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Good news for the earth’s climate system?

Filed under: — group @ 6 February 2010

Guest Commentary by Jim Bouldin (UC Davis)

How much additional carbon dioxide will be released to, or removed from, the atmosphere, by the oceans and the biosphere in response to global warming over the next century? That is an important question, and David Frank and his Swiss coworkers at WSL have just published an interesting new approach to answering it. They empirically estimate the distribution of gamma, the temperature-induced carbon dioxide feedback to the climate system, given the current state of the knowledge of reconstructed temperature, and carbon dioxide concentration, over the last millennium. It is a macro-scale approach to constraining this parameter; it does not attempt to refine our knowledge about carbon dioxide flux pathways, rates or mechanisms. Regardless of general approach or specific results, I like studies like this. They bring together results from actually or potentially disparate data inputs and methods, which can be hard to keep track of, into a systematic framework. By organizing, they help to clarify, and for that there is much to be said.

Gamma has units in ppmv per ºC. It is thus the inverse of climate sensitivity, where CO2 is the forcing and T is the response. Carbon dioxide can, of course, act as both a forcing and a (relatively slow) feedback; slow at least when compared to faster feedbacks like water vapor and cloud changes. Estimates of the traditional climate sensitivity, e.g. Charney et al., (1979) are thus not affected by the study. Estimates of more broadly defined sensitivities that include slower feedbacks, (e.g. Lunt et al. (2010), Pagani et al. (2010)), could be however.

Existing estimates of gamma come primarily from analyses of coupled climate-carbon cycle (C4) models (analyzed in Friedlingstein et al., 2006), and a small number of empirical studies. The latter are based on a limited set of assumptions regarding historic temperatures and appropriate methods, while the models display a wide range of sensitivities depending on assumptions inherent to each. Values of gamma are typically positive in these studies (i.e. increased T => increased CO2).

To estimate gamma, the authors use an experimental (“ensemble”) calibration approach, by analyzing the time courses of reconstructed Northern Hemisphere T estimates, and ice core CO2 levels, from 1050 to 1800, AD. This period represents a time when both high resolution T and CO2 estimates exist, and in which the confounding effects of other possible causes of CO2 fluxes are minimized, especially the massive anthropogenic input since 1800. That input could completely swamp the temperature signal; the authors’ choice is thus designed to maximize the likelihood of detecting the T signal on CO2. The T estimates are taken from the recalibration of nine proxy-based studies from the last decade, and the CO2 from 3 Antarctic ice cores. Northern Hemisphere T estimates are used because their proxy sample sizes (largely dendro-based) are far higher than in the Southern Hemisphere. However, the results are considered globally applicable, due to the very strong correlation between hemispheric and global T values in the instrumental record (their Figure S3, r = 0.96, HadCRUT basis), and also of ice core and global mean atmospheric CO2.

The authors systematically varied both the proxy T data sources and methodologicalvariables that influence gamma, and then examined the distribution of the nearly 230,000 resulting values. The varying data sources include the nine T reconstructions (Fig 1), while the varying methods include things like the statistical smoothing method, and the time intervals used to both calibrate the proxy T record against the instrumental record, and to estimate gamma.


Figure 1. The nine temperature reconstructions (a), and 3 ice core CO2 records (b), used in the study.

Some other variables were fixed, most notably the calibration method relating the proxy and instrumental temperatures (via equalization of the mean and variance for each, over the chosen calibration interval). The authors note that this approach is not only among the mathematically simplest, but also among the best at retaining the full variance (Lee et al, 2008), and hence the amplitude, of the historic T record. This is important, given the inherent uncertainty in obtaining a T signal, even with the above-mentioned considerations regarding the analysis period chosen. They chose the time lag, ranging up to +/- 80 years, which maximized the correlation between T and CO2. This was to account for the inherent uncertainty in the time scale, and even the direction of causation, of the various physical processes involved. They also estimated the results that would be produced from 10 C4 models analyzed by Friedlingstein (2006), over the same range of temperatures (but shorter time periods).

So what did they find?

In the highlighted result of the work, the authors estimate the mean and median of gamma to be 10.2 and 7.7 ppm/ºC respectively, but, as indicated by the difference in the two, with a long tail to the right (Fig. 2). The previous empirical estimates, by contrast, come in much higher–about 40 ppm/degree. The choice of the proxy reconstruction used, and the target time period analyzed, had the largest effect on the estimates. The estimates from the ten C4 models, were higher on average; it is about twice as likely that the empirical estimates fall in the model estimates? lower quartile as in the upper. Still, six of the ten models evaluated produced results very close to the empirical estimates, and the models’ range of estimates does not exclude those from the empirical methods.


Figure 2. Distribution of gamma. Red values are from 1050-1550, blue from 1550-1800.

Are these results cause for optimism regarding the future? Well the problem with knowing the future, to flip the famous Niels Bohr quote, is that it involves prediction.

The question is hard to answer. Empirically oriented studies are inherently limited in applicability to the range of conditions they evaluate. As most of the source reconstructions used in the study show, there is no time period between 1050 and 1800, including the medieval times, which equals the global temperature state we are now in; most of it is not even close. We are in a no-analogue state with respect to mechanistic, global-scale understanding of the inter-relationship of the carbon cycle and temperature, at least for the last two or three million years. And no-analogue states are generally not a real comfortable place to be, either scientifically or societally.

