Ice builds up on a pier along the shoreline of Lake Michigan, U.S.
© AFP/GettyImages/File Scott Olson

PARIS (AFP) - For much of its history, climate change has faced indifference or ignorance, thanks mainly to sceptics who challenged the sometimes-sketchy evidence and fossil-fuel lobbyists who dismissed it as nothing more than a greenmongering scare.

Thirty years ago, only a tiny number of individuals -- "climate scientists and the granola-and-sandals brigade," says US historian Spencer Weart -- took notice of the idea that unbridled burning of oil, gas and coal might eventually mess up the climate system.

In fact, the apocalyptic fear of the mid-1970s was not global warming -- but global cooling.

This was the notion that Earth was about to be plunged into a deep freeze, as shifts in its orbit and axis unleashed a catastrophic drop in warmth from the Sun.

In 1977, the big media buzz was for a book called "The Weather Conspiracy: The Coming of the New Ice Age," which conjured fears of a snowball planet where survivors eked out a troglodytic life in beaver skins.

But evidence for the greenhouse effect was already trickling out.

The 15th plenary session of the UN-sponsored Earth Summit, 1992, Rio de Janeiro
© AFP/File Daniel Garcia

By the end of the 1970s, warming had tipped the balance over cooling in the battle for expert opinion as to which way the climate was heading.

In 1979, the US National Academy of Sciences issued a landmark report, backing predictions that a doubling of carbon dioxide (CO2) would cause atmospheric warming of between 1.5-4.5 degrees C (2.7-8.1 degrees F).

In the 1980s, further research added intriguing new pieces to the global warming puzzle. But scientists fretted over the many remaining blanks and debated fiercely over what the picture actually meant.

Although some saw a looming threat, no action was taken politically, given the backlash against environmentalism in the era of former US president Ronald Reagan.

Things changed in 1988, a summer of record heat and droughts in the United States, when James Hansen of the Goddard Institute of Space Studies at the National Aeronautics and Space Administration (NASA) delivered his now-famous testimony to Congress.

Hansen declared he was 99 percent certain that the man-made greenhouse effect had been detected -- and that it was starting to affect the climate.

Although Hansen came under fire by fellow scientists who thought his pronouncements premature or even alarmist, the media splashed his testimony and "global warming" entered the general vocabulary.

A military vehicle survey the situation as water floods the streets of New Orleans
© AFP/File Robyn Beck

Within months, the UN and the World Meteorological Organisation (WMO) set up a paramount scientific authority, the Intergovernmental Panel on Climate Change (IPCC), tasked with assessing greenhouse gases and their impact on the climate.

In 1992, the Rio Summit delivered the UN Framework Convention on Climate Change (UNFCCC), which in turn fathered the Kyoto Protocol on tackling greenhouse gases.

The IPCC has issued four reports since 1990, delivering judgements that are progressively more emphatic -- call it gloomy -- about the nature and severity of climate change.

They have also become profoundly influential, forcing sceptics into silence, prompting fossil-fuel companies to display green credentials and encouraging President George W. Bush to acknowledge climate change as a long-term challenge.

Weart, who is director of the Center for the History of Physics at the American Institute of Physics (AIP) in College Park, Maryland, says two other factors have been big in changing opinion in the United States.

One is former US vice president Al Gore who "has changed elite opinion" with his docu-movie "An Inconvenient Truth", said Weart.

And in 2005, Hurricane Katrina was seen by many Americans as proof of climate change, even though experts say that it is impossible to connect this single event with global warming.

"Awareness about climate change in the United States these days is about the same as in Europe," Weart said in an interview. "But the willingness to do something about it is much lower."

©AFP