Science stunner: “Clouds Appear to Be Big, Bad Player in Global Warming” — an amplifying feedback (sorry Lindzen and fellow deniers)

The best evidence is that the climate is now being driven by amplifying feedbacks (see Study: Water-vapor feedback is “strong and positive,” so we face “warming of several degrees Celsius”), most notably:

In spite of all evidence to the contrary, the deniers/delayers/inactivists, led by MIT’s Richard Lindzen, have argued that negative feedbacks dominate the climate system.  In particular, they have asserted that clouds are a negative feedback.  A major new study in Science from  “Observational and Model Evidence for Positive Low-Level Cloud Feedback” (subs. req’d) is thus a potentially huge — and worrisome — piece of research.

I’m in an all-day meeting, so I’m mainly going to reprint the study abstract, the accompanying Science news story, “Clouds Appear to Be Big, Bad Player in Global Warming” (subs. req’d), and the press release from the University of Miami’s Rosenstiel School of Marine and Atmospheric Sciences, who led the study (with the Scripps Institution of Oceanography, my old stomping ground snorkeling reef).

It is worth noting that the one climate model the researchers found was “particularly realistic” in modeling the cloud feedback, the Hadley Center’s HadGEM1, finds, “When carbon dioxide is doubled, the model warms the world by 4.4°C; the median of the models for a doubling is 3.1°C.”  Considering that we are headed toward more than a tripling of CO2 concentrations this century, that is very, very worrisome.

Figure 1

FIGURE: Leaky clouds. Decades-long records show that when sea surface temperature (SST) warms, cloud cover””especially from low clouds (bottom)””decreases (blues, top), letting in more sunlight.

Let’s start with the PR:

Strong Evidence That Cloud Changes May Exacerbate Global Warming

Virginia Key, Fla. “” The role of clouds in climate change has been a major question for decades. As the earth warms under increasing greenhouse gases, it is not known whether clouds will dissipate, letting in more of the sun’s heat energy and making the earth warm even faster, or whether cloud cover will increase, blocking the Sun’s rays and actually slowing down global warming.

In a study published in the July 24 issue of Science, researchers Amy Clement and Robert Burgman from the University of Miami’s Rosenstiel School of Marine and Atmospheric Science and Joel Norris from Scripps Institution of Oceanography at UC San Diego begin to unravel this mystery. Using observational data collected over the last 50 years and complex climate models, the team has established that low-level stratiform clouds appear to dissipate as the ocean warms, indicating that changes in these clouds may enhance the warming of the planet.

Because of inconsistencies in historical observations, trends in cloudiness have been difficult to identify. The team broke through this cloud conundrum by removing errors from cloud records and using multiple data sources for the northeast Pacific Ocean, one of the most well-studied areas of low-level stratiform clouds in the world. The result of their analysis was a surprising degree of agreement between two multi-decade datasets that were not only independent of each other, but that employed fundamentally different measurement methods. One set consisted of collected visual observations from ships over the last 50 years, and the other was based on data collected from weather satellites.

“The agreement we found between the surface-based observations and the satellite data was almost shocking,” said Clement, a professor of meteorology and physical oceanography at the University of Miami, and winner of the American Geophysical Union’s 2007 Macelwane Award for her groundbreaking work on climate change. “These are subtle changes that take place over decades. It is extremely encouraging that a satellite passing miles above the earth would document the same thing as sailors looking up at a cloudy sky from the deck of a ship.”

What was not so encouraging, however, was the fact that most of the state-of-the-art climate models from modeling centers around the world do not reproduce this cloud behavior. Only one, the Hadley Centre model from the U.K. Met Office, was able to reproduce the observations. “We have a long way to go in getting the models right, but the Hadley Centre model results can help point us in the right direction,” said co-author Burgman, a research scientist at the University of Miami.

Together, the observations and the Hadley Centre model results provide evidence that low-level stratiform clouds, which currently shield the earth from the sun’s radiation, may dissipate in warming climates, allowing the oceans to further heat up, which would then cause more cloud dissipation.

