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« Lovelock, AGW and democracy | Main | Visser et al on the divergence problem »
Monday
Mar292010

On rainforest sensitivity

A couple of days ago, I posted on the news that Dr Simon Lewis, a rainforest expert from the University of Leeds, has filed a complaint about an article written by Jonathan Leake at the Sunday Times. Leake's article concerned the IPCC's use of "grey" literature to support a claim that the Amazon is very sensitive to drops in rainfall and that as much as 40% was in danger of being wiped out by small reductions in precipitation.

The use of grey literature is not disputed, but Lewis has complained that the article's headline, presumably written by an editor rather than Leake himself, implied that the sensitivity claim was false. This, he says, is not the case, "there is a wealth of scientific evidence suggesting that the Amazon is vulnerable to reductions in rainfall". It is just that the citation was "bizarre".

In this second piece on the complaint, I'm going to take a look at the science supporting Dr Lewis's position.

Dr Lewis helpfully expands on his understanding here:

It is very well known that in Amazonia tropical forests exist when there is more than about 1.5 meters of rain a year, below that the system tends to ‘flip’ to savanna, so reductions in rainfall towards this threshold could lead to rapid shifts in vegetation. Indeed, some leading models of future climate change impacts show a die-off of more than 40% Amazon forests, due to projected decreases in rainfall. The most extreme die-back model predicted that a new type of drought should begin to impact Amazonia, and in 2005 it happened for the first time: a drought associated with Atlantic, not Pacific sea-surface temperatures. The effect on the forest was massive tree mortality, and the remaining Amazon forests changed from absorbing nearly 2 billion tonnes of CO2 from the atmosphere a year, to being a massive source of over 3 billion tonnes.

In support of his position, Lewis cites a number of authorities and I will look at these in turn.

Daniel Nepstad

When the Amazongate story first broke, Daniel Nepstad was one of the first to defend the accuracy of the claim (while again acknowledging the incorrect citation). Nepstad works at the Woods Hole Research Center, a green campaigning organisation and issued a statement declaring that 40% was the correct figure. Nepstad is slightly unclear about the true source of the figure, saying that the authors of the grey report used by the IPCC had got the information from "IPAM", which turns out to be another green NGO. He then talks about having found that 15% of the Amazon was severely drought stressed in 1998 and that in a later article he had shown that "half of the forests of the Amazon depleted large portions of their available soil moisture during seasonal or episodic drought".

Astute readers will notice that this is not the same thing as saying that 40% would be wiped out by small reductions in rainfall. Indeed, as Nepstad himself notes in a report published in 2007 (and one that was not cited by Dr Lewis)

One of the great ecological puzzles of the Amazon forests is their ability to withstand severe seasonal drought with no visible signs of drought stress.

As far as I can tell, it appears that the Amazon is quite able to deal with drought, even severe drought. For dieback to take place, it requires repeated drought. 

Philips et al 2009 (PDF)

Oliver Philips is a colleague of Simon Lewis at Leeds University and indeed Lewis himself is among the 66 (!) authors. As far as I can tell, Lewis reckons this is among the key pieces of evidence to support his claim, but it is hard to see why. The study looks at the severe Amazonian drought in 2005 and found that in these circumstances the Amazon turns from a carbon sink into a net emitter of carbon. Philips et al seem to concur with Nepstad that it is prolonged drought that is the problem:

Prolonged tropical droughts can kill trees...and some models predict climate-induced Amazon dieback this century.

I see nothing in the paper that could support a claim that 40% of the Amazon could be wiped out by small changes in rainfall.

In fact this is a position that Dr Lewis himself seems to agree with. In a recent post at RealClimate he trenchantly sets forward his views on what matters regarding Amazon dieback. Discussing the findings in Philips et al he points out that trees were affected by the major drought, but that this is not the key point:

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 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.

So, everyone agrees that dieback of the Amazon is predicated on repeated droughts. In order to justify the 40% claim of the IPCC we therefore need to see that small but repeated reductions in rainfall cause dieback.

Models

The evidence that repeated droughts will take place appear to be largely based on application of models. In his PCC complaint, Dr Lewis cites Huntingford et al and Nepstad et al, but in his RealClimate article he points to a paper by Bett et al as well. Before looking at these I want to discuss a couple of points made in the RC article.

Firstly, there is considerable doubt over the model output, in particular with respect to the idea that Amazonian rainfall will decrease in a warming world:

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.

But he also sets out the IPCC view on these models. Mostly, he says, the modelling work has been ignored by the IPCC, who cite Betts and Huntingford and make the infamous 40% claim. But, he reiterates, this claim is correct:

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.

You will note that what he states as the preconditions for Amazon dieback here are slightly different to those he gives in the complaint. Putting these together we really have three conditions

  • that the Amazon will move to a new, lower rainfall regime (repeated drought)
  • that trees are sensitive to repeated drought
  • that 40% of the Amazon is close to this threshhold.

The second point seems undeniable, so I don't propose to look into it any further. I will accept Dr Lewis's figure of 1.5m of rainfall per annum as the correct one. However the question of whether the Amazon will move to a regime of repeated droughts looks more interesting.

Will the Amazon dry up?

I am grateful to Professor Hector Maletta of the Universidad del Salvador in Buenos Aires, who left a link to his draft paper on the science of Amazon deforestation. I would urge readers to get hold of this paper themselves, because it is remarkable stuff, much of which bears directly on the question of the IPCC's 40% statement.

The dieback sections of Professor Maletta's paper examine four different modelling studies - Cox, Nepstad, Betts and Lenton all of whom predict rapid large-scale dieback and replacement of rainforest by savannah. I think we can say with some confidence that these papers are the ample evidence referred to by Dr Lewis.

