release from warming permafrost and decreased CO2 absorption by warmer seas that also act in the near term. Other positive loops that accelerate glacial flow rates and melt, affect sea level.
Corrective negative feedbacks to sequester CO2 operate in the longer term.
It seems we have initiated a global system shift to a different state. To reverse this shift wouldn’t we have to reduce the amount of CO2 in the atmosphere? This implies reducing CO2 emissions to less than the rate of sequestration, not just slowing the rate of increase in emissions. Since current trends are for CO2 emissions to continue to increase is there in fact any real prospect avoiding rapid global warming?
27 May 2006 at 4:12 PM
How long would that extra 25% of our emissions remain in the atmosphere if we were to stop emitting CO2 today? Tens of thousands of years? Hundreds of thousands of years?
[Response:Some of it (10% or so) for hundreds of thousands of years. This was the topic of my first post at realclimate! David]
27 May 2006 at 5:28 PM
The article makes sense to me, as far as the last deglaciation is concerned. However I have a problem with the LIA. If Scheffer et al were able to identify a feedback response, does this imply that the LIA was a global event (or at least more widespread than the IPCC thought it was)?
[Response: Experiments using coupled climate-carbon cycle models such as Gerber et al (2003) [Gerber, S., Joos, F., Bruegger, P.P., Stocker, T.F., Mann, M.E., Sitch, S., Constraining Temperature Variations over the last Millennium by Comparing Simulated and Observed Atmospheric CO2, Climate Dynamics, 20, 281-299, 2003] suggest that the hemispheric-mean cooling of the LIA indicated by the reconstructions featured in the IPCC TAR are consistent with pre-industrial CO2 variations, and that significant greater hemispheric-mean temperature variations would actually be inconsistent the CO2 record of the past millennium. –mike]
If there was a feedback within a 100 year period, I guess that it could have been caused by cooling prior to this (the LIA started, I believe, one or two centuries before the period studied). I take your point about a CO2 spike in current times, but do their results imply that the feedbacks respond faster during a cooling period than during a warming period?
27 May 2006 at 6:42 PM
It seems to me there’s a curious quirk of a result like this though, that it actually REDUCES climate sensitivity, as measured by temperature change associated with a given CO2 increase - because the positive feedback is to increase the CO2 for a given temperature.
That’s doesn’t mean it makes things better - it makes things worse because anthropogenic CO2 is enhanced by naturally released CO2 from the positive feedback. But it’s perhaps a limitation of just looking at a doubling of CO2 in describing the results of climate models.
[Response:No it doesn’t - because classical ‘climate sensitivity’ is only defined for constant CO2 so these feedbacks just don’t come into it. The confusion between the articifical construct ‘climate sensitivity’ and the real question of how climate is sensitive to increasing emissions is very common though. - gavin]
27 May 2006 at 7:26 PM
Over the whole 420,000 years of Vostok data, the linear regression between CO2 levels (lagging with many hundreds to many thousands of years) and temperature (derived from dD), was some 8.1 ppmv/K.
Taking the 1.5-4.5 K warming of the IPCC range of model projections, this would lead to an extra 12-36 ppmv of CO2 in full equilibrium (after thousands of years…), due to warmer ocean temperatures. Or some 4-13% extra over the 280 ppmv induced by humans to reach a CO2 doubling. Or some 1.56-5.1 K warming (which is lower than the 1.6-6.0 K derived from the model by Sheffer ea.) instead of the original 1.5-4.5 K projection.
Further I wonder how Sheffer ea. could derive anything from the miniscule changes in CO2 levels in one century of the LIA. The variation in temperature over the past millennium was between 0.2 K (MBH98/99) and 1.0 K (Huang, bore holes), which means a CO2 variation of 1.6-8 ppmv. The effect of this on temperature is unmeasurable… (BTW, the variation in CO2 between MWP and LIA was near 9 ppmv in the Taylor Dome ice core).
[Response: The numbers you cite for “the variation in temperature over the past millennium” are nonsensical (the range of total variation only differs by about 0.4C for the full range of reconstructions, such as shown in this previous post). For actual quantitative comparisons between observed pre-industrial CO2 variations and what is expected given estimated temperature variations and their uncertainties, see the Gerber et al (2003) paper cited above. The comparisons are consistent with 2xCO2 sensitivities within the conventionally cited range of 1.5 to 4.5, but not much higher. –mike]
If we will need a panic button or not, depends of what the real effect of a CO2 doubling will be, but the CO2 feedback seems of less importance here…
[Response: Another mistake you seem to be making is that you’re regressing glacial-interglacial CO2 against Vostok temperature, which is a measure of the Antarctic temperature changes. Then you’re applying that coefficient to the global mean temperature. It’s a fallacy to take the Antarctic temperature swings as representative of the magnitude of the global mean, or even of the Southern Hemisphere mean. –raypierre]
27 May 2006 at 9:29 PM
Re 14
The amount of knowledge and evidence already justifies pushing the red button, and has justified pushing it for some time. This weekend, ND and MN has daily max temps in the 90s and humidity, but trees have yet to completely leaf out. Earlier this month, TV meteorologists sounded out below normal May temps … but not anymore. Monthly average temperatures in the Upper Midwest have near or above the historical averages at climate stations since 2001. Nobody wants to get accused of pushing panic buttons and feel a loss of credibility. Too bad it seems to be that way, otherwise we may have acted years ago to reduce emissions.
[Response:Hang on, my rhetorical fluorish of the “Stop the Press” button at IPCC seems to have confused several people (this post, #14, and #8). I meant to say, should the IPCC, which is soon going to start printing its next Climate Scientific Assessment report, stop the press, to revise its estimate of the climate sensitivity or future warming. I did not mean to imply that we should not be concerned about CO2 emissions (the button being whether to take climate change seriously or not). My apologies for all the confusion. David]
28 May 2006 at 5:16 AM
To the Note 6: “If we cut emission by about half, uptake would balance release and atmospheric CO2 would stabilize. David”
certainly, this would hold true, if the uptake capacity of atmosphere and for CO2 was constant in the future. But taking in mind increased cumulative CO2 rise (or is this increased rise in CO2 due to increased emissions, not due to decreasing absorbing capacity of ecosystems?) and continuing increasing temperature, the amount of “equilibrium carbon stop” needed will be higher from year to year, or?
[Response:Yeah, you’re right. Cutting emissions enough to balance natural uptake today would only stabilize CO2 until the ocean and land uptake saturates, at which point CO2 would start to rise unless emission were cut further. David. ]
28 May 2006 at 6:54 AM
David, re your response about which big Red button should be pressed, it was I who proposed that it should be the Really Big one in #4. There was no need for you to apologise for my corruption of your message
As Ray pointed out in his reply to Ferdi, the correlation between temperature and CO2 in the Vostock core is irrelevant to climate in the northern hemisphere where virtually all the people of the world live. The real danger from positive feedback is a repeat of the end of the Younger Dryas when Greenland temperatures jumped by 10C in three years and by 20C in thirty years [Alley, R. “The Two Mile Time Machine”, 2000.] That would have led to temperature changes in the bread baskets of the world which would not have been so severe, but the effect to the water cycle stretched as far south as the Amazon Basin [Maslin, M.A., and S.J. Burns, “Reconstruction of the Amazon Basin effective moisture availability over the last 14,000 years” Science, 290, 2285-2287 (2000)]. There is no evidence that positive feedback from CO2 or methane was the driving force for that event.
Ray argues that the models are already including the effects of water vapour, but I am arguing that they are not doing it correctly. The models cannot reproduce the amount of cooling during the Younger Dryas, and that can only be because the water vapour sensitivity is wrong. In fact, we know that is true from “Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe” by Rolf Philipona et al. GRL, 2005. Ray’s greenhouse effect of water vapour in the upper troposphere is irrelevant, because the atmosphere is in a state of LTE there! And we know from the MSU and radiosonde measurements that the upper troposphere is hardly warming, and what warming is happening is probably due to the Asian Brown Cloud.
[Response: What you said I pointed out was not in fact what I pointed out. CO2 is global, and your remarks about regional influence are completely unrelated to my point, which was simply that Antarctic deuterium temperature fluctuations are not the same as global mean temperature fluctuations, which (in the ice age problem) are not even themselves necessarily the temperature that feeds back on CO2. Therefore Engebeen’s correlation likely underestimates the feedback, insofar as one can estimate it at all from data of this sort. The comments in your last paragraph are so completely wrong, and in a way we’ve gone over so many times before, that I won’t bother responding again. –raypierre]
28 May 2006 at 10:39 AM
Re #17
About
“The real danger from positive feedback is a repeat of the end of the Younger Dryas when Greenland temperatures jumped by 10C in three years and by 20C in thirty years [Alley, R. “The Two Mile Time Machine”, 2000.]”
