12 July 2010

Deep into Amazonian Mud

With respect to the kerfuffle over a statement by the IPCC on the Amazon, I have been somewhat aware of the various claims, counterclaims, accusations, apologies, threatened lawsuits, demands for even more apologies, demands for retracted apologies and overall stridency that is endemic to blog debates over climate change. I haven't discussed the topic on this blog, because I didn't really know enough to say anything about it. But I spent a bit of time over the weekend looking into the issue, and here in capsule form is what I learned.

First, the IPCC made a statement in its Fourth Assessment Report:
Up to 40% of the Amazonian forests could react drastically to even a slight reduction in precipitation; this means that the tropical vegetation, hydrology and climate system in South America could change very rapidly to another steady state, not necessarily producing gradual changes between the current and the future situation (Rowell and Moore, 2000).
The citation for this statement is as follows:
Rowell, A. and P.F. Moore, 2000: Global Review of Forest Fires. WWF/IUCN, Gland, Switzerland, 66 pp. http://www.iucn.org/themes/fcp/publications /files/global_review_forest_fires.pdf.
The link is dead, but you can find it here in PDF, and it says:
Up to 40% of the Brazilian forest is extremely sensitive to small reductions in the amount of rainfall.
The paragraph in which that sentence appears is cited to the following paper:
D. C. Nepstad, A. Veríssimo, A. Alencar, C. Nobre, E. Lima, P. Lefebvre, P. Schlesinger, C. Potter, P. Mountinho, E. Mendoza, M. Cochrane, V. Brooks, Large-scale Impoverishment of Amazonian Forests by Logging and Fire, Nature, 1999, Vol 398, 8 April, pp 505
The problem, as is now widely known, is that Nepstad et al. provide no scientific support for the claim "Up to 40% . . .".

Fortunately, Nepstad issued a statement (PDF) on this issue soon after it broke, and confirmed the misciting in Rowell and Moore:
The authors of this report [Rowell and Moore] interviewed several researchers, including the author of this note, and had originally cited the IPAM website where the statement was made that 30 to 40% of the forests of the Amazon were susceptible to small changes in rainfall.
Are you following this so far?

Nepstad suggests that the IPCC statement as written was correct but that (a) Rowell and Moore missed some relevant citations, and (b) in any case, a more recent publication of his could have been used to support the claim being made by the IPCC. Let's address these in turn.

(a) The claim made in Rowell and Moore appears to have absolutely no scientific basis at all. In The Telegraph, Christopher Booker summarizes a range of blog-reader/commenter-contributions to identifying the provenance of the statement on the IPAM website alluded to by Nepstad. The original source is simply a website, no longer live but found in the internet archives, and shown to the right. This is where the trail ends for Rowell and Moore.

We can conclude unambiguously that the citation of Rowell and Moore by the IPCC was improper as it was not only "grey literature," but also devoid of scientific support for the claims that it advanced that were repeated in the IPCC.

(b) So what about Nepstad's implication that his 2004 article could have simply been inserted into the IPCC sentence in question, and all would have been fine?

I find this suggestion to be false. I have read Nepstad et al. 2004, and you can too at this PDF. There is nothing in that paper that can be used to support the "Up to 40% . . ." statement in the IPCC. Let me be clear -- that paper could have been used to support other statements, but not the statement which actually appeared in the IPCC. To put this another way, had the IPCC simply exchanged the citation of Rowell and Moore (2000) for Nepstad et al. (2004) the IPCC would have been equally as guilty of making a claim without support in the scientific literature. This is not to say that the specific claim made by the IPCC cannot be supported by the scientific literature, only that Nepstad et al. (2004) does not provide such support. That said, I cannot find any scientific support for the specific claim advanced by the IPCC (and apparently, neither can anyone else! Ironically enough, there is a trail leading from that very IPCC section to evidence counter to the contested statement).

