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Panel: Global Warming 'Very Likely' Caused by Humans

A long-awaited report says global warming is "very likely" man-made, the most powerful language ever used on the issue by the world's leading climate scientists, delegates who have seen the report said Thursday.

And it says the disturbing signs are already visible in rising seas, killer heat waves, worsening droughts and stronger hurricanes.

There was another signal, too: The City of Light dimmed the lights.

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Slowly, starting first with the iconic Eiffel Tower and then spreading to the hotel where many scientists were staying, Paris quieted and dimmed ever so slightly, even as those still fine-tuning the document burned the midnight oil.

The report being released Friday from the Intergovernmental Panel on Climate Change — a group of hundreds of scientists and representatives of 113 governments — unanimously portrays the science of global warming as an existing and worsening threat, officials told The Associated Press.

"There's no question that the powerful language is intimately linked to the more powerful science," said study co-author Andrew Weaver of the University of Victoria.

Weaver said it is all based on science that is rock-solid, peer-reviewed, conservative and consensus: "It's very conservative. Scientists by their nature are skeptics."

The scientists wrote the report, based on years of peer-reviewed research; government officials edited it so that it would receive the required unanimous approval by world governments.

In the end, there was little debate on the strength of the wording about human activity most likely to blame.

"That is a big move. I hope it is a powerful statement," said Jan Pretel, head of the department of climate change at the Czech Hydrometeorological Institute.

The panel quickly agreed Thursday on two of the most contentious issues: attributing global warming to man-made burning of fossil fuels and connecting it to a recent increase in stronger hurricanes.

Negotiations over a final third difficult issue — how much sea level rise is predicted by 2100 — went into the night Thursday with a deadline approaching for the report.

While critics call the panel overly alarmist, it is by nature relatively cautious because it relies on hundreds of scientists, including skeptics and industry researchers.

"I hope that policymakers will be quite convinced by this message," said Riibeta Abeta, a delegate whose island nation, Kiribati, is threatened by rising seas. "The purpose is to get them moving."

It took delegates just 90 minutes to agree on the signature statement which describes how sure scientists are about global warming being caused by man.

The answer — "very likely" — translates to a more than 90 percent certainty.

What that means in layman's language is "we have this nailed," said top U.S. climate scientist Jerry Mahlman, who originated the percentage system.

"They're hearing through the science that this is appropriate," Mahlman, a reviewer of panel's work but not an author or editor, said. "I'm pretty happy with the 'very likely' designation."

That phrase is an escalation from the panel's last report in 2001, which said warming was "likely" caused by human activity.

There had been speculation that the participants might try to up the ante too "virtually certain" man causes global warming, which translates to 99 percent chance.

The Chinese delegation was resistant to strong wording on global warming, said Barbados delegate Leonard Fields and others.

China has increasingly turned to fossil fuels for its huge and growing energy needs and it asked that an ambiguous footnote be added to the "very likely" statement.

The footnote reads, "Consideration of remaining uncertainty is based on current methodology," according to an official who was at the negotiations but was sworn to secrecy.

Meanwhile, the U.S. government delegation was not one of the more vocal groups in the debate over whether warming is man-made, said other countries' officials. And several attendees credited the head of the panel session, Susan Solomon, a top U.S. government climate scientist, with pushing through the agreement so quickly.

The Bush administration acknowledges that global warming is man-made and a problem that must be dealt with, Bush science adviser John Marburger has said. However, Bush continues to reject mandatory limits on so-called "greenhouse" gases, even as he acknowledges the existence of climate change.

But this is more than just a U.S. issue.

"What you're trying to do is get the whole planet under the proverbial tent in how to deal with this, not just the rich countries," Mahlman said Thursday. "I think we're in a different kind of game now."

The panel, created by the United Nations in 1988, releases its assessments every five or six years — although scientists have been observing climate change since as far back as the 1960s. The reports are released in phases, with this one being the first of four this year.

The next report is due in April and will discuss the effects of global warming.

But there are some elements of that in the current document.

The report will say that global warming has made stronger hurricanes, including those on the Atlantic Ocean, such as Hurricane Katrina, according to Fields, the Barbados delegate, and others.

They said the panel agreed that an increase in hurricane and tropical cyclone strength since 1970 "more likely than not" can be attributed to man-made global warming.

The scientists said global warming's connection varies with storms in different parts of the world, but that the storms that strike the Americas are global warming-influenced.

That's a contrast from the 2001 which said there was not enough evidence to make such a conclusion. And it conflicts with a November 2006 statement by the World Meteorological Organization, which helped found the IPCC. The meteorological group said it could not link past stronger storms to global warming.

Fields — of Barbados, a country in the path of many hurricanes — said the new wording was "very important." He noted that insurance companies — which look to science to calculate storm risk — "watch the language, too."

Another contentious issue is predictions of sea level rise. Scientists are trying to incorporate concerns that their early drafts underestimate how much the sea level will rise by 2100 because they cannot predict how much ice will melt from Greenland and Antarctica.

In early drafts, scientists predicted a sea level rise of no more than 23 inches by 2100, but that does not include the ice sheet melts.

The report is being edited in English, then must be translated into five other languages. It will be a 11-15 page summary for policymakers in most of the world's countries.