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Up is Down, Brown is Green (with apologies to Orwell)

Filed under: — eric @ 15 March 2010

In the alternate universe of Fox News, Anthony Watts, and many others, up is down. Now, it appears, brown is green. Following the total confusion over the retraction of a paper on sea level, claims of another “mistake” by the IPCC are making the rounds of the blogosphere. This time, the issue is the impact of rainfall changes on the Amazon rainforest.

A study in 2007 showed that the forest gets greener when it rains less. A new study, by Samanta et al. in Geophysical Research Letters shows that the earlier work was flawed. Aided by an apparently rather careless press release, this is being used as evidence that the Amazon is less sensitive to rainfall changes than the IPCC claimed. But the Samanta et al. paper actually does not address the central questions at all. It only addresses whether a single anomalous rainfall year had an impact that is measureable and interpretable from a satellite sensor. The conclusion is that they could not detect a change. As noted in a commentary from Simon Lewis, University of Leeds, “the critical question is how these forests respond to repeated droughts, not merely single-year droughts.”

Lewis – a broadly published expert on tropical forests – makes a number of additional important points in his commentary below. Bottom line: IPCC gets it right as usual.

—————
Guest Commentary by Simon Lewis, University of Leeds, UK

The new Samanta et al. study uses sensors on satellites to assess the colour of the rainforest canopy in the dry season of the year 2005, compared to the dry seasons of the years 2003 and 2004. More detected green colour in 2005 may suggest that the forest is being more productive (more green leaves photosynthesising), or more brown colours may suggest leaves dying and less productivity, than the previous years. The results show that 2005 was little different to the previous years, despite the strong drought.

This is important new information, as in 2007, a paper using broadly the same satellite-based method showed a strong ‘greening-up’ of the Amazon in 2005, suggesting tolerance to drought (Saleska et al. 2007, Science). The new study shows that those results were not reproducible, but also highlight the extreme caution that should be attached to satellite studies generally in this field, with instruments in space collecting data which is then used to infer subtle changes in the ecology of tropical forests.

In contrast to the 2007 paper, Oliver Phillips, myself, and others, published a paper in Science last year, using ground observations from across the Amazon, showing that while the 2005 drought did not dramatically change the growth of the trees compared to a normal year, as Samanta et al. also show, the deaths of trees did increase considerably. The new study of Samanta et al. does not contradict the Phillips et al. study, which itself shows the Amazon is vulnerable to drought via impacts on tree mortality. The Phillips et al. paper showed that remaining Amazon forest trees changed from absorbing nearly 2 billion tonnes of CO2 from the atmosphere annually over recent decades, as tree growth has been exceeding mortality, to being a large, but temporary, source of over 3 billion tonnes, from the elevated tree mortality associated with the 2005 drought event.

The evidence for the possibility of a major die-back of the Amazon rainforest is due to two factors,

1. That climate change induced decreases in rainfall in the dry season occur, and

2. The trees cannot tolerate these reductions in rainfall.

The Samanta paper does not directly address the first point; this is addressed using global circulation models (of which some, but not all, show a strong drying trend for the east of the Amazon over the 21st century). The second point is only addressed in a limited way. The critical question is how these forests respond to repeated droughts, not merely single-year droughts. The forests are of course able to withstand these single droughts (otherwise there would be no rainforest!) — it is their ability to survive an increased frequency of the most severe droughts that is critical to answer. Drought experiments, where a roof is built under the forest canopy to reduce rainfall, show that most forest trees survive a single year’s intense drought, in agreement with the ground observations in the 2005 drought, but can’t persist with repeated years of drought. The Samanta study does not address this point at all.

In conclusion, the new Samanta et al. study lends further weight to the emerging picture of the impact of the 2005 drought: that tree growth was relatively unaffected, but tree mortality increased, contributing temporarily to accelerating the rate of climate change, rather than as usual reducing it, via additions of carbon to the atmosphere from the dead trees. The mortality was far from catastrophic, but the impact on the carbon cycle was globally significant. This is hardly the ‘no impact’ of the 2005-drought on the forest suggested in various news reports.

I should add that there is considerable uncertainty associated with the models suggesting decreases in rainfall, and uncertainty as to how Amazon forests may react (especially when one considers the impacts of deforestation, logging, and fire combined with climate change impacts). But this uncertainty is being chipped away at by scientists, a task in which the Samanta et al. paper assists.

Oddly, the Boston University press release to accompany the paper was titled, “New study debunks myths about Amazon rain forests”. The opening line runs: “A new NASA-funded study has concluded that Amazon rain forests were remarkably unaffected in the face of once-in-a-century drought in 2005, neither dying nor thriving, contrary to a previously published report and claims by the Intergovernmental Panel on Climate Change.” So, have scientists, myself included, been peddling myths? Have respected journals being publishing them? Have the IPCC? The answer is no, no and no.