Still, based on these low estimates of gamma, the authors suggest that surprises over the next century may be unlikely. The estimates are supported by the fact that more than half of the C4-based (model) results were quite close (within a couple of ppm) to the median values obtained from the empirical analysis, although the authors clearly state that the shorter time periods that the models were originally run over makes apples to apples comparisons with the empirical results tenuous. Still, this result may be evidence that the carbon cycle component of these models have, individually or collectively, captured the essential physics and biology needed to make them useful for predictions into the multi-decadal future. Also, some pre-1800, temperature independent CO2 fluxes could have contributed to the observed CO2 variation in the ice cores, which would tend to exaggerate the empirically-estimated values. The authors did attempt to control for the effects of land use change, but noted that modeled land use estimates going back 1000 years are inherently uncertain. Choosing the time lag that maximizes the T to CO2 correlation could also bias the estimates high.

On the other hand, arguments could also be made that the estimates are low. Figure 2 shows that the authors also performed their empirical analyses within two sub-intervals (1050-1550, and 1550-1800). Not only did the mean and variance differ significantly between the two (mean/s.d. of 4.3/3.5 versus 16.1/12.5 respectively), but the R squared values of the many regressions were generally much higher in the late period than in the early (their Figure S6). Given that the proxy sample size for all temperature reconstructions generally drops fairly drastically over the past millennium, especially before their 1550 dividing line, it seems at least reasonably plausible that the estimates from the later interval are more realistic. The long tail–the possibility of much higher values of gamma–also comes mainly from the later time interval, so values of gamma from say 20 to 60 ppm/ºC (e.g. Cox and Jones, 2008) certainly cannot be excluded.

But this wrangling over likely values may well be somewhat moot, given the real world situation. Even if the mean estimates as high as say 20 ppm/ºC are more realistic, this feedback rate still does not compare to the rate of increase in CO2 resulting from fossil fuel burning, which at recent rates would exceed that amount in between one and two decades.

I found some other results of this study interesting. One such involved the analysis of time lags. The authors found that in 98.5% of their regressions, CO2 lagged temperature. There will undoubtedly be those who interpret this as evidence that CO2 cannot be a driver of temperature, a common misinterpretation of the ice core record. Rather, these results from the past millennium support the usual interpretation of the ice core record over the later Pleistocene, in which CO2 acts as a feedback to temperature changes initiated by orbital forcings (see e.g. the recent paper by Ganopolski and Roche (2009)).

The study also points up the need, once again, to further constrain the carbon cycle budget. The fact that a pre-1800 time period had to be used to try to detect a signal indicates that this type of analysis is not likely to be sensitive enough to figure out how, or even if, gamma is changing in the future. The only way around that problem is via tighter constraints on the various pools and fluxes of the carbon cycle, especially those related to the terrestrial component. There is much work to be done there.


References

Charney, J.G., et al. Carbon Dioxide and Climate: A Scientific Assessment. National Academy of Sciences, Washington, DC (1979).

Cox, P. & Jones, C. Climate change – illuminating the modern dance of climate and CO2. Science 321, 1642-1644 (2008).

Frank, D. C. et al. Ensemble reconstruction constraints on the global carbon cycle sensitivity to climate. Nature 463, 527-530 (2010).

Friedlingstein, P. et al. Climate-carbon cycle feedback analysis: results from the (CMIP)-M-4 model intercomparison. J. Clim. 19, 3337-3353 (2006).

Ganopolski, A, and D. M. Roche, On the nature of lead-lag relationships during glacial-interglacial climate transitions. Quaternary Science Reviews, 28, 3361-3378 (2009).

Lee, T., Zwiers, F. & Tsao, M. Evaluation of proxy-based millennial reconstruction methods. Clim. Dyn. 31, 263-281 (2008).

Lunt, D.J., A.M. Haywood, G.A. Schmidt, U. Salzmann, P.J. Valdes, and H.J. Dowsett. Earth system sensitivity inferred from Pliocene modeling and data. Nature Geosci., 3, 60-64 (2010).

Pagani, M, Z. Liu, J. LaRiviere, and A.C.Ravelo. High Earth-system climate sensitivity determined from Pliocene carbon dioxide concentrations. Nature Geosci., 3, 27-30


378 Responses to “Good news for the earth’s climate system?”

  1. 201
    Philippe Chantreau says:

    I don’t understand this business of “the Earth can’t go Venus-like.” Whether or not it’s true, what in the he#* is the point of comparing Earth to some inferno planet that can sustain no life whatsoever? Because we supposedly can’t warm to several hundred degrees, I’m supposed to believe it’s all good? What kind of idiocy is that?

    It’s like those “skeptics” who insist humans are too small and feeble to affect something as large as the climate and then compare the consequences of human activities to the largest cataclysms of Earth’ history, trying to make them look small in comparison. As if only major cataclysms were worth considering.

    Ah, that sweet freedom from any logical train of thought…
    Must be fun to be a skeptic.

  2. 202
    Septic Matthew says:

    196, Mac Crawford: Septic Matthew should go to post # 92 (Susan Kraemer): “I realize that the year
    3000 is outside the relevant policy time period, but as a matter of morbid interest
    – what sea level is expected by 3000?

