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Drought effect on rainforests is negligible

Opinion More bad news today for the International Panel on Climate Change (IPCC), as another of its extravagant ecopocalypse predictions, sourced from green campaigners, has been confirmed as bunk by scientists.

The UN body came under attack earlier this year for suggesting that 40 per cent of the Amazonian rainforests - dubbed the "lungs of the planet" by some for their ability to turn CO2 into oxygen, and also seen as vital on biodiversity grounds - might disappear imminently. This disaster would be triggered, according to the IPCC's assessment, by a relatively slight drop in rainfall of the sort to be expected in a warming world.

Unfortunately it now appears that just such conditions have already occurred, and in fact the Amazonian jungles were unaffected.

Perhaps unsurprisingly, the IPCC projection originated in a study produced in 2000 by campaigning group WWF, which was also implicated in the IPCC's equally invalid prediction that the glaciers of the Himalayas will all have melted within a generation from now.

According to the WWF report (pdf), which was not subject to scientific peer review - it was written by a freelance journalist and published by WWF itself - drying-up of forests will lead to runaway wildfires that will destroy the jungle and perhaps the entire planetary ecosystem. The document is full of phrases such as "the year the world caught fire". It warns of imminent doom caused by drought cycles:

The world faces a positive feedback cycle in which climate change, exacerbated by forest fires and deforestation, increases the frequency of the El Niño phenomenon, which in turn causes more forest burning.

The world faces warmer more violent weather, and more forest fires ... scientists believe the whole Amazon itself is threatened, with the rainforest being replaced by fire-prone vegetation. This has global consequences ...

It was bad enough that the IPCC included this in its 2007 Fourth Assessment Report. But now it has been conclusively disproven - so much so that even IPCC members pour scorn on it, though they haven't retracted or amended their original endorsement of it.

NASA-funded scientists analysing the past decades of satellite imagery of the Amazon basin say that in fact the rainforests are remarkably resilient to droughts. Even during the hundred-year-peak dry season of 2005 the jungles were basically unaffected.

IPCC member speaks

"We found no big differences in the greenness level of these forests between drought and non-drought years," says Arindam Samanta of Boston university, lead author of the new study based on NASA's MODIS sat data.

"Our results certainly do not indicate such extreme sensitivity to reductions in rainfall," adds Sangram Ganguly of the NASA-affiliated Bay Area Environmental Research Institute, another study author.

Even the IPCC itself now regrets listening to WWF.

"The way that the WWF report calculated this 40 per cent was totally wrong," according to IPCC member Jose Marengo, commenting on the new research.

Which raises the question of why his colleagues referenced the WWF polemic in their 2007 report on what the world can expect: and why they still publish it today on the web as part of their considered opinion.

Samanta, Ganguly and their colleagues also consider that their results debunk another controversial paper published in 2007, which said that the 2005 drought was actually good for the rainforests, causing them to "green up" due to more sunlight from cloudless skies.

These results are "not reproducible", according to the new analysis, which indicates that in fact nothing much changed down on the Amazon during the 2005 dry spell.

Samanta, Ganguly et al's paper, Amazon forests did not green-up during the 2005 drought, is published in Geophysical Research Letters (subscriber link). ®


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