“This is somewhat of a vicious cycle potentially exacerbating global warming,” said Clement. “But these findings provide a new way of looking at clouds changes. This can help to improve the simulation of clouds in climate models, which will lead to more accurate projections of future climate changes. ”

One key finding in the study is that it is not the warming of the ocean alone that reduces cloudiness — a weakening of the trade winds also appears to play a critical role. All models predict a warming ocean, but if they don’t have the correct relationship between clouds and atmospheric circulation, they won’t produce a realistic cloud response.

“I am optimistic that there will be major progress in understanding global cloud changes during the next several years,” said Norris. “The representation of clouds in models is improving, and observational records are being reprocessed to remove spurious variability associated with satellite changes and other problems.”

Both Clement and Norris, who is a professor of atmospheric and climate science at Scripps, have received National Science Foundation Faculty Early Career Development awards for their work on climate change. The National Oceanic and Atmospheric Administration Climate Program Office also provided support for this research.

Here is the study abstract:

Feedbacks involving low-level clouds remain a primary cause of uncertainty in global climate model projections. This issue was addressed by examining changes in low-level clouds over the Northeast Pacific in observations and climate models. Decadal fluctuations were identified in multiple, independent cloud data sets, and changes in cloud cover appeared to be linked to changes in both local temperature structure and large-scale circulation. This observational analysis further indicated that clouds act as a positive feedback in this region on decadal time scales. The observed relationships between cloud cover and regional meteorological conditions provide a more complete way of testing the realism of the cloud simulation in current-generation climate models. The only model that passed this test simulated a reduction in cloud cover over much of the Pacific when greenhouse gases were increased, providing modeling evidence for a positive low-level cloud feedback.

Finally, here is the accompanying Science news story by Richard Kerr:

Clouds Appear to Be Big, Bad Player in Global Warming

Climate researchers have long viewed clouds’ reaction to greenhouse warming as the key to understanding the world’s climatic fate. As rising carbon dioxide strengthens the greenhouse, will some clouds thicken and spread, shading the planet and tempering the warming? Or will they thin and shrink, letting in more sunshine to amplify the warming? The first reliable analysis of cloud behavior over past decades suggests””but falls short of proving””that clouds are strongly amplifying the warming. If that’s true, then almost all climate models have got it wrong.

The new study “confirms with observations that low clouds are critical for the climate system’s response,” says climate modeler Gerald Meehl of the National Center for Atmospheric Research in Boulder, Colorado. But “it’s really a challenge for models” to simulate that response, he adds. If real-world cloud amplification works the way the study indicates, researchers say, global warming could be even worse than the typical model predicts.

Clouds have been a climate conundrum in part because no one has been keeping an eye on them the way the weatherman has been recording temperature for more than a century. On page 460, climate researcher Amy Clement of the University of Miami in Florida and colleagues consider the two best, long-term records of cloud behavior over a rectangle of ocean that nearly spans the subtropics between Hawaii and Mexico. Other researchers had compiled one of the records from eyeball estimates of cloud cover made by mariners who passed through the region from 1952 to 2006. The other record, which runs from 1984 to 2005, came from satellite measurements, which Clement and her colleagues adjusted to account for calibration shifts from one satellite to the next.   Figure 1  Leaky clouds. Decades-long records show that when sea surface temperature (SST) warms, cloud cover””especially from low clouds (bottom)””decreases (blues, top), letting in more sunlight.

Between them, the observations recorded the two major climate shifts that roiled the North Pacific during the periods they covered. In a warming episode that started around 1976, the ship-based data showed that cloud cover””especially low-altitude cloud layers””decreased in the study area as ocean temperatures rose and atmospheric pressure fell. One interpretation, the researchers say, is that the warming ocean was transferring heat to the overlying atmosphere, thinning out the low-lying clouds to let in more sunlight that further warmed the ocean. That’s a positive or amplifying feedback. During a cooling event in the late 1990s, both data sets recorded just the opposite changes””exactly what would happen if the same amplifying process were operating in reverse. “All of the elements of a positive feedback are there,” Clement says.