    Thank you. I am sorry that I missed that. I have read “almost all” of the posts in order, but I missed those.

    199, Lynn Vincentnathan: Have you ever had the duty of defrosting your SunFrost refrigerator (the one that save 90% electricity)? I thought so.

    No (I live in a semi-arid climate, and my freezer has been frost-free for more than a decade, as long as I have lived here), but I don’t doubt your description. Even a septic sceptic can’t doubt everything.

  3. 203
    simon abingdon says:

    Ray #192 (Thanks for responding)

    You suggest I look up (1) Convergent infinite series and (2) Clausius-Clayperon.

    (1) Is it true that a doubling of the CO2 level in the atmosphere will produce a fixed rise in temperature? If so, the temperature rise resulting from an infinite succession of CO2 doublings appears to me not to be convergent. Do different considerations apply to water vapour?

    (2) Clausius-Clayperon is about phase changes and latent heat. As the sun comes up I often see the clouds disappearing as if by magic. No problem with the phase change to water vapour there. Are you saying that the GHG warming effect of more water vapour cannot happen in practice because of the energy needed to effect the phase change from clouds?

    #195 Brian Dodge

    At any time clouds cover more than 60% of the earth´s surface. The potential supply of water vapour as a result of heating is effectively inexhaustible. Local effects are trivially unimportant.

  4. 204
    Anand Rajan KD says:

    Mr. Machanick:
    155.Much as I dislike schadenfreude, the news that climate denier Chris Monckton has come down with heat stroke is a delicious irony. No doubt he thinks it’s a case of frostbite.

    Kind of like how Phil Jones felt that the death of the denier John Daly was cheering news, isn’t it? I totally agree.

    Mr. Reismann
    “In the previous thread, I asked you some questions. I did not see your answers though? Did I miss them? Or are you unable, or unwilling to answer them?”

    I am sorry for not answering to your earler ‘hunter gatherer’ post.

    Jim Bouldin:
    There are many posts on this thread – some of which you have responded to – suggesting that climatic ‘unknowns’ are at play which could negate the significance of the values for gamma as per this study. This is in fact, in your original post too. You say:

    “We are in a no-analogue state with respect to mechanistic, global-scale understanding of the inter-relationship of the carbon cycle and temperature…”

    This is problematic for several reasons:
    1) By this small backdoor you leave open in your main post and comments, various commenters claim that various factors have not been taken into account and therefore higher gamma values are possible after all. The paper does the exact opposite – it constrains gamma, given all the same uncertainties.

    [Response: No, you're misunderstanding. The study constrains gamma given the limitations of our knowledge of past millennial temperatures and CO2 concentrations. The point is that if the future conditions move outside the range of those in the past millennium, the estimates might not apply well. But the time it will take for that to become evident is uncertain, and the authors' estimates give us at least some idea of feedback rates until then, and a starting point from which to estimate future rates as other carbon cycle processes change.]

  5. 205
    Jerry Steffens says:

    186

    “any increase in (tropospheric) temperature (for whatever reason) will release water vapour (from cloud evaporation) leading to a further increase in temperature (GHG effect of water vapour).”

    Think about it for a second: When a cloud forms, water vapor turns into liquid; when the cloud evaporates, liquid turns into water vapor. There is no net change in the amount of water vapor.

  6. 206
    Edward Greisch says:

    199 Lynn Vincentnathan: Our sun cannot go supernova or even nova. It is too small. It will go red giant briefly in something like 5 billion years, then become a white dwarf [burned out cinder]. The Earth will go Venus some time before the sun reaches the red giant phase, perhaps in 2 ± 1 billion years.

    If we sane up and quit burning fossil fuels, we have at least a billion years to evacuate to other solar systems.

  7. 207
    simon abingdon says:

    #205 Jeffrey Stevens

    Sorry, I didn’t realize that water (liquid) behaves as a GHG like water vapour. Er, does it? (When temperatures rise, clouds decrease, water vapour increases. So more GHG effect. No?)

  8. 208
    simon abingdon says:

    #205 Jerry Steffens

    Apologies Jerry, got you now. (Couldn’t spell Clapeyron either).

  9. 209
    John E. Pearson says:

    203: Simon says: “the temperature rise resulting from an infinite succession of CO2 doublings appears to me not to be convergent.”

    Where you gonna get all that carbon?

  10. 210
    David B. Benson says:

    Barton Paul Levenson (185) — You can write that again!

    Lynn Vincentnathan (199) — The 5 m per century or thereabouts during Meltwater pulse 1A was surely sped up by the low sea stand with Antactic ice all the way out over the current continental shelf. Then a small rise in sea level gave a disproportionately large amount of melted ice, leading to more rise in sea level and so on. Maps of the Anarctic continental shelf clearly show the massive drainage channels off the current coast of West Antarctica.

    The current situation is constrained by the narrow exit channels in Greenland and West Antarctica (although for Pine Island and vicinity this maybe streches the meaning of narrow; check the scale on your map). So while I certainly expect an S-shaped curve for the forthcoming sea level rise, I don’t expect the maximum rate to be anything like 5 m per century. HOwever, glaciologists are always working on better ice melt models and I suggest reading what they have to say.

  11. 211
    David B. Benson says:

    Edward Greisch (206) — Less than that before Terra loses all its hydrogen and so dessicates; see a fairly recent issue of Scientific American.