However, the evidence seems highly questionable at best. For example Nepstad suggests that more than half of the rainforest could be gone by 2030. As Maletta puts it:

These dire predictions (mostly inspired by the Amazon 2005 drought and recent El Niño episodes) emerge not from a global or regional model, but as a possible result of the hypothetical persistence of then-recent events (up to the early 2000s) plus the purely theoretical hypothesis of a 'tipping point' to be hypothetically reached if deforestation advances past some unknown percentage of tree cover, thus possibly triggering an 'abrupt change' process of unknown duration. The critical percentage of tree cover that would trigger the dieback process, if it exists, is unknown, though hypothesized to be 30%.

 Nepstad's findings, says Prof Maletta, should be treated with caution in view of...

  • the lower rates of deforestation observed in recent years
  • improved protection of fragile areas
  • increasing establishment of protected areas in the frontier of deforestation
  • lack of data on crucial issues such as the very existence of a tipping point, and parameters such as the critical value for the tipping point in case it exists, the time it would take for the subsequent process to complete, and the reversibility or irreversibility of the process.

And as Maletta point out, even those who have been the main proponents of the idea of Amazon dieback say that "it remains just a theoretical possibility without much in the way of empirical evidence". This is a long way from Dr Lewis's "ample published evidence".

Both the Cox and Lenton studies predicate the idea of Amazon dieback on the idea of the development of persistent El Nino conditions, another point discussed by Maletta. The problem with this hypothesis is that according to the IPCC,

there there is no consistent indication at this time of discernible future changes in ENSO amplitude or frequency"

As readers will note, this is a serious blow to the idea of a persistent El Nino if this is really required to bring about persistent drought and therefore dieback in the Amazon. However, Lenton at least, choose to differ from this finding, saying, without providing supporting evidence, that a transition towards a higher ENSO amplitude will happen within a millennium. So even Lenton, who is out of kilter with the IPCC consensus, thinks that global warming will only affect amplitude (which will not make El Ninos more persistent or permanent, as required by the dieback hypothesis) and moreover that it will only do this on rather long timescales. This makes Nepstad's claims of Amazonian dieback in the next twenty years look, well, interesting.

In conclusion

A few days reading of the literature is not enough to draw definitive conclusions, but it appears to me that Dr Lewis's position - that there is "ample evidence" that the Amazon will move to a lower rainfall regime is one that is at best debatable and may in fact not be a fair representation of the literature. If any readers want to investigate this claim further, or indeed if anyone wants to dig into the other aspects of Lewis's claims - that large areas of the Amazon receive rainfall close to the 1.5m threshold and that there is the possibility of Atlantic-driven drought as well as El Ninos - I'd be interested to hear from you.

 

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Reader Comments (67)

So, everyone agrees that dieback of the Amazon is predicated on repeated droughts. In order to justify the 40% claim of the IPCC we therefore need to see that small but repeated reductions in rainfall cause dieback.

Not quite. It's a substained reduction in rainfall below a certain theshold over 40% of the rain forrest in the Amazon

ie. You could get a substained reduction but still have rainfall above the threshold to cause a die off.


Nick

Mar 29, 2010 at 12:39 PM | Unregistered CommenterNick

It's not global warming (CO2), it's local deforestation

Roni Avissar and David Werth, Global Hydroclimatological Teleconnections Resulting from Tropical Deforestation, Journal of Hydrometeorology, Volume 6, Issue 2 (April 2005), pp. 134–145

http://ams.allenpress.com/perlserv/?doi=10.1175%2FJHM406.1&request=get-abstract

Mar 29, 2010 at 1:01 PM | Unregistered CommenterHans Erren

[Snip. Sorry, there is an unthreaded post for this kind of thing. And I posted about this story already too]

Mar 29, 2010 at 1:02 PM | Unregistered Commenterbarry woods

That's really valuable Bishop - even though I only skimmed it and am unlikely to delve further this week, it reminded me of the problems with forecasting of rainfall on the Sahel. (Check the end of July's National Geographic article for another amusing illustration of how regional models predicated on increasing AGW are retroactively 'tuned' - in this case fifteen years later - to fit real world data that goes determinedly in the other direction from the droughts that were originally and scarily depicted.) The Sahel being the other end of the spectrum from the Amazon ecosystem-wise I guess, but perhaps exhibiting the same general problems with regional forecasting ten, twenty or thirty years out? Oh no, I forgot, at thirty years the horrible, unpredictable weather becomes the smooth and predictable climate. So that's OK then. As you were.

Mar 29, 2010 at 1:15 PM | Unregistered CommenterRichard Drake

Interesting piece. There probably was an overstatement in the Times headline, however that shouldn't be taken to mean that Lewis et al are now a stamp of authority on the original IPCC 40% statement.

No matter how qualified these guys are, they still don't represent the "Gold Standard" of the current science. The whole purpose of the IPCC - thousands of people, peer review, checks and balances, lines of consultation - has now rightly been scrutinised and found wanting, however those ideals of - checks and balances etc - should not be thrown out and we just take Simon Lewis and RealClimates press releases and Climate Progress's PCC complaint as evidence that the 40% statement would have still been acceptable by any governmental panel, past or future.
When you take the organisation of this PCC complaint, together with the WWF now belatedly saying they had an "editing" slip, saying they did have a reference available at the time - but still to something from an advocacy organisation - the whole episode smacks of a section of alarmists - NGOs RC, and Joseph Romms Climate Progress attempting to co-opt the authority of the IPCC.
I think there is a danger that they will claim this credibility, at least in the fickle media, if the PCC complaint does any more than result in a mild rebuke for the original headline.

Mar 29, 2010 at 1:16 PM | Unregistered CommenterSteve2

I think your conclusions are correct.
So-called experts "declaring that 40% was the correct figure" add nothing of value unless they can back it up with clear evidence, which it appears they cannot.
Similarly what 'some models show' is equally meaningless. The only thing that such models show is the preconceptions of the people who devised the models.