Even so, positive low-cloud feedback was only a supposition until the group looked at another sort of satellite measurement of the second natural climate shift. That showed that when decreasing cloud cover let the sun leak through, the additional solar heating was large enough to account for much of the ocean warming. A positive feedback operating in the decades-long climate shifts “is real,” Clement concludes. And other studies link cloud changes in the northeastern tropical Pacific to atmospheric changes across the Pacific.

But is such a feedback actually working to amplify global warming? To get some indication, Clement and her colleagues checked the archives of a study in which the international Coupled Model Intercomparison Project compared the results of 18 global climate models run under standardized conditions. Clement and her colleagues tested whether each model was properly simulating each element of the positive cloud feedback they had found in the northeastern Pacific.

When the results were in, only two models showed low clouds producing a positive feedback as observed. One of them stood out from the pack. The HadGEM1 model from the U.K. Met Office’s Hadley Center in Exeter produced patterns of warming and circulation changes during greenhouse warming that resembled those of all 18 models averaged together””the best guide available. The group also concluded that HadGEM1’s simulation of meteorological processes in the lowermost kilometer or two of the atmosphere””where the key low-lying clouds reside””is particularly realistic.

As it happens, the HadGEM1 model is among the most sensitive of the 18 models to added greenhouse gases. When carbon dioxide is doubled, the model warms the world by 4.4°C; the median of the models for a doubling is 3.1°C. That gap raises a red flag for Clement. “We tend to focus on the middle of the range of model projections and ignore the extremes,” she says. “I think it does suggest serious consideration should be given to the upper end of the range.”

Climate researchers agree that Clement and her colleagues may be on to something. “There’s been a gradual recognition that this rather boring type of [low-level] cloud is important in the climate system,” says climate researcher David Randall of Colorado State University, Fort Collins. “They make a good case that in [decadal] variability there is a positive feedback. The leap is that the same feedback would operate in global climate change.” The study tends to support an important role for marine low clouds in amplifying global warming, he says, but it doesn’t prove it.  One clear contribution of the study, Randall says, is to point the way toward more reliable climate models. The paper “is definitely a reasonable approach to deciding which models to pay the most attention to,” he says. In its previous international assessments, Randall notes, the Intergovernmental Panel on Climate Change assumed that all models are created equal. “I think we have to get away from that.”

The time to act was yesterday.


34 Responses to Science stunner: “Clouds Appear to Be Big, Bad Player in Global Warming” — an amplifying feedback (sorry Lindzen and fellow deniers)

  1. tidal says:

    Could we please catch a break somewhere? Anywhere?

  2. MarkB says:

    I hope the word “stunner” was meant to be sarcastic. It’s hardly a “stunner” that observations indicate a positive cloud feedback. It is a very important study, however, as direct observations have been fairly limited on the cloud response.

    [JR: It’s a stunner to deniers, assuming they care about peer-reviewed literature rather than their own echo chamber of anti-scientific speculation. But I still think it’s a big deal.]

  3. Adam Sacks says:

    Here’s a break:

    Proper management of degraded grasslands (roughly 10 billion acres on today’s planet) using the co-evolutionary grazer-grassland relationship, could, among many other benefits, sequester enough gigatons of atmospheric carbon to bring us back to pre-industrial levels over a period of ten to twenty years.

    The catch, as always, is public education (where the skeptics are winning) and political action (where the fossilists are winning). We could start by telling the truth about our greenhouse gas emissions: of course we need to reduce them to zero NOW, but their relevance is dwarfed by forces already in motion beyond our control.

    Whether returning to pre-industrial atmospheric carbon levels would disengage positive feedback loops seems to be unknown (has anyone even asked that question?), but restoring soils worldwide would be a good step in any case, for many many reasons.