    However, I have read that the average span for a mammalian species is a million years. As Homo Spaiens has been around for about 200,000 years we’ll do quite well to survive for another million. The point is that a million years ought to be a unit of political time; unfortunately it seems that (almost) everybody is more short-sighted with even IPCC only looking one ten-thousanth so far ahead.

  12. 212
    Baghdad Bob says:

    first time here. “Baghdad Bob” comes immediately to mind.

    EVERYTHING IS FINE!! EVERYTHING IS FINE!! THE TITANIC IS NOT SINKING!!! WE’RE DOING “SCIENCE”.

    HAHAHAHAHAAHAHAHAHAHAHAHA

    LMFAO! HAHAHAHA.

  13. 213
    simon abingdon says:

    #209 John E. Pearson

    “Where you gonna get all that carbon?” Search me. It was Ray (#195) who introduced infinite series. I just said that the earth’s supply of water vapour was inexhaustible, which to all intents and purposes it is.

    I just wanted to know why the potential global warming effects of H2O aren’t at least an order of magnitude more serious than those of CO2. Any idea why not?

  14. 214
    simon abingdon says:

    Correction. Ray #192.

  15. 215
    Completely Fed Up says:

    “201
    Philippe Chantreau says:
    13 February 2010 at 12:13 PM
    what in the he#* is the point of comparing Earth to some inferno planet that can sustain no life whatsoever? ”

    Because it shows that the common denialotrope of the saturated gassy argument is, well, a load of marsh gas.

    If it were true, Venus would be a lot cooler. After all, we’ve only got ~400ppm, whereas Venus as ~950,000ppm.

    This is quite a long way away from the denialists who claim that AGW is not going to be a problem because of Beers’ Law kicking in any moment now…

  16. 216
    David B. Benson says:

    simon abingdon (213) — Assuming nearly constant relaitive humidity (think about why that is highly likely), raising the air temperature a bit means it holds a bit more water. That’s all. So it is an amplification of the global warming provided by CO2, etc.

  17. 217
    Jacob Mack says:

    Warming oceans… well, much of that heat goes down to deep depths and water has such a high hear capacity, though over time we should see warmer oceans that is not what is being shown over the last few years. That the recent interannual cooling could not be explained is just recently being explained.

  18. 218
    simon abingdon says:

    #216 David B. Benson

    “Assuming nearly constant relative humidity (think about why that is highly likely)…” Thanks David, I’ll have to sleep on that one.

    However, if I have a closed box containing air and water vapour and I raise the temperature of the box and its contents, the RH will decrease, will it not? OK, if the box originally contained some liquid water, I can see that raising the temperature might cause some of the water to evaporate, but why would that have the exactly compensating effect of keeping the RH constant? Certainly once all the water has been evaporated any further temperature increase could only decrease the RH, wouldn’t you say?

    However, I do remember Hansen saying something about RH being a constant but I didn’t understand it then. So why, as a matter of intuition, doesn’t global warming imply decreasing global RH?

    David, I expect you’re lucky enough to be able to see this whole scenario at a glance. Me, I’m still at the level of struggling with why the square of the sum of the integers should be the sum of the cubes (without actually doing the algebra).

  19. 219

    Mangeclous (#189)–

    Interesting name, that.

    But in response to your question, the only near-real time global number I know of is on Dr. Roy Spencer’s site, which posts preliminary global lower-troposphere numbers daily. Here’s a URL:

    http://discover.itsc.uah.edu/amsutemps/

    Its a back door, kind of.

    Today’s value is from the 11th, and shows that the anomaly is .36 F. The troposphere has been very warm so far in 2010–warmer, I think, than any time except the height of the ’98 El Nino.

  20. 220
    Jim D says:

    Re: 218. The atmosphere is not a closed box. The ocean surface is an effectively infinite source of water vapor, so the atmospheric water vapor content is limited mostly by the atmospheric temperature.

  21. 221
    David B. Benson says:

    simon abingdon (218) — If the RH goes up, the water precipitates out. If the RH goes down, it doesn’t until there is more evaporation. Globally it seems to be the case that the RH is close to constant as is the precipitation, although total precipitation is expected to increase (think about that for a bit). Just where the precipitation occurs is a very important question for agriculture.

  22. 222
    Mangeclous says:

    #219 Kevin McKinney:

    Thanks a lot -btw, my nickname is borrowed from one of the fiction characters that most made me laugh.

    About the link you provide, I already knew it, but I’m unable to realize what the figures mean exactly. For example, if I take “near surface layer (ch4)” I would expect the result to refer to the layer where most of humans live everyday’s life, that is, near Earth’s surface. But the temperatures range from -17 to -16 degrees Celsius, which is not what one would expect as a global mean for that layer.

    I know absolute values for global temperature are not very meaningful and that what matters is the long-term trend, but 30 Celsius degrees of offset with the usual values stated for global mean temperature seems a bit too much difference and makes me think “near surface layer (ch4)” may not be as near the surface as I thought.