What is particularly disturbing is the double standards exhibited by these people. For years and years, the newspapers have been exaggerating and overstating the case for climate change, and they remained silent. Now the wind is blowing in the other direction and suddenly they are kicking up a fuss.

Mar 29, 2010 at 1:16 PM | Unregistered CommenterPaulM

It seems to me that you are doing a really excellent job of investigative journalist.

Referring back to a previous thread... if the Guardian spent more man-hours on journalism and less on censoring comments they might (just might) come up with something half as good.

Mar 29, 2010 at 1:50 PM | Unregistered CommenterCaroline

But Bish, it must be right, for so much could depend on this. There is even ANOTHER statement from Woods Hole Res C, this time signed by 19, count them 19, Amazon Experts, including of course S.L. and D.N. from your article..
Just read the headline, it says it all:

Scientists’ statemen on recent press release on Amazon susceptibility to reductions in
rainfall: no Amazon rainforest “myths” have been debunked.

http://www.whrc.org/assets/scientists_amazon_response.pdf

So, it must be true, whatever it is that needs to be true, or alternately, whatever it is that needs to be debunked, rebutted or refuted, has been comprehensively, or not as the case may be.

Mar 29, 2010 at 2:10 PM | Unregistered CommenterChuckles

1.5m doesn't sound an awful lot for a 'rainforest' - you must get nearly that much in Scotland!

Mar 29, 2010 at 2:23 PM | Unregistered CommenterJames P

Astute readers will notice that this is not the same thing as saying that 40% would be wiped out by small reductions in rainfall.

Astute readers will notice that the same reference contains this, which clearly does support that claim:

In 2004, we estimated that half of the forest area of the Amazon Basin had either fallen below, or was very close to, the critical level of soil moisture below which trees begin to die in 1998.

This statement has more references.

Mar 29, 2010 at 2:34 PM | Unregistered CommenterFrank O'Dwyer

I remember hearing a lecture from the engineer who was part of the team that adjusted the "lean" of the Tower of Pisa. Their models showed that it should have fallen down some time before. Models cannot tell you the whole story.

Mar 29, 2010 at 3:01 PM | Unregistered Commentermontysmum

Frank

Nepstad 2004 is here. It's a modelling study. The figures they give are for the severe drought of 2001. This therefore doesn't get at the issue at hand of how much land is close to the 1.5m threshhold.

I've read several of the references you give, but I'm not aware that any of them get at the 40% figure. If you can point me to a pertinent one, that would be helpful.

Mar 29, 2010 at 3:01 PM | Unregistered CommenterBishop Hill

This might sound a little off-topic but it is directly related. One of the reasons drought causes rainforests to die back, is because it is so warm at the equator. C3 plants make up most of the rainforests and they are succeptible to die-back when conditions are hotter and when there is less rainfall.

The reason C3 plants need so much precipitation where it is hot is because the stomata that take in CO2 also transpire some water. The hotter it is, the more water is lost as a result of this.

But the stomata size is directly related to how much CO2 there is. When there is less CO2, the stomata size increases and even more water is transpired/evapourated through the stomata. When there is increased CO2 levels, the stomata size decreases and less water is lost.

The C4 plants (mostly grasses, read savanna) use a different Carbon fixation pathway and are thus less succeptible to lower CO2 levels, drought and hot conditions.

The Amazon drew back significantly in the ice age when both precipitation was lower and CO2 levels fell below 200 ppm for large parts of the ice age. This is the most extreme case of drought (and CO2 stomata size/feedback) that has actually occured (outside of a climate model).

So, with higher CO2 levels, I imagine the rainforests can take a little more drought than otherwise.

Now. I'm sure some enterprising modelers like Cox and Betts (cited above) can then build in a secondary feedback from increased CO2 and global warming whereby less water transpiration from the C3 rainforests results in even less daytime water vapour in the air, thereby less rainfall, even more drought and then even less Carbon uptake and so on and so on.

The modelers can put together any result one wants.

http://www.kuuvikriver.info/uploads/science/Amazon_dieback_under_climate-carbon_cycle_projections_for_the_21st_century.pdf

Mar 29, 2010 at 3:09 PM | Unregistered CommenterBill Illis

I agree with Hans Erren; over use of chain saws may increase the CO2 levels locally in the Amazon, but that is not the cause of deforestation, it is the cutting of trees. It is anthropomorphic, but not AGW.

Also, please remember that although the Andes are in the way, the water from Peru does fail in the Amazon as rain, and given the existence of La Niña and El Niño, which are caused by changes in the Pacific oceanic currents, which in turn, are due to solar heating of the water, any changes in the rainfall are due to solar heating.

Mar 29, 2010 at 3:15 PM | Unregistered CommenterDon Pablo de la Sierra

In 2005 there was supposedly a 'serious' drought in the Amazon, and yet the rainforest 'greened up'. It is far more resilient than thought.

Although drought encourages additional fires, the smoke is not all bad. In a dense rainforest only the top of the canopy gets sunlight, and dense shadows are cast on the leaves and vegetation below. Photosynthesis there is limited by the poor level of light, whereas on the top of the canopy there is more light than needed (the limiting factors are then CO2 and water). When the atmosphere is somewhat hazy due to smoke there is a tremendous amount of light dispersed in all directions, including on both sides of leaves. The reduction in light reaching the top of the canopy has no effect on photosynthesis there, since it is not light limited, but the dispersed light finds leaf surfaces that are usually shadowed, so light limited for photosynthesis. Moreover, the locally increased level of CO2 due to burning trees will increase photosynthesis, even when water becomes limited, because a higher level of CO2 causes the leaf stomata to close up, thus reducing transpiration and loss of moisture. Plants can grow at the same or faster rate with a lot less water provided they have higher CO2.