  4. Will says:

    I wonder what the time-frame for this feedback is? Is there a threshold temperature, or do they expect there has already been reduced cloud cover?

  5. paulm says:

    Considering that we are headed toward more than a tripling of CO2 concentrations this century, that is very, very worrisome.

    Very very well put:)

  6. Alex J says:

    Wow, Adam, that would be one super system of grasslands if it can put away more than 15 additional gigatons of CO2/~4 gigatons carbon equivalent annually (at today’s emission and natural absorption rates). Every potential solution should be looked into, but I’ve come to the conclusion that a healthy dose of skepticism is warranted in the realm of the magic bullet.

  7. From Peru says:

    There are posted in the wattsupwiththat site (among with meaningless episodes of cool weather in Argentina and elsewhere) two articles in Geophysical Research Letters that seem to show quite the opposite thing about the Pacific Area. They are:

    1)”Influence of the Southern Oscillation on tropospheric temperature”: WUWT claims that this showed that most of warming since 1977 was caused by the numerous positive ENSO events. WUWT quotes from the article

    “The surge in global temperatures since 1977 can be attributed to a 1976 climate shift in the Pacific Ocean that made warming El Niño conditions more likely than they were over the previous 30 years and cooling La Niña conditions less likely”

    “We have shown that internal global climate-system variability accounts for at least 80% of the observed global climate variation over the past half-century.”

    2)”On the determination of climate feedbacks from ERBE data”( ERBE means “Earth Radiation Budget Experiment”): it analyses satellite data about radiative forcing over the tropics, and found a strong negative feedback in the shortwave radiation forcing not considered in climate models. They conclude that this negative feedback constrains climate sensitivity to C02 doubling from just 0,5ºC to 1,5ºC.

    These are peer-reviewed articles in a prestigious scientific magazine. It is not the usual stuff found in denialist sites. Maybe there is some quote-mining in the WUWT site, but the abstracts are fully shown.

    This two articles (specially the second) seem to point in the opposite direction than this one in Science.

    Can someone , please, check the full articles if you have a Geophysical Research Letters subscription, I don´t. I found the full text of the second in WUWT, but not the first.

    What’s going on here? What mess of data and interpretations there are about the tropics? Do you have any idea?

    [JR: The first is an “atrocious paper,” as RealClimate puts it, with a couple of debunking links here. The second is Lindzen, and thus has the presumption of being crap. It always astounds me that a serious journal like GRL publishes a piece by Lindzen that ignores the dozens of papers that utterly disagree with and/or conflict with and/or refute his conclusions. The literature, which is based on actual observations and the paleoclimate record, as well as models of the data and that record, constrains the lower end of the climate sensitivity (though not the upper end as much). The possibility that the climate sensitivity to CO2 doubling is under 2°C is quite, quite small, and, as Hansen and many others have demonstrated, that is in any case the sensitivity to fast feedbacks. The sensitivity of the climate to CO2 doubling over a time span of many decades is almost certainly considerably higher than 3°C, and possibly closer to 6°C. The publication of that article as written is really an embarrassment to GRL.]

  8. MarkB says:

    While I haven’t read published Lindzen paper, it seems likely he’s making the same mistakes described here:

    In short, Lindzen has been relying on data that has seen been discovered to be in error and has been corrected. Lindzen had not accounted for the correction. Additionally, the conclusion also makes assumptions regarding his pet Iris hypothesis.

    I’m more familiar with the “Southern Oscillation” paper and it is indeed pretty bad, but the comments made in public venues by one or more of the authors don’t exactly mesh with the paper. There seems to be an assumption that if someone publishes a paper, whatever they say that’s remoted related to it is an accurate reflection of what was published.

  9. Rabid Doomsayer says:

    Joe, do we still have ten years to turn things around? It would seem that the required timeframe is now somewhat shorter, and it was a year or so ago that you wrote that.

