Scientists predict surge in global warming after 2009

Posted Fri Aug 10, 2007 0:32am AEST
Updated Fri Aug 10, 2007 7:18am AEST

ABC NEWS

http://abc.net.au/news/stories/2007/08/10/2001247.htm

A study forecasts that global warming will set in with a vengeance after 2009, with at least half of the five following years expected to be hotter than 1998, which was the warmest year on record.

Climate experts have long predicted a general warming trend over the 21st century spurred by the greenhouse effect, but this new study gets more specific about what is likely to happen in the 10 years after 2005.

To make this kind of prediction, researchers at Britain's Met Office, which deals with meteorology, have made a computer model that takes into account such natural phenomena as the El Nino pattern in the Pacific Ocean and other fluctuations in ocean circulation and heat content.

Study author Douglas Smith says a forecast of the next decade is particularly useful, because climate could be dominated over this period by these natural changes, rather than human-caused global warming.

In research published in the journal Science, Dr Smith and his colleagues predict that the next three or four years will show little warming, but there will be overall warming over the decade.

"There is ... particular interest in the coming decade, which represents a key planning horizon for infrastructure upgrades, insurance, energy policy and business development," the authors noted.

They say the real heat will start after 2009.

Until then, natural forces will offset the expected warming caused by human activities, such as the burning of fossil fuels, which releases the greenhouse gas carbon dioxide.

Models based on history

To check their models, the scientists used a series of "hindcasts" - forecasts that look back in time - going back to 1982, and compared what their models predicted with what actually occurred.

The researchers found that factoring in the natural variability of ocean currents and temperature fluctuations yields an accurate picture.

This differs from other models, which mainly consider human-caused climate change.

"Over the 100-year timescale, the main change is going to come from greenhouse gases that will dominate natural variability, but in the coming 10 years the natural internal variability is comparable," Dr Smith said.

Soot study

In another climate change article in the online journal Science Express, United States researchers have reported that soot from industry and forest fires have a dramatic impact on the Arctic climate, starting around the time of the Industrial Revolution.

Industrial pollution brought a seven-fold increase in soot - also known as black carbon - in Arctic snow during the late 19th and early 20th centuries, scientists at the Desert Research Institute found.

Soot, mostly from burning coal, reduces the reflectivity of snow and ice, letting Earth's surface absorb more solar energy and possibly resulting in earlier snow melts and exposure of much darker underlying soil, rock and sea ice.

This in turn led to warming across much of the Arctic region.

At its height from 1906 to 1910, estimated warming from soot on Arctic snow was eight times that of the pre-industrial era, the researchers said.

- Reuters