By Environment Correspondent Alister Doyle
OSLO | Tue Apr 16, 2013 6:25am EDT
(Reuters) - Scientists are struggling to explain a slowdown in climate change that has exposed gaps in their understanding and defies a rise in global greenhouse gas emissions.
Often focused on century-long trends, most climate models failed to predict that the temperature rise would slow, starting around 2000. Scientists are now intent on figuring out the causes and determining whether the respite will be brief or a more lasting phenomenon.
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Theories for the pause include that deep oceans have taken up more heat with the result that the surface is cooler than expected, that industrial pollution in Asia or clouds are blocking the sun, or that greenhouse gases trap less heat than previously believed.
The change may be a result of an observed decline in heat-trapping water vapor in the high atmosphere, for unknown reasons. It could be a combination of factors or some as yet unknown natural variations, scientists say.
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Some experts say their trust in climate science has declined because of the many uncertainties.
"My own confidence in the data has gone down in the past five years," said Richard Tol, an expert in climate change and professor of economics at the University of Sussex in England.
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Weak economic growth and the pause in warming is undermining governments' willingness to make a rapid billion-dollar shift from fossil fuels. Almost 200 governments have agreed to work out a plan by the end of 2015 to combat global warming.
"The climate system is not quite so simple as people thought," said Bjorn Lomborg, a Danish statistician and author of "The Skeptical Environmentalist" who estimates that moderate warming will be beneficial for crop growth and human health.
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The IPCC will seek to explain the current pause in a report to be released in three parts from late 2013 as the main scientific roadmap for governments in shifting from fossil fuels towards renewable energies such as solar or wind power, the panel's chairman Rajendra Pachauri said.
According to Pachauri, temperature records since 1850 "show there are fluctuations. They are 10, 15 years in duration. But the trend is unmistakable."
A little bit of good news on an otherwise sad day.