    [JR: You can’t really connect this to a timeframe like that. Guess I”ll have to blog on that.]

  10. Tom says:

    Please use the term positive feedback rather than amplifying feedback. “positive feedback” what all of my engineering courses called this and it’s the term you fill find in dictionaries and encyclopedias.

    [JR: I’m glad you studied engineering. I studied physics, where that term is also widely used. I am not writing for engineers or physicists, however,. “Positive feedback” is a confusing term for many since 1) it has a positive connotation for the general public and 2) it is not intrinsically precise. “Amplifying feedback” is crystal clear.]

    What this shows, more than anything else, is that the mathematical models for climate change are still fundamentally up in the air. If the impact of ocean temperature in cloud formation is not known, how could anyone have accurate predictors?

    JR: how has anyone “demonstrated” anything about temperature change to atmospheric CO2? That means that the models have some provability in them — that they have predictors that are correlate with the temperature trends we’ve actually seen in the last 30 years. Who has done that? If nobody has, I strongly recommend you avoid the use of that particular word.

    Which models out there predict the trend towards global cooling that we have actually measured over the past 10 years?

    [JR: Ahh, you’re been duped by the deniers and their long-debunked talking points. Why didn’t you say so in the first place!!!]

  11. TokyoTom says:

    Joe, perhaps you meant “worth noting” instead of “worth nothing”?

    [JR: Darn that voice dictation software! Good catch!]

  12. Lou Grinzo says:

    I remember a long time ago, possibly when I was a kid, how one of the “shocking” things that scientist wannabes would scare each other with was the fact that if the Earth were just a little further from the sun we’d all freeze, and if it were just a little closer we’d be cooking. (Paraphrasing, obviously.)

    I think we’re finding out, via all these feedback revelations, that the conditions needed to create the extremely human-friendly environment we’ve enjoyed for thousands of years might be even more precarious than we suspected. Pump too much CO2 into the atmosphere at a time when there’s 1.6 trillion tons of carbon in the permafrost, a nice ice cap on the North Pole, etc., and pretty soon you trigger a cascade of overlapping feedbacks that were primed and ready to rock.

    The feedback that still scares me spitless is the permafrost melt, but the others don’t exactly ease my mind.

  13. Brooks Bridges says:

    In a previous life I was a control system engineer and positive feedback was “bad”. I once watched a horrifying film of an airplane attempting to set a record for high speed at low altitude without a working stability augmentation system (because air plane’s response in this regime totally different from normal, augmentation was required). The wings curled right up at one point due to g forces caused by the pilot’s POSITIVE feedback amplifying the air plane’s natural tendencies rather than correcting them.

    I agree with JR that most people will not have this kind of picture of “positive feedback” to understand just how bad “positive” feedback is. Amplifying feedback, I think, is a very understandable term.

    You also seem to miss, perhaps deliberately, what the deniers also keep studiously ignoring: all errors found in the models so far (that I’m aware of) have invariably been errors that UNDERESTIMATE warming because they were not aware of various amplifying feedbacks.

    Why would you think finding such errors is an argument against trusting them? Concentrate on the fact that they keep finding new amplifying feedbacks and ask yourself what are the odds they will suddenly find a negative one that eliminates warming. You’re gambling our future on those odds.

  14. Chris Colose says:

    I would take great care in not overselling the results of this paper. The paper provides reasonable evidence that low-level cloud feedback is positive in the Northeast Pacific (only about 115° to 145°W, 15° to 25°N) on decadal timescales. Evaluating long-term information about trends in cloud cover is very dicey right now (see Amato Evan, Heidinger, and Vimont 2007 on ISCCP data for instance), and the paper only applies to a relatively small area of the globe. What’s more, many arguments for cloud feedback (either negative or positive) focus on high clouds which influence the OLR, while this paper focuses on low clouds which influence the albedo more than other kinds.