Meanwhile, down below the top of the canopy, these leaves are receiving a higher concentration of CO2 and a higher level of light due to the scattering effect of smoke, as well as better penetration of the light where, due to water stress, there has been some leaf shedding in the upper canopy.. Even though moisture is reduced, the overall effect will be growth due to better photosynthesis, requiring less moisture due to the closing of the stomata.

It is thus to be expected that even when precipitation is reduced, the effects of slight top canopy thinning, and of more diffuse light and higher CO2 due to increased fire is to increase the growth of the trees that are not fired. The idea that tree burning simply dumps loads of CO2 back into the atmosphere, reduces vegetation and is all negative is simplistic nonsense - the byproduct is an improved level of photosynthesis in the rest of the forest, thus sequestering CO2, which can outweigh the liberation of CO2 from limited burning. Of course, there is a level of burning to surviving trees where this breaks down, but the Amazon in 2005 was nowhere near that level: fires were only 30% or so more than in an average year.

There is thus a perfectly natural feedback mechanism to cope with drought, provided drought is not too deep or too prolonged. Models that don't take this into account are simply junk.

I have done quite a few posts on CO2 and plants: here's a start:

http://buythetruth.wordpress.com/2009/06/13/photosynthesis-and-co2-enrichment/

http://buythetruth.wordpress.com/2009/08/15/co2-enrichment-and-plant-nutrition/

http://buythetruth.wordpress.com/2009/07/11/growth-of-crops-weeds-co2-and-lies/

Mar 29, 2010 at 3:16 PM | Unregistered CommenterScientistForTruth

Bishop,

The point is that you quoted from Nepstad's statement but why not the more obviously relevant piece of it that I did? It's like you are trying to argue that his own statement does not support his statement, by quoting the wrong part of it!

As for Nepstad 2004, that does support the claim:

This study points to the widespread effect of drought on Amazon forests, and the vulnerability of Amazon forests to small declines in rainfall or increases in ET. Rainfall and ET are nearly equal across the Amazon during most years, with total rainfall falling below ET during years of severe drought. Such droughts may become more common if ENSO events continue to be frequent and severe, if rainfall is inhibited by defor- estation or smoke, and if warming trends continue. Increases in ET of only 15% or similar reductions in rainfall can lead to severe soil moisture deficits over roughly half of the Amazon (Fig. 9).

In his statement Nepstad also makes it clear that this means the level at which the trees get wiped out.

Mar 29, 2010 at 4:16 PM | Unregistered CommenterFrank O'Dwyer

Frank, the passage you quote from Nepstad 2004 is wrong on several counts.

1) Firstly, it's simply wrong. It's from a summary (Discussions) at the end of the paper and it directly contradicts both the main body of the text and the abstract. The area that could experience severe moisture deficits (defined by the paper as less than or equal to 25% of local maxima) is 31%. The 'roughly half' should have been attached to 'moderate drought deficits' (<50% local max). The paper found that 51% of the area could experience those.

2) It's wrongly applied. The paper is mostly about flammability. It briefly discusses reductions in biomass production resulting from reduced soil moisture but the only effect it attaches to this quantified area suffering severe moisture deletion is fire. Dieback is all about permanently shrinking forests. Fire doesn't preclude regrowth. So what Nepstad 2004 actually supports is that about a third of the forested area could be susceptible to temporary shrinkage by fire if rainfall is reduced - or ET increased - by 15%. That is a helluva long way from saying that up to 40% could suddenly become permanently deforested.

3) That 31% is mostly in the most heavily logged parts of the basin, so the chances are it'll be cut down before reduced rainfall gets a chance to burn it down.

In short, not only did Nepstad's own statement not support his statement but his statement didn't support his statement and neither his statement nor his statement supported the IPCC's statement. Clear?

Mar 29, 2010 at 5:25 PM | Unregistered CommenterVinny Burgoo

As I understand it the climate modelers admit they can not model clouds and water vapor influences. I recall research, including some modeling, that precipitation will increase rather than decrease as temperatures rise. This alternative seems to be ignored in the dialog about the Amazon rain forests will react to increased global temperatures.

For Nepstad, Lewis and Leake to have any relevancy, should not they have to disprove the increased precipitation hypothesis?

Mar 29, 2010 at 5:52 PM | Unregistered CommenterPaddy

I went looking for historical data of rainfall trrends in the Amazon basin. The two recent articles unfortunately are both behind pay walls. One says there is a trend towards lower rainfall noting "changes in the circulation and oceanic fields after 1975 suggest an important role of the warming of the tropical central and eastern Pacific on the decreasing rainfall in northern Amazonia, due to more frequent and intense El Niño events during the relatively dry period 1975–98." http://www.springerlink.com/content/29qvrd87dp5bcpr2/
The second indicates that there is no discernible trend - "On the whole, there is no strong evidence for believing that the rainfall regime in the Amazon basin is undergoing appreciable change." http://lba.inpa.gov.br/conferencia/apresentacoes/resumos/208.html

Can someone find and post actual rainfall data for the last 50 plus years?

Mar 29, 2010 at 6:00 PM | Unregistered CommenterBernie

Vinny,

The area that could experience severe moisture deficits (defined by the paper as less than or equal to 25% of local maxima) is 31%.

I believe this is the area that did experience severe moisture deficits - i.e. before considering the effect of any further rainfall reduction.

In the discussion he is talking about what will result under the assumption of an additional rainfall reduction or ET change of 15%. In the body of the paper it also says that a 15% error in ET can result in a twofold change in area of severe moisture deficits.

Mar 29, 2010 at 6:37 PM | Unregistered CommenterFrank O'Dwyer

Frank, we're both wrong. My error: 31% is, as you say, the area that the Nepstad model reckoned had 'experienced' severe moisture deficits in 2001. (I shouldn't have put the 'could' in. My typing fingers were probably trying to signal something about the inappropriateness of using 'experience' when writing about modelled results.) Yours: What further rainfall reduction? 31% was a modelled snapshot of a past event, not an estimate of a new baseline. You have perhaps been misled by Nepstad's recent statement, in which, somewhat oddly, he failed to mention that the 2004 results he (mis-)summarized (and misapplied) were for a single year.