Here it is worth adding that Simon Lewis, of the University of Leeds, who filed a complaint against the UK Sunday Times (here in PDF), muddies the waters a bit. While Lewis presents a range of issues, with respect to the contested claim made by the IPCC, Lewis argues that the IPCC is qualitatively correct:
there is a wealth of scientific evidence suggesting that the Amazon is vulnerable to reductions in rainfall. The IPCC statement itself is poorly written, and bizarrely referenced, but basically correct.
By "basically correct" Lewis explains that the Amazon is sensitive to rainfall and that reductions below a 1.5 m per year threshold can lead to massive tree die offs. Let me simply accept these statements as true, while noting at the same time what should be abundantly obvious -- these claims are not at all what the IPCC claimed. They are very different claims. They both invoke the Amazon and precipitation, but they are substantively different claims. Again, substituting the two papers mentioned by Lewis for Rowell and Moore (2000) as sources for the contested statement would not make the IPCC claim any better cited or accurate. The IPCC would have to have written a different set of claims.

The bottom line here? The IPCC did indeed make a claim in its report that is unsubstantiated in the literature that it cited in support of the claim. Further, the specific claim being made also appears to be unsubstantiable -- that is, there is nothing in the literature to support the specific claims being made. The IPCC could have said something else -- perhaps something even more alarming about the Amazon -- but it did not. For the IPCC this degree of sloppiness and lack of attention to accuracy is troubling.

Those claiming that there is nothing to see here are simply wrong -- the IPCC botched this one. The various defenses of this issue are an embarrassment. The IPCC simply made a mistake. Pretending that it did not cannot help either the IPCC or the cause for action, and will likely have the opposite effect, as anyone who takes a moment to look at the issue, as I did, will see the same evidence that I did. At the same time, it should also be said that the breakdown here has to do with the fidelity of the IPCC assessment process and not the substance of climate science. That the IPCC botched this particular claim does not make its opposite claim true.

The Amazon error in the IPCC occurred in almost the exact same manner as the 2035 Glacier error. It reflects a lack of attention to detail and accuracy, two criteria that one might think are the lifeblood of a process of assessment. In the end it may simply be an innocent mistake, but a mistake nonetheless. In this respect, both the Amazon and Glacier errors are far less troubling than the issue of how the IPCC has handled disasters and climate change, which goes beyond sloppiness.

In my self-education on this subject I came across some other problems in that section related to the Amazon, including the laundering of grey literature in an apparent effort to escape the IPCC publication deadline. But that will have to await another day, enough mudding for me for now.


  1. The best summary of the matter so far.

  2. You need to look at the WWF statement of 31 January


    the WWF letter of 7 February ...


    and the "update" from the WWF on 10 February.


    all of which is set out in context here ...


  3. So everywhere we look, we see hype, exaggeration, and often downright dishonesty. Eevn worse, we see sloppiness and incompetence, extreme bias, and sometimes active manipulation of the process by activist scientists.

    The studies are sloppy, lacking in transparency, unaudited and unreplicated. The assessments are worse. The defenses of the assessments, whenever errors are pointed out, are even more incompetent than the mess made of the original work.

    I have absolutely no confidence that the "science" which supports the claim of consensus (non-transparent, unaudited, unreplicated studies) is of any better quality than the incompetent siting of thermometers, Briffa's magic single tree, Mann's upside down proxy, Rahmstorf's embarassing stats bungle, Jones' fake Chinese data, the SST WAG, or Steig's Antarctic tail-chasing. Everything these guys touch turns out to be garbage.

    My prediction -- eventually, despite all the stonewalling, competent scientists, statisticians and software engineers are going to audit and replicate every important study, database, climate model and assessment done by these turkeys. And we are going to see that the gross incompetence of the IPCC's hype and exaggeration are going to be typical of a lot of the rest of the work.

    Honest, competent scientists like your father are going to be unfairly tarnished by the fallout from that embarrassment.

  4. -3-Richard

    Thanks for these links.

    WWF is simply wrong when it stated:

    "However, unlike the statement about Himalayan glaciers, the reference [to the "40%" claim] was drawn from an authoritative source, was factually correct and is supported by the peer-reviewed literature."

    WWF is among those who cannot point to peer-reviewed literature to support its claim. Where it did point to was a defunct website. Presumably WWF knew this. Not good.

  5. Your link to Nepstad 2004 links back to 1999

  6. "So everywhere we look, we see hype, exaggeration, and often downright dishonesty." Except, er, in the case at hand, apparently, where the only issue is understatement. Way to Fail.

    At the end of the day, the IPCC made a statement that was basically right, if a little understated. In the midst of thousands of pages of documentation. Its unpaid reviewers failed to check it - probably on account of their awareness that it was basically right. Appallingly damaging for a document edited by God Himself; rather less so for one edited by human beings.