    So while independent lines of evidence may favor a positive cloud feedback (and certainly a sensitivity within the IPCC 2007 limits), this particular paper is not really a suitable reference for net positive cloud feedback on global and long-term timescales in a climate change situation, but rather is a good building block upon which further research needs to be conducted. Evaluating this cloud feedback from one model that is an outlier in this regard is not ideal either.

    As far as Lindzen, I’d prefer if general comments on that paper were reserved until it’s actually published. The comments made by Lindzen at Watts Up With That uses outdated data which I discuss in detail at my website (linked above by MarkB), however the pre-print of his new GRL article to be submitted uses the more up-to-date non scanner Edition 3 data, yet the results still do not match with the comparison done by Wong et al 2006, who analyze both net radiation and ocean heat storage between models and observations. I do not believe that Lindzen applied the rev1 corrections which reduce the OLR relative to Edition3 (see Table 1 in Wong et al.) and thus may bring Lindzen’s figure 1 closer to models time series. It doesn’t effect the net however. I’ll probably look at this in more detail and correspond with authors of ERBE data in the near future, but I do not believe his analysis is going to get far in demonstrating a negative feedback.


  15. dhogaza says:

    What this shows, more than anything else, is that the mathematical models for climate change are still fundamentally up in the air. If the impact of ocean temperature in cloud formation is not known, how could anyone have accurate predictors?

    “Not known” is not the same as being “unbounded”. Uncertainty regarding clouds is the primary reason why climate sensitivity to CO2 doubling is thought to lie with the *range* 2-4.5C, rather than in a more narrow range.

  16. Alex J says:

    Here’s another one being represented in the blogosphere as proof of the hopelessness of models:

    The study basically seems to affirm that the models don’t fully account for amplifying feedbacks, but of course it’s spun to suggest they could just as easily be badly wrong in our favor. And the author (whoever that might be) states that “If present rates of fossil-fuel consumption continue, the doubling of carbon dioxide from fossil fuels will occur sometime within the next century or two”. That seems like a bit of an odd, loose range, particularly given that even two of the IPCC scenarios have it exceeding 800 ppm by 2100. And that’s using those models that seem to be missing some feedback.

  17. Tom says:

    Our moderator notes: “I’m glad you studied engineering.”

    My interest is in people understanding the science behind the claims. To get clarity rather than smoke and fog.

    [JR: That is BS, of course, since you wrote above “Which models out there predict the trend towards global cooling that we have actually measured over the past 10 years?” Such an anti-scientific statement is all smoke and fog. Post elsewhere.]

  18. Tom says:


    “I agree with JR that most people will not have this kind of picture of “positive feedback” to understand just how bad “positive” feedback is. Amplifying feedback, I think, is a very understandable term.”

    Anyone who wants to understand feedback had better understand about both positive and negative feedback. Complex systems — like the weather — clearly have both. Thinking that one is “bad” and the other “good” provides a knee-jerk understanding to a complex system.


    [JR: Tiresome. Everyone else but you understands that positive feedbacks in the climate system are “bad” for the human race and indeed most of life on this planet — particularly given how many positive feedbacks there are and the rather alarming paleoclimate record. But that’s why you’re a denier. You’ve come to the wrong blog.]

  19. TomG says:

    Joe, by all means please continue using the term, “amplifying feedback.”
    We don’t need the word games that some people are playing.
    While most people associate the word positive with good, in climate change it means nothing but bad.

  20. Kaj Luukko says:

    Isn’t there a “chicken or egg” situation with this study? Witch one came first? Dissipation of the clouds OR increase in ocean temperature? What if dissipation of clouds caused the ocean to warm?

    Another thing: Warmer ocean means more evaporating sea water. Where does it go and what does it cause? More clouds and cooling somewhere else on the globe?

  21. David B. Benson says:

    Adam Sacks (3) — yes, removing excess CO2, methane and NOx will have the desired effect of restoring the climate to a more natural “balance”. The time scale is centennial.