Mar 29, 2010 at 7:05 PM | Unregistered CommenterVinny Burgoo

If you got to www.sciencedaily.com and key into search option Amazon drought and rainfall you will find the following article, posted I think on March 12th with the following title, 'New Study Den bebunks Myth about vulnerability of Amazon rainforest to drought' which is more or less to debunk of Nepstad and cohorts

Mar 29, 2010 at 7:50 PM | Unregistered Commentercarol

That came out funny for some reason. Try again. If you go to www.sciencedaily.com and key in search option words amazon drought and rainfall it will take you to an article posted on March 12th, 'New Study debunks myth about vulnerability of Amazon rainforest to drought' and is clearly aimed at Simon Lewis and the IPCC forecast.

Mar 29, 2010 at 7:53 PM | Unregistered Commentercarol

Carol

Interesting to compare that article to the discussion of it at RealClimate.

Mar 29, 2010 at 8:19 PM | Registered CommenterBishop Hill

Your Grace. In your opening remarks you say: "Leake's article concerned the IPCC's use of "grey" literature to support a claim that the Amazon is very sensitive to drops in rainfall."

Doesn't that mean that the Amazon is very sensitive to the DROPS in rainfall. That is, could AGW mean that the drops in rainfall are getting bigger, and therefore damaging the vegetation more than smaller drops would? As in raindrops keep falling on my head.

OMGIWTWT.

:-)

Mar 29, 2010 at 8:25 PM | Unregistered Commentermondo
Mar 29, 2010 at 8:50 PM | Unregistered CommenterRichard North

@Richard North,

Thank you Richard, I was about to post that link. Popular place the Amazon.

Mar 29, 2010 at 9:24 PM | Unregistered CommenterChuckles

Vinny,

Yours: What further rainfall reduction? 31% was a modelled snapshot of a past event, not an estimate of a new baseline.

Eh? The paper provides an estimate of the area of forest (31%) that has already experienced severe drought. In the discussion it then says that about 50% of forest is vulnerable IF there is a further 15% reduction in rainfall (or the equivalent change in ET).

Does this statement from the peer reviewed literature support the claim of the IPCC? It certainly seems so to me. Does the author think so, too? Yep. Do the experts still stick to that claim and find the IPCC statement appropriate even now? Yes.

Now, if you want to argue that the paper is wrong or that conclusion is not supported by the paper, what you need to do is not to tell me but rather to submit a comment to the journal and get it past peer review. If you want to argue that the IPCC claim itself is wrong, go do some research and likewise, get it published in the literature. Or point to something already peer reviewed that says different. This 'blog science' BS won't do.

Until you do that you're just some guy on a blog claiming that the experts are fools, and thumbing your nose at people who've actually done some heavy lifting, while you yourself have already misread the paper you claim is wrong.

Mar 29, 2010 at 9:32 PM | Unregistered CommenterFrank O'Dwyer

Frank: 'The paper provides an estimate of the area of forest (31%) that has already experienced severe drought.'

No. That was an estimate of the area that *did* experience severe drought.

Frank: 'In the discussion it then says that about 50% of forest is vulnerable IF there is a further 15% reduction in rainfall (or the equivalent change in ET).'

No. That sentence was included as support for the preceding 'Discussion'. If it wasn't invented out of nothing - and it surely wasn't - then it came from the main body of the text; and if it came from the main body of the text, it got mangled in the coming. Your IF *is* invented, however. Read it again.

Frank: 'Does this statement from the peer reviewed literature support the claim of the IPCC? It certainly seems so to me. Does the author think so, too? Yep. Do the experts still stick to that claim and find the IPCC statement appropriate even now? Yes. ... peer review ... IPCC ... peer reviewed ... you're just some guy on a blog claiming that the experts are fools, and thumbing your nose at people who've actually done some heavy lifting, while you yourself have already misread the paper you claim is wrong.'

Astonishing, isn't it? I'm not happy that 'some guy on a blog' like myself can so easily find holes in the work of experts (and in what those experts say about their own work), but the holes are there. What are you going to do? Ignore them? Activists and elected representatives and scientists and various mixtures of the three keep telling us that this is a holy body of work, that it cannot be questioned, that we must change the way we live or else. But it's not holy. It's a normal human endeavor. Nor is it wholly holey. Some of the experts are indeed fools and some of them have been corrupted by ego or politics but most of them are honest, competent toilers who do the best they can (and still make mistakes).

Mar 29, 2010 at 10:35 PM | Unregistered CommenterVinny Burgoo

@ Nick

Not quite. It's a substained reduction in rainfall below a certain theshold over 40% of the rain forrest in the Amazon

ie. You could get a substained reduction but still have rainfall above the threshold to cause a die off.

I'm not quite following - is it ' below a certain theshold ' or ' above the threshold'

Mar 29, 2010 at 11:21 PM | Unregistered Commenterclawga

Frank, what on earth is wrong with you? Do you deliberately argue with people just for the fun of it or do you really believe what you write?

Read this and then give me your revised opinion of Nepstad and his work: http://eureferendum.blogspot.com/2010/03/dishonesty-multiplied.html

Mar 29, 2010 at 11:35 PM | Unregistered CommenterDr. J.Kolberg

Vinny,

Frank: 'The paper provides an estimate of the area of forest (31%) that has already experienced severe drought.'

No. That was an estimate of the area that *did* experience severe drought.

You have simply restated what I said.

Frank: 'In the discussion it then says that about 50% of forest is vulnerable IF there is a further 15% reduction in rainfall (or the equivalent change in ET).'

No. That sentence was included as support for the preceding 'Discussion'. If it wasn't invented out of nothing - and it surely wasn't - then it came from the main body of the text; and if it came from the main body of the text, it got mangled in the coming. Your IF *is* invented, however. Read it again.

