CLIMATE scientists hit back at the sceptics today with research they say has uncovered the “fingerprint” of manmade global warming.
Researchers 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 influence not being the chief driver of climate change.
The clues were unravelled using a forensic technique called “optimal detection” that gives different factors – natural and human – an equal chance to explain the changes seen.
Dr Peter Stott, from the Met Office Hadley Centre in Exeter 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.”
The research was published in the journal Wiley Interdisciplinary Reviews: Climate Change.
The new research involved drawing together evidence from more than 100 climate change studies, many of which were conducted since the last major Intergovernmental Panel on Climate Change (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 0.5C. The earth is getting warmer at the rate of about 0.16C per decade.
These trends are reflected in recent measurements from deep below the surface of the oceans. In all the large ocean basins – the Atlantic, Pacific and Indian – the same warming pattern is seen.
“Over 80% of the heat trapped in the climate system, as related to greenhouse gases, is being exported into the oceans, and we can see that happening,” said Dr Stott.
Warmer temperatures had led to more evaporation from the surface of the oceans, most noticeably in the sub-tropical Atlantic, he said. As a result, the sea was getting saltier.
Evaporation in turn affected humidity and rainfall. The atmosphere was getting more humid, as climate models had predicted, and amplifying the water cycle.
What this meant was that more rain was falling in high and low latitudes and less in tropical and sub-tropical regions around the equator.
“The whole of the water cycle is changing,” said Dr Stott, speaking at the Science Media Centre in London. “Wetter regions are getting wetter and dry regions are getting drier.”
The study found that 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, he said.
Dr Stott said: “I just hope people will make up their minds informed by the scientific evidence.”
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