This is the interpretation of Alley of isotope variation, it could be something different. But Antarctic isotopes are not representative for global temperature why would Greenland summit isotope-temperatures be representative of NH temperatures? It is not even true for South Greenland:
http://www.geol.lu.se/personal/seb/Geology.pdf.pdf
28 May 2006 at 11:03 AM
Re 15
It might have been warmer in the midwest but most of Europe was cooler than average in May.I suppose neither of these facts will bear any relationship to the global temperature after all they are just local events.
[Response:All of these local effects go into the statistics, so they do influence the mean. But if there are more warm anomalies than cold, the global anomaly will be warm. That’s what averaging means. -gavin]
28 May 2006 at 11:26 AM
I know some global warming deniers who have jumped from “global warming isn’t happening” to “global warming is not human caused” to the latest “it is too late to do anything about it.” The old version of this was simply that global warming is an on/off switch - once any global warming happens, well degree does not matter and that is it, let’s move on. But that I think has proven too obviously wrong - I mean the answer is pretty self-evident; it is like saying there is no difference between a mild sunburn, and catching on fire.
However I’m seeing feedback seized on as the next version of the ‘too late’ trope. “We have all that methane under the permafrost in siberia, and the hydrates under the iceaps. Feedback has already reached the point where they are all going to be released; this will dwarf human emissions, so there is no point in doing anything about those human emissions.” Early days on this one , but I’m betting you’ll be hearing more about it. The intersting thing about it is it may provide additional evidence of how driven by the loonies the denier side is. This trope is not put foward by the few scientists or even much in evidence among the institutes who claim be scientific. It is strickly among the loonies who don’t even make global warming their main focus - for whom global warming denial is just one belief alongside a number of other “interesting” views. But I’m going to make a prediction. Within the next twelve months you are going to hear well known deniers add the “it’s too late; the climate has tipped; the coming of the methane is inevitable” to their standard list. I’m posting it here, both because it is relevent to the subject you are discussing and because I’m making my prediction publicly, so that the accuracy (or otherwise) may be tested. If a talking point that is not put forward currently by any global warming denier with scientific credentials or even any major denier think tank becomes a position advocated either by such think tanks or those with such credentials, I think it will be a tiny piece of additional evidence that such denial is indeed politics driven and not merely a maverick scientific viewpoint.
28 May 2006 at 11:58 AM
re 19. I also said that monthly average temperatures in the Upper Midwest were above historical averages since 2001.
I could have added that annual temperature averages were above historical averages for the last nine years in a row and that Jan-Apr temperature averages in ND and northern MN clearly show warming trends which are based on 100-110 mean temperature averages at NOAA climate stations. However, I already said all that and I provided my link to the plots many times to RC.
Strong regional trends over a 100-110 year period is much more significant than than one or a couple days or months of above or below the official recent 30 year National Weather Service averages which are used to define normal for temperatures at climate stations.
re 20. I think you missed that … bwe know what’s happening but our day to day lives are a struggle enough, and besides, what one person does or doesn’t do is insignificant. Get a life.
28 May 2006 at 12:26 PM
As a non scientist who took statistics a long time ago I struggle to understand the analysis of all the data that is presented here on this site. Though I suspect I am able to get the general gist of the fact that according to the general consensus we may be in for some significant climate change begining now and progressing into the commimg centuries, the consequences of which we probably cannot fully asses at the present time.
I suspect that Gar Lipow is not far off the mark with regards as he calls them “Loonies” However what I find much more disturbing is those who are crazy like foxes and have enormous vested interests such as the oil and energy industries. They have both the money and the power to sway the general public opinion and are more than able thus to have their way.
Case in point an article in today’s New York Times business section: http://www.nytimes.com/2006/05/28/business/28coal.html?hp&ex=1148875200&en=2cffad8d8e32d294&ei=5094&partner=homepage
talks about what is happening with coal. The discussion seems to focus on the application of cleaner tecnnology to reduce soot emissions and reduce things like acid rain. That certainly may sound like a good idea. Though it seems to me to miss the point entirely. I think that any carbon dioxide emitting energy source regardless of how currently inexpensive it may seem at the moment has to have the cost of the long term societal consequences factored in to the bottom line. In other words if the use of cheap coal will in the long term be a big part of accelerating climate change and if that change can be shown to have deleterious effects on the livelihoods of of societies through drought and famine and floods etc… then they should only be allowed to embark on such business ventures if they are held accountable for the consequences from the get go. As I see it now if these scenarios should come to pass they will suffer no consequences whatsoever. So they feel free to pursue their profits at any cost and since they will appear to be selling cheap energy (the real costs of which will be denied) the ignorant public will be a willing participant in this unfolding global fiasco. ‘CO2: they call it pollution, we call it Life!’ is not in my opinion as funny as it seems at first glance.
[Response:That’s exactly why some kind of regulatory environment for CO2 is needed, and why the market won’t take care of it all by itself. There are regulations in place (despite attempts to weaken and dismantle them) that control soot, sulfur compounts, nitrogen compounds and (soon) mercury, and therefore companies spend money on the technology to reduce emissions of these. However, there are no market signals that represent the environmental costs of CO2 emissions, so a company would have to be crazy — indeed irresponsible in the fiduciary sense — to spend extra money reducing CO2 emissions, for example by building IGCC plants and providing for sequestration. Right now, burning coal in pulverized coal plants makes great economic sense, and there is no reason in the world it won’t expand — as indeed it is doing. The tragedy is that a coal plant will have a 50-60 year capital life, perhaps more. If a company took the long view and figured in the cost of capturing and sequestering CO2, not only would IGCC plants look cheaper than pulverized coal, but even coal with IGCC would start to look less economically attractive than various alternatives. –raypierre]
28 May 2006 at 12:51 PM
Re# 16
Alexander, you said:
“But taking in mind increased cumulative CO2 rise (or is this increased rise in CO2 due to increased emissions, not due to decreasing absorbing capacity of ecosystems?)”
I used available data on global 2003-2005 fossil fuel use and its CO2 emissions and the 2006 Jan-APR Mauna Loa CO2 concentration measurements and the following might address your question:
Using 2006 JAN-MAY 11 hourly CO2 measurements provided by NOAA Earth Systems Research Laboratoryâ??s Carbon Cycle Greenhouse Gases Group, I derived a January increase of 2.98 ppmv CO2 over 2005 January concentration. Please note, my calculations are based upon preliminary data.
Is that increase attributable to increased fossil fuel use?
Global fossil fuel use data from BPâ??s Statistical Review of World Energy, June 2005 provided the following coal, oil and natural gas production for 2003 and 2004. I estimated 2005 data using conservative percent increase.
Coal
2003- 5.185 billion tons
2004- 5.538 billion tons
2005- 5.954 billion tons (7.5 percent increase)
Oil
2003- 28.1 billion barrels
2004- 29.3 billion barrels
2005- 30.8 billion barrels (5 percent increase)
Natural Gas
2003- 92,053 billion cu ft.
2004- 94,462 billion cu ft.
2005- 97,298 billion cu ft. (3 percent increase)
Global Tons of CO2
Coal
2004- 12.671 billion tons
2005- 13.621 billion tons
Oil
2004- 12.851 billion tons
2006- 13.494 billion tons
Natural Gas
2004- 5.526 billion tons
2005- 5.691 billion tons
Total CO2
2004- 31.048 billion tons
2005- 32.807 billion tons
1 GtC corresponds to ~3.67 Gt CO2
2.12 GtC or ~7.8 Gt CO2 correspond to 1 ppmv CO2 in the
atmosphere.
Source:
D. Schimel,et.al,CO2 and the carbon cycle. Pages 76-86
in [IPCC 95])
The January 2006 Mauna Loa CO2 increase over 2005 was 2.98 ppmv, or 23 billion tons of CO2.
So, I conclude that the January 2006 increase was equivalent to 74 percent of total 2004 global fossil fuel CO2 emissions.
CO2 uptake by ocean and terrestrial sinks is not immediate and uptake is affected by temperature.
The energy and CO2 data are readily available to compare January 2006 increase against any successive Januaries from 1958 to 2005. If you are interested, I can provide more comparisons.
I hear many different explanations for the dramatic Jan 2006 over 2005 increase. None were based on analysis - just thow out lines such as fires, El Nino (?), very cold winter in Europe and Russia, China and India energy use. The January CO2 increase is not faulted by the measurement process itself. The Keeling team have a rigid, quality-controlled standard of excellence.
So, any suggestions to add to the “cause” list?
28 May 2006 at 1:40 PM
I think that, in general, processes in which one component lags another and is the effect of that cause or that they share a common cause, the lagging component will display a diminution in response to changes of a shorter period than the period of the lag.