The reality is that the IPCC have largely ignored the papers on the model results of decreasing rainfall in the east of the Amazon, and the diverse evidence used to assess the sensitivity of these forests to such rainfall reductions. There are a couple of lines in IPCC Working Group I (“New coupled climate-carbon models (Betts et al., 2004; Huntingford et al., 2004) demonstrate the possibility of large feedbacks between future climate change and vegetation change, discussed further in Section 7.3.5 (i.e., a die back of Amazon vegetation and reductions in Amazon precipitation).”). And in Working Group II there is a now infamous single sentence:

“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 statement is not as carefully worded as it should be, and incorrectly referenced, but basically scientifically correct and defensible with recourse to the peer-reviewed literature available at the time. Rainforest persists above a threshold of rainfall, below which one finds savanna. If this threshold is crossed a landscape dominated by rainforest can ‘flip’ to savanna. Therefore a ‘slight’ reduction can lead to a ‘dramatic’ reaction. Of course, evidence of a shift to a new lower rainfall climate regime is needed, and evidence of large areas of forest close to that rainfall threshold would be required for the IPCC statement to be reasonable; there is ample published evidence for both.

Overall the conclusions in the IPCC 2007 Fourth Assessment Report are strengthened (because the anomalous result of the Saleska et al. 2007 paper appear to be at fault), not weakened, by the new Samanta et al. study as their press release implies.

Update: Saleska responds, pointing out that a) their 2007 paper is not contradicted by Samanta et al. (2010); b) nor is the IPCC report weakened by either paper. Confused? Then read what he has to say: here.


235 Responses to “Up is Down, Brown is Green (with apologies to Orwell)”

  1. 1
    Lynn Vincentnathan says:

    I guess the logic at Fox News et al. is that unlike Eternal Truths that never change, science just keeps changing and changing, as new and better evidence comes in, and better, more elegant theories are thought up to explain it. Ergo, dump science.

    But that’s not all. Glen Beck is dumping religion, as well, if that religion has anywhere in any of it’s literature or preaching the words “social justice.”

    So now that we’ve dumped science and religions, what next….”back to the trees”? Oh, yeah, that metaphor is out, so I guess it’s “blindly back to the trees,” assuming there are any trees left (see above).

  2. 2
    cervantes says:

    As a climate science layperson (I am a social scientist) I faced the problem most people do of trying to decide what to believe about the apparent controversy over the AGW hypothesis when it just wasn’t possible for me to invest the time in deep learning about the scientific issues. It was apparent that this matter was very important so I spent what time I could on it, and got the basic ideas in hand. The atmosphere is largely transparent to visible and UV light, which warms the ground; but it contains gases which are opaque to IR and so some of the heat that is radiated back gets trapped. That’s why we have a livable climate in the first place, and it makes perfect sense that if you increase the pct. of gases opaque to IR, all things being equal, the temperature goes up. I saw that there were controversies over feedback mechanisms and possible mechanisms that promote stasis; the size of this effect resulting from human activities; how long C02 stays in the atmosphere; the actual temperature record; the possibility of other effects being more powerful than human activity; etc. I knew I couldn’t learn enough to sort all this out myself, but two factors have convinced me:

    1) It is clear that the vast majority of people who truly are expert in the field believe that AGW is real and that consequences could be very damaging for humans and other creatures. I know how science works and that it does no accommodate conspiracies against the truth. Errors happen and can persist for a while, but they get fixed.

    2) The tactics of deniers are not credible. They misrepresent evidence, engage in ad hominem attacks and other fallacious arguments, they continually premise shift, when challenged they change the subject, they use obfuscation and argument by assertion; they are funded by people with a vested interest in a particular conclusion; and more.

    So, that’s good enough for me. It ought to be enough for everyone in the corporate news media as well, but apparently it is not.

    [Response: The trouble with the media is that an honest asssessment of the situtation -- e.g. "Scientists actually have a clue what they are talking about, and random TV personalities and bloggers do not" doesn't make for very entertaining reading.--eric]

  3. 3
    Luke Lea says:

    ““Up to 40% of the Amazonian forests could react drastically to even a slight reduction . . .” Coulda, woulda, shoulda. The word “could” rules out very little.

  4. 4
    RickA says:

    “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 author states that “The statement is not as carefully worded as it should be . . .but basically scientifically correct and defensible . . .”

    This statement made it through the review process – and passed muster – even though it was alarmist – ”
    could react drastically”.

    Then a slight change is shown not to cause drastic change and the statement looks to be to strong.

    The author points out it is only one year – but still – as always when science makes statements which are to strong – they got burned.