    Ultimately, then, what does this demonstrate? Nothing? Or next to nothing? Let us all hope this crucial argument runs and runs ...

  7. Thank you for the excellent summary - clear, concise and unequivocal. So is Nobre et al. 2005 article you mentioned at Climate Audit a dead end?

  8. Its obvious why the WWF fought so hard to establish their claim: visions of a $60 billion dollar profit off of an Amazonian carbon credit scam...


    I never see these claims addressed when someone is hyperventilating about nefarious fossil fuel funded conspiracies.

  9. Seems to me that there's (at least) a couple of issues at stake here. The primary of these is about the workings of the IPCC WG2, which I would say has a damn tough job given the state of knowledge, but as has been pointed out repeatedly at this blog, could have done a hell of a lot better. In the future it will certainly have to if it wants to avoid stories like this coming back to do more harm than alarm.

    The second is the claim itself, which I'm personally interested in. Nepstad pretty clearly argues (demonstrates?) that precipitation reduction in the Amazon = forest destruction.
    What sort of evidence is there that global warming leads to less precipitation in the Amazon? Are there Amazon rainfall measurements good enough to correlate with rising temperatures? I simply don't know much on the topic.


  10. It was a simple thing to begin with - it could have been, as *was* certainly simply forgotten. The Sunday Times PCC complaint, the blogs which kept going after Leake, the Samanta et al press release and reaction, the retraction and the 'gloating' after the retraction kept it alive.

    I could easily point out to some "egregious fabulists" supporting the IPCC on this issue.

    I totally agree that "if the IPCC Amazon statement is not right", it does not mean that its opposite "is right".


  11. -7-timbird

    Thanks for your comment. I can see your point. In the big picture of things, it is probably true errors in the IPCC don't really matter. In fact, even if all of WG2 was invented from whole cloth it wouldn't "matter".

    Bu the thing is, science is all about details. And the reason that we trust scientific institutions is because they sweat the details. If scientific institutions were to start overlooking the details, well, then they wouldn't be scientific institutions anymore, they'd be more like blogs;-)

    As I have often said, the issues with the IPCC are about scientific integrity, not climate politics. Those interested in scientific integrity want the details right. For climate politics broad brushes are OK. Hopefully this distinction makes sense.

  12. Excellent and clear summary. Congratulations.

  13. Nevermind, I seem to have cleared the matter up for myself by reading the IPCC report.
    The main support for Amazon forest reductions come from modeling studies. The "Amazongate" claim seems like a bit of a supplement, but the %40 number might lend itself to being understood that %40 of the Amazon is at risk.

    But yeah, thanks to anyone that did the hunting on this story, we now have ourselves a pretty interesting drama :)

  14. MZ,
    the IPCC AR4 WG1 forecasts INCREASED precipitation over most of the Amazon, and especially over the upper part of the basin and the rainforest. At the nonforest eastern and southern borders of the basin, some increase is forecast for the rainy season, and some decrease (very small, for obvious reasons) in the dry season.
    Moreover, the rainforest is a region with no dry season, and an average rainfall of about 3500 mm/yr. "Droughts" do not cause rainfall to drop below 2500 mm in that region, let alone below 1500 mm. The whole Nepstad theory is speculative, like Cox's, who at least says that the mechanism for the forest's "dieback" is "well understood" (I have my doubts) but the existence of thresholds is not proven (let alone their numerical value) and that the empirical validity of the whole thing is not known.

  15. Timbird -7, Roger -12:
    You are both right, the statement as such does not matter much. What matters is the fact that IPCC auhtors and people close to 'the political project' enagage in face saving activities, i.e. rhetorical strategies to show that they were either basically right; or that it could turn out even worse; or that a few errors are to be expected in a thousand page document [pick your favourite according to the occasion].

    Time and again this has become the mantra of many who are sympathetic to the official line on AGW and climate policies. They do not realize that they are doing a disservice to the cause.

  16. Roger,

    Excellent analysis. However, when it is characterized as a mere "mistake," I tend to disagree.

    Genuine mistakes are random. Whether it is Holland, Amazon, Himalayan glaciers or Mt. Kilimanjaro, each of these overstates a problem associated with global warming. There does not seem to be an equal number of errors in the opposite direction (i.e., understating the problem and relying on non-peer reviewed literature to do so).

