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An enormous U.N. report on the scientific data behind global warming was made available Monday, yet it offers little concrete explanation for an earthly oddity: the planet’s climate has hit the pause button.

Since 1998, there has been no significant increase in global average surface temperature, and some areas -- notably the Northern Hemisphere -- have actually cooled. The 2,200-page new Technical Report attributes that to a combination of several factors, including natural variability, reduced heating from the sun and the ocean acting like a “heat sink” to suck up extra warmth in the atmosphere.

One problem with that conclusion, according to some climate scientists, is that the U.N.'s Intergovernmental Panel on Climate Change (IPCC) has limited the hiatus to 10-15 years. Anastasios Tsonis, distinguished professor at the University of Wisconsin – Milwaukee, believes the pause will last much longer than that. He points to repeated periods of warming and cooling in the 20th century.

'I know that the models are not adequate ... they don’t agree with reality.' — Anastasios Tsonis, distinguished professor at the University of Wisconsin – Milwaukee

“Each one of those regimes lasts about 30 years … I would assume something like another 15 years of leveling off or cooling,” he told Fox News.

That goes well beyond the window the IPCC has acknowledged, which Tsonis and other scientists believe will significantly change the predictions for temperature rise over the next century.

“I know that the models are not adequate,” Tsonis told Fox News. “There are a lot of climate models out there. They don’t agree with each other – and they don’t agree with reality.”

In fact, the IPCC's massive, complex new report acknowledges that none of the models predicted the hiatus. The authors write that it could be due to climate models over-predicting the response to increasing greenhouse gases, or a failure to account for water vapor in the upper atmosphere.

The bottom line – no one saw it coming.

“Almost all historical simulations do not reproduce the observed recent warming hiatus,” the report states.

Tsonis was pleased that the IPCC acknowledged that natural variability may have played a part in the stall in upward temperature trends. But he said the report’s authors totally ignored groundbreaking research he presented six and four years ago that fully explained such “pauses." He attributes them to an intricate interaction of oceanic and atmospheric modes which either warm or cool the planet on a time scale of decades.

Judith Curry, chair of the School of Earth And Atmospheric Sciences at Georgia Tech, says the IPCC is taking a huge credibility hit over the hiatus – and its pronouncement that it is 95 percent certain that human activity is responsible for most global warming.

“I’m not happy with the IPCC,” she told Fox News. “I think it has torqued the science in an unfortunate direction.”

That torquing, she suggests, is because the money in climate science (the funding, that is) is tied to embellishing the IPCC narrative, especially the impacts of global warming. She is critical of the IPCC’s leadership as well, in particular its chairman, Rajendra Pachauri.

“They have explicit policy agendas,” Curry told Fox News. “Their proclamations are very alarmist and very imperative as to what we should be doing. And this does not inspire confidence in the final product.”

Other scientists argue passionately against such talk.

Penn State’s Michael Mann – who authored the famous “hockey stick” graph showing a stunning rise in temperatures in the late 20th century – believes this latest IPCC report only confirms what he has been arguing for years. That the Earth is warming, and humans are to blame.

“We cannot explain the warming through natural causes,” he told Fox News. “It can only be explained by the increased greenhouse gas concentrations from human fossil fuel burning.”

Mann goes so far as to say that if you remove the "noise" from the recent pause in temperature rise, human activity is to blame for 100 percent of the global warming.

Tsonis strongly disagrees. He acknowledges that human activity is likely having an impact on climate, but adds “Nobody has ever proven for 100 percent that the long-term warming is man-made. In my educated guess I will think something like less than 30 percent.”

Judith Curry believes the approach the IPCC takes to climate change is fundamentally flawed. Consensus-seeking, she says, introduces bias into the science.

“They don’t challenge it and say, well, how might this be wrong?” she told Fox News. “What are all the different reasons or ways this could be wrong? And once you start looking at it that way, you come up with a lot of different answers.”