Tropical forests may dry out and become vulnerable to devastating wildfires as global warming accelerates over the coming decades, a senior scientist has warned.
Soaring greenhouse gas emissions, driven by a surge in coal use in countries such as China and India, are threatening temperature rises that will turn damp and humid forests into parched tinderboxes, said Dr Chris Field, co-chair of the UN's Nobel prize-winning Intergovernmental Panel on Climate Change (IPCC).
Higher temperatures could see wildfires raging through the tropics and a large scale melting of the Arctic tundra, releasing billions of tonnes of carbon into the atmosphere that will accelerate warming even further, he said.
Field, director of global ecology at the Carnegie Institute, told the American Association for the Advancement of Science meeting in Chicago at the weekend that the IPCC's last report on climate change in 2007 had substantially underestimated the severity of global warming over the rest of the century.
The report concluded that the Earth's temperature is likely to rise between 1.1C and 6.4C by 2100, depending on future global carbon emissions. "We now have data showing that from 2000 to 2007, greenhouse gas emissions increased far more rapidly than we expected, primarily because developing countries, like China and India, saw a huge upsurge in electric power generation, almost all of it based on coal," Field said. The next report, which Field will oversee, is due in 2014 and will now include future scenarios where global warming is far more serious than previous reports have suggested, he said.
Field said that if the tropics became dry enough for fires to break out, tropical forests would pass a "tipping point" from absorbing carbon dioxide from the atmosphere to releasing it.
"Tropical forests are essentially inflammable. You couldn't get a fire to burn there if you tried. But if they dry out just a little, the result can be very large and destructive wildfires. It is increasingly clear that as you produce a warmer world, lots of forested areas that had been acting as carbon sinks could be converted to carbon sources," he said. The result could lead to runaway warming.
Field's warning was echoed by French scientists, who said the IPCC's estimate that sea levels would rise around 40cm by 2100 was likely to be a best case scenario.
Former US vice-president Al Gore, who spoke at the meeting on Friday night, called for a globally coordinated stimulus to tackle climate change. "We've now reached the stage where continuing on our present course will threaten the entirety of human civilisation," he said.
• This article was amended on Thursday 19 February 2009. We quoted a scientist describing tropical forests as "essentially inflammable". Inflammable means "liable to catch fire" (Collins); non-flammable was meant.
