Published on
the Herald Scotland

Fresh Evidence Global Warming Is Man-Made

John von Radowitz

Cooling towers and smoke stacks are seen at the Vresova coal gasification plant near the city of Sokolov, February 3, 2010. (REUTERS/Petr Josek)

Climate scientists hit back at the sceptics today with new research they say has uncovered the "fingerprint" of man-made global warming.

Researchers working like detectives investigating a crime compared real observational evidence with data from computer simulations to see how they matched up.

They concluded there was an "increasingly remote possibility" of human behaviour not being the chief driver of climate change.

The clues were unravelled using a forensic technique called "optimal detection" in which different factors - natural and human - were given equal consideration.

They covered a wide range of trends affecting land and sea temperature, the saltiness of the oceans, humidity, rainfall and Arctic sea ice.

Also included was warming in the Antarctic, which has more recently been attributed to human influence.

Dr Peter Stott, from the Met Office Hadley Centre in Exeter, who co-led the study, said: "What we've shown in this paper is that the fingerprint of human influence has been detected in many different aspects of climate change.

"We've seen it in temperature and increases in atmospheric humidity, we've seen it in salinity changes ... we've seen it in reductions in Arctic sea ice and changing rainfall patterns.

"What we see here are observations consistent with a warming world. This wealth of evidence we have now shows there is an increasingly remote possibility of climate change being dominated by natural factors rather than human factors."

Publication of the research in the journal Wiley Interdisciplinary Reviews: Climate Change comes amid controversy over the reliability of climate-change science.

Scientists have found themselves under pressure to provide fresh evidence after the University of East Anglia (UEA) e-mails scandal and criticism of the Intergovernmental Panel on Climate Change (IPCC).

Two inquiries are now being held into accusations based on leaked e-mails that UEA scientists manipulated and suppressed climate change data.

In a separate set-back for the scientists, the IPCC - whose researchers influence global government policy - admitted it had issued flawed information about the rate at which Himalayan glaciers were melting.

The new research involved drawing together evidence from more than 100 climate change studies, many of which were conducted since the last major IPCC report in 2007.

It showed that, on a global scale, predictions made about the effects of greenhouse gas emissions match actual trends seen over the past 50 years.

Since 1980, average global temperature has increased by about 0.5˚C. Currently, the Earth is getting warmer at the rate of about 0.16˚C per decade.

The study found natural forces such as volcanic eruptions and cyclical changes in the brightness of the Sun could not explain what was happening to the world's climate, said Dr Stott.

For example, solar heating would have warmed both upper and lower layers of the atmosphere, the stratosphere and troposphere. However, what was seen was that while the stratosphere had cooled, the troposphere had warmed.

Asked if the new research would help silence those who question man-made climate change, Dr Stott said: "I just hope people will make up their minds informed by the scientific evidence."

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