Again:

Increases in ET of only 15% or similar reductions in rainfall can lead to severe soil moisture deficits over roughly half of the Amazon (Fig. 9).

Can lead, not did lead. They can lead to that IF the reduction occurs. The discussion also names some of the mechanisms that can lead to that reduction. It doesn't say they have already occurred.

Look, this isn't even scientific argument it is basic reading comprehension.

I'm not happy that 'some guy on a blog' like myself can so easily find holes in the work of experts (and in what those experts say about their own work), but the holes are there.

No they aren't. Yours is the work that anybody on a blog can find holes in.

What are you going to do? Ignore them?

Pretty much. They don't seem to exist.

Mar 30, 2010 at 12:10 AM | Unregistered CommenterFrank O'Dwyer

Dr Kolberg,

Read this and then give me your revised opinion of Nepstad and his work: http://eureferendum.blogspot.com/2010/03/dishonesty-multiplied.html

It is pure ad hominem directed at Nepstad - North's arguments if valid apply even more forcefully to himself, since he himself is a major source of the whole trumped up controversy and relied upon by Leake.

The difference is that Nepstad is an expert with relevent credentials and publications and North is just another clown with a blog, helpfully layering his amateur and self-serving interpretation on top of what the real experts have to say.

Let him put his review of the literature into a formal article and get it past peer review. Maybe then it will be of some value.

Mar 30, 2010 at 12:25 AM | Unregistered CommenterFrank O'Dwyer

"Frank: 'In the discussion it then says that about 50% of forest is vulnerable IF there is a further 15% reduction in rainfall (or the equivalent change in ET).'"

In other words, IF there is a further reduction in rainfall, (following an already exceptional period of drought), then 50 percent of the forest is "vulnerable" to fire. This does not support any argument that the forest will "flip" to savannah. Nor even does it support an argument that 50 percent (or any lesser figure) will succumb to fire.

More to the point, the paper is referring to the secondary effects of fire. The IPCC is referring to a "slight reduction in precipitation" as the PRIMARY cause of conversion to savannah. Fire or complex causation is not mentioned.

Given that the climate is cyclical - as indicated by long term observation - and that periods of drought are followed by periods of above average rainfall (as has been the case since 2005), the most likely effect of fire damage in the bulk of the forest (excepting only ecotonal areas) would be grow back, with the forest slowly regenerating.

It does not follow that, where the climate favours forest growth, savannah encroachment will follow when the forest is destroyed. Experience shows that, within 20-30 years, the forest has regenerated to the extent that it requires expert knowledge to distinguish between it an virgin forest. Furthermore, updated modelling indicates that the climate will continue to favour forest growth.

Thus, Nepstad 2004 cannot be used to support the IPCC claim. Nepstad's proposition should be taken from what is said on the label on the tin. Drought renders forests prone to fire ... I'm shocked! It does not in any way support a claim that 40 percent of the forest could convert to savannah.

Mar 30, 2010 at 12:39 AM | Unregistered CommenterRichard North

Richard North,

Before I get into your claims, what credentials have you got to interpret the literature?

Why should anyone believe your review of the literature?

How many papers or reviews have you had published on climate or the amazon in the peer reviewed literature? (The sunday papers don't count.)

How long have you been studying the Amazon? (For comparison, Nepstad has been doing so for over 20 years).

Have you ever even visited the Amazon?

Mar 30, 2010 at 12:54 AM | Unregistered CommenterFrank O'Dwyer

Frank

I really do not give a tuppeny toss whether you "get into my claims" or not. The literature and the claims thus made stand or falls on what is published ... the claims are either coherent or they are not, according to the evidence and the reasoning adduced by the authors. The argument, however, stands or falls on the totality of the evidence, and not on the limited perspective of any one author or group of authors. Nepstad's claims do not support the IPCC ... either in themselves or in the context of a wider framework - and you are clearly not capable properly of interpreting them.

.

Mar 30, 2010 at 1:06 AM | Unregistered CommenterRichard North

Richard North,

you are clearly not capable properly of interpreting them.

And presumably you are? Please provide some reasons why. How long have you been studying climate and the amazon? What are your scientific credentials?

Have you ever been to the amazon rainforest? I have seen pictures of Nepstad working in the rainforest but none of you. Can you post some?

I asked these and similar questions before but you forgot to answer.

The argument, however, stands or falls on the totality of the evidence, and not on the limited perspective of any one author or group of authors.

How many authors do you think you are? You are just one author, are you not?

Oh wait, you're not even one author, are you - If I'm not mistaken, you've never had any relevant scientific study published at all.

That and your complete lack of relevant expertise and experience would make your perspective seem rather limited indeed, wouldn't it?

Mar 30, 2010 at 1:40 AM | Unregistered CommenterFrank O'Dwyer

Frank

Entertaining though your diversion is, it rather proves the point. You raise spurious arguments about Nepstad 2004, which clearly demonstrate a limited capacity for logical interpretation, fail then to adduce any further evidence and then devote your limited talents to raising a smokescreen when you are caught out. Doesn't work here ... the technique is too transparent and, frankly, quite boring. I can't even be bothered to educate you on quite how and why you are wrong. You wouldn't understand anyway.

Mar 30, 2010 at 1:50 AM | Unregistered CommenterRichard North

The following abstract is of an RA paper by Lloyd (Leeds, same univeristy as Lewis!) and Farquhar (ANU) seems to have been overlooked, perhaps because it confirms the views of North et al, and refutes O'Dwyer.

I recommend reading more papers by these authors as they very politely demolish much of what passes for "climate science" with the O'Dywers.

