Page last updated at 16:44 GMT, Saturday, 30 January 2010

Harrabin's Notes: IPCC under scrutiny

In his regular column, BBC environment analyst Roger Harrabin considers whether another mistake by the Intergovernmental Panel on Climate Change has come to light.

Amazon Rainforest (IPCC)
An IPCC statement on the fate of the Amazon has been questioned

After the Intergovernmental Panel on Climate Change (IPCC) admitted it had made a mistake in its Himalaya glacier forecast in its Fourth Assessment Report, climate "sceptics" are busy searching the rest of the panel's report for more mistakes.

It appears that this week, they have found one. In parts of the blogosphere it has been dubbed "Amazongate".

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.

Euro-sceptic blogger Richard North said: "The IPCC also made false predictions on the Amazon rainforests, referenced to a non-peer reviewed paper produced by an advocacy group working with the WWF.

"This time though, the claim made is not even supported by the report and seems to be a complete fabrication," he observed.

The IPCC statement is basically correct but poorly written, and bizarrely referenced
Dr Simon Lewis
Leeds University

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."

I have tried to contact the lead author of Working Group II to ask why his team cited WWF not the journals - but without success so far.

My guess is that NGO reports often offer an easy synthesis of already-published evidence.

In my experience, NGO papers are often both accessible and accurate - though clearly written from a point of view.

But it is obvious that the next IPCC report will have to be much more meticulous about flagging up the provenance of its sources.

There will need to be more clarification of what is known as "grey" literature (not peer-reviewed) and IPCC panel participation.

It all points to the need for much greater transparency, though that will throw up issues of its own for a body striving to offer a coherent view to policymakers of an issue dominated by risk, uncertainty and values, rather that unambiguous science.

Just this week, for instance, there were two pieces of published research in Science and Nature suggesting that the very worse effects of climate change may have been overestimated.

The researchers of both papers say they are still concerned about man-made climate change, though.

The unfinished science of climate change goes on.

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