A response with a millennium lag will look smoothed on a centennial time scale, one with a century lag will look smoothed on a decadal time scale, etc.
From the little I know of ice core evidence I am left with the impression that the CO2 response lags considerably => 500 years. Such a CO2 response mechanism, if this is a single mechanism, would be unlikely to be able to track sub centennial variations which is what I believe has been shown for the Little Ice Age record.
Alternatively there could be different mechanisms or even a reversal from effect to cause between these two examples. It is not clear to me that a single mechanism could be responsible for both.
I do not know how discriminating the ice core records are on decadal scale nor if anyone has looked for a second response with a short lag in these records. Absence of any short term CO2 signal in the presence of short term termperature signals would speak against a CO2 response to temperature with a short time lag, at least during that epoch.
Regarding the near future; If the lag is very short (< =10 years) , it might not be possible to extract the CO2 response from the CO2 cause prior to it all being a postmortem exercise unless a significant reduction in emissions occurs. If the lag is long (>200 years) the response will not be significantly excited if the problem is solved in time that remains to do so. I would think that the worry would lie in the lag being of the order of the problem, say 30-60 years as that could give rise to a strong, and so far hidden, response extending for another 30-60 years even if all the combustion stopped tomorrow.
What, perhaps, is needed is a significant signal in known CO2 emissions that can be looked for in the record to show the lag time in any response mechanism that is in the current regime.
Sadly I can not think of one, not even the Oil Crisis 1973 or a war, that would be likely to show this up. I do not know if general emissions are sufficiently well recorded to analyse the C02 record for any lag.
Even if it is, then given that the atmosphere is out of balance due to the rapidity of the rise, one might expect a predominance of an “apparent” CO2 leading signal due to the effects of CO2 sinks, as the CO2 level moves from being a response more to the total emissions to an equillibrium where it reflects more the rate of emissions. Detecting a lagging signal might not therefore be feasible given the uncertainties involved.
A possibility that such a response exists leaves us with the interesting prospect that until we make a significant dent in the emissions we might never know how bad the problem is.
I apologise for being long winded and vague on the evidence but if a strong ~50 year C02 reponse to temperature exists then it would be very bad news and if it can not be ruled out then perhaps it should be factored in to the limits of its possible range.
28 May 2006 at 1:44 PM
My apologies, I did not notice that I am the second Alexander , the long ramble about lagging signals by me.
28 May 2006 at 2:31 PM
Here’s an interesting publication about Vostok ice leads and lags:
Mudelsee, M., The phase relations among atmospheric CO2 content, temperature and global ice volume over the past 420 ka
Quaternary Science Reviews 20 (2001) 583-589
http://www.uni-leipzig.de/~meteo/MUDELSEE/publ/pdf/lag.pdf
28 May 2006 at 3:50 PM
[Moderator: Nonsense deleted]
Raypierre,
I know that Vostok dD at most represents SH sea surface temperatures, but - although there were time shifts between SH and NH - the NH temperature variations over the glaciations/deglaciations were not that different.
- I checked ice sheet growth over the Eemian, which is roughly compatible with Vostok dD (a lag of a few thousand years). This was measured by d18O in N2O, which I suppose represents global ice sheet growth.
- As ice sheet growth was mainly over land and mainly over the NH, I suppose that NH temperatures were lower in the NH than in the SH during the glacials (and higher during interglacials, as there is more land, which warms faster).
- If temperatures in the NH were lower during glaciations, then global temperatures were lower than measured as dD in Vostok. And the global temperature variation during the transitions were higher, but result in the same variation in CO2 changes.
- Consequently, the result of temperature increases even gives less extra CO2 than in my previous calculations…
- Btw, according to the Gerber model runs, most of the CO2 changes follow temperature changes already within 1-2 decades. Thus it is no wonder that such an effect is not measurable in the current CO2 and temperature trend. Only with fast changes like El Nino, a variation in CO2 increment follows temperature changes after some 6 months. Similar changes are measurable in plant growth.
[Response: You miss the point about the LGM. The LGM temperature drop pattern is not a very good analog for global warming, since the interhemispheric asymmetry in the former is much greater than the latter, especially as equilibrium is approached. Which temperature do you want to pick to make your analogue? Some estimates of LGM SH midlatitude cooling are as little as 2-3C, putting them in the same ballpark as the temperature change from anthropogenic global warming. That would (naively) imply that if the feedbacks worked the same way you could get maybe 100ppm boost from the CO2 feedback. Maybe you’d even get more, since in the LGM you expose a lot of new forestable land as you deglaciate, tending to offset what the ocean might be doing. It’s really really hard to use the LGM as an analogue for what happens under anthropogenic global warming, but insofar as one is going to do it at all your numbers are way too optimistic. –raypierre]
28 May 2006 at 4:38 PM
>think you missed that … bwe know what’s happening but our day to day lives are a struggle enough, and besides, what one person does or doesn’t do is insignificant. Get a life
Huh? I’m trying to see how it what you say relates to what I wrote. I’m pretty sure that the only people I talked about were flavors of global warming denialists. I made a testable prediction of the next denialist line. Don’t see how that is such a terrible thing to do. Don’t know what is wrong with people doing what they can.
28 May 2006 at 5:46 PM
Re: #23
First of all, here is a plot of montly CO2 concentration from Mauna Loa since 2000. There are two clear trends. First, there is a steady secular increase, which is signficantly described by a quadratic curve. This fit indicates a rate of increase
R = 2.11 + 0.0952 (t - 2003.17)
where R is the increase rate in ppmv/yr., t is the time in years. Second, there is an annual variation.
We can subtract both the secular increase and the average annual variation, leading to a “CO2 anomaly,” which is plotted here. From this we see that the CO2 anomaly for Jan. 2006 is not at all out of line; in fact it’s very small. We can also see that Jan. 2005 had a rather large *negative* anomaly. Therefore the difference between Jan. 2006 and Jan. 2005 is large, constituting the rate for 2006 (from the above formula, 2.38 ppmv/yr) + anomaly for Jan. 2006 (small positive) - anomaly for Jan. 2005 (sizeable negative).
However, most of the departure from normal of the Jan.2005 - Jan.2006 difference is due to the large *negative* anomaly from 2005. Hence the exaggerated growth of CO2 from one January to the next really says a lot more about how *low* the level was (compared to long-term trend) in 2005, than about how high it was in 2006.
28 May 2006 at 5:48 PM
re 27. I was trying to give examples of what people have said to me when I brought up the fact that global warming is out of control and is being driven by our greenhouse gas emissions. When they give up on trying to say global warming isn’t really happening, they’ve said there’s nothing they can do about it anyway which would matter. I agree with you that people need to do what they can to reduce their own emissions, even though it may seem to not matter. It’s a moral issue to do what we know is right, not wrong. It’s wrong to use fuel excessively with no regards for the many very serious consequences from a more rapid rate of global warming.
28 May 2006 at 6:27 PM
Ray, for those who have a single theory they keep reposting, tempting you to either rebut again or again swear off answering — perhaps RC could provide a linkable stock rebuttal page?
Reminding the posters you’ve rebutted them before won’t stop them; new readers however need to see your early, patient, detailed, footnoted attempts to explain why such ideas aren’t supported in the research.
Point being to educate new readers who can’t tell which of you to believe in the absence of any footnotes from either of you! (wry grin here). “Use the cites.”
28 May 2006 at 8:45 PM
To clarify, are these papers suggesting the warming may be underestimated because of stronger positive feedbacks in the carbon cycle, or were such feedbacks largely excluded from consideration in the IPCC projections?
Also, I understand there have been studies assessing the effect of CO2 fertilization under real world conditions, but I wonder if there’s been much follow-up on the effect warming will have on long-term sequestration by phytoplankton, and how quickly that might become a factor. This was the last I saw on diatoms.
28 May 2006 at 10:52 PM
Alex, try these (papers citing the article in Science)
http://scholar.google.com/scholar?hl=en&lr=&q=link:OZ_IIKty1mwJ:scholar.google.com/
28 May 2006 at 10:53 PM
I would just like to remind all posters that they should always carefully review their posts before submitting them. Real Climate have provided a nice mechanism for this process.
A submission may be clear in your head, but, sometimes a crucial letter, word or sentence may be missing causing confusion and resulting in to and from posts that would have been unnecessary if the originating post was correctly submitted.
Pat, I think your post 21 had something missing, I feel you missed a sentence to establish the context for the last paragraph. Also I do not like acronyms, excepting those that are widely understood, for example I am not sure what “bwe” means.
