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http://in.reuters.com/article/2013/08/16/us-climate-report-idINBRE97F0KM20130816
The panel will try to explain why global temperatures, while still increasing, have risen more slowly since about 1998 even though greenhouse gas concentrations have hit repeated record highs in that time, led by industrial emissions by China and other emerging nations.
An IPCC draft says there is "medium confidence" that the slowing of the rise is "due in roughly equal measure" to natural variations in the weather and to other factors affecting energy reaching the Earth's surface.
Scientists believe causes could include: greater-than-expected quantities of ash from volcanoes, which dims sunlight; a decline in heat from the sun during a current 11-year solar cycle; more heat being absorbed by the deep oceans; or the possibility that the climate may be less sensitive than expected to a build-up of carbon dioxide.
"It might be down to minor contributions that all add up," said Gabriele Hegerl, a professor at Edinburgh University. Or maybe, scientists say, the latest decade is just a blip.
The main scenarios in the draft, using more complex computer models than in 2007 and taking account of more factors, show that temperatures could rise anywhere from a fraction of 1 degree Celsius (1.8 Fahrenheit) to almost 5C (9F) this century, a wider range at both ends than in 2007.
The low end, however, is because the IPCC has added what diplomats say is an improbable scenario for radical government action - not considered in 2007 - that would require cuts in global greenhouse gases to zero by about 2070.
Temperatures have already risen by 0.8C (1.4F) since the Industrial Revolution in the 19th century.
Experts say that the big advance in the report, due for a final edit by governments and scientists in Stockholm from September 23-26, is simply greater confidence about the science of global warming, rather than revolutionary new findings.
The panel will try to explain why global temperatures, while still increasing, have risen more slowly since about 1998 even though greenhouse gas concentrations have hit repeated record highs in that time, led by industrial emissions by China and other emerging nations.
An IPCC draft says there is "medium confidence" that the slowing of the rise is "due in roughly equal measure" to natural variations in the weather and to other factors affecting energy reaching the Earth's surface.
Scientists believe causes could include: greater-than-expected quantities of ash from volcanoes, which dims sunlight; a decline in heat from the sun during a current 11-year solar cycle; more heat being absorbed by the deep oceans; or the possibility that the climate may be less sensitive than expected to a build-up of carbon dioxide.
"It might be down to minor contributions that all add up," said Gabriele Hegerl, a professor at Edinburgh University. Or maybe, scientists say, the latest decade is just a blip.
The main scenarios in the draft, using more complex computer models than in 2007 and taking account of more factors, show that temperatures could rise anywhere from a fraction of 1 degree Celsius (1.8 Fahrenheit) to almost 5C (9F) this century, a wider range at both ends than in 2007.
The low end, however, is because the IPCC has added what diplomats say is an improbable scenario for radical government action - not considered in 2007 - that would require cuts in global greenhouse gases to zero by about 2070.
Temperatures have already risen by 0.8C (1.4F) since the Industrial Revolution in the 19th century.
Experts say that the big advance in the report, due for a final edit by governments and scientists in Stockholm from September 23-26, is simply greater confidence about the science of global warming, rather than revolutionary new findings.
