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U.N. Report Confirms Human Activity to Blame for Earth's Warming Climate

Top climate scientists have warned that global warming is here, it's caused by human activity, and the impact including rising sea levels could persist for centuries. That's the consensus announced by an authoritative UN group including scientists from 113 countries. Lisa Bryant reports on the findings released Friday by the Intergovernmental Panel on Climate Change.

More intense storms; rising sea levels and higher temperatures: people being forced to flee their homes because of changing weather patterns -- the findings presented by the Intergovernmental Panel on Climate Change (IPCC) amounted to the toughest wake-up call aired to date by 2,500 of the world's leading climate scientists.

U.N. Environment Program head Achim Steiner told reporters in Paris Friday that the world can no longer afford to ignore global warming. "It shifts from doubting to having to act, even if the last element of certainty is not yet there," Steiner said. "I think anyone who would continue to risk inaction on the basis of evidence presented here will one day in the history books be considered irresponsible."

Humans need to act, Steiner and other experts say, because human activity is the principle cause of rising temperatures and their effects in recent decades. The report says our use of fossil fuels like oil and gas, our agricultural activities, and the other ways we exploit our planet have all produced heat-trapping greenhouse gases. The panel's new report predicts that temperatures will continue to rise between 1.8 degrees and 4 degrees Fahrenheit in this century alone.

More worrying, those temperature rises will continue over the new few centuries - even if we take action to reduce our greenhouse gas emissions. Senior U.S. government scientist Susan Solomon co-chaired the panel that prepared the report.

"In terms of direct observations of climate change, the key conclusion is that warming of the climate system is now unequivocal," she said. "And that's evident in observations in air and ocean temperatures, melting of snow and ice, rising of global mean sea level."

The report updates a previous report, released in 2001. And the scientists noted this survey is based on numerous studies that have taken place since then, and a more solid scientific consensus on global warming. Six years ago, the IPCC said only that global warming was "very likely" caused by human activity. This time, the group says it's 90 percent confident that man is responsible for rises in global temperatures.

The study tried to predict what we can expect in the coming decades. Sea levels may rise between 18 and 58 centimeters by the end of the century. We have already seen more intense storms and hurricanes, and the report says we'll very likely see more of these dramatic weather patterns in future years.

How will this affect humans? Well, says the U.N.'s Steiner, that all depends on where you live. "If you're an African child born in 2007, it's likely that by the time you're 50 years old you may in fact be faced with new diseases, you may be faced with new droughts, events in your life. You may even have to leave the areas you live in because some projections show that Africa may have 30 percent of its coastal infrastructure affected by the end of this century as a result of sea level rise."

And if you're born in South Asia, water may flood your home, and you may become an environmental refugee.

But much of the report is cautious and scientific. It is a consensus document, drafted and edited by hundreds of scientists. Some environmentalists feared the process might water down its conclusions.

IPCC chairman Rajendra Pachauri says the broad consensus is what gives the findings their credibility. "This is the strength of the IPCC process -- it's essentially the scientists, the experts who are the ones who assess and provide the knowledge. But it's something that's discussed and debated by governments. And since we accept everything by consensus, the implication is that whatever is finally accepted and approved has the stamp of acceptance of all the governments of the world."

Some panel members, such as Susan Solomon, are also clearly reluctant to step out of their scientific role. This is her answer to one reporter, who asked her what message the report sends to politicians, and what should be done: "I can only give you something that's going to disappoint you sir -- and that is that it's my personal, scientific approach to say that it's not my role to try to communicate what should be done. I believe that is a societal choice."

The report has already sparked calls for action. French President Jacques Chirac called Friday for an environmental and political revolution to save the planet.

Washington was more cautious. White House official Sharon Hays called it a significant report that will be valuable to policy makers.

Eduard Toulouse, a climate change expert at World Wildlife Fund France, agrees the panel's findings give countries like the United States, which has yet to sign the Kyoto global warming protocol, no more excuses for inaction. "Now the scientific statements are very clear," he said.."It is not possible to argue anymore and to wait, because the scientists tell us we have to act very quickly to cut our emissions of greenhouse gases if we want to avoid dramatic climate change."

Toulouse also says the European Union must push for cutting greenhouse gas emissions by 30 percent by 2020. The 27-member bloc is currently debating new steps to take.

Individuals can also make a difference, the UN's Steiner says, cutting their own emissions to levels way below those set by the Kyoto Protocol. There's no excuse, he says, for the public to sit back and do nothing.