    So, I see this series of errors to be part of a biased mindset regardless of whether it is intentional or not.


  17. Interesting comment from the Economist:

    "Martin Parry, who in 2007 was co-chair of the relevant [about Netherlands] IPCC working group, says there was not a conscious decision to highlight negative effects, but to highlight important ones, as measured by such things as scale and irreversibility. The important effects are negative ones: this is why people are worried about climate change. A tendency for the IPCC process to produce outputs more worrying, at the margins, than its inputs does not necessarily show bias. It may reflect accurate expert assessment. But the risk that it is a sort of self-reinforcing groupthink merits attention."


  18. Hector M. -15,

    There is no evidence that GCM's of whatever flavor have any skill at regional forecasting. Globally, an increase in temperature should lead to an increase in precipitation, but there's a wide range in the rate of increase between models. Increased precipitation is also a negative feedback. The models with the highest rate of increase of precipitation with temperature have the lowest climate sensitivity.

  19. DeWitt (19): The prediction of increased precipitation on the Eastern Andes and the Amazon basin is indeed produced by models only, but most models agree on that (the chart in AR4 reports only forecasts that are supported by more than 66% of models). There was a wider variability in earlier models (in the 1990s), but not any more.
    Of course, the fact that Nepstad's and others' idea of increasing dryness collides with AR4 is no scientific proof of their error (models can also err, as we abundantly know), but it would be interesting to watch how Nepstad goes against the IPCC report, and with what arguments (either empirical or simulation based).

  20. We have come to the same conclusion as Roger, and said so back in March 2010 in our response to Nepstad et al.'s dueling press release issued against our press release (http://cliveg.bu.edu/download/amazongate/amazongate.html). It is not clear why Nepstad, who has done excellent work on Amazon forests, is so insistent on defending the indefensible. Soon after our press release, he bombarded us with emails every day to issue a correction - we said no. He is an IPCC AR5 author now (WG2 Chapter 4 on Terrestrial Ecosystems) - hopefully, he will correct his mistakes in the AR5.

  21. -21-Ranga

    Many thanks for this link.

    "Defending the indefensible" also has been characteristic of the IPCC response to the disasters issue involving my research.

    It is an unwinnable position.

  22. Of course in the real world outside of models, the Amazon, according to satelite data, is substantially greening up overall. Nepstad knows that and tries to downplay it but really you'd imagine he'd be happier.

    I presume it must be an affront to 25 years of pessimism to discover that business as usual actually means continued greening of the planet. Clearly in order to solve a problem it actually has to exist in the first place.

    Anyway no climate modeler can, hand-on-heart, support any attempt to use their models for regional studies. The models are not remotely adequate for such use. That fact alone negates much, if not all, of the IPCC "impacts" effort. High time we substituted all this pessimistic, anecdotal speculation with hard data.

  23. Rajendra Pachauri also expressed his views regarding the Amazon forests controversy (see the text under the heading "Amazon Rainforest" here: http://www.e360.yale.edu/content/feature.msp?id=2264). He blames the media for initiating this controversy and badly distorting the facts. He accuses blogs and other articles for pointing out that non-peer refereed material was used but claims that "the paragraph in question accurately presented results in the literature it cited." He concludes "On March 18, 18 respected rainforest scientists from Brazil, the U.S., and the U.K. issued a lengthy statement reaffirming the IPCC’s conclusion that up to 40 percent of the Amazon rainforest is at risk because of climate change" with a now defunct link (WHRO reconfigured their website recently; that statement can be found here - click on "Nepstad et al.'s Press Release Criticizing BU Press Release" at http://cliveg.bu.edu/download/amazongate/amazongate.html)

    Nepstad et al.'s statement does NOT reaffirm the IPCC conclusion. At best, it tries to justify that statement in retrospect. Nepstad himself tries to further expound on his assertions but quickly withdraws when Dr. North and others question him (http://wattsupwiththat.com/2010/06/27/booker-north-and-willis-on-the-ipcc-amazongate-affair/#more-21151).

    Rajendra Pachauri speaks in a tone at the UN (http://news.bbc.co.uk/2/hi/science_and_environment/10112136.stm) that is different than the one he has voiced in the Yale Environment 360 publication (reference in the first paragraph) and elsewhere (BBC Greenroom Feature http://news.bbc.co.uk/2/hi/science/nature/8740049.stm) where he talks of a "The discovery of a mistake in our AR4 report ..." Only one mistake in the entire AR4?