    It would be better to stick to the science and not try to spin the science to spur political action – then you don’t have to back down in the face of new evidence.

    [Response:Try re-reading this artice again, slowly, and thoughtfully. You'll realize your comment should be directed elsewhere.--eric]

  5. 5
    Carl says:

    ” .. contributing temporarily to accelerating the rate of climate change, rather than as usual reducing it, via additions of carbon to the atmosphere from the dead trees.”
    How was this “accelerating the rate of climate change” measured [edit]

  6. 6
    tharanga says:

    This is not the first time a press release has provided a poor description of a work or its context.

    Given that many journalists and bloggers simply regurgitate the press release instead of reading and understanding the paper and other related papers, this is clearly a problem.

    So why do bad press releases continue to appear?

  7. 7
    SecularAnimist says:

    RickA wrote: “It would be better to stick to the science and not try to spin the science to spur political action”

    Yes, it would certainly be better for corporations like ExxonMobil, which alone makes about ONE HUNDRED MILLION DOLLARS PER DAY IN PROFIT from fossil fuels, if climate scientists who understand that a rapid phaseout of fossil fuel consumption is urgently needed if we are to have any hope of averting the most catastrophic outcomes of AGW, would just stick to the science and keep their mouths shut about that so as not to “spur political action” to save civilization from destruction.

  8. 8
    MapleLeaf says:

    What the Samanta et al. paper does not address is how the forest responds to multi-year droughts or in months/years following the drought. Research into how the Boreal forest responds to drought has shown that the most significant die back/mortality was not observed during the year of the drought but in subsequent years.

    For example,

    Impacts of a regional drought on the productivity, dieback, and biomass of western Canadian aspen forests. 2008. Hogg, E.H.; Brandt, J.P.; Michaelian, M. Canadian Journal of Forest Research 38(6): 1373-1384.

    This seems to be consistent with the findings of Lewis et al. (2009).

  9. 9
    Completely Fed Up says:

    “So why do bad press releases continue to appear?”

    Because there’s no downside to doing so (no repercussion if shown wrong: see how the howls of protest at “censorship” when Phil Jones was asked if a paper he’d read was worth including in the IPCC), but there’s a downside to trying properly: it takes more effort.

  10. 10
  11. 11
    Hank Roberts says:

    > ” .. contributing temporarily to accelerating the rate of climate change,
    > via additions of carbon to the atmosphere from the dead trees.”

    Carl, that’s simple arithmetic. Is there a step you don’t want to accept?

    –> A big temporary increase in dead trees (measured from the satellite)
    —-> an increase in CO2 to the atmosphere (they’re made of CHON)
    ——-> increasing CO2 faster changes climate faster (Arrhenius et al.)

  12. 12
    Carl says:

    CFU, no acceleration is shown there. Hank R, I was asking for measurements, not theory.

  13. 13
    John Peter says:

    Gavin

    From model-data comparisons 461

    “[Response: Actually I'm writing a post on this now. But if you have a library look up some letters between Lewis Kaplan and Plass in Tellus in 1960. - gavin]

    Googling “Kaplan and Plass in Tellus” helped me find this:

    http://www.americanscientist.org/issues/feature/2010/1/carbon-dioxide-and-the-climate/1

    The good news is that your January American Scientist paper is one of the best I have read. It should be required reading for all denier, skeptic and yes warmer “scientists”. Congratulations.

    The bad news is that I liked it so much I purchased (24 hour access to) the pdf, an action I almost never take with on-line publications. Imagine my surprise to receive an edited version – some (very important) sections had been elided because “the original article ran to more than 6000 words … too much to be included here”. I was keenly disappointed.

    I chatted with “Greg” at Sigma Xi who was as surprised as I was, recovered to say this rarely happened, tried to be helpful, etc.,etc. I had already copied and printed your paper (tsch, tsch) – but that’s not my point. Why they edited without your knowledge – Sigma Xi yet – is beyond me.

    Surely you can find a way to make the full paper available on the internet with a new reference. It is really worth it

  14. 14
    Completely Fed Up says:

    “12
    Carl says:
    15 March 2010 at 2:43 PM

    CFU, no acceleration is shown there.”

    Yes there is. Look at the first 30 year average, the middle 30 year average and the last 30 year average.

  15. 15
    Gerda says:

    This is the second reference to Orwell I have read in 10 minutes. The other was a reaction to the recent goings on at the Texas Board of Education.

  16. 16
    Carl says:

    CFU, I can’t see any acceleration due to the 2005 Amazon drought.

  17. 17
    Kate says:

    Thanks Eric, I was hoping RC would cover this issue. I read the NASA study and thought it would be something like this – single year vs long-term trend. Nevertheless, it’s nice to have it confirmed (and translated) over here. Keep up the good work.