    So the URL you provide is exactly what I was looking for, just as long I understand how to “read” it. :)

    Thanks a lot for your attention and have a nice day,

  23. 223
    L. David Cooke says:

    RE: 221

    Hey David,

    In relation to precipitation, I suspect that RH is not the only factor… It is likely that chemistry, aerosol density and size also plays a part. However, the greatest impact may be related to the upper tropospheric temperature and insolation. Too warm near the surface and even with adiabatic cooling we end up at 250mb with super saturated air parcels, according to recent NASA Intex and British Canadian Arctic surveys.

    My recent experience of RH variability and precipitation ranges between 65 and 90%. So I do not know that RH as related to temperature as a constant would be a valid conclusion. Going further we also have the issue of insolation (due to Ozone depletion) or GHG’s delaying phase change.

    (As to regional precipitation increase/deficits there was a paper out of NASA about 2 years ago suggesting that it seems that in the Sub-Tropical regions that normal weather conditions associated with low pressure ridges seem to demonstrate extremes. Meaning warm, dry conditions to the SW and deluges in the NE quadrants of tropical low pressure (cyclonic) systems were observed in the Indian Ocean region during the Monsoon season.)

    Part of the confusion may be relate to the various states of matter, for instance, clouds (visible) versus water vapor (invisible). In essence, 1 cu meter of cumulus cloud should contain roughly 1 gm of water meaning it has an inherent 2500 calories less heat content due to its state. Where as water vapor would contain roughly 2500 calories more heat per meter per parcel of air. If I recall correctly that would also apply for ice crystals versus the visible water vapor in clouds…

    I suspect that the physical state of H2O has as much to do with RH as temperature. The issue is that the reverse is likely not true, temperature does not seem to be the only driver of the physical state of H2O, at least in the Earths atmosphere… The end result would seem to remove RH as much of an indication of temperature…, IMHO…

    Cheers!
    Dave Cooke

  24. 224
    Edward Greisch says:

    201 Philippe Chantreau: Those who are talking about Venus are NOT the denialists. They are the extreme AGWers.

    209 John E. Pearson: There is far more than enough carbon available, most of it undiscovered, and hopefully never discovered. Check “cosmic” abundances, meaning solar system abundances.

    211 David B. Benson: Thanks. Once we get off of Earth, we should be able to populate the galaxy within 64 Million years if we only hop to stars that enter the local Oort cloud. But we do a lot of speciation [branching] in that time.

    RealClimate: You are missing a huge public relations opportunity. See:
    http://climateprogress.org

    Vancouver, Canada just had the warmest January on record, forcing postponement of some Olympic events!!! Olympic officials are blaming it on El Nino, which is pure fiction. It is global warming. It rained on the snow they trucked in. So right now do a big article on AGW vs Olympics and put it in the big newspapers. My son lives in Vancouver, so I have independent confirmation of the hot January.

  25. 225
    Ian says:

    During an interview at the BBC on February 12 2010, Professor Jones from the CRU at the University of East Anglia was asked:

    “Do you agree that according to the global temperature record used by the IPCC, the rates of global warming from 1860-1880, 1910-1940 and 1975-1998 were identical?”

    In answer he gave the following figures for trends in global temperatures:

    Period Length Trend (oC per decade) Significant
    1860-1880 21 0.163 Yes
    1910-1940 31 0.15 Yes
    1975-1998 24 0.166 Yes
    1975-2009 35 0.161 Yes

    The differences in these trends were not statistically significantly different.

    He also noted that from 1995-2009 the trend was 0.12C /decade although this was not quite significant at the 95% level

    From these figures it seems that there have been warming trends pre the industrial revolution no different from that seen in the latter part of the 20th century and that since 1995 there has been a decrease of about 25% in global temperature despite an increasse of about 8% in C02 concentration.

    [Response: None of these data are "preindustrial"--Jim]

    These data don’t seem to unequivocally support the claims that anthropogenic CO2 is the major driver of post industrial revolution increases in global temperature and that unless CO2 levels are reduced the global temperature will increase with catastrophic consequences.

    Are the denialists correct to be sceptical?

    [Response: Skepticism itself is never the problem. Everyone should be skeptical to some degree. Denying evidence because of preconceptions or bias is the problem. The interview with Jones is being passed around among denialists as some sort of “proof” that he’s admitted defeat, or AGW is wrong, or something or other. The very question itself reveals a kind of ignorance of the significance of historical data.
    There have been many times in the past, far far earlier than these, when temperature rose at the rate we have seen over the past few decades. This is not evidence that AGW is somehow falsified. Please re-read that statement. The relevant question here is one of proper attribution of the cause(s) of the observed global warming over the last century+. And on that, the evidence is clear that greenhouse gases are, far and away, the most likely cause of this warming. The rationale for that is beyond what can be explained here in a few sentences, but the main point is: the fact that temperatures have changed rapidly in the past, for whatever reason, has little relevance to the physical attribution of recent changes, which is based on a very solid knowledge of the physics of the planetary system. Go the “start here” link of this site and start reading. Then read some more. Then some more. Then you will begin to understand that this is a topic that has a great deal of sophisticated evidence behind it, contrary to the simplistic explanations you will find in the media and on the internet. Hope that helps.–Jim

  26. 226
    Brian Dodge says:

    Lynn Vincentnathan — 13 February 2010 @ 11:21 AM said
    “For comparison each of Greenland and West Antarctica is estimated to be losing about 150 km^3 per year..”

    but according to “Changes in the Velocity Structure of the Greenland Ice Sheet”
    Eric Rignot and Pannir Kanagaratnam Science 17 February 2006: Vol. 311. no. 5763, pp. 986 – 990 DOI: 10.1126/science.1121381

    “Accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year.”