  22. Alex J says:

    I suspect that Joe isn’t the only one concerned about connotation, although his concern is coming from a different part of the spectrum. But for Tom, how about “amplifying positive feedback”? Yes, a mouthful, but to the layman who doesn’t spend much time looking up scientific terms, it can help to be descriptive. A strengthening or intensification is the first thing that comes to mind when I see the word “amplifying”. And that’s exactly the effect discussed in this article. It’s as basic as that.

  23. Gail says:

    I am very worried about this. (um, terrified much, heart beating in panic?)

    Just today I noticed that the lotus leaves (too late to upload pix, will do tomorrow on the blog) are exhibiting the same dreaded signs of death – turning yellow in a bizarre pattern of shrinking along veins.

    Now, my lotus lives in a pond. So even though trees are all suffering from well-known symptoms of drought (whether or not that is actually the cause, certainly, it is warmer and drier), but obviously, the lotus in the pond isn’t and has never suffered from drought.

    The same can be said for trees and shrubs at nurseries, which presumably are watered or irrigated, and they also are showing signs of drought – yellowing, browning, dropping leaves.

    So, if it isn’t drought causing the drought-like symptoms, what is it?

    UV radiation, or the composition of the atmospheric gasses? Some other causative agent?

    Any of which is terrible if true, news, for growing crops for food.

  24. Tom says:

    “Joe, by all means please continue using the term, “amplifying feedback.” ”

    I couldn’t imagine Joe’s doing anything else. Since his agenda is providing a connotation, I’m not surprised he provides no bread crumbs on the Internet for people seeking to rationally understand this new way of saying “positive feedback”.


    [JR: Enough. How can anyone question my use of words who writes “his agenda is providing a connotation” — probably the most meaningless thing anyone has ever posted here. Anyway, this isn’t “new” — as 10 seconds on Google will show anyone. It was actually my editor at William Morrow three years ago who asked me to use a different phrase, for two reasons — one, the reason I said (some people have the wrong connotation) and second, because most people don’t even know what the phrase means anyway. I used “vicious cycle” for a while, but hen I saw another scientist use “amplifying feedback” and that was obviously a superior term. In any case, aside from the availability of Google, anyone who actually reads the post will see the term “positive feedback” used, so Tom the Denier’s conspiracy falls apart. You should look elsewhere to spread your misinformation and time-wasting comments.]

  25. AlexJ says:

    Tom: Attenuating feedback? In this case, I think that would be “good” from a human perspective. But I don’t think there’s any real science suggesting negative feedbacks will counter climate change, at least on human-friendly timescales. Particularly when the forcing factor is still ramping up.

    Now here’s hoping this doesn’t get stuck in moderation as my other comments seem to have.

  26. TomG says:

    Hello Vangel…I thought perhaps it might be you.

  27. Maybe you can clarify for me, and maybe others, why is NOT the ocean surface temperature the dominant factor.
    The higher the temperature, the greater the water vapor pressure and the larger the evaporation rate.
    Ocean warming should lead to more moisture in the air and more rain (and snow), is that true? Did I miss something?
    More moisture in the air, like CO2 gas, also traps more heat on the earth atmosphere.
    If rain, storms, typhoons, cyclones, tornadoes increase in frequency, the faster a higher temperature balance is reached.
    {This is not an universal view, at a lecture I heard a prediction of less rain, as Global Warming continues}.

    From this simple-minded view, I would expect smaller snowpacks, earlier snowmelts, faster snow and glacier runoff and greater damage from Global Warming, or, what some of you call “Positive Feedback”, whatever that means (3 degs in Eng. Tell no one. Thnx).

    [JR: This is all happening.]

  28. Omega Centauri says:

    Michael,evaporation and the ability of the atmosphere to hold water increase at the same rate. So the simple physics based assumption is that atmospheric humidity (humidity is percentage of the atmospheres ability to hold water vapor used up), and amount of cloud cover would be unchanged. Now, second order effects,such as a greater percentage of heat going into evaporation rather than direct heating might change things a bit, but that is where the professional meteorologists/climatologists need to be involved.