  18. 18

    cervantes (2),

    That’s indeed the kind of logical thinking that we have to make more people aware of. I collected some hints as to how laypeople can decide who to believe on a complex topic such as global warming:
    http://ourchangingclimate.wordpress.com/2009/02/08/who-to-believe/

  19. 19
    mike roddy says:

    What about the increased fire probability from higher temperatures alone, apart from drought? Lynas mentioned it, but I’d like to see citations. My interest would be for temperate forests as well as tropical ones.

  20. 20

    If you think the CRU data is false, why not go to http://www.knowyourplanet.com/climate-data/ and take a look at it? It is displayed in a interactive format and you should be able to find a measurement stations somewhere reasonable close to you. Enjoy!

  21. 21
  22. 22
    Dappled Water says:

    “Drought experiments, where a roof is built under the forest canopy to reduce rainfall, show that most forest trees survive a single year’s intense drought, in agreement with the ground observations in the 2005 drought, but can’t persist with repeated years of drought. The Samanta study does not address this point at all.”

    http://eebweb.arizona.edu/faculty/saleska/Ecol596L/Readings/Nepstad.07_Drought.mortality_Ecology.pdf

  23. 23
    RickA says:

    #7 – SecularAnimist:

    It doesn’t matter how much money Exxon makes per day. That doesn’t change the fact that the Working Group II infamous sentence was phrased stronger than it should have been, and oversold the science.

    Now “slight reduction” is being spun to mean multiple years of drought instead of a single year of drought.

    In hindsight, the Working Group II infamous sentence should have been scaled back, and never used the phrase “slight reduction”.

    It overstated the science. RealClimate is now saying – well it was akwardly phrased – but defensible. It is a multiple year thing not a single year thing.

    Thats what I mean when I say stick to the science. Lets not hype things up – lets stick to the facts. It is easier that way when later science shows that something has been oversold or hyped.

  24. 24
    ghost says:

    The Accuweather Climate Blog seems to have picked up the tone of the press release sound bite. Could someone knowledgeable please correct them over there? :)

  25. 25
    Kjell Arne Rekaa says:

    The:
    …uncertainty as to how Amazon forests many react…
    Should have been:
    …uncertainty as to how Amazon forests may react…
    I think?
    Otherwise a frightening good article – I hope more of us “main street” people starts to understand the possible consequences of such positive feedbacks…

    [Response: Fixed, thanks.--eric]

  26. 26
    JimD says:

    Can we focus on the science please and not the yah boo nonsense. Being juvenile doesn’t get the point across very well – and some of us are actually interested in facts rather than personalities and propaganda.

    Many thanks.

  27. 27
    Arindam Samanta says:

    Folks,

    The press release accompanying the GRL article disputed the following IPCC AR4 (2007) claim –

    “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). It is more probable that forests will be replaced by ecosystems that have more resistance to multiple stresses caused by temperature increase, droughts and fires, such as tropical savannas.”

    for two reasons: (1) this is presented as the consensus view by quoting Rowell and Moore, 2000. (2) There was more than a slight reduction in precipitation during the third quarter of 2005 and, most of the drought-impacted forest area for which we have uncorrupted satellite greenness data showed no enhanced or reduced greenness levels (third quarter average EVI values) as compared to non-drought years (between 2000 and 2008).

    It is only in this context that the material in the press release and the GRL must be understood. We do not dispute any other results related to this theme in these two documents.

    Respectfully,
    Arindam Samanta (on behalf of the authors of the GRL papers).

    [Response: Dear Arindam,

    Thanks for the response.

    On the IPCC statement, as I have said it is not as well-worded as it ought to be. Strictly, perhaps it can be taken as having one of two different meanings,

    1. That the IPCC mean that small reductions in precipitation at any given time cause a drastic response (of which your paper ably shows that for satellite-monitored 'greenness' there is no such drastic response, and is an important paper I will certainly cite), or

    2. They mean responses of vegetation to mean climate regimes with differing precipitation (of which your paper says little).

    It seems clear to me that the sentence is about responses to a shift from one climate regime, the recent past and present day, to another, with less precipitation, in the future (it is the IPCC climate change impacts report after all, and they do say '... not necessarily producing gradual changes between the current and the future situation').

    If meaning two of the sentence is taken, then what the IPCC say is reasonable, defensible, basic science: warm lower-rainfall environments tend to be dominated by savanna, while warm higher-rainfall environments tend to be dominated by rainforest, with a threshold amount of rainfall separating which vegetation type one finds. If substantial areas of the Amazon are in a climate regime close to the savanna-rainfall threshold, which diverse evidence suggests they are, then there may be a vegetation shift if rainfall consistently decreases in the future due to climate change.

