Environmental Changes Due to global warming

The research, by some of Britain's leading experts on climate change, shows that even severe cuts in deforestation and carbon emissions will fail to save the emblematic South American jungle, the destruction of which has become a powerful symbol of human impact on the planet. Up to 85% of the forest could be lost if spiralling greenhouse gas emissions are not brought under control, the experts said. But even under the most optimistic climate change scenarios, the destruction of large parts of the forest is "irreversible".

Vicky Pope, of the Met Office's Hadley Centre, which carried out the study, said: "The impacts of climate change on the Amazon are much worse than we thought. As temperatures rise quickly over the coming century the damage to the forest won't be obvious straight away, but we could be storing up trouble for the future."

Tim Lenton, a climate expert at the University of East Anglia, called the study, presented at a global warming conference in Copenhagen today, a "bombshell". He said: "When I was young I thought chopping down the trees would destroy the forest but now it seems that climate change will deliver the killer blow."

The study, which has been submitted to the journal Nature Geoscience, used computer models to investigate how the Amazon would respond to future temperature rises.

It found that a 2C rise above pre-industrial levels, widely considered the best case global warming scenario and the target for ambitious international plans to curb emissions, would still see 20-40% of the Amazon die off within 100 years. A 3C rise would see 75% of the forest destroyed by drought over the following century, while a 4C rise would kill 85%. "The forest as we know it would effectively be gone, " Pope said.

Experts had previously predicted that global warming could cause significant "die-back" of the Amazon. The new research is the first to quantify the long-term effect.

Chris Jones, who led the research, told the conference: "A temperature rise of anything over 1C commits you to some future loss of Amazon forest. Even the commonly quoted 2C target already commits us to 20-40% loss. On any kind of pragmatic timescale, I think we should see loss of the Amazon forest as irreversible."

Peter Cox, professor of climate system dynamics at the University of Exeter, said the effects would be felt around the world. "Ecologically it would be a catastrophe and it would be taking a huge chance with our own climate. The tropics are drivers of the world's weather systems and killing the Amazon is likely to change them forever. We don't know exactly what would happen but we could expect more extreme weather." Massive Amazon loss would also amplify global warming "significantly" he said.

"Destroying the Amazon would also turn what is a significant carbon sink into a significant source."

Jones said the study showed that tree growth in high latitudes, such as Siberia, would increase, but would be unlikely to compensate for the carbon stocks lost from the Amazon. Even with drastic cuts in emissions in the next decade, scientists say that there will only be around a 50% chance of keeping global temperatures rises below 2C.

This best-case emissions scenario is based on emissions peaking in 2015 and quickly changing from an increase of 2-3% per year to a decrease of 3% per year. For every 10 years this action is delayed, the most likely temperature rise increases by 0.5C.

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