Review
Effects of rising temperatures and [CO2]
on the physiology of tropical forest trees
Jon Lloyd1,* and Graham D. Farquhar2
1Earth and Biosphere Institute, School of Geography, University of Leeds, Leeds LS2 9JT, UK
2Environmental Biology Group, Research School of Biological Sciences, Australian National University,
Canberra, Australian Capital Territory 0200, Australia
Using a mixture of observations and climate model outputs and a simple parametrization of leaf-level
photosynthesis incorporating known temperature sensitivities, we find no evidence for tropical forests
currently existing ‘dangerously close’ to their optimum temperature range. Our model suggests that
although reductions in photosynthetic rate at leaf temperatures (TL) above 308C may occur, these are
almost entirely accountable for in terms of reductions in stomatal conductance in response to higher leafto-
air vapour pressure deficitsD.This is as opposed to direct effects ofTL on photosyntheticmetabolism.
We also find that increases in photosynthetic rates associated with increases in ambient [CO2] over
forthcoming decades should more than offset any decline in photosynthetic productivity due to higherD
or TL or increased autotrophic respiration rates as a consequence of higher tissue temperatures.We also
find little direct evidence that tropical forests should not be able to respond to increases in [CO2] and
argue that the magnitude and pattern of increases in forest dynamics acrossAmazonia observed over the
last few decades are consistent with a [CO2]-induced stimulation of tree growth.
Keywords: review; photosynthesis; climate change; plant growth

Mar 30, 2010 at 2:12 AM | Unregistered CommenterTim Curtin

Richard North,

You raise spurious arguments about Nepstad 2004

No I am pretty sure that was you. So anyway, what did the experts say about your arguments when you put them forward for peer review?

Or didn't you believe it when you said that "the argument, however, stands or falls on the totality of the evidence, and not on the limited perspective of any one author or group of authors". After all you are not even as many as one author yourself, and you haven't been looking at the 'totality' of the evidence as long as any one who has actually worked on the topic has. So probably an idea for those guys to give your novel ideas the once-over, wouldn't you say? Have they done so or is there some reason they have overlooked your devastating critiques? Could the problem be that they are reading the scientific literature and not your blog?

Maybe you can also help me with this. If the perspective of someone such as Nepstad (who has worked on this full time for over 20 years and has actually been to the rainforest) is 'limited', according to you, what is the appropriate adjective for your perspective? As far as I can see your perspective would appear to be that of an unqualified and partisan rank amateur who has worked part-time on the topic for something less than 20 hours. One who has probably never even studied a single tree in your back garden, never mind the rainforest in the Amazon basin.

And besides, as you said the literature and the claims thus made stand or falls on what is published, and your claims are not published, are they? Nowhere that counts I mean. Isn't that right? Well if it wasn't right I think you would have mentioned it by now.

Mar 30, 2010 at 2:17 AM | Unregistered CommenterFrank O'Dwyer

Frank

The smokescreen continues ... more and more smoke, which enables you to put greater distance between yourself and the "threat" - that's what a destroyer does when it is outgunned ... so the analogy is entirely apt. Having raised spurious points, which are then challenged, you fail to address the issues raised and instead pour out oily smoke - not that I care. Your bluster does not impress. It is tiresome and childish - and getting repetitive.

Mar 30, 2010 at 3:08 AM | Unregistered CommenterRichard North

Still no answer Frank. Looks like you fail!

I've been lurking on BH for the last couple of years and have read almost every comment posted, including yours. I often found your arguments reasonable although rarely agreed with them. Not once did I classify you as a troll, until now!.

Nepstad's perspective is not narrowed due to his experience, it's narrowed by his desire for the 'right' results. He is working as an advocate, not as a scientist.

Mar 30, 2010 at 6:49 AM | Unregistered CommenterDr. J.Kolberg

Tim Curtin,

The following abstract is of an RA paper by Lloyd (Leeds, same univeristy as Lewis!) and Farquhar (ANU) seems to have been overlooked

Why, no it doesn't. It cites Lewis's work in support, and Lewis later cites it in support!

Why it's almost as if these experts are more familiar with each other's work than any of you are.

Mar 30, 2010 at 9:50 AM | Unregistered CommenterFrank O'Dwyer

Dr Kolberg,

Still no answer Frank. Looks like you fail!

Still no answer to what? Perhaps you mean North hasn't answered my questions. Why that would mean a failure on my part I can't imagine.

Nepstad's perspective is not narrowed due to his experience, it's narrowed by his desire for the 'right' results. He is working as an advocate, not as a scientist.

Maybe Nepstad is an advocate or maybe that is just you looking through your own shit colored glasses due to your own desire to hear only the 'right' results. But there is no doubt at all Nepstad has been working as a scientist. He has, for example, got his ass down in the rainforest performing drought experiments.

We cannot say the same about North, though we can certainly see that he is working as an advocate not a scientist. I doubt he has even performed a study on so much as a single tree in his own garden or the local park, and I'd say the nearest he has got to the Amazon is amazon.com.

Does that matter? Yes, probably. Most of North's 'literature review' consists of statements and liberal interpretations from North which he merely claims are supported by the literature, or are what the papers 'really mean' (even though some of the expert authors never mention it in their papers and have even issued statements to the contrary). North even deems himself competent to tell us that 'climate is cyclical' - surely there is no end to this renaissance man's talents? Perhaps he will juggle a canteen of cutlery after he is done telling dozens of scientists they have made trivial mistakes.

Mar 30, 2010 at 10:08 AM | Unregistered CommenterFrank O'Dwyer

Frankie boy

Maybe Nepstad is an advocate or maybe that is just you looking through your own shit colored glasses due to your own desire to hear only the 'right' results. But there is no doubt at all Nepstad has been working as a scientist. He has, for example, got his ass down in the rainforest performing drought experiments.

Temper tantrums as well?

An advocate is one who presents a case on behalf of a person or organisation, in pursuit of a specific outcome. By any measure, Nepstad is an advocate. He may be "working as a scientist" but adopting scientific method as a means of advoacacy does not a scientist make.

