Questions have been raised by recent research into droughts in the Amazon. Our Amazon expert, Dr Richard Betts discusses the issue of Amazonian drought.
The recent paper, published in the journal Science, on the 2005 and 2010 Amazon droughts, by Lewis and co-authors, raises the obvious question - are the predictions of 'Amazon die-back' becoming reality?
It is now more than a decade since the Met Office Hadley Centre's earlier climate model was found to project long-term drought and forest loss in the Amazon due to future climate change. Other models, including more recent Met Office models, give less extreme results. However, instead of rushing to say "Look - it's happening!" we need to look very carefully at whether these could be just natural events instead.
Indeed, this is just one example of a whole new aspect of climate science - detection and attribution of climate change impacts. We are now confident that global temperatures are increasing, and that this is most likely due to human greenhouse gas emissions, but as for saying whether this is the cause of events such as the Amazon droughts and Australian floods there's much more work to do there.
It is very easy to perceive trends or changes in data when, in fact, it is just random noise.
Understanding of the processes, including controlled experiments as far as possible, are key to attributing changes to their causes.
This will be one of the most challenging tasks of writing the IPCC Fifth Assessment Report. There is already a huge appetite for news on the apparent impacts of climate change, and we can expect to see papers or 'grey literature' reports emerging which attempt to attribute impacts such as ecological changes, food shortages and humanitarian disasters.
The science community's task in IPCC AR5 will be to objectively assess this evidence and establish the true, scientifically well-founded picture. After the controversy over statements on the Amazon in the IPCC Fourth Assessment, establishing the facts over Amazon drought will be top priority.