Global warming endangers Amazon

A warmer world could mean the loss of the Amazon rainforest and yet more global warming as levels of carbon dioxide increased in the atmosphere.

"This is a simplified picture," Tom Wigley of the US National Centre for Atmospheric Research told the AAAS.

"If we warm the world then some climate models suggest that precipitation will decrease in the Amazon basin. That part of the world would get warmer and that would have some pretty dramatic effects on the vegetation in that rainforest area."

The rainforests are already being logged, burned and cleared for farmland, but global warming could have an even more dramatic effect, he warned.

Prof Wigley said: "If we killed off the rainforest by warming the climate we would add more carbon dioxide and that would give more warmth and that is a really good example of a positive feedback. And in some model simulations, that turns out to be very large indeed. It inflates the amount of warming by maybe 30%.

"But it is very uncertain. Modelling the climate is difficult. Modelling the interactions between vegetation and climate is even more difficult."