North even deems himself competent to tell us that 'climate is cyclical' - surely there is no end to this renaissance man's talents?

Now your slip is showing. I think you will find that Marengo, Coe et al and Zeng et al, inter alia, are deeming themselves competent to tell us that the Amazonian climate is cyclical. Nepstad, Lewis, and others, however, seem to be interpreting the 2005 drought as part of a trend ... positing that low rainfall conditions might continue. Bit naughty that ...

And Nepstad et al, to say nothing of you, have a leeeetle problem if they want to make a big deal about a 15 percent drop in rainfall increasing the vulnerability of the forest (Nepstad 2004). The context was the 2001 drought ... that was followed by the 2005 drought, when in some areas there was a precipitation deficit of 85 percent. And hey! The forest is still there ... except of course the bits the naughty ranchers chopped down ... but then, "sea surface temperature anomalies" do such strange things, doncha know (see Nepstad 2008).

Perhaps he will juggle a canteen of cutlery after he is done telling dozens of scientists they have made trivial mistakes.

How very strange ... and there I was thinking that it was the "scientists", like that famous climate scientist and former railway engineer, Rajendra Pachauri, who was saying that the mistake (singular) was "trivial". I must slap my wrists and say three Hail Marys ... I thought the Amazon "mistake" was serious.

But, of course, we now know that the IPCC relied on a document from an advocacy group (WWF), the authors of which (neither of them climate scientists .. one being a free-lance journalist) had accidently omitted the crucial supporting reference (without the "scientists" of the IPCC noticing).

We also now know that the WWF authors (one of which was a free-lance journalist) plucked their 40 percent figure from a web site of another advocacy group (IPAM), and now seek to substantiate it with a narrative produced by the self-same advocacy group, which is also not peer-reviewed.

So, the IPCC used a non peer-reviewed source, the lead author of which was a free-lance journalist, which in turn relied on another non peer-reviewed source, the reference to which was accidentally omitted. Silly me, thinking that that was a serious "mistake"!

But I now know better. Not only wasn't it "serious" ... dear me, no! It wasn't a "mistake" at all. The "expert authors" have issued statements! So that's alright then! Sorted.

With love

Northie

Mar 30, 2010 at 11:11 AM | Unregistered CommenterRichard North

Richard North,

An advocate is one who presents a case on behalf of a person or organisation, in pursuit of a specific outcome. By any measure, Nepstad is an advocate.

By any measure you are an advocate.

By no measure are you a qualified expert competent to perform a review of the literature.

So, the IPCC used a non peer-reviewed source, the lead author of which was a free-lance journalist, which in turn relied on another non peer-reviewed source, the reference to which was accidentally omitted. Silly me, thinking that that was a serious "mistake"!

If you think that was a serious mistake why then do you recommend people repeat the mistake by listening to you? You yourself are an unqualified journalist producing non-peer reviewed material on the same topic, are you not?

Mar 30, 2010 at 11:21 AM | Unregistered CommenterFrank O'Dwyer

Frankie darling ...

You yourself are an unqualified journalist producing non-peer reviewed material on the same topic, are you not?

Terribly gauche making all these assumptions, don't you think. Writing the odd spot in a daily rag (usually as a co-author) does not a journalist make ... I'm no more a journalist than you are a spinster aunt (are you?).

As to unqualified, does a PhD help? Of course, it was only in epidemiology, and I know that some people think that a PhD is a qualification as a researcher ... which is what I do for a living ... but they could be wrong. Some people might even think that my PhD is more relevant than little Rajendra's PhDs in economics and electricity distribution, but they might be wrong as well.

With love

Northie (Dr)

Mar 30, 2010 at 11:35 AM | Unregistered CommenterRichard North

Frank.

Why so much insistence on the unfortunately devalued 'Peer Review'.

From what I've been reading in the last few months it should be called 'Pier Revue'

Nepstad, Jones, Mann et al are dragging the entire scientific establishment into the gutter and you really don't seem to care in the slightest. I gave a lecture recently in a local high school and was introduced as a scientist (apparently the principle couldn't remember that I'm actually a microbiologist) which promted some smart arse in the audience to shout 'not a climate one I hope!' wherupon the audience burst into fits of laughter. This was in Norway, one of the bastions of AGW.

Mar 30, 2010 at 12:59 PM | Unregistered CommenterDr. J.Kolberg

Richard North,

You yourself are an unqualified journalist producing non-peer reviewed material on the same topic, are you not?
Terribly gauche making all these assumptions, don't you think.

Excellent, so you are not a journalist but you have a Ph.D in an unrelated discipline and your blog science is in fact peer reviewed? What work have you done that is relevant to the Amazon rainforest, how many articles have you had published so far and in which scholarly journals do they appear?

I am 100% persuaded by your argument that it is a grave mistake rely on 'grey literature' such as blogs by advocates. That is why I have stopped looking to your blog for information on the Amazon and I am pleased to hear you urge others to do likewise. I am however eager to read the peer reviewed studies you have authored. Please post links to them.

Can you also tell me roughly how long you have been working in this field? You may use a stopwatch if necessary.

Mar 30, 2010 at 1:09 PM | Unregistered CommenterFrank O'Dwyer

Dr Kolberg,

Why so much insistence on the unfortunately devalued 'Peer Review'.

That it is a mistake to rely on grey literature instead of peer review is North's argument. I'm simply pointing out the obvious - his own articles are grey literature.

As for peer review it isn't the be all and end all, sure. But life is short and it is a start.

Nepstad, Jones, Mann et al are dragging the entire scientific establishment into the gutter and you really don't seem to care in the slightest.

I care a lot that 'blog scientists' have managed to smear the integrity of hundreds of working stiff scientists - I just have a different idea of who the culprits are than you do.

Mar 30, 2010 at 1:37 PM | Unregistered CommenterFrank O'Dwyer

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