Earth’s climate appears to be changing more quickly and deeply than a benchmark UN report for policymakers predicted, top scientists said ahead of international climate talks starting today in Poland.
Evidence published since the Intergovernmental Panel for Climate Change’s (IPCC) report in February last year suggested that future global warming may be driven not just by things over which humans have a degree of control, such as burning fossil fuels or destroying forest, a climate experts told reporters.
Even without additional drivers, the IPCC has warned that current rates of greenhouse gas emissions, if unchecked, would unleash devastating droughts, floods and huge increases in human misery by century’s end.
But the new studies indicate that human activity may be triggering powerful natural forces that would be nearly impossible to reverse and that could push temperatures up even further.
At the top of the list for virtually all of the scientists canvassed was the rapid melting of the Arctic ice cap.
“In the last couple of years, Arctic Sea ice is at an all-time low in summer, which has got a lot of people very, very concerned,” said Robert Watson, chief scientific adviser for Britain’s department for environmental affairs and chairman of the IPCC’s previous assessment in 2001.
“This has implications for Earth’s climate because it can clearly lead to a positive feedback effect,” he said in an interview.
When the reflective ice surface retreats, the Sun’s radiation — heat — is absorbed by open water rather than bounced back into the atmosphere, creating a vicious cycle of heating.
“We had always known that the Arctic was going to respond first,” Mark Serreze of the National Snow and Ice Data Center in Boulder, Colorado, said by telephone. “What has us puzzled is that the changes are even faster than we would have thought possible.”
New data on the rate at which oceans might rise has also caused consternation.
“The most recent IPCC report was prior to ... the measurements of increasing mass loss from Greenland and Antarctica, which are disintegrating much faster than IPCC estimates,” said climatologist James Hansen, head of NASA’s Goddard Institute for Space Studies in New York.
Unlike the Arctic ice cap, which floats on water, the world’s two major ice sheets — up to 3km thick — sit on land.
The IPCC’s most recent assessment “did not take into account the potential melting of Greenland, which I think was a mistake,” said Watson, the former IPCC chairman.
For coastal dwellers, even a relatively small loss of their ice could prove devastating. IPCC estimates of an 18cm to 59cm rise by 2100 has been supplanted among specialists by an informal consensus of 1m, Serreze said.
The 192-member forum at the UN Framework Convention on Climate Change (UNFCCC) comes midway through a two-year process launched in Bali for braking the juggernaut of global warming.