'Amazon drought affects global warming'

British and Brazilian scientists believe the widespread drought was even worse than the "once-in-a-century" dry spell in 2005.

According to the study published in the journal Science, frequent severe droughts like the ones in 2005 and 2010 will turn the world’s largest rain forest into a source of the gases which accelerate global warming.

Trees and other vegetation act as a sponge absorbing heat-trapping carbon dioxide as they grow. This keeps the plants cool, but when CO2 is released they die and rot.

"If events like this happen more often, the Amazon rain forest would reach a point where it shifts from being a valuable carbon sink slowing climate change to a major source of greenhouse gases that could speed it up," said lead author and ecologist at the University of Leeds Simon Lewis.

Scientists found that last year’s drought caused rainfall shortages over a 3 million square kilometer area of the Amazon forest, compared with 1.9 million square kilometer in the 2005 drought.

The 2010 drought was also more intense and caused higher tree mortality with three major epicenters, while the 2005 drought was mainly focused in southwestern Amazon.

Findings suggest that the Amazon forest would not absorb its usual 1.5 billion metric tons of carbon dioxide from the atmosphere in both 2010 and 2011.

The dead and dying trees would also release five billion metric tons of gas in the following years, making a total impact of about eight billion metric tons.

In comparison, the United States emitted 5.4 billion metric tons of carbon dioxide from fossil fuel use in 2009.

The 2010 drought also dried up major Amazon Rivers and isolated thousands of people who depend on boat transportation.

More intense droughts will also make the Amazon forest more vulnerable to fires and large parts of the forest could turn into a savannah-like ecosystem by the middle of the century with less animal and plant biodiversity.