Global cooling theories put scientists on guard

Gerard Wynn, Reuters 9 May 08;

LONDON (Reuters) - A new study suggesting a possible lull in manmade global warming has raised fears of a reduced urgency to battle climate change.

The U.N. Intergovernmental Panel on Climate Change (IPCC), a group of hundreds of scientists, last year said global warming was "unequivocal" and that manmade greenhouse gas emissions were "very likely" part of the problem.

And while the study published in the journal Nature last week did not dispute manmade global warming, it did predict a cooling from recent average temperatures through 2015, as a result of a natural and temporary shift in ocean currents.

The IPCC predicted global temperature increases this century of 1.8 to 4 degrees Celsius.

So the Nature paper has sparked worries that briefly cooler temperatures may take the heat out of action to fight the threat of more droughts and floods, while a debate about the article's findings has also underlined uncertainty about such forecasting.

Most scientists oppose the minority that has used the present lull in warming to cast doubt on the size of threat from manmade global temperature rises.

"Let's say there wasn't much of a warming for the next 10 years, how will the public and politicians play this out?" said Bob Watson, former IPCC head and current chief scientific adviser to Britain's environment ministry.

He said it was important to explain that fluctuations were an expected part of a general, manmade warming trend.

"We need a group of scientists very carefully to evaluate that paper, do they agree, to what degree is there uncertainty, and then explain to the public and politicians what it means," he said.

Climate scientists agree that natural climate shifts, as the world's oceans suck up or spew out heat, could temporarily mask mankind's stoking of warming though year-on-year increases in greenhouse gas emissions.

In Bali in December, governments launched two-year climate talks to try to clinch a tougher successor to the existing Kyoto Protocol on global warming.

But worries about the impact on competitiveness by slowing carbon emissions -- by curbing the use of fossil fuels -- are already fraying those efforts. Russia said last week it would not dampen its economic growth.

DOUBT

The reaction to the Nature paper has underlined uncertainty about climate forecasting, as well as the fact that a minority of global warming doubters has not gone away.

Britain's Met Office Hadley Centre is sticking to its forecasts made last year that half of the five years after 2009 would "quite likely" be the hottest on record, partly due to manmade warming.

Meanwhile six climate scientists offered on Thursday to bet 5,000 euros ($7,730) that the Nature article's forecast of cooling or no warming globally from 2000-2015 was wrong.

"We think not -- and we are prepared to bet serious money on this," say the scientists, led by Stefan Rahmstorf, professor of physics of the oceans at Germany's Potsdam Institute for Climate Impact Research, in a comment posted at realclimate.org/

The original Nature article's lead author, Leibniz Institute's Noel Keenlyside, acknowledged on Friday that recent data showed much more warming that he had forecast through 2007, but stood by a "stabilization" of temperatures from 2005-2015.

He blamed shifts in ocean currents and temperatures, thought also to be the cause of the plateau in temperatures since 1998.

Gary Yohe, climate scientist at Wesleyan University in Connecticut, said that opponents of tougher action on global warming in the United States had seized on the Nature report as a sign that climate change was slowing down.

Bjorn Lomborg, the Danish author of "The Skeptical Environmentalist", said a slowdown in warming might help governments focus on smarter, long-term solutions rather than being panicked into action.