Indian students and Greenpeace activists display posters urging Secretary of State Hillary Clinton and President Obama to act against “global warming,” during a visit by Clinton to New Delhi on Monday, July 20, 2009. (AP Photo)

(CNSNews.com) – Virtually all changes in global atmospheric temperatures in the late 20th century were the result of nature rather than human activity, according to a new peer-reviewed study, one of whose authors predicted Friday was “sure to cause a stir.”

“It goes against the orthodoxy,” said climate scientist Chris de Freitas of New Zealand’s Auckland University. The new findings called into question the politically-correct, politically-motivated assumptions driving the climate change debate, he said.

De Freitas and Australian scientists John McLean and Bob Carter reported that at least 80 percent of climate variability tracked over the past half a century could be attributed to internal climate-system factors including the El Nino-Southern Oscillation (ENSO) Pacific warming phenomenon and its cooling twin, La Nina.

This left little room for human-caused factors like emissions of carbon dioxide (CO2) and other so-called greenhouse gases. Intermittent volcanic activity, producing significant cooling, was found to have been a factor.

The paper was published Thursday, following a six-month peer review process, in the American Geophysical Union’s Journal of Geophysical Research.

The Australasian trio compared the ENSO and the rise and fall of lower-atmospheric temperatures between 1958 – when continuous records of those temperatures began – and 2008, and found that the one closely correlated with the other, with a lag of around seven months between the ENSO and the temperature variation.

“The sequence of the lagged relationship indicates that ENSO is driving temperature rather than the reverse,” the paper states.

The results showed that the oscillations accounted for some 80 percent of the rise and fall in temperatures, leaving “little room for CO2” as an attributable factor, De Freitas said Friday.

He described the data as established, reproducible, and “out in the open.”

The scientists’ finding flies in the face of the assertion by the United Nations’ Intergovernmental Panel on Climate Change, in a series of reports, that “global warming” is occurring, is primarily the result of human activity, and requires urgent action.

Advocacy groups warn of catastrophic consequences including rising sea levels, extreme weather patterns and drought, and governments across the planet are exploring ways to combat the problem, mostly through costly cap-and-trade schemes – setting a limit on greenhouse gas emissions and encouraging trading in emissions permits.

A major climate conference in Copenhagen in December aims to produce a new global agreement which may include binding emission-reduction targets and deadlines.

U.N. climate chief Yvo De Boer told the BBC World Service Thursday that wealthy nations will have to put at least $10 billion “on the table” in Copenhagen. “That will allow developing countries to begin preparing national plans to limit their own emissions, and to adapt to climate change.”

De Freitas, based at Auckland University’s School of Geography and Environmental Science and with 30 years of climate science under his belt, does not deny that atmospheric CO2 concentration is rising, but questions the effect that that is having, and in particular whether it is dangerous.

He said the climate debate has been “degraded” by politics, ignorance, “end is nigh” alarmist hype, and the argument that the science has been settled.

The notion of “consensus” is unscientific, he added. “Science is meant to be robust debate.”