    Two points on the curve don’t allow determination of whether the 130km^3 increase is sigmoid, linear, or exponential growth, but I wouldn’t wager something I couldn’t afford to lose (like Miami, New Orleans, or the ports of Oakland & Seattle) on the outcome.

    simon abingdon — 13 February 2010 @ 1:31 PM
    “At any time clouds cover more than 60% of the earth´s surface. The potential supply of water vapour as a result of heating is effectively inexhaustible. Local effects are trivially unimportant.”
    My apologies for not answering you seriously.
    According to http://www-das.uwyo.edu/%7Egeerts/cwx/notes/chap08/moist_cloud.html, the theoretical amounts of vapor in a cloud varies from 0.1 t0 25 grams per cubic meter, and the droplet (water and ice) content varies from 1.2 to 7.7 grams/m^3, with high, cold base clouds having a larger portion of liquid to vapor but less total water content. Because of the effects of precipitation removing water and mixing with dry air, the observed droplet content ranges from 0.002 g/m^3 in cirrus clouds to a maximum of 1.5 g/m^3 in continental cumulonimbus. A large number of measurements shows that half of all stratiform clouds have a droplet content of less than 0.1 g/m^3. A 10km thick cloud would on average have only a kg or so of water per m^2, about the same as contained in the top mm of the ocean, which also cover about 60% of the earths surface.

  27. 227
    Leo G says:

    Edward Greisch

    {RealClimate: You are missing a huge public relations opportunity.}

    The only problem with this, is that last year we had a record cold spell of about 6 weeks. in Dec/Jan.

    You know the old saw, this is weather, not yet climate.

    By the by, just watched the woman’s mogul event from Cypress Mtn.
    In the rain and a bit foggy, the gold goes American, silver Canadian, Bronze American. Absoloutly the best moguls event I have seen so far!

    Jim, just wanted to tell you how much I appreciate your article, and replies. I understand a bit more this week then last, and am really enjoying this journey. Keep up the good work!

    [Response: Thanks ever so much Leo. You stay on this journey, because it is a beautiful and meaningful one! And life requires beauty and meaning, or it's nothing at all.--Jim]

  28. 228
    Andy says:

    Since we are all quoting our abode’s feet above sea level like it was our zodiac sign or cholesterol number: For those of you who may live nearby or otherwise have a burning desire to figure out this sea level rise stuff controversy; here’s an upcoming conference in Corpus Christi, Texas http://www.sealevelrise2010.org/
    Good town for beers and the weather is usually perfect in early March. BTW I’m a 16 (feet above MSL).

    Also, Dr. Eli at Rabbett Run found someone who translated Solomon’s paper into plain English. Actually plain German and then Eli brought it into the English language.

    http://rabett.blogspot.com/2010/02/low-lands.html

  29. 229
    Richard Steckis says:

    185
    Barton Paul Levenson says:
    13 February 2010 at 5:18 AM

    RS: [Miskolczi] has a point. AGW believers just hate it.

    “BPL: If you think there is any scientific merit at all to Miskolczi’s jackass paper, you are a scientific illiterate.”

    Miskolczi argues his point at http://miskolczi.webs.com/Answers_to_some_criticism.htm

    I would respect him and his theory well above your amateurish attempts to discredit him.

    [Response: But why? When there is an obvious nonsense in his derivation and the basic confusion of assuming a current observation must be an immutable fact, why can't you - as a proclaimed scientific thinker - see past your desire for him to be correct and just acknowledge that this isn't the magic bullet people have claimed? Do you in fact acknowledge that any of the anti-GW science that I would claim is purely crank nonsense, is indeed crank nonsense? Or does all of it have some merit? I guess what I'm asking is whether there is anything that even you consider nonsense? Take your pick - G&T, Khillyuk+Chilingar, 'the iron sun', Velikovsky, Beck etc. - gavin]

  30. 230
    Richard Steckis says:

    #181, Richard & “The earth cannot have a ‘Venus syndrome.’”

    “Now this is where we lay people diverge from the scientists — any scientist will tell you that we certainly will have a Venus syndrome (runaway warming) when the sun goes supernova.”

    We are about a billion years away from that so what is your point?

    “According to Hansen (who really knows his science well), the sun is slowly but surely becoming brighter over the eons”

    In geological terms an Eon is about a billion years. Again, what is your point? This has nothing to do with current warming.

    “AND you add in the fact that we are releasing CO2/CH4 into the atmosphere a lot faster than in past warming events”

    And the current warming event is no more different than other warming events in the holocene record in both temperature and rate of temperature increase.

    “AND you consider that Jim Hansen is a nice guy who doesn’t understand just how evil human nature is”

    Human nature is not inherently evil. Stop being an amateur philosopher.

  31. 231
    John E. Pearson says:

    224: Ed. there is a finite amount of carbon in the universe. The poster suggested otherwise.

    213: Simon sez: I just wanted to know why the potential global warming effects of H2O aren’t at least an order of magnitude more serious than those of CO2. Any idea why not?