    The correct thing is to admit that a mistake has been made and offer to do a better job in the next assessment. The wrong thing to do is to deny it, justify it, malign the messenger, etc. - which only reinforces the thought that something really smells bad here.

  24. -24-Ranga

    Thanks for the links at WUWT, which is a remarkable comment thread. In that thread, Nepstad says this:

    "The IPCC statement is talking about future reductions in precipitation below the current variable rainfall regime. In other words, droughts more severe than 2005, 2001, 1998, or a century ago. . . We are discussing periods of intense drought that have occurred in the past and will occur in the future. If those future drought episodes are more severe than in the past, then lots of damage from drought and fire could ensure. This is the nub of the IPCC statement."

    How one gets from "slight reduction in precipitation" to unprecedented droughts is beyond me. In other words, Nepstad is claiming that the IPCC statement actually means the literal opposite of what its says. Oy.

  25. Roger: You said it precisely! That has been our argument with Nepstad all the while. We do not dispute that these forests will suffer if faced with more frequent and intense droughts. We only disputed the wording in that particular paragraph and the message it sends. Nepstad, on the other hand, has consistently insisted that the real meaning of those words is these forests will suffer great damage from intense and frequent droughts. The IPCC assessment is a NOT a holy book - so folks can read whatever meaning they want from the text. It has to be a precise document ...

  26. Dr Myneni
    Thanks for your clear and precise statement above. It greatly supports those of us who feel that some very good science on Amazon precipitation and other factors has been very poorly represented by the said IPCC statement, and were puzzled by continued support lent to the statement.

  27. Wery nice overview, Professor Pielke!

    I would like to add that even if the Nepstad (or the Nobre) paper(s) had stated what the IPCC stated in AR4 - the evidence wouldn't exactly be overwhelming.
    I'm sure that most people that read MSM not only believe that there is some evidence for the looming Amazonian cathastrophe in one or two articles, but I'm sure that they imagine that there is an abundance of research that point at this direction.

    It's really quite ironic, that the AGW-proponents who so often invoke the "overwhelming consensus" argument, in this case are defending themselves by saying something like "Hah! Look, there actually is ONE article that supports the IPCC claim!".

    Now that you (and Shub Niggurath, North etc.) have shown that this single article does no such thing, then it's just beyond ironic.

    This is actually one of my main complaints about the AGW camp: That yes, there are thousand of articles supporting all the details in the IPCC reports, BUT when it comes to many details (as in the Amazon detail) there are only a handful, one or in worst case none that actually scientifically supports each detail.

    I am 100% sure that the broad public indeed imagines that all local, regional and temporal details that they're told about in MSM are each and everyone supported by a multitude of scientific evidence.
    This is simply not the case.

  28. Dr Pielke,
    On the Climate Audit thread, you mentioned AR4's reference Nobre et al. (2005), or more completely:
    Nobre, C.A., Assad, E.D. and Oyama, M.D., Mudança ambiental no Brasil: o impacto do aquecimento global nos ecossistemas da Amazônia e na agricultura, Scientific American (Brazilian Edition), Edição Especial n. 12.

    If you're still interested in same, the Scientific American Brasil special edition containing this article can be purchased at this location:

    Cost is R$11.40 ~= USD 6.45

  29. The Dutch Report, which can be found here (
    http://www.pbl.nl/en/publications/2010/Assessing-an-IPCC-assessment.-An-analysis-of-statements-on-projected-regional-impacts-in-the-2007-report.html) says the following on Page 74. This brings some closure to this debate.

    "Up to 40% of the Amazonian forests could react drastically to even a slight reduction in precipitation; this means that the tropical vegetation, hydrology and climate system in South America could change very rapidly to another steady state. (C6; minor)

    We have a minor comment to make on this statement, which originates from Section 13.4.1 of Chapter 13 (page 596). The statement was based on Rowell and Moore (2000), which is a peer-reviewed report by the World Wide Fund for
    Nature and the International Union for Conservation of Nature (WWF/IUCN) on a global review of forest fires, and not a study on changes in vegetation due to climate change. That report, in turn, was mainly based on Nepstad et al. (1999) (in Nature). In our opinion, both documents were not the most obvious choice of
    reference in this case, as their focus is on forest fires (and logging). More adequate
    peer-reviewed, scientific journal literature would have been available to support this statement, such as Cox et al. (2000; 2004) (C6). This minor comment has no consequences for the IPCC conclusions in the various Summaries for Policymakers."