    Your response implies you think meaning one is correct, which is mistaken (logically it can't hold as a proposition). Had your paper cited the IPCC chapter and the sentence you object to and why - which it doesn't - the misunderstanding could have likely been addressed at the review stage.

    Details aside, it’s the 'debunking Amazon myths' headlines, and quotes about putting right 'muddled understanding', and, "The way that the WWF report calculated this 40% was totally wrong, while [the new] calculations are by far more reliable and correct,” that are problematic and have unnecessarily confused people. There are no calculations in the WWF report (it’s a review), nor are there any new calculated updates on the IPCC ‘up to 40%’ statement in the Samanta paper, and the ‘muddled understanding’ quote highlights the ‘twin pressures’ facing the Amazon, as logging and climate change, when outright deforestation is certainly the number one current pressure in the context of the quote.

    I know the media regularly run out of control (its happened to me several times), but in my view it is critical to try and put things right. Most journalists and bloggers will help put things right once they know there is a problem, but you have to tell them.

    With best wishes,

    Simon]

  28. 28
    JiminMpls says:

    #16 Carl

    2005 was the hottest year on record. The dead and decaying trees in the Amazon contributed to that.

    Satisfied?

    Of course, that’s a rather absurd statement, but expecting a measurable impact from a net 5 GT increase in carbon dioxide is absurd, so the answer fits the question.

  29. 29
    jcrabb says:

    4 months of decreased rainfall seems an extreme interpretation of ‘slight’.

  30. 30
    Dave E says:

    #23
    “That doesn’t change the fact that the Working Group II infamous sentence was phrased stronger than it should have been, and oversold the science.”
    Infamous sentence? How many sentences are there in the report? Have you ever tried to write a substantive work where every sentence you write exactly expresses your thoughts, while simultaneously insuring that your thoughts are in sync with mountains of published material?
    If this is the best you can do as criticism, you should give it up.

  31. 31
    Jean B. says:

    Well, it looks like the press release was carefully worded, and referring back to Anthony Watts article on his blog which is criticized at the beginning of the RC article, i see no wrong claim there…
    Hiss main argument is written in bold : “The IPCC is under scrutiny for various data inaccuracies, including its claim – based on a flawed World Wildlife Fund study — that up to 40% of the Amazonian forests could react drastically and be replaced by savannas from even a slight reduction in rainfall.”

    That looks very close to what Arindam Samanta writes here in the comments:
    The press release accompanying the GRL article disputed the following IPCC AR4 (2007) claim –
    “Up to 40% of the Amazonian forests could react drastically to even a slight reduction in precipitation [...] It is more probable that forests will be replaced by ecosystems [...] such as tropical savannas.”

    [Response: The point is that it would be very surprising if one year of low precipitation would matter very much. The Saleska paper, though, suggested it did, and not only that, but in the opposite direction to what one would expect. That was news. now, the new Samanta paper suggests that actually, no, one year of low precip isn't very important.

    Watts' title of his post is: "Amazon more drought resistant than claimed [by IPCC]“. Anyone reading that who was not 100% familiar with the text of the papers involved would assume that this means “Amazon is not as damaged by drought as IPCC claims”. That’s why I called Samanta’s press release “careless”, and it is why Watts post is disingenuous.–eric]

  32. 32
    jimt says:

    Dr Samanta @27

    As pointed out in the post, “The critical question is how these forests respond to repeated droughts, not merely single-year droughts”. How can a study based on a single-year be used to dispute any predictions about long term impacts of climate change (i.e. long term changes in rainfall patterns)?

    I am curious as to what or who motivated the press release? Was it genuine concern from the authors that one small sentence in the IPCC may be wrong (or could be interpreted as such, depending on how “slight reduction in precipitation” was interpreted), or was it simply an attempt to generate some publicity? Was the press release written by the authors or by a PR consultant/advisor?

    [Response: Dr. Samanta and colleagues are of course welcome to answer your question if want to spend their time responding to queries on blogs, but I have to say I object to the insinutation here about scientists motivations. I have little doubt Samanta et al. were not aware of how easily their press release would get misued and abused. I've been in the same boat myself. No matter how carefully one words the press release, some people will misunderstand it, whether on purpose or out of naivete.--eric]

  33. 33
    Francis says:

    Here in Southern California, foresters are well aware of the impacts of multi-year drought — bark beetle mortality is skyrocketing in drought-stressed pine populations in the San Bernardino Mountains east of Los Angeles.

  34. 34
    Hank Roberts says:

    Question for Dr. Samanta if I may — I’d read that the opposite of the way jcrabb did, a “slight reduction” in an article about climate change would seem to me to mean an ongoing longterm change.

    Do you think that Rowell and Moore’s “slight reduction” was intended to include a reduction during one calendar quarter of one year? Wouldn’t that be considered natural variation in precipitation?