    Dunno where you got your number from. I gather you just pulled it out of thin air? I’m no climate scientist and I suggest if you’re serious and not just trolling I suggest you start reading some of these books: http://www.amazon.com/Principles-Atmospheric-Physics-Chemistry-Richard/dp/0195093623 and Weart is excellent but he doesn’t do the math. http://www.aip.org/history/climate/co2.htm

    That being said, I’ll hazard a guess. I hope some of the RC guys will correct me if I get too far off base here. The upper atmosphere is cold and consequently very dry. There is very little water up there. The water mainly precipitates out lower down in the form of rain/snow/etc. CO2 doesn’t rain out. CO2 and water both have distinct “windows” (transparent regions in their respective absorption spectra) that allow infrared to escape. The windows don’t all overlap. Some of H2O’s windows are closed by CO2′s absorption in the upper atmosphere. Thus it warms. This stuff is pretty well understood by now as far as I can tell although it annoys me no end that I can’t calculate the temperature increase for a given increase in CO2. It’s hard and I don’t have the weeks or month that it would take to do even an idealized calculation, although I’m trying to read BPL’s (Barton Paul Levenson’s) stuff which is also pretty good. It’s a difficult subject. If you try to learn this stuff from blogs you’ll fail, especially if you try to learn it from denialist blogs which spout enormous amounts of nonsense, like the common denialist claim that absorption by H2O trumps absorption by CO2. Physics matters. You have to pay attention to it if you want to learn the subject.

  32. 232
    Richard Steckis says:

    224
    Edward Greisch says:
    13 February 2010 at 10:30 PM

    “Vancouver, Canada just had the warmest January on record, forcing postponement of some Olympic events!!! Olympic officials are blaming it on El Nino, which is pure fiction. It is global warming. It rained on the snow they trucked in.”

    Where is your evidence that it is global warming. YOU HAVE NONE.

    Of course it is El Nino driven.

  33. 233
    Richard Steckis says:

    For those who want to know why the “Venus Syndrome” cannot happen on earth. Just a preliminary. Do your own research for the rest.

    http://www.scientificamerican.com/article.cfm?id=twisted-sister-venus-earth

  34. 234
    Hank Roberts says:

    > Olympic officials are blaming it on El Nino, which is pure fiction.
    > It is global warming.

    Er, no. It is El Nino, as it was the last time.

    Same for the snowfall on the Atlantic seaboard, it is El Nino, as it was the last time. http://initforthegold.blogspot.com/2010/02/hill-of-snow.html

    It’s likely we’ll see more El Nino conditions with global warming.

    You can’t attribute any single weather event to any single cause. It’s more complicated than that.

  35. 235
    Pekka Kostamo says:

    #173 Risk estimate guidelines used in the Netherlands:

    “The commission initially set the acceptable risk for complete failure of every “dyke ring” in the country at 1 in 125,000 years.
    However the cost of building this level of protection was deemed too high, so the acceptable risk was set according to region as follows:

    * North and South Holland (excluding wieringermeer): 1 per 10,000 years
    * Other areas at risk from sea flooding: 1 per 4,000 years
    * Transition areas between high land and low land: 1 per 2,000 years”

    http://en.wikipedia.org/wiki/Delta_Works

    There is a recent program of improvements, costing abot 1 billion annually.

  36. 236
    Ian says:

    Thank’s Jim for your considered response. I don’t think the interview did in any way suggest Prof Jones didn’t believe in AGW or that it was all a big mistake. It is interesting that you comment on higher temperatures in the past but is there any data that gives information on previous global temperatures when CO2 levels were as high or higher than they are now? I

  37. 237
    Edward Greisch says:

    227 Leo G: Yes, I know the old saw. That doesn’t change the publicity value. Vancouver also had a record warm winter on 2006, per Climate Progress. If you are in Vancouver and that is where the record cold was last winter, notice that your variability has increased. As we said before, GW means Wilder weather. You can’t depend on the snow any more. The climate is now undependable, and undependability has publicity value as well. People need a climate that they can depend on.
    So make the article about what the olympic committee has to do to make sure that the snow is good for the winter olympics, now that we have AGW. Do the winter olympics have to be in farther from the equator or indoors?

  38. 238
    simon abingdon says:

    #220 Jim D “The ocean surface is an effectively infinite source of water vapor, so the atmospheric water vapor content is limited mostly by the atmospheric temperature.”

    Thanks Jim, you reinforce my point for me.

    So let me restate my original question (#186):

    Considering water vapour, any increase in (tropospheric) temperature (for whatever reason) will release water vapour (from cloud/ocean evaporation) leading to a further increase in temperature (GHG effect of water vapour). Since clouds/oceans are an effectively inexhaustible supply of fresh water vapour this effect should cause catastrophic run away. It doesn’t. Why not?

    [Response: Because it rains. - gavin]

  39. 239
    Edward Greisch says:

    225 Ian: I count the year 1750 as the start of the Industrial Revolution. It has to do with the invention of the steam engine.

  40. 240
    simon abingdon says:

    #221 David B. Benson “If the RH goes up, the water precipitates out.”

    Water doesn’t precipitate out until the RH reaches 100%, or does it?

