Leaked draft of climate report struggles with drop in warming

The cover of the IPCC's fourth assessment report to the U.N., "Climate Change 2007: Synthesis Report," more frequently referred to as AR4. (Intergovernmental Panel on Climate Change (IPCC))

An unreleased draft of the U.N.’s next major climate report reportedly states that scientists are more certain than ever that man’s actions are warming the planet -- even as the report struggles to explain a slow-down in warming that climate skeptics have seized upon.

Global surface temperatures rose rapidly during the 70s, but have been relatively flat over the past decade and a half, according to data from the U.K.’s weather-watching Met Office. Climate skeptics have spent months debating the weather pattern, some citing it as evidence that global warming itself has decelerated or even stopped.

"The absence of any significant change in the global annual average temperature over the past 16 years has become one of the most discussed topics in climate science," wrote David Whitehouse of the Global Warming Policy Foundation in June. "It has certainly focused the debate about the relative importance of greenhouse gas forcing of the climate versus natural variability."

A draft of the upcoming AR5 report by the Intergovernmental Panel on Climate Change (IPCC), which is set for final release in Oct. 2014 and used by governments around the world, offers a variety of explanations for the mystery, Reuters reported, from ocean storage of heat to volcanoes.

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“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,” explained Reuters environment correspondent Alister Doyle.

The draft expresses “medium confidence” that the slowing in global warming "due in roughly equal measure" to those factors, Reuters said.

"It might be down to minor contributions that all add up," said Gabriele Hegerl, a professor at Edinburgh University told the news agency. Or maybe the latest decade is simply a statistical blip, an anomaly in a larger trend.

Climate bloggers were quick to dismiss all of the possible explanations for the slow down in heating up.

"All of these fatuous figures are pulled out of the air to support the IPCC ideologies and not based upon any statistical analysis or science," said Marc Morano, a particularly outspoken climate skeptic who writes the popular blog Climate Depot.

The U.N. arm responsible for the report released a statement to FoxNews.com on Monday stating that it was premature to draw conclusions from the leaked draft.

“The text is likely to change in response to comments from governments received in recent weeks and will also be considered by governments and scientists at a four-day approval session at the end of September,” the statement said. “It is therefore premature and could be misleading to attempt to draw conclusions from it.”

The report stresses that scientists are now 95 percent certain that man’s actions are responsible for global warming, and that action is key to avert a coming crises.

“The report is simply an exclamation mark on what we already knew: Climate change is real and it continues unabated, the primary cause is fossil fuel burning, and if we don’t do something to reduce carbon emissions we can expect far more dangerous and potentially irreversible impacts on us,” climate scientist Michael Mann wrote to Climate Progress.

The U.N. agency's report is sure to face intense scrutiny. The 2007 iteration was widely lambasted over flaws and sloppy information, notably the claim that global warming would cause the Himalayas to melt by 2035.