Climate Scientists Struggle to Explain Warming Slowdown

April 22, 2013

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, says Reuters.

Getting this right is essential for the short and long-term planning of governments and businesses ranging from energy to construction, from agriculture to insurance. Many scientists say they expect a revival of warming in coming years.

  • 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.

Some experts say their trust in climate science has declined because of the many uncertainties. The UN's Intergovernmental Panel on Climate Change (IPCC) had to correct a 2007 report that exaggerated the pace of melt of the Himalayan glaciers and wrongly said they could all vanish by 2035.

  • A rapid rise in global temperatures in the 1980s and 1990s -- when clean air laws in developed nations cut pollution and made sunshine stronger at the earth's surface -- made for a compelling argument that human emissions were to blame.
  • 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 toward renewable energies such as solar or wind power.

Temperature records since 1850 show fluctuations, and the IPCC has consistently said that fluctuations in the weather, perhaps caused by variations in sunspots or a La Nina cooling of the Pacific, can mask any warming trend and the panel has never predicted a year-by-year rise in temperatures.

Experts say short-term climate forecasts are vital to help governments, insurers and energy companies to plan.

Source: "Climate Scientists Struggle to Explain Warming Slowdown," Reuters, April 16, 2013.

 

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