The Amazon forest currently absorbs about 2 billion tonnes of carbon a year and acts as a carbon sink. A group of scientists used a computer model to determine how the forest responds to the ongoing global warming. They assumed that greenhouse-gas emissions will follow current UN projections, and that average temperatures will go up by 3 degrees Celsius by 2100.

Their main simulation indicates that by 2050, the forest will take in 5% less carbon than it now releases — that is, it turns into a source of carbon.

The researchers are careful about interpreting the results, as their computer simulation relies on a lot of factors, each with a certain uncertainty.

However, the main message is that climate change is likely to have severe consequences on the ability of the Amazon rainforest to act as a carbon sink, they say.