    I know this is complicated and there is a lot of field work going on, and that one question is whether the vegetation is getting most of its moisture from groundwater or from rainfall on leaves directly absorbed.

    With a temperate-zone experience, I’ve tended to equate a change in precipitation with a change in groundwater availability–which might not change much with due to a change in rainfall in one calendar quarter.

    Serious question, I don’t know most of the details about rainfall and plants in the area. I’d actually thought the article was more about the satellite sensors, data, and analysis at this point and was expecting some ‘ground truth’ information later on to tie the color change in the pictures to the actual changes on the ground.

  35. 35
    Mark A. York says:

    Whew! Andy Revkin Tweeted this so-called debate between Lindzen and Hadi ….of the U. of BC. Wow. Life as we know it will be no problem at 600 ppm of CO2. Both agree that the models are Ouija boards. Unbelievable. Well, it is considering the players. No wonder media is so confused. Both disagreed with the NASA films the moderator showed.

    http://www.youtube.com/watch?v=gJwayalLpYY

  36. 36
    MapleLeaf says:

    Hank Roberts@ 34. See my earlier post regarding delayed response of Boreal forest in Canada to drought. Also, it has been well established that the Amazon forest can be a net source of CO2 during drought periods. In fact, a study by Dr. Phillips in 2009 demonstrated that. This from ScienceDaily:

    “The 2005 drought sharply reversed decades of carbon absorption, in which Amazonia helped slow climate change.

    In normal years the forest absorbs nearly 2 billion tonnes of carbon dioxide. The drought caused a loss of more than 3 billion tonnes. The total impact of the drought – 5 billion extra tonnes of carbon dioxide in the atmosphere – exceeds the annual emissions of Europe and Japan combined.”

    And relevant here:

    Visually, most of the forest appeared little affected, but our records prove tree death rates accelerated. Because the region is so vast, even small ecological effects can scale-up to a large impact on the planet’s carbon cycle,” explained Professor Phillips.”

    And

    “But in 2005 this process was reversed. Tree death accelerated most where drought was strongest, and locations subject even to mild drying were affected. Because of the study, we now know the precise sensitivity of the Amazon to warming and drought.

    If repeated, Amazon droughts will accelerate climate warming and make future droughts even more damaging.”

    I agree with Hank that this study focuses on the response of the canopy during the drought. Phillips et al. have clearly noted that while visually all may seem well with the Canopy during the drought, that is in fact not the case.

    Quoted text from: http://www.sciencedaily.com/releases/2009/03/090305141625.htm

  37. 37
    Craig Allen says:

    RE John Peter #13:

    Excelent article GavinEric and Simon. Comprehensive and very readable. Perfect for a couple of my friends who are interested in the science and who are beginning to relize that the denialist position is mostly bluster and noise.

    Thanks John for the heads up about the purchasable pdf being an edited version. I would have purchased and printed several copies and then been very peeved. I’ll set to work copying and pasting the online version into a word doc.

  38. 38
    Steve Bloom says:

    Re #32 reply: “Dr. Samanta and colleagues are of course welcome to answer your question if want to spend their time responding to queries on blogs, but I have to say I object to the insinutation here about scientists motivations. I have little doubt Samanta et al. were not aware of how easily their press release would get misued and abused. I’ve been in the same boat myself. No matter how carefully one words the press release, some people will misunderstand it, whether on purpose or out of naivete.–eric”

    That’s far too generous unless you want to argue they didn’t know what “myth” means. Whoever wrote that press release was angling for controversy.

  39. 39
    jimt says:

    Eric @32 says “I have to say I object to the insinutation here about scientists motivations. I have little doubt Samanta et al. were not aware of how easily their press release would get misued and abused.”

    As a research scientist myself I would never insinuate anything about “scientists motivations” in general (I know they are infinitely variable), but I do find this sort of press release very puzzling, and I am genuinely curious about who wrote it and why. I know (from personal experience) that university press units sometimes encourage researchers to “sex-up” their research, and that there are many external pressures to increase citation rates (hence to exaggerate the implications of ones papers) – regardless of ones personal motivation for doing science. If the authors genuinely believed the IPCC report needed correcting, fair enough (but why do it via press release?). If they – or whoever wrote the press release – was just trying to generate some interest in their paper, then they should be be more careful.
    In the current “climate” it seems very naive to think that a press release claiming to “dubunk myths” and contradict claims by the Intergovernmental Panel on Climate Change would not be used and abused by climate deniers. And I really am baffled why the authors would bother making such a statement given the limitations of the study – in terms of saying anything about climate change impacts.

  40. 40
    Frank Giger says:

    My fear for the Amazon is that climate change studies on impacts resulting in less forest are rather like discussing erosion displacing earth at a strip mine.