28 May 2006 at 10:54 PM
Re: 30
>When they give up on trying to say global warming isn’t really happening, they’ve said there’s nothing they can do about it anyway which would matter. I agree with you that people need to do what they can to reduce their own emissions, even though it may seem to not matter. It’s a moral issue to do what we know is right, not wrong. It’s wrong to use fuel excessively with no regards for the many very serious consequences from a more rapid rate of global warming.
Ah. I’d agree with the provision that it is more collectively wrong than individually wrong. Yes there are things one individual can do. But mostly there are things we as a society can do. I can bicycle when practical but I can’t take a train in my town cause there are none.
Similarly decarbonizing the grid will be a collective, not an individual choice. A few well-to-individuals can buy hybrids and convert them to plug-in hybrids on their own, or even buy expensive electric cars. But until these are massed produced, available at the lot these won’t be an option for most of us. And so on. So it is not a question of individual guilt - it is a question of social choices.
28 May 2006 at 10:55 PM
RE 28: It seems to me that in the anomaly graph there is also some signal (i.e. a period of about 3 years). Of course, the time series is far too short to be convincing, but still it does not appear like just random noise. On even more shaky basis there might be a relation to the Dow Jones index (http://home.xtra.co.nz/hosts/cwwebsite/history_dow_jones_index.htm) which purportedly is somehow dependent on industrial activity level. Some broad trends appear to be coincident.
Regards,
29 May 2006 at 12:48 AM
Re: #36
I too think the data (the “CO2 anomaly”) is not just random noise. However, the point I was really driving at is that the change from Jan. 2005 to Jan. 2006 is definitely *not* unusual, given the behavior of the CO2 concentration since 2000.
As for an approximately 3-yr. period in the CO2 anomaly, it’s best to look at the entire time series. I took the whole montly data set from Mauna Loa and generated a new curve in the same manner: subtract from the data a quadratic secular trend and the average annual variation to generate the “CO2 Anomaly.” The result is plotted here. Note that these are *not* the same anomalies plotted before, because the quadratic secular-trend curve which has been subtracted is that based on the entire time series, not just the series since 2000.
The most notable feature is the precipitous drop in CO2 anomaly in the early 1990s. This was discussed before; posts suggested as possibilities an association with el Nino, as well as with the collapse of the Soviet economy.
There are visible signs of an ~ 3-yr. period throughout the time series. A Fourier power spectrum is shown here. The most notable feature is the tall peak at very low frequency, which does *not* correspond to any real periodicity. Note there is a significant peak at frequency 0.275 cycle/yr., corresponding to period 3.63 yr. However, this peak could be indicative of a period, or it could indicate only a “characteristic timescale.” It could even represent neither, being only a manifestation of the “red noise” character of the CO2 anomaly curve. In fact the interpretation of peaks in a Fourier power spectrum — especially at low frequencies — is a *very* tricky business (Foster, G. 1996, Astron. J., 111, 541).
29 May 2006 at 7:49 AM
I was unaware that temperatures could be derived from ice core data. Could I have a link to an explaination of “dD?” Is this a derivative, or a delta? what is ‘D?’
29 May 2006 at 8:22 AM
>37
jhm, here’s a quick answer, and an example of how you can find such answers.
Read just the bit I quoted below for the answer to your question; see the whole paper for a good explanation.
This is from the first hit produced by Google Scholar using this string:
+temperature +”ice core data” +dd
Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica
JR Petit, J Jouzel, D Raynaud, NI Barkov, JM � - Nature, 1999 - earth.unh.edu
…
Ice cores give access to palaeoclimate series that includes local
temperature and precipitation rate, moisture source conditions,
wind strength and aerosol fluxes of marine, volcanic, terrestrial,
cosmogenic and anthropogenic origin. They are also unique with
their entrapped air inclusions in providing direct records of past
changes in atmospheric trace-gas composition….
The ice record
The data are shown in Figs 1, 2 and 3 (see Supplementary Infor-
mation for the numerical data). They include the deuterium content of the ice (dD ice, a proxy of local temperature change), the dust content (desert aerosols), the concentration of sodium …
That’s been cited by 848 subsequent papers.
I suggest you read the whole thing, search for it with Google Scholar.
29 May 2006 at 10:11 AM
About the ice cores, There is a connection between isotope rates and temperature but especially in (Ant-)Arctic areas also with precipitation. The complexity has been shown in this Ph.D thesis:
http://igitur-archive.library.uu.nl/dissertations/2006-0323-200235/index.htm
Conclusion:
“It is emphasised that isotopic variations in the hydrological cycle are complex, even in a relatively stable area such as Antarctica. Therefore one should be careful when quantifying climate signals over a period of several years on the basis of ice-core data.”
However since the deep ice cores of Antarctica are very difficult to date with very few hard data points, Jouzel et al (EPICA Dome C) and Petit et al (Vostok) appear to have a used rather simple algoritms to wiggle match precipitation rate with isotope ratio and age. At least this appears when the “layer thickness” is correlated with the isotope ratio. r2>95% That’s highly improbable and it seems to proof direct dependency, or circular reasoning, so to say. Consequently, the variation that Michael Helsen identifies would have definite implications for both chronologies and temperature interpretation.
http://home.wanadoo.nl/bijkerk/EPICA-CO2-LH-dD.GIF
For instance, Look at the near identical shape of the last spikes of both deuterium and clearly lagging CO2 (dD). Assuming normal second or higher order response characteristics, this strongly suggest a near simultaneous start.
29 May 2006 at 10:33 AM
RE #36
Pekka, many thanks for the link to that fascinating chart. It tells much about the industrialization of the US before and after the WWII but it does not have much direct, certain relationship to atmospheric CO2 concentrations. Certainly, the IT, dot.com industry added a lot of growth and gambling to world stock trading. However, a graph of US or world consumption of coal, oil and gas will track with the upward momentumn of Wall Street.
I will post some data on post-1981 global fossil fuel production in a later submittal. Thanks again for this unique piece of historical record.
29 May 2006 at 11:45 AM
What would be the current absolute temperature increase of the atmosphere,
with respect to the above :
“Both papers conclude that warming in the coming century could be increased by carbon cycle feedbacks, by 25-75% or so”
Would like to read IPCC trend compared to the papers suggested increase. in degrees K.
thanks
29 May 2006 at 1:39 PM
This page (http://www.realclimate.org/index.php?p=311) does not render properly in Opera, on a PC running XP. Figure A sometimes partially appears, and there’s a Figure B? I usually don’t have problems with this site in Opera.
As to the feedbacks: Is it just me, or is pretty much every scientific (as opposed to political) estimate of the rate of climate change an underestimate?
29 May 2006 at 5:59 PM
re 35.
I still think it is individually wrong to use fuel excessively, and there should be individual quilt for doing that. Two summers ago I visited a place that makes extravagant yachts that use enormous amounts of fuel. Their business was and probably still is booming.
29 May 2006 at 7:57 PM
Re #40: Andre, it appears you saw what you wanted to see in that dissertation. It simply asserts that it is more reliable to average temp data over several years, i.e., temp data plotted for individual years will tend to have larger error bars than a running average. Is this any sort of surprise? Do any scientific conclusions relying on ice core data depend on having precise temps for individual years?
30 May 2006 at 1:19 AM
Methinks arguments and speculation regarding atmospheric Carbon Dioxide will continue for some time. Regardless of possible climatic effects, in my opinion an overage of pollution alone is sufficient justification for burning less fossil fuel. Another justification is to cool off the oil wars.
A combination of Net Zero appropriate architecture and plug in hybrid vehicles could quickly cut carbon emissions in half or more. Visit calcars.org and read about Net Zero architecture with photovoltaics.
30 May 2006 at 2:24 PM
Re: #46
I do not reject your support for Net Zero architecture and plug-in hybrid vehicles. But, I do urge you and others sharing your view to dwell on some of the real facts of life in America and likely all developed nations.
1) most all of us are in debt up to our ears and are still paying the mortages on our 64 million owner-occupied dwellings. So, we are not about to put a “FREE” sign (who could afford two morgages?) on the lawn and build a Net Zero home.
2) we drive our cars, SUVs and whatever we own, for about 10 years on average. To abandon our car for a hybrid (even if our line of credit still has some cash available) will flood used car lots with cheaper cars the less wealthy among us will purchase and drive.
3.)there is no way, no way at all, to “quickly cut carbon emissions in half or more”. That regrettable fact deserves some attention when contributors wing all kinds of carbon-cutting suggestions without trying to imagine and help us see how a credit-strapped America will respond or - even how impractical it might be to plant trees without having, in place, a means to water them.
I could go on for days with examples of the “lets do this or that” as if the average Joe and Jane are eager to spend big bucks on a “solution” they have no clue will make a difference.
