Gerard Wynn, PlanetArk 29 Sep 09;
LONDON - Global temperatures may be 4 degrees Celsius hotter by the mid-2050s if current greenhouse gas emissions trends continue, said a study published on Monday.
The study, by Britain's Met Office Hadley Center, echoed a U.N. report last week which found that climate changes were outpacing worst-case scenarios forecast in 2007 by the U.N.'s Intergovernmental Panel on Climate Change (IPCC).
"Our results are showing similar patterns (to the IPCC) but also show the possibility that more extreme changes can happen," said Debbie Hemming, co-author of the research published at the start of a climate change conference at Oxford University.
Leaders of the main greenhouse gas-emitting countries recognized in July a scientific view that temperatures should not exceed 2 degrees above pre-industrial levels, to avoid more dangerous changes to the world's climate.
The IPCC shared the 2007 Nobel Peace Prize for its fourth assessment report, or AR4. One finding was that global temperatures could rise by 4 degrees by the end of the 2050s. Monday's study confirmed that warming could happen even earlier, by the mid-2050s, and suggested more extreme local effects.
"It's affirming the AR4 results and also confirming that it is likely," Hemming told Reuters, referring to 4 degrees warming, assuming no extra global action to cut emissions in the next decade.
One advance since 2007 was to model the effect of "carbon cycles." For example, if parts of the Amazon rainforest died as a result of drought, that would expose soil which would then release carbon from formerly shaded organic matter.
"That amplifies the amount of carbon dioxide that goes into the atmosphere and therefore the global warming. It's really leading to more certainty," said Hemming.
DRASTIC
Some 190 countries will try to reach an agreement on how to slow global warming at a meeting in Copenhagen in December.
Chinese President Hu Jintao won praise for making a commitment to limit emissions growth by a "notable" amount, at a U.N. climate summit in New York last week. Other leaders made pledges to agree a new climate pact.
Temperature rises are compared with pre-industrial levels. The world warmed 0.7 degrees last century, scientists say.
A global average increase of 4 degrees masked higher regional increases, including more than 15 degrees warmer temperatures in parts of the Arctic, and up to 10 degrees higher in western and southern Africa, Monday's study found.
"It's quite extreme. I don't think it's hit home to people," said Hemming. As sea ice melts, the region will reflect less sunlight, which may help trigger runaway effects.
Such higher Arctic temperatures could also melt permafrost, which until now has trapped the powerful greenhouse gas methane, helping trigger further runaway effects, said Hemming.
"There are potentially quite big negative implications."
The study indicated rainfall may fall this century by a fifth or more in part of Africa, Central America, the Mediterranean, and coastal Australia, "potentially more extreme" than the IPCC's findings in 2007.
"The Mediterranean is a very consistent signal of significant drying in nearly all the model runs," said Hemming. A 20 percent or more fall is "quite a lot in areas like Spain already struggling with rainfall reductions in recent years."
(Editing by Andrew Roche)
Four degrees of warming 'likely'
David Shukman, BBC News 28 Sep 09;
In a dramatic acceleration of forecasts for global warming, UK scientists say the global average temperature could rise by 4C (7.2F) as early as 2060.
The Met Office study used projections of fossil fuel use that reflect the trend seen over the last 20 years.
Their computer models also factored in new findings on how carbon dioxide is absorbed by the oceans and forests.
The finding was presented at an Oxford University conference exploring the implications of a 4C rise.
The results show a "best estimate" of 4C being reached by 2070, with a possibility that it will come as early as 2060.
Richard Betts of the Met Office Hadley Centre described himself as "shocked" that so much warming could occur within the lifetimes of people alive today.
"If greenhouse gas emissions are not cut soon then we could see major climate changes within our own lifetimes," he said.
"Four degrees of warming averaged over the globe translates into even greater warming in many regions, along with major changes in rainfall."
Big burn
The model finds wide variations, with the Arctic possibly seeing a rise of up to 15C (27F) by the end of the century.
Western and southern parts of Africa could warm by up to 10C, with other land areas seeing a rise of 7C or more.
In its 2007 assessment, the Intergovernmental Panel on Climate Change (IPCC) said the average warming by the end of the century would probably lie between 1.8C and 4C (3.2-7.2F), though it did not rule out the possibility of larger rises.
Key to the Met Office calculations was the use of projections showing fossil fuel use continuing to increase as it has done for the last couple of decades.
"Previously we haven't looked at the impact of burning fossil fuels so intensely," said Dr Betts.
"But it's quite plausible we could get a rise of 4C by 2070 or even 2060."
Dr Betts and his colleagues emphasise the uncertainties inherent in the modelling, particularly the role of the carbon cycle.
But he said he was confident the findings were significant and would serve as a useful guide to policymakers.
The presentation at Oxford's Environmental Change Institute came as negotiators from 192 countries were gathering in Bangkok for the latest set of prepatory talks in the run-up to December's UN climate summit.
Major governments of developing and industrialised nations are committed to a deal that would keep the global temperature rise to 2C, which many regard as a threshold for "dangerous" climate change.
