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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

What the science says...

The IPCC statement on Amazon rainforests was correct, and was incorrectly reported in some media.

An article in a British newspaper claimed that the Intergovernmental Panel on Climate Change (IPCC) published wrong information about the Amazon Rainforest in their 2007 report. The issue centred on the statement that about 40% of the Amazon was susceptible to the effects of drought, or more specifically "slight reductions in rainfall".

The Amazon is the world's largest tropical rainforest, and due to its immense size, has a global effect on the Earth's climate. Despite being well adapted and resilient to wet and dry periods which occur throughout the year, the rainforest is vulnerable to extended periods of drought. Any major decline in the health of the Amazon rainforest is likely to impact the world climate.

The skeptic claims relate to section 13.4.1 of the IPCC Fourth Assessment Report (2007) which made the statement: '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 reference is to a non-peer reviewed report prepared by the World Wide Fund for Nature (WWF) which itself cites an original peer reviewed study (Nepstad 1999) as the basis for the claim. The citations in the WWF and IPCC reports are not complete, Nepstad 1994, Nepstad 1999 and Nepstad 2004 support the claim that up to half the Amazon rainforest were severely affected by drought. Further studies, carried out since the 2007 IPCC report, reinforce the Amazon's susceptibilty to long term reductions in rainfall .

The IPCC could have avoided confusion by simply citing the peer reviewed studies themselves, rather than the WWF report and perhaps "slight reduction" should have been better defined or qualified. Despite the error in citation, the statement made by the IPCC is factually correct. Maybe the last word should go to the lead author of the papers upon which the statements were based, Daniel Nepstad, who made a public press release to clear up the mainstream media confusion over the subject. Nepstad concludes:

"In sum, the IPCC statement on the Amazon was correct. The report that is cited in support of the IPCC statement (Rowell and Moore 2000) omitted some citations in support of the 40% value statement.

Updated on 2010-10-30 by Rob Painting.

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