Personal choices will only go so far but mega-decisions driven by an almost-martial law attitude will start moving the Northern people towards the 60 to 70 to 80 percent carbon reductions needed to help our children survive.
by John McCormick
[Response: It’s because of the capital life issues you raise that it’s so important to get moving on putting the right market signals in place right now. Putting strong market incentives in place now will assure that emissions will start to go down in the next 20 years as capital assets are retired and replaced. It would have been better to have started this 20 years ago, but better late than never. –raypierre]
30 May 2006 at 6:54 PM
Re #47 Raypierre is of course right, that we are currently making big infrastructure changes, in the US and elsewhere. A house or building from 2010 will stand a long time, a car from 2012 will run for a long time, so we want them to be as energy efficient as possible.
That said, I suspect the typical American could reduce energy use some 10% fairly easily. During the California electric crisis, we cut electricity use 10%, and those interviewed for TV news said, I didn’t really do anything, just turn off the light when I left the room and turned off my computer when I wasn’t using it and … Perhaps carpooling or taking public transit once or twice a week, or taking the train or bus for vacation rather than the plane, and living a little more consciously in the house. Then the policy people and the technology people could work a little less feverishly to find solutions (though reducing carbon emissions 60% or more will still be hard).
30 May 2006 at 8:20 PM
RE #48
Karen, power control areas are 133 electric grid rings that connect regional electric power to regional demand across the nation. They are connected one to another and are the means to avoid a widescale blackout if a plant or transmission line goes down. Perhaps you know this but not many people have any idea how fragile is the US electric grid now.
Looking to a possible near-future crash program to reduce US CO2 emissions, power stations will be primary targets. Of the 1,000+ gigawatts of generating capacity, 60 percent are coal, oil,gas-fired and emitted, in 2004, 2.3 billion tons of CO2, or, 32 percent of US 7.12 billion tons.
Now, big infrastrcuture changes come into play. The top 14 power control areas, in terms of CO2 emissions, emitted about one billion tons of CO2 from their total 212 Gigawatts of capacity. They are all within a 300 mile radius of Louisville. Bottom line: 20 percent of US generators supply electricity to about 100 million customers and deliver 14 percent of US CO2 emissions to the earth’s atmosphere.
I say this as an avowed environmental activist with 30 years of lobbying for the coal strip mine reclamation law, clean air act and acid rain control and against utility deregulation.
RealClimate may not be a suitable page to discuss engineering challenges but we do have to pay some attention to those pesky numbers behind all of our hopes that we can somehow make the problem of climate change become more manageable by cutting 60 or 80 percent of our carbon use.
I too believe we can shave 10 percent off our individual energy use. That is a down payment on the more than $200 billion in infrastructre replacement the fractured and recalcitrant electric utility industry faces.
31 May 2006 at 9:38 AM
Re #27 (comment):
Raypierre, I have purchased (again…) the two articles in GRL to know the details of what was done. For the Torn and Harte paper, which used Vostok data, it is indeed clear that the difference between straight-forward local temperatures (derived from dD) and SH temperatures (derived from corrected dD) over 360,000 years is quite large.
This gives 9.1 ppmv/K for local Vostok temperatures (over the full 420,000 years, I calculated 8.1 ppmv/K), against 14.6 ppmv/K for the SH. For the LGM-Holocene transition, the (probably SH) slope is 17 ppmv/K.
But what happened in the NH? That is the important question. For what I have read in the past, the NH has much larger temperature swings between glacials and interglacials, due to more land, which means more ice building during ice ages and higher temperatures in interglacials. But higher NH temperature variations implicate higher global temperature variations and a lower response of CO2, as these are globally known (within the error margins of the ice cores…).
I didn’t find NH data which corresponds to the full Vostok time record, but the Greenland ice core data span the last glacial, including the LGM-Holocene transition. From the Greenland ice core data, one can derive a local temperature change of ~20 K between the LGM and the Holocene (with an extra peak just before the Younger Dryas), derived from d18O in ice. The corresponding NH (or global?) temperature according to the univ. of Leeds, item 7.5, might be around 10 K between LGM and Holocene. Global temperature shifts then would have been around 8-9 K (with the corrected SH temperature swing and assuming the “Leeds factor” as NH temperature). The change in CO2 levels in the same period is ~80 ppmv, that gives a slope of ~10 ppmv/K. A little more than I derived from the full Vostok (local) temperatures, but less than what is calculated by Torn and Harte.
If we assume that the 10 ppmv/K is right, then the IPCC model range would be 1.58-5.3 K for 2xCO2. The lower end still seems benign, the middle range (3->3.3 K) still critical and the higher range still a disaster, with or without CO2 feedback…
I haven’t checked the Scheffer ea. data yet (based on MWP-LIA changes), and rapid changes due to ENSO events may be of interest too.
31 May 2006 at 11:15 AM
Re 49, 48 & 47. “Dr. Hansen isn’t running for office. But Mr. Gore might be, and even if he isn’t, he hopes to promote global warming as a political issue. And if he wants to do that, he and those on his side will have to learn to call liars what they are.” Washington Post.
Re 49, 48 & 47. Shaving 10% of individual energy use will make no difference what so ever. Here in Europe every man women and child uses twice their share of the world’s energy. Reducing that by 10% would still leave we Europeans using 80% more than is fair. In the United Sates the figure is 5 times their share and reducing that by 10% would leave each American with 350% more than they are entiled to.
Since Kyoto was first proposed, the UK has stabilised its total CO2 emissions at around 600 million tons per annum. Meanwhile the US has increased its emissions by around 700 million tons. In other words, even if we in Britain had stopped burning any fossil fuels, global greenhouse gas emissions would have increased because of the US!
The good news is that if the US did halve its energy consumption then the standard of living in the US would still be above that of the UK, which is perfectly adequate for a civilised society.
The bad news is that both the UK and the USA will have to go even further. However, it will be forced on them by soaring oil prices now that we have passed Peak Oil. However, we must have a global agreement to cut fossil fuel use, otherwise when we have used all that expensive oil we will be roasting in a hell of our own making.
31 May 2006 at 1:57 PM
Here’s a source I hope the RC contributors or Coby for the ‘ill-considered’ list will check. It may be one of the places some of the odd and unsupported ideas come from — for example the claim that CO2 is already absorbing all the infrared it can. This is all footnoted to early 1990s sources on the site.
http://brneurosci.org/co2.html
31 May 2006 at 2:57 PM
To those who argue we cannot make quick emissions cuts, for example #47:
> 3.)there is no way, no way at all, to “quickly cut carbon emissions in half or more”. That regrettable fact deserves some attention when contributors wing all kinds of carbon-cutting suggestions without trying to imagine and help us see how a credit-strapped America will respond or - even how impractical it might be to plant trees without having, in place, a means to water them.
Of course there is a way - there are many ways. (I do agree with Mr. McCormick’s contention that the US debt will be a very major problem, because it will severely limit the federal government’s ability to drive or finance change.) It’s just that we don’t like any of them, because they change the current economic structure. Taxes could go way up on GHG-producing products, auto fuel efficiency could be mandated at a very high level, new houses could be net contributors to the grid, etc. Americans are unwilling to consider these options because they are “left-wing,” “socialist,” or in some other way are thought to inhibit individualism. But there are lots of ways we could immediately and drastically reduce our emissions. Or, we could wait for climate change to reduce our emissions by reducing our numbers. Pay now, or pay later. Maybe with your children’s lives.
1 June 2006 at 10:29 AM
Re #51 - I don’t see how you define what is a “fair share” of the world’s energy. Are you referring to average individual energy consumption? You then remark on how Europeans and Americans use more than their “fair share” - meaning others use less, and if all people used their “fair share” we would still be at the same level of energy use, right? I don’t understand this at all. Also, it appears you define an “adequate” standard of living for a civilized society as that of the UK. Why is this? Could you give us some insight into the calculus you are using?
1 June 2006 at 11:32 AM
Re #54 The figures I quoted were what I remembered from a BBC broadcast, so they may be inaccurate or garbled. If you go to Fig 5 on page 4 of this PDF file from a WWF site, you will see that Western Europe’s ecological footprint is five times that which is sustainable, and North America’s is nine times. http://assets.panda.org/downloads/asialpr2005.pdf . It seems that the average foot print is two global hectares, so as you point out even if Britain and the US restricted themselves to the average then the world would still be consuming at twice the sustainable rate. OTOH if both N. America and W. Europe restriced themaselves to the current average, there would be a huge reduction in the resulting average consumption.
The main point is that NA and WE consumption is unsustainable and it will have to be curbed by governments, otherwise it will be enforced on us by India and China grabbing thier share. How can you stop them in a free market?
As far as the UK having an adequate standard of living, in fact it is now too high. A recent survey revealed that compared with 50 years ago when 80% of people were happy, the figure is now 30%. It seems clear to me that we are now too rich for our own good.