  30. -30-Ranga

    Thanks for this link. Here are those two papers:

    Cox, P.M., R.A. Betts, C.D. Jones, S. Spall and I.J. Totterdell, 2000. Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model. Nature, 408, 184-187.

    Cox, P.M., R.A. Betts, M. Collins, P. Harris, C. Huntingford, C.D. Jones, 2004. Amazon dieback under climate-carbon cycle projections for the 21st century. Theor. Appl. Climatol. 78, 137–156. (doi:10. 1007/s00704-004-0049-4)

    I have seen these papers, and see nothing in them to support the IPCC statement as written. Again, a simple substitution of the Cox references for the Rowell and Moore citation is not sufficient to fix this issue.

    The PBL report suggests that this is a mere citing problem and the claim as cited is correct. I do not think that this assertion stands up. It is more than a simple citing error -- the substance was wrong because of the misciting.

  31. A tangential issue: Nepstad, Lewis and others have sought to prop up the plausibility of the '40%' claim in AR4 by citing Philips et al, a 2009 study of the 2005 Amazonian drought that attributed that year's huge tree mortality solely to the drought. A new study concludes that much of the tree loss was in fact due to a single massive chain of storms. It hasn't been published yet. Here's the press release:


    That's the beauty of science! Theories are perpetually updated and revised. (Or not. It'll be interesting to see whether Nepstad and Lewis revise their arguments in the light of Negron-Juarez et al.)

  32. Dr. Pielke: The blogosphere appears to be missing a significant part of the Amazongate problem. In preparation for AR4, a group of scientists compared the projections of various GCM's for the Amazon and published a paper on the subject (JGR, (2006), 111, D02111), which was cited by WG1. The abstract states:

    "The global climate models for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC 4AR) predict very different changes of rainfall over the Amazon under the SRES A1B scenario for global climate change. Five of the eleven models predict an increase of annual rainfall, three models predict a decrease of rainfall, and the other three models predict no significant changes in the Amazon rainfall.”

    Citing Nobre 2005 - an inaccessible article in Portuguese in the Brasilian edition of Scientific America with no specific references to the primary literature - Section 13.4 (p 596) of WGII makes the following technically correct, but incomplete, statement:

    “several AOGCM scenarios indicate a tendency towards ‘savannisation’ of eastern Amazonia”

    In the WGII SPM (p 14), the public is told with >80% confidence that:

    “By mid-century, increases in temperature and associated decreases in soil water are projected to lead to gradual replacement of tropical forest by savanna in eastern Amazonia.”

    So the IPCC process works as follows: 1) A group of scientists summarize the literature in preparation for AR4. 2) Ignoring or unaware their work, WGII authors include only the scary part of this information in their report, but cautiously describe this as a "tendency" without a time frame. 3) The public is told that that the east Amazon rainforest will be gone in fifty years. (This was the projection of only one of the 11 GCM's mentioned above.)

    As for Dr. Neptstad - who wants the public to know that the conclusions of WGII were correct even if some of the details were wrong - the discussion section of his 2007 paper - which he claims supports the IPCC's conclusion - begins with:

    “The seasonally dry forest of the Tapajos is an extremely drought-tolerant ecosystem. Our partial throughfall exclusion simulated effective rainfall of 1120, 1130, and 630 mm during the second through fourth years of the study period (eight months in the final year), well below evapotranspirational water loss of 1400–1500 mm/yr … But, surprisingly, the mortality of large trees (.10 cm dbh) began only during the final year of the experiment (Fig. 5). This drought tolerance is conferred in part by deeply penetrating root systems that absorb soil water to depths of at least 11 m…”

    According to the paper, Dr. Nepstad's study site receives less rain than 95% of the Amazon AND has a relatively low ground water table. After 50-65% of the rainfall was mechanically diverted from the site from late Jan 2000 to Dec 2004 (see Methods section), Nepstad reports visible damage occurred only in the fourth year - leaving one to wonder what happened during last year. In any case, Nepstad's work doesn't come close to supporting the IPCC's statement that "40% of the Amazon could react drastically to even a slight reduction in precipitation".