    I want to thank Chris @14.We shouldn’t get too carried away by these early results. They are only minor further cause to be concerned about potential feedbacks. I only read the sciencedaily abstract, but that claimed that the driving mechanism was change in atmospheric circulation, i.e. winds, that was responsible for the observed changes. The likelihood, that feedbacks in other parts of the ocean counteract this one should be considered to be reasonably high. There is enough worrying settled science out there, that we don’t need to cherrypick the preliminary studies.

  29. Chris Colose says:

    Actually, on a more technical note, evaporation goes up much less rapidly than the increase in saturation pressure of the atmosphere. The actual saturation vapor pressure goes up nearly exponentially with temperature, depending upon the conservation of relative humidity. As the climate warms, the amount of moisture in the atmosphere ( governed by the Clausius-Clapeyron equation), is expected to rise much faster than the total precipitation amount, which is governed by the surface heat budget through evaporation.


  30. J4zonian says:

    Alex j.

    Allan Yeoman has said that increasing soil organic matter just 1.6% on all arable land (8.5% of all land area) would sequester all of the industrial age’s CO2. The Marin Carbon Project, for one, is experimenting with grazing and human consuption of native perennial bunch grasses, and permaculture and organic farming and homesteading methods can contribute hugely to solutions to this and other ecological problems.

    Skepticism is good, but even if the math is quite a bit off it’s clear that dirt is one of the best tools to keep civilization going long enough for it to become something worth keeping. Organic agriculture ought to be included as a wedge or 2 at least. (which makes the current attacks on it in Congress even more counterproductive and amplifyingly stupid.) As with climate cahnge, more investigation should be done, certainly, but the inexactness of numbers shouldn’t prevent us from transforming agriculture and forestry as rapidly as possible.

  31. tired says:

    The study shows that, in a given region, there were few clouds at the same time that it was hot. It doesn’t provide proof that it was the hot weather which caused clouds to disappear. It could have been viceversa: the lack of clouds favored a hot weather. Correlation does not imply causation, but in this case it is not even clear the direction of the causation, if there is one.

  32. Hank Roberts says:

    Full text is posted on a blog, here:

    ‘tired’ can’t have read it, or wants ‘proof’ beyond what the observations describe.

  33. ChrisB says:

    The discussion of low-level cloud cover versus sea surface temperature doesn’t address the question of where the water vapor goes that must evaporate from the warmer water surface. Assuming the observations and models are correct–increased sea surface temperatures counterintuitively mean less cloud cover rather than more–what do you suppose happens to the water vapor that must evaporate into the atmosphere from the warmer water? It has to eventually precipitate back to Earth somewhere. Is this where the predictions of increased violent weather come from?

  34. “Is this where the predictions of increased violent weather come from?”

    (Hopefully if I bollocks this answer up to severely, someone smarter (or, at least, better educated on the subject) will step in and fix my mistakes.)

    The short answer is, “yes, with qualifications.” The qualifications make for a longer answer.

    The increased evaporation will make for increased precipitation … somewhere. This, by itself, will not make for an increase in the violence of the weather. Violence in a weather system will almost always be associated with wind. If the clouds are langorously dumping buckets of water on you, this might be quite disasterous but typically not what one would call “violent.”

    However, since global warming involves the importation of substantial levels of “new” energy into the climate (“new” because anthropogenic forcings are preventing this energy from radiating back into space the way they had been in the pre-industrial era), that energy can get invested in a variety of typically bad things, which also include wind.

    Thus, while there is some evidence to suggest that atlantic hurricanes might become more frequent, there is rather good evidence to suggest that such hurricanes as do arise will be, on average, more powerful. The energy picked up from the oceans will (the argument runs) make the winds more violent. Also, it is quite possible that formerly rare occurances such as mesocyclones ( will likely become more common as the energy levels jump up to levels over land that will support such destructive events.