1 June 2006 at 11:49 AM
At what point do we consider geoengineering as a response to abate global warming? I am specifically thinking of placing screens in space to regulate the amount of sunlight reaching the planet and/or disbursing aerosols above the troposphere to reflect away sunlight. Moreover, what are the risks to the biosphere from such schemes? I would greatly appreciate it if you could direct me to the literature on geoengineering and climate change.
1 June 2006 at 11:56 AM
>geoengineering
Maybe a big cloud of coal dust launched into space (wry grin). That’d show those photovoltaic people, cut their efficiency ….
1 June 2006 at 12:15 PM
Remember natural variation happens. Imagine trying to undo a big cloud of dust in space blocking sunlight, or a big cloud of sulfates in the stratosphere, if the sun happened to become a bit less bright afterwards.
The good thing about fossil carbon is it could be used in a way intelligently designed — not so much as to push the climate into warming, and enough to avoid slipping into cooling.
Apparently we did that well until about the 1600s.
1 June 2006 at 2:20 PM
Geoengineering is not the answer. Why geoengineering won’t work:
1. Governments, corporations, and individuals will create what they want, not necessarily what the planet needs, just as occurs now. Planet-scale geoengineering involves worldwide cooperation and agreement - we can’t even agree now that global warming is a threat, never mind agreeing to something as minor as Kyoto, never mind agreeing to governmental environmental control.
2. When you don’t know all the complexities of your life support system, it is foolish to experiment with it. I doubt we will ever know enough to be able to accurately control our environment (though we may soon be forced to try) because it is an evolving system, and because the complexity of the earth’s systems is truly staggering.
3. Planet-scale geoengineering is completely out of harmony with the natural world - it makes us God/gods. It assumes that we have a right to live at any cost, but no other species unless it suits us. This is a common developed-world/Judeo-Christian belief, and it is one reason we are in such trouble now. We currently have the creative and destructive powers of minor gods, but not the wisdom to know how to use those powers.
1 June 2006 at 2:54 PM
Geoengineering may be in the future, as a necessary evil. I agree with Brian’s points above, but I would say this:
Geoengineering could work, we are resourceful and clever creatures. The problem is it would take a few planets and a few multi-decade trials before we would get it right. Imagine the waste disposal problem, getting rid of the many spoiled planets created in the learning process…
I can’t help smirking a bit at the irony involved. Surely the geoengineering solutions would be tested out on all those wonky computer models, right? This is what the sceptics think is the prudent course, ignore the model warnings but then design and execute massive planet wide experiments based on same.
1 June 2006 at 3:19 PM
“Fix Venus and Mars First” should be our approach.
Sunshade between Venus and the Sun; mirror on the far side of Mars, at the Lagrange points, eh?
2 June 2006 at 9:37 PM
George wrote in comment #56: “At what point do we consider geoengineering as a response to abate global warming? I am specifically thinking of placing screens in space to regulate the amount of sunlight reaching the planet and/or disbursing aerosols above the troposphere to reflect away sunlight. Moreover, what are the risks to the biosphere from such schemes?”
How would you like to take conscious control of your liver, your kidneys, your intestines, your lungs, your lymphatic system, etc, and direct their functioning at the cellular level with your conscious mind? And once you do so, you never get to stop — if you don’t consciously direct them and coordinate them to perform their biological functions at every moment, they’ll simply stop, and if you make an error in your instructions to them, they will fail and you will die.
Do you think that “you” — your conscious mind — could do a better job of directing and coordinating the functions of these organs than “nature” does?
With that in mind, do you think that human “engineers” can do a better job of “running” the Earth’s climate, ecosystems, and the biosphere than “nature” does?
Someone once said of George W. Bush that “he was born on third base and thinks he hit a triple”.
Sometimes, something like that seems to me to apply to the human species. We were “born” into a rich, diverse, wonderful living Earth, and have been enjoying the vast bounty that it freely bestows upon us for thousands of years, and we have come to think that we are “gods” and we can take over and run the whole show better than billions of years of evolution have made the whole show quite capable of “running” itself without our “help”.
What hubris cometh before a fall!
3 June 2006 at 11:43 AM
Re #60 (”I can’t help smirking a bit at the irony involved. Surely the geoengineering solutions would be tested out on all those wonky computer models, right? This is what the sceptics think is the prudent course, ignore the model warnings but then design and execute massive planet wide experiments based on same.”):
What makes it even more ironic to me is that it seems like you have to know what is going on with the climate due to greenhouse gases to way higher precision in order to do some sort of geo-engineering to counteract act it than you do to counteract it by simply reducing or sequestering greenhouse gas emissions. (And, of course, then in addition, you have to know to high accuracy the effect that your geo-engineering solution will have…and how these effects will interact.)
Another irony is that many of the people throwing out these ideas are of the libertarian or conservative bent who complain about the evil’s of government intervention and regulation, the U.N., and such. However, their proposed solution seems to be one that can only work on a big government scale with massive amounts of international cooperation. By contrast, while approaches like Kyoto do involve international agreements and government action, they can be (and are being) implemented in market-based ways such as through emissions trading so that they are much more flexible and market-oriented approaches to finding solutions.
3 June 2006 at 5:40 PM
Little of what has been said here so far speaks to the viability of geoengineering solutions to the potential of run-away global warming. It is should also be stressed that we have already altered the biosphere through excessive carbon dioxide emissions. Geoengineering could be a rational means to stablize the environment. In the long run, I agree humans must institute appropriate regulations of its changes to the planet.
5 June 2006 at 10:27 AM
Thanx for this entry on positive feedbacks (I’ve been away from the net for a few weeks). I understand that scientists can only work with stuff they can work with (quantify, etc), which doesn’t mean other stuff isn’t happening or might not happen.
As people living on this planet, OTOH, we should follow the prudent route of thinking the worst could happen, and do whatever we can to stave it off at the personal level; at home, work, school, church; at the various levels of government from local to national to international. I can’t think of a better way for me to spend my spare time…..
I’m reading Cliffnotes Statistics (gearing up to teach statistics again after a decade), and came across this on p. 70: “A small, but important real-world difference may fail to reach significance in a statistical test. Conversely, a statistically significant finding may have no practical consequence.”
[Response: Welcome back. I was wondering why we hadn’t heard from you in a while. When looking at significance tests, make sure to keep an eye out for the distinction between those that assume a Gaussian underlying distribution and those that are independent of the underlying distribution (or rely on some a priori estimate of it). Also, one must keep in mind that if one looks at a hundred results, it’s a pretty sure bet that one of them will be significant at the 1% level. –raypierre]
5 June 2006 at 1:03 PM
RE: #64, George mentions a “potential run-away global warming”. It is more than a potential if we continue to “engineer” the planet’s atmosphere. That said, correcting our folly will never (time, money and confidence level are not there) include a geoengineering solution.
We must get this thread back onto the reality track
7 June 2006 at 11:58 AM
re #52 by Hank Roberts
I don’t understand your dismissing T.J. Nelson out of hand. Because he had some cited references from ancient 1992? Is the science of Beer’s Law, e.g., now outdated? Is it “odd” just now, or was it always odd?? Actually, while I don’t have the bona fides to credibly assess, I found his article extremely learned, intuitively believable, and devoid of snide and strident comments. The latter, btw, while cute, unfortunately detract from what otherwise what might be valid science.
[Response: A lot of rubbish is written in a way that seems learned. The problem isn’t that science has changed, but that a lot of the material on the web site mentioned in #52 is based on a fundamental misunderstanding of basic physics. For example, it’s not Beer’s law that is at issue but that the greenhouse effect depends on how much radiation gets out the top of the atmosphere for a given surface temperature, and that relies not on the saturated part of the CO2 band but the unsaturated part in the wings. The reference to the old “1990’s” literature, I think, was not meant to imply that the fundamental physics has changed, but that the site refers to “old” skeptics arguments that have for the most part fallen out of fashion. Skeptics keep recycling lies and misleading statements long after they’ve been debunked, but even these arguments wear out after a while, so the skeptics have to move on to new and better ways of misleading the public. –raypierre]
14 June 2006 at 7:29 PM
Maybe i didn’t understand the rules? I didn’t want to discuss economic impacts, etc. but it still apears we have an elephant in the room that isn’t being considered in any of the articles here or wikipedia.
My concern is we appear to be releasing between 1% (absolute best case) to 3-5% of solar influx in hydrocarbon and nuclear heat sources, (at the moment, growing steeply). Since it appears that orbital variations can account for about 6.8% solar variation,
(http://en.wikipedia.org/wiki/Milankovitch_cycles ) aren’t we talking about a significant challenge to Gaia?
(and everybody else that lives on this rock?)