  33. In response to Roger's Comment 31:
    Yes, even if the IPCC AR4 had cited Cox et al. (2006) instead of Rowell and Moore (2000), that paragraph would still be questionable. Cox et al. (2006) conclude that "we are still a long way from being able to estimate the probability of such an ecological catastrophy in the real Earth system." The catastrophy being Amazon die-back. How we go from here to "Up to 40% of the Amazonian forests could react drastically to even a slight reduction in precipitation ..." is anyone's guess.

  34. An interesting article appeared in this recent issue of Geophysical Research Letters (Widespread Amazon Forest Tree Mortality From A Single Cross-Basin Squall Line Event by Negron-Juarez et al., 2010). See the Press Release from the American Geophysical Union at http://www.agu.org/news/press/pr_archives/2010/2010-17.shtml

    This is an excerpt from the abstract of this article: "Here we demonstrate that a single squall line (aligned cluster of convective storm cells) propagating across Amazonia in January, 2005, caused widespread forest tree mortality and may have contributed to the elevated mortality observed that year. Forest plot data demonstrated that the same year represented the second highest mortality rate over a 15-year annual monitoring interval. Over the Manaus region, disturbed forest patches generated by the squall followed a power-law distribution (scaling exponent alpha =1.48) and produced a mortality of 0.3-0.5 million trees, equivalent to 30% of the observed annual deforestation reported in 2005 over the same area. Basin-wide, estimated tree mortality from this one event was 542±121 million trees, equivalent to 23% of the mean annual biomass accumulation estimated for these forests. "

    Now, Nepstad had argued at WUWT that the Phillips et al. Science 2009 study as the most direct evidence of the impact of 2005 drought on Amazon forests to further his support of the controversial paragraph in the IPCC WG2 AR4, which is the theme of this thread.

    "See Phillips et al. Science 2009, who found a spike of tree mortality following the 2005 drought in a few dozen permanent forest plots scattered across the region. (It is hard to think of more direct evidence than this. And, by the way, once a drought kills trees in a forest, its susceptibility to further disturbance through fire increases, as has been demonstrated experimentally (Ray et al 2005 Ecol Applic.) and observationally (Cochrane et al. 1999 Science))."

    In this new GRL paper, Negron-Juarez et al. write that:
    "Interestingly, a recent study [Phillips et al., 2009] found elevated tree mortality in forest inventory plots across the Amazon basin (including the BIONTE plots), and suggested that elevated tree mortality was caused by the 2005 drought alone. Our study shows that widespread disturbance produced by a single squall line event in January 2005 must be considered as contributing factor to the high mortality observed in that year, particularly in the Central and Eastern Amazon."

    While the new study does not invalidate the Phillips et al. Science 2009 study, it does suggest that at the very least one needs to revisit Phillips et al. data and analysis.

  35. Dr Myneni
    I've been trying to determine whether the squall event had any influence on the FLUXNET data gathered from the storm affected regions. The time of measurement is not immediately obvious from the Materials and Methods of Philips et al 2009 - which is surprisingly very detailed (for a Science paper).

    Incidentally, even we noted the absent data for 2006 pixels in Saleska et al Science brevia paper. It is missing from their RealClimate comment as well. Has their response paper appeared yet? Very interested in seeing how they resolve the differences.

    News: The Wall Street Journal picks up on this post.


    A widely cited claim by the IPCC that Himalayan glaciers would all but vanish by 2035 was debunked. Another stunner about a potential 40% decline in the Amazonian rainforest "appears to have absolutely no scientific basis at all," according to Roger Pielke, Jr., an environmental studies professor at the University of Colorado. Other attention-getting IPCC assertions turn out to have been based on the work of environmental pressure groups and popular magazines.

  36. First line should read "whether the squall event had any influence on the RAINFOR data..."

    Philips et al measured living standing trees obviously, not prostate, fallen ones.


  37. An obvious solution would be to just make the WG reports shorter. Then they wouldn't have so much minutia and noise to edit. Same number of eyeballs on fewer pages ought to yield higher quality.

  38. Response to 37: The new GRL article questions the tree mortality attribution to drought by Phillips et al. Could not read the full WSJ article - had to subcribe ... Thanks!!!