    Unless the rate of deforestation by humans has been greatly reduced, that is.

  41. 41
    Ike Solem says:

    This is the disputed quote: “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).”

    First, if you want to see a good example of how this kind of work (climate effects on ecosystem behavior via satellite analysis) should be done, please read this:

    Behrenfeld (2006) “Climate-driven trends in contemporary ocean productivity” Nature

    http://www.gfdl.noaa.gov/bibliography/related_files/mjb0601.pdf

    We find a clear, strong correspondence between MEI [multivariate ENSO index] variability and SeaWiFS [satellite] -based anomalies in NPP [net primary productivity] (r2 5 0.77, P , 0.005) and SChl [surface chlorophyll]. An increase in the MEI (that is, warmer conditions) results in a decrease in NPP and SChl, and vice versa. This relationship emphasizes the pre-eminent role of climate variability on ocean productivity trends. The observed physical–biological coupling between NPP and the MEI [multivariate ENSO index] functions through an effect of climate on water column stratification. Climatic changes that allow surface warming cause an increase in the density contrast between the surface layer and underlying nutrient-rich waters. For the global stratified oceans, the density difference
    between the surface and a depth of 200 m provides a useful measure of stratification. Monthly anomalies in this stratification index exhibit similar trends as the MEI for the SeaWiFS period. Importantly, enhanced stratification suppresses nutrient exchange through vertical mixing. Conversely, surface cooling favours elevated vertical exchange. Phytoplankton in the ocean’s upper layer (that is, the populations observed from space) rely on vertical nutrient transport to sustain productivity, so intensified stratification during a rising MEI period (Fig. 2b) is accompanied closely by decreasing NPP (Fig. 2b) (r2 5 0.73, P , 0.005)

    Note that:

    1) They examine this over an eight-year period, a long enough time frame to make the conclusions more robust.

    2) They raise interesting issues related to the Amazon:

    Modelling studies suggest that shifts in ecosystem structure from climate variations may be as or more important than the alterations in bulk integrated properties reported here

    Hence, the authors of the recent GRL paper did nice work sorting out flaws in earlier research, but their press release claim about the IPCC quote isn’t substantiated for that reason alone – satellite data might be entirely missing changes in species composition. That’s not the only reason, either.

    Furthermore, in evaluating such things, it’s good to look for other examples:

    VANCOUVER, Canada, Mar 10, 2009 – The sheer magnitude of the devastation left by this tiny beetle is shocking on its own. “The pine beetle kill”, as it’s known to British Columbians, refers to the millions of hectares of trees left for dead in the wake of the voracious insect. Forestry officials in Canada’s westernmost province estimate the volume of wood lost to be around 620 million cubic metres – roughly equivalent to 15 million logging truck loads.

    According to a B.C. Ministry of Forests report, roughly half of the province’s pine trees are now destroyed by the bug, with the most extensive damage occurring in the central Canadian Rockies, where two-thirds of the region’s lodgepole pine forests have been transformed into a sea of orange needles.

    Now, is a rough guess of 40% loss really so unreasonable? The Amazon may or may not be as robust as the Canadian pine forests – but the IPCC statement seems fair enough, doesn’t it? Why attack it with a press release blurb unrelated to the actual subject of the paper?

  42. 42
    Edward Greisch says:

    Simon Lewis: Please go over that “roof” thing again. Don’t trees absorb water through their roots in the ground? So how does a roof over a few trees affect the ground water? Did you somehow block the flow of ground water as well? Surely you can’t build a roof big enough to affect ground water?

    [Response: The roof thing... here are some pictures... http://www.whrc.org/southamerica/drought_sim/index.htm
    You build a sloping retractable roof under the canopy to shift water away from your 'drought' plot, and dig a trench around the area with the roof (and dig around the control plot) to stop some of the lateral movement of the water back in once it reaches the soil (you're totally right that the trees get their water through their roots). Then you monitor the water in the soil, photosynthesis, tree mortality etc in your pair of plots to assess the impacts of controlled decreases in water availability on the forest.--Simon]

  43. 43
    Alan of Oz says:

    RE #19 The CSIRO has done a lot of work on AGW’s impact on busfires. See http://www.csiro.au/science/Climate-Change-Fire-Weather.html to get you started. You might also want to check out how fire weather risk is measured via something known as the forest fire index (FFI).

    Also a shameless plug for a bushfire story I posted on slashdot http://slashdot.org/firehose.pl?op=view&id=3586459

  44. 44

    KnowYourPlanet #20, nice service; but please do not repeat false memes, not even in order to refute them. Rather, build the message around a positive meme. Like ‘redundancy’…

  45. 45
    Gilles says:

    “#16 Carl

    2005 was the hottest year on record. The dead and decaying trees in the Amazon contributed to that.

    Satisfied?”