Wasn’t trying to be a smartass, really think this should concern us?
Please be so kind as to educate me if my ‘facts’ err?
[Response: Your energy numbers are all wrong. A little more care in looking around on the web would have given you reliable numbers. These are easy numbers to get, so there’s no excuse for being so speculative. From Eric Weinstein’s Physics World, ( http://scienceworld.wolfram.com/physics/EnergyUsage.html ) the world power use is 1.28 x 10**13 Watts. Using the surface are of the Earth, this amounts to .025 Watts per square meter. Absorbed solar radiation is on the order of 250 Watts per square meter. The heating from energy use, averaged globally, is utterly insignificant compared to solar energy, and also unimportant compared to the indirect effect of industry via the CO2 radiative effect (about 4 W/m**2 for a doublling). As for your comment regarding Milankovic (also partly wrong in the numbers because you fail to distinguish seasonal local variations from global means) I don’t understand that at all. –raypierre]
14 June 2006 at 8:02 PM
I’m getting into this a bit late, and guess what, I haven’t read it all yet. At this level of conversation I’ll stick to asking “questions”.
Considering that H2O is a, or ultimately the, major GG, will we see a turnaround in runaway greenhouse (the point where natural forces dominate, and even total economic collapse won’t stop it) while there’s still more water to evaporate from the oceans? What natural forces will stop it before that point? Could this mean the end of all life on earth? Are we looking at why we’ve never been (provably) contacted by ETs, because they all followed similar paths and never made it much beyond us?
14 June 2006 at 11:34 PM
No Venus runaway possible here. There is a post on this site specifically about Venus, you should have a look.
15 June 2006 at 5:12 AM
Re 69 & 70 I don’t think Dan was proposing that Earth would turn into a Venus. They are very different. Venus is heated by carbon dioxide and kept cool by sulphur dioxide clouds. Earth is heated by water vapour and kept cool by water clouds. Thus Earth has a built in thermostat which prevents it heating above about 40C. The greater the greenhouse effect, the thicker the clouds that are produced. It is a negative feedback. That is why life has existed for 3,500,000,000 years
But it has only held on by the skin of its teeth on several occasions, and one of these is about to occur again, when the Arctic sea ice melts and Arctic temperatures jump by 12 C or more, just as they have in Svaldbard this year
[Response: I’m not aware of any built in thermostat mechanism that keeps the Earth below 40C. In fact, I’ve run plenty of simulations that get warmer than that, given enough CO2. What did you have in mind? Lindzen’s paper from the 1980’s is based on incorrect radiation, questionable models of convection and an unrealistic assumption about the vertical distribution of water vapor. –raypierre]
15 June 2006 at 5:36 AM
raypierrie,
Excuse me? You may be right, however, most of my numbers cames straight from this site, and ( http://en.wikipedia.org/wiki/Image:World_energy_consumption%2C_1970-2025%2C_EIA.png ). My estimate on insolation is not really speculative, as i used the solar constant (429 btu/sq.ft./hr.) shining on a normal disk of earth radius - 35% reflectance, (obtained from my Halliday & Resnicks), and must only be a quite high ballpark. The reality has to be (much?) lower. Your reference to ( http://scienceworld.wolfram.com/physics/EnergyUsage.html ) doesn’t seem to address this at all?
Still, it would be great if you’d show me where i err, as i really don’t see how seasonal variations, due to incidence angle, affects the integrated whole earth energy balance.
[Response: Ray is right. The solar energy incident on the Earth’s surface is the solar ‘constant’ (~1365 W/m2 - can we stick to metric units please?) divided by 4 (to account for the surface area of the disk vs. the sphere) and multiplied by the co-albedo (~0.7 - your 35% albedo number is slightly too high), giving around 240 W/m2. Total energy consumption is around 412 quadrillion Btu / yr = 412*1055*10^15/(5.1*10^14 area of the earth)/(3600*24*365 seconds in a year) = 0.027 W/m2 - 4 orders of magnitude smaller…. -gavin]
15 June 2006 at 6:49 AM
gavin,
I’m an engineer. We lack the large brains inherent in earth scientists, so we deal in complexity reductions. Let me attempt one here? We live in a large insulated box, that has an internal and external heat source? This box has achieved a thermal equilibrium of sorts. We’re at the moment increasing the r factor of the boxes insulation at the same time releasing 300-500 quadrillion btu’s/yr of extra internal heat source. Lets not quibble about magnitude, the fact that we’re messing with (thank you for the 4 orders of magnitude, some relief there!), a (moderated by feedback?) equilibrium still concerns me. (But less now, thanks!)
And i still don’t see any way seasonal variations effect an integrated whole earth balance.
15 June 2006 at 12:29 PM
Ray, surely you are aware of my scepticism of the models. It is the paleoclimatic record which shows that the global mean temperature has never risen above 40C. Moreover, if Lindzen were right with his “Iris theory” then the warmth of the Eemian could never have happened. My ideas are original, but not new. I have since discovered that they had already been proposed by
Ou http://www.earthinstitute.columbia.edu/generalInfo/CEImembers/about/Ou_JournalClimate.pdf ,
Wally Broecker (of course) http://www.columbia.edu/cu/record/archives/vol21/vol21_iss28/record2128.14.html , and G.C.Simpson [
(1928). “Some Studies in Terrestrial Radiation.” Memoirs of the Royal Meteorological Society 2(16): 69-95.,
(1928). “Further Studies in Terrestrial Radiation.” Memoirs of the Royal Meteorological Society 3(21): 1-26.]
[Response: I’m not aware of geological evidence that would preclude temperatures over 40C ever having occurred over the past 3.5 billion years. There’s no positive evidence for such warm temperatures, but it’s too strong a statement to say that it couldn’t happen. The prevailing theory for the generally moderate temperatures over the long term is the CO2 weathering thermostat, though there are suggestions that a methane regulation mechanism might have been dominant instead before the oxygenation of the atmosphere. That’s very different from saying the temperature wouldn’t exceed 40C no matter how high the CO2 or methane got. The Broecker press release you linked states only that he thought water vapor reductions could have accentuated LGM cooling (more precisely stated, that reductions in relative humidity could have lead to more cooling than the standard models). This could well be true, but not on the basis of Broecker’s evidence, which rested on a rather faulty interpretation of the Andean mountain glacier data (see my GRL paper on Huascaran isotopes). In any event, there’s no suggestion there of a thermostat at the high end. Ou’s paper rests on a highly questionable assumption regarding maximization of entropy production., and in the end is a kind of low-cloud thermostat mechanism; he does predict a limitation on maximum temperature, but neither the reasoning nor the predicted behavior of low clouds is borne out by any cloud-resolving dynamical simulations I’m aware of. None of these things have anything to do with the matters regarding radiative transfer fundamentals you used to bring up earlier in the history of RealClimate. I haven’t read these two old Simpson papers, which date back to the early days of radiative transfer when people were still sorting out some very basic points, but if they deal with the subject matter I think they do, it is discussed and disposed of in Goody and Yung’s book, under the heading of “Simpson’s Paradox.” –raypierre]
15 June 2006 at 5:18 PM
On another thread on this site, I asked for the data showing that we (humanity, civilization) have 10 years to make significant reductions in GHGs; after that, the degree of climate change will (sooner or later) be sufficient to end life and lifestyle as we know it. This thread seems a much more appropriate place to talk about that, as climate change inevitability is all about feedbacks and tipping points.
Hank Roberts pointed me to this article:
http://pubs.giss.nasa.gov/abstracts/submitted/Hansen_etal_1.html
which was helpful. From the article:
“The Earth’s climate system has great thermal inertia, yielding a climate response time of at least several decades for changes of atmosphere and surface climate forcing agents [Hansen et al., 1983].” p. 2
Is this still considered to be true? If so, then the Arctic is melting due to GHGs from decades ago. Uh oh. Or pollution (ozone, methane, and soot) as the authors suggest?
For the Arctic sea ice to melt, its temperature must rise above the freezing point of sea water. For that to happen, the ice must absorb energy to rise to the freezing point, then must absorb more energy to change state. If we weren’t measuring the ice temperature/heat content, we don’t know how long the time lag has been before the ice actually started melting. Has anyone been measuring the temperature of the sea ice? More from the article:
“Satellite data indicate a rapid decline, ~9%/decade, in perennial Arctic sea ice since 1978 [Comiso, 2002], raising the question of whether the Arctic has reached a ‘tipping point’ leading inevitably to loss of all warm season sea ice [Lindsay and Zhang, 2005]. Indeed, some experts suggest that “…there seem to be few, if any, processes or feedbacks that are capable of altering the trajectory toward this “super interglacial” state - free of summer sea ice” [Overpeck et al., 2005].
