Once more, we find that the IPCC WG2 made an error.  Only the error is not what is being trumpeted by deniers.

There was a dire warning in chapter 13 of the report of IPCC Working Group II:

“Up to 40% of 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,” it observed.

“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.”

Closer inspection reveals that the authors referenced for this work are, in fact, an expert linked to environmental group WWF and a green journalist.

Sounds, like the same type of issue as the Himalayan glacier error, citing the grey-literature, rather than the peer-reviewed literature. But on closer inspection the text of the IPCC is correct, and consistent with the science. The error was lazy citation. They should have cited the peer-reviewed literature, rather than a report from WWF.

A blunder perhaps, but maybe of a different kind, because there is indeed plenty of published science warning about drought in the Amazon.

Authors of some of that research are not happy that the IPCC chose to reference WWF rather than the basic science itself.

Dr Simon Lewis from Leeds University, who co-authored a paper on the Amazon in the journal Science, says the forest is surprisingly sensitive to drought.

He told me: “The IPCC statement is basically correct but poorly written, and bizarrely referenced.

“It is very well known that in Amazonia, tropical forests exist when there is more than about 1.5 metres of rain a year, below that the system tends to ‘flip’ to savannah.

“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 two billion tonnes of CO2 from the atmosphere a year, to being a massive source of over three billion tonnes.”

So, it appears that, unlike in the case of “Glaciergate”, the IPCC’s science may be right but its referencing wrong.

Dr Lewis’s Science paper came too late for the Fourth Assessment Report’s deadline.

But, he said: “They should have cited the papers by Peter Cox and colleagues on the modelling side, and a paper by Dan Nepstad on a massive drought exclusion experiment.”

So yes, this does count as an error in the IPCC, but it is not an error that affects the conclusions of the IPCC, not in the slightest. The conclusions on Amazon sensitivity to drought are correct, only the citation is problematic.

And again this error is in the WG2, not in the WG1 which is tasked with determining the magnitude of the warming trend, and its cause (our GHG emissions).

UPDATE: Given that this really is a non-scandal, it seems some deniers have resorted to lying in order to convince people that this nongate is a real gate:

The IPCC authors reference a WWF/IUCN report, which Delingpole and North say doesn’t include… [the 40% figure]:

The assertions attributed to them, that “up to 40% of the Amazonian forests could react drastically to even a slight reduction in precipitation” is nowhere to be found in their report.

But if you spend all of five minutes with the WWF/IUCN paper, you come across this passage:

Up to 40% of the Brazilian forest is extremely sensitive to small reductions in the amount of rainfall.

And that observation is drawn from a paper in Nature (Vol 398, 8 April, pp505). So should the IPCC authors have bothered to source the material right back to Nature, instead of relying on a WWF/IUCN piece of gray literature? Probably. Should North and Delingpole have checked to make sure their allegations that the IPCC authors were making stuff up had merit before leveling the charge? Absolutely.

There is no excuse for this type of lazy reporting, yet it as all too common these days.

4 thoughts on “Amazon(non)gate

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  1. Good post. Thanks for posting a link on my page. I’m glad to have that clarified. It was, in my estimation, lazy referencing rather than a mistake.

  2. @ Susann

    Thanks. Yep it was just a lazy reference, yet despite what has been claimed the reference does support the text in the IPCC (see the post update).

    It still would have been better to cite the primary literature directly, but not really a big deal.

    BTW not sure what page you are referring to.

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