ABC News Online, Posted Tue Feb 24
The risk posed to mankind and the environment by even small changes in average global temperatures is much higher than believed even a few years ago, a study said.
The study, published by the Proceedings of the National Academy of Sciences in the US, updated a 2001 assessment by the Inter-governmental Panel on Climate Change (IPCC) that looked at temperature changes and the risks they pose.
"We have to assume that the risks of negative impacts of climate change on humans and nature are larger than just a few years ago," said Dr Hans-Martin Fussel, one of the authors of the report.
The study found that even small increases to global mean temperatures could produce the kinds of conditions singled out as "reasons for concern" in the 2001 assessment.
Those included risks to threatened systems such as coral reefs or endangered species and extreme weather events like cyclones, heat waves or droughts.
Other "reasons for concern" involved the way the impact of climate change is distributed, the aggregate damage caused and the risk of "large scale discontinuities" such as the de-glaciation of the Greenland ice sheets.
The report says there is "growing evidence that even modest increases in GMT (global mean temperature) above levels circa 1990 could commit the climate system to the risk of very large impacts on multiple century time scales."
It is the third report published in recent weeks carrying grim news about climate change.
On February 15, a report by the Carnegie Institution's Chris Field, a former member of the IPCC, warned that greenhouse gases have accumulated more rapidly in the atmosphere between 2000 and 2007 than anticipated.
Three weeks before that, a study by Susan Solomon - the senior scientist at the National Oceanic and Atmospheric Administration - said changes in surface temperature, rainfall and sea level are "largely irreversible for more than 1,000 years after CO2 emissions are completely stopped."