“Could the Greenland ice sheet survive if the Arctic were ice-free in summer and fall? It has been argued that not only is ice sheet survival unlikely, but its disintegration would be a wet process that can proceed rapidly [Hansen, 2004, 2005]. Thus an ice-free Arctic Ocean may have implications for global sea level, as well as the regional environment, making Arctic climate change centrally relevant todefinition [sic] of dangerous human interference.” p. 24-25
“We suggest that the conclusion that a ‘tipping point’ has been passed, such that it is not possible to avoid a warm-season ice-free Arctic, with all that might entail for regional climate and the Greenland ice sheet, is not warranted yet. Better information is needed on the present magnitude of all anthropogenic forcings and on the potential for their reduction. If CO2 growth is kept close to that of the alternative scenario, and if strong efforts are made to reduce positive non-CO2 forcings, it may be possible to minimize further Arctic climate change.” p. 25
It seems that some experts think a tipping point has already been passed for the Arctic, and therefore, Greenland, while the authors of this paper do not. Further, they feel this tipping point can be avoided if strenuous action is taken immediately (see the last sentence of the quote). However, they make no claims of having scientific evidence to ‘guarantee’ this. From another article (sorry, I do not have the original reference):
http://www.peopleandtheplanet.ca/
“In early 2004, a surprising course [sic] began to publicize the risk of one such event, the U.S. Department of Defence, the Pentagon, released to Fortune magazine its analysis of the security implications of “a plausible scenario for abrupt climate change.”
“It suggested that it was plausible that the Gulf Stream could stall by 2010. This would be caused by rapidly melting polar ice changing the salinity of the ocean. The ice is fresh water and its release would push down on the more saline currents, slowing and potentially stopping the vast ocean conveyor belt of currents. If the Gulf Stream were to stall, the Pentagon study anticipated widespread social and institutional collapse as droughts led to collapses in food production, displaced environmental refugees pressed on other borders for resources, soil erosion increased and wind speeds across Texas picked up … The Pentagon concluded that the risks of climate change were more significant than the risk of terrorism.
“To avoid the “tipping point” described above, we need reductions of [GHGs of] 80% by 2050, of 30% by 2020.”
I don’t understand at all how reducing GHGs by 2020 and 2050 will avoid a tipping point that will occur in 2010? This scenario was described as “plausible,” and 2010 is only four years away; even if it’s not 2010, but 2020, surely there are enough GHGs currently in the atmosphere to accomplish this?
Thanks for your patience…and let no one construe that passing tipping points is an excuse for doing nothing.
[Response: The “tipping points” refererred to above are somewhat speculative but within the realm of possibility — though the “European ice age” response to a thermohaline shutdown begins to look somewhat less plausible as a consequence in light of recent thinking on the role of sea ice in past responses, though there may be other serious consequences of thermohaline shutdown. Remember, though, that if there are tipping points, nobody is sure precisely where the thresholds are, so reducing emissions at any time gives you a better chance of not having passed one. Moreover, it is highly likely that there are several thresholds in the climate — melting of Greenland, melting of the West Antarctic ice sheet, some major shift in El Nino (perhaps), desertification of the Amazon, clathrate release, carbon release from arctic soils, probably many more we haven’t thought of yet. Each of these would have a different threshold. The less far we go from the familiar climate range of the past two million years, the less likely we are to encounter something really bad. Thus, even if we couldn’t do better than stabilizing at 2xCo2, there are still a lot more impacts that will set in between 2xCO2 and 4xCO2, so it’s still worth the effort to stabilize at 2xCO2. I do hope we can do better than that. –raypierre]
15 June 2006 at 10:06 PM
“Re 69 & 70 (& 71) I don’t think Dan was proposing that Earth would turn into a Venus. They are very different. Venus is heated by carbon dioxide and kept cool by sulphur dioxide clouds.”
Yes, actually I was thinking of a “Venus syndrome”, and for the moment, still am. Has the negative feedback effect of H2O clouds been proven to happen? I’m thinking higher temperatures, probably throughout the atmosphere, would mean H2O would have to go to a higher altitude to condense to clouds, putting a thicker blanket between us and the drier air above, maybe meaning the percent of cloud cover would remain about the same. Also (and maybe part of the cause of the previous effect) condensation to clouds causes heating, just as evaporation causes cooling. I’ll accept your view as long as all this has been considered.
“That is why life has existed for 3,500,000,000 years”
But keep in mind that in about that span of time, the sun has grown hotter by about 25% (James Lovelock), so all bets are at least in doubt.
15 June 2006 at 11:39 PM
Dan, please see Lessons From Venus , which explains why the Venus syndrome can’t happen here.
[Response: At least not for a billion years or so. I should provide a clear disclaimer that the discussion Rasmus and I provided in the Venus article was based on clear-sky water vapor feedback. Nobody has brought clouds into the picture in a convincing way, and it’s a matter that badly needs to be rectified. It’s actually hard to rule out a runaway cloud-based greenhouse effect on Earth, because clouds are so optically thick in the infrared. I don’t think it’s at all likely, but whether it happens is a race between the cloud cooling and the cloud warming effect. The reason I say it’s hard to rule it out on first principles is that some of the parameter sets in the ClimatePrediction.net ensembles do seem to run away. These were just discarded for the most part, but they ought to be looked at so as to provide a better understanding of the physics involved in the runaway. (well, we don’t know whether it’s a real runaway, since the runs were stopped before equilibrium). As I said, I don’t think this is a likely scenario, and it’s probable that the runs with a “runaway” cloud feedback would fail to match 20th century temperatures. However, we’d learn something by finding out what was going on in those runs, and refining our picture of why we don’t expect real clouds to behave that way. On the other hand, given recent evidence of a very warm early Paleocene Arctic, I wouldn’t completely discount a surprise cloud warming effect we haven’t factored in. –raypierre]
16 June 2006 at 5:30 PM
I think geoengineering (e.g., increasing polar albedo by large-scale spraying of titanium dioxide, possibly on some kind of flotation device for the polar seas) merits research as a component of our response to climate change. Of course it should not become an excuse to continue unsustainable carbon emissions, nor an excuse to cut climate research (as some deniers would argue). But, at the same time, geoengineering should not fall victim to the idea that “we shouldn’t play God;” alas we already are playing God via our carbon emissions.
We should evaluate potential solutions primarily on their technical and economic merits. That doesn’t mean losing sight of Earth as our spiritual home, but it does mean not letting dogma become our primary guide.
16 June 2006 at 10:33 PM
Re: #78. Ron, I know from nothing about titanium or your idea (suggestion) to increase polar albedo by large scale spraying of titanium dioxide. You say it merits research as a component of our response to climate change.
Here is what I know of the Arctic ice: it is melting rapidly. Over the past 30 years the annual average sea-ice extent has decreased by about 8 percent, or nearly one million square kilometers.
Here is what I learned from a USGS 2005 report on Titanium Statistics and Information about the cost of titanium on the world market:
Price:
Because of a significant increase in demand, prices of titanium metal products rose considerably. The year end unit value of titanium sponge ranged from US$3.55 to US$6.44 per pound in 2004, a significant increase compared with that of 2003. The yearend price range for titanium scrap also reflected market conditions, increasing to between US$3.80 and US$4.00 per pound in 2004 from between US$1.50 and US$1.70 per pound in 2003.
So, titanium sponge ranged in 2004 from $7100 to $12,880 per ton and titanium scrap from $7600 to $8000 per ton. I wonder what it would cost to spread titanium dioxide on the Barrows airport runway?
16 June 2006 at 10:59 PM
Ray, thank you for your long response. I hadn’t guessed the cloud unknowns were of such importance to a potential runaway greenhouse effect. It helps that you mention the Arctic, where cloud warming is expected to outweigh cloud cooling. Now I’ve a question: Is Arctic cloud cover increasing?
17 June 2006 at 5:25 AM
I gather from Raypierre’s comments that the recent study on the Arctic 55mya gave some rather alarming results. Is there any chance of a blog-post about the study, the results and what the implications may be? That would be extremely helpful!
[Response: Writing an article on this is next on my queue. I’ve bumped it ahead of Part III of the circulations and warming post. Very, very interesting stuff. Those who want to get a peak at it should look for recent papers authored by “Brinkhuis” on Nature.com. –raypierre]
17 June 2006 at 8:04 AM
Ray,
Please allow me to expand on a few points I made in my previous short post #74 by responding to your response.
Lack of geological evidence for global mean temperatures ever exceeding 40C seems to me to be good grounds for assuming it to be true. Moreover, if temperatures above those levels had occurred in the past, then life as we know it would have been destroyed, as nearly happened during the PT mass extinction.
As you say, mechanisms associated with atmospheric CO2 are generally regarded as having controlled past climates, but I an arguing,