    Obviously nobody answered Carl correctly – and saying that the high 2005 temperature is the consequence of the CO2 emitted by the Amazon forest after the …2005 drought is of course totally surrealist. So did this CO2 contribute to an acceleration AFTER 2005? obviously not since 2005 is still the warmest year following GISS (but not other measurements). In any case, a ” temporary, source of over 3 billion tonnes” has absolutely no effect on the total CO2 level and hence on temperatures which react with a much longer timescale, so the only reasonable and quick answer to Carl would have been : No, of course !!!

    Another funny thing here :
    “The evidence for the possibility of a major die-back of the Amazon rainforest is due to two factors,

    1. That climate change induced decreases in rainfall in the dry season occur, and

    2. The trees cannot tolerate these reductions in rainfall.

    The Samanta paper does not directly address the first point; this is addressed using global circulation models (of which some, but not all, show a strong drying trend for the east of the Amazon over the 21st century)”

    So a strong drying trend is shown by “some, but not all” models. Obviously this is by no means a certitude. Again, and as usual, predictions are based on the fact that models are uncertain. If you raise the uncertainty, you raise the errors bars, meaning that more and more models will predict catastrophic (and wrong) predictions. So we have the first weird result that the more uncertain the models are, the more action is needed.

    But there is worse, much worse. We KNOW that Amazon forest is shrinking, at an accelerated rate. But not because of droughts, that have not yet been observed to increase. Because of ecological pressure, deforestation, both for use of wood and use of land for agriculture. Now what do you think would be the result of a reduction of fossil fuels? a diminishing, or an increasing pressure on biomass ? biomass is the only source of carbon apart from fossil fuels. Brazil is the main producer of biofuels, through sugar cane, and this needs land. So the result is rather obvious to predict – and does not rely on uncertain GCM, but simple and basic logics and sense of reality. Very weird, indeed…

  46. 46
    Gilles says:

    Sorry hadn’t read #28. But then saying ” but tree mortality increased, contributing temporarily to accelerating the rate of climate change” is disingenuous, since absolutely no significative “acceleration of the rate” is visible at all.

  47. 47
    Gilles says:

    “In normal years the forest absorbs nearly 2 billion tonnes of carbon dioxide. The drought caused a loss of more than 3 billion tonnes. The total impact of the drought – 5 billion extra tonnes of carbon dioxide in the atmosphere – exceeds the annual emissions of Europe and Japan combined.”

    Yes.. if the enhanced mortality is not compensated in the next years by an increase of CO2 absorption, which is quite possible if old dead trees are replaced by new growing ones; the peak of mortality in France during the heat wave in 2003 was almost exactly compensated by a decrease in 2004 – obviously because the main effect was an advance of some months of the death of old people. It’s meaningless to consider only short term events, you have to take a global average on relevant timescales. That’s why speaking of an acceleration of the warming is also meaningless, unless it has been proved that the phenomenon is significative on the long term.

  48. 48
    Eli Rabett says:

    Eric, given the constant coverage of the IPCC’s alleged mistakes it is difficult to believe that Samanta, et al, were innocents playing with matches. Even if the release was written by a public information officer, they had the obligation to review and correct it.

    Eli would be a lot more impressed if Samanta had written the same response to the various denialist blogs and news media that have picked up the ball he threw out onto the playing field and are running with it. What say we do an experiment and repost Samanta’s mea not culpa on Climate Audit and similar to see what happens. Wanna bet what happens?

    [Response: Eli: I can understand with your sentiments, but among the many differences between us and people like Steve McI. and Roger Pielke Jr is that we don't accuse or insinuate that other people of dishonest or nefarious motivations without substantive evidence. And it any case it is irrelevant to the point here. The science speaks for itself very unambiguously in this case.--eric]

  49. 49
    Edward Greisch says:

    I thought “a slight decrease in rainfall” meant a “permanent” slight decrease in rainfall, so I didn’t see a problem with the thinking. A permanent slight decrease could cause a switch.
    Doesn’t the jungle “generate or regenerate its own rain”? So wouldn’t there be a positive feedback?

    47 Gilles: “significative”: Are you George W. Bush?

  50. 50
    Leonard Weinstein says:

    The IPCC claim was that the rainforest was excessively sensitive to a slight decrease in rainfall. Anyone would know that a severe and prolonged lack of rain would be bad, but that was not the claim. The IPCC claim is wrong, and trying to relate that to the more extreme situation is incorrect.

    [Response: You are reading things into the IPCC that aren't there. The IPCC does not say "a slight, shortlived, one-year long anomaly" will matter. The implication is obviously that a prolonged decrease will matter. IPCC was arguably less than precise here, but they probably didn't realize anyone would be so foolish as to think they meant weather, rather than climate.--eric]


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