    If it doesn’t, then as long as the water remains in the vapour phase (RH below 100%) any rise in temperature would enable an increase in Absolute Humidity without a phase change back to liquid (precipitation). This increase in AH should mean an increase in the GHG effect of the atmospheric water vapour, leading to increased global temperature, enabling a further increase in AH, leading to unstable runaway given the effectively inexhaustible availability of more water vapour.

    Since this effect is obviously not seen in practice, there must be something missing. What is it?

    Ray (#192) suggests there’s a convergent infinite series somewhere (where exactly?) or that the answer lies in phase change considerations (Clausius-Clapeyron) but I don’t yet see how.

    Perhaps if I knew enough physics I wouldn’t ask the question; maybe one of the residents could explain it in suitably simple terms for me.

  41. 241
    simon abingdon says:

    #226 Brian Dodge

    Thanks for the data. In the context of global warming I don’t have a feel for whether such figures are significant or not. In particular, can you draw a comparison for me between the warming effect of a cloud “sample” and its “equivalent” water vapour that would result from a rise in temperature?

  42. 242
    Jimbo says:

    OT
    I’d like some commentors’ views on this BBC interview with Professor Phil Jones of the Climate Research Unit (CRU).

    “He said he stood by the view that recent climate warming was most likely predominantly man-made.

    But he agreed that two periods in recent times had experienced similar warming. And he agreed that the debate had not been settled over whether the Medieval Warm Period was warmer than the current period.
    …..
    “I’m a scientist trying to measure temperature. If I registered that the climate has been cooling I’d say so. But it hasn’t until recently – and then barely at all. The trend is a warming trend.”"

  43. 243
    Jimbo says:

    Ooops! Forgot to give the source for the Jones interview:
    http://news.bbc.co.uk/2/hi/science/nature/8511701.stm

  44. 244
    Neil says:

    I love the “beauty and meaning stuff”. And on Velntine’s Day to boot. I think I’ll go start a coccolith ranch and power it with photovoltaics.

  45. 245
    kai says:

    @jim -225
    I agree with you that the fact that there were temperature rises similar of the recent one before, with a lot less CO2, does not mean that the current one is not CO2-linked. However, it shows that the attribution to CO2 by default (because we can not find something else) is much less convincing. For this central argument to still hold water, the models should be able to simulate all the previous rises without CO2, just from their other forcing. Do they? If not, AGW is dead because it means that there are unknown factor in the climate that are not included in the models, but that can cause a temperature increase equivalent to what is currently observed…

  46. 246
    Neil says:

    Figure S10 from the Frank Paper is beautiful and made me all warm and fuzzy:
    “Figure S10. Despite the ensemble calibration methods applied and the consistent instrumental target, the choice of a particular large-scale temperature reconstruction over another yields a wide variety in estimates of γ. In general all distributions have a very long upper tail, with largest γ obtained for Mann2008 and smallest γ for Frank2007. Some of the reconstructions tend to yield more closely spaced median estimates (colored dots) for the different time periods (e.g., MannJones2003) whereas
    others tend to display high sensitivity to the chosen time period (e.g., Mann2008). The bimodal distribution for the Frank2007 record is a result of the generally weaker correlation between the CO2 and temperature over the full 1050-1800 period – a characteristic which results from the early “exit” from warm Medieval conditions in comparison to the CO2 peak ~ 1200. Similar features are seen in Briffa2000 and Hegerl2007, for example.”

    doi: 10.1038/nature08769 SUPPLEMENTARY INFORMATION

    The “good news” for the rest of us is the paleo stuff is pretty much noise. [edit]

  47. 247
    Uli says:

    Re: Barton Paul Levenson(#88):
    I agree with L. David Cooke(#104) exept for reducing the number of zones. I find 10 degrees a good choice. Seasons are neccessary but more difficult to implement and less important then proper heat transfer.
    I think you should first increase the heat transfer between the bands so, that you get about 6 Petawatt polwards heat flow per hemisphere at 40 degrees latitude. You should get then Te>200K at B=9, and Ts<310K at B=1. You could post the updated version to compare.
    Im not sure about the meaning of most of the column titels, maybe you could explain it.

  48. 248
    Uli says:

    Re: Barton Paul Levenson(#88):
    I agree with L.David Cooke(#104) exept for reducing the number of zones. I find 10 degrees a good choice. Seasons are neccessary but more difficult to implement and less important then proper heat transfer.
    I think you should first increase the heat transfer between the bands so, that you get about 6 Petawatt polwards heat flow per hemisphere at 40 degrees latitude. You should get then Te>200K at B=9, and Ts<310K at B=1. You could post the updated version to compare.
    Im not sure about the meaning of most of the column titels, maybe you could explain it.

  49. 249
    Completely Fed Up says:

    “240
    simon abingdon says:
    14 February 2010 at 4:10 AM

    #221 David B. Benson “If the RH goes up, the water precipitates out.”

    Water doesn’t precipitate out until the RH reaches 100%, or does it?”

    It will precipitate out of an airmass that is on average about 60% RH.

  50. 250
    Completely Fed Up says:

    I haven’t noticed any of the whiners complaining about Baghdad Bob’s post.

    They were all “oh, you’re damaging ‘our’ cause with your rudeness”, but they’re nowhere to be found.

    Too there were others saying “both sides are being terrible”. Yet they are seriously absent too.

    Indicative of reporting bias hiding behind false balance?

    Hey, I’m not saying anything, I’m just asking the question.


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