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UN Report: Humans 'Most Likely' Cause Global Warming

Some of the world's leading scientists say mankind is very likely behind recent global warming, and that temperatures and sea levels will continue to rise. In this VOA report, Lisa Bryant has more on the conclusions presented by the Intergovernmental Panel on Climate Change from Paris.

The panel says the world's temperatures, which have recently registered historic highs in some places, will likely keep rising by between 1.8 and four degrees Celsius this century. The sea level will also rise. And it is very likely, the panel says, that human activity is largely responsible for the recent temperature hikes.

Because the report is a consensus document, reviewed by hundreds of scientists from 113 nations, its findings are considered authoritative.

Achim Steiner, head of the United Nations Environmental Program, told reporters in Paris the report shifts the debate from doubting whether mankind is contributing to global warming to acting on it.

"It is an unequivocal set of pieces of evidence put before the world about how fossil fuel use, agriculture and land-use change are fundamentally affecting the systems on our planet." he said. "I think, it is critical that we look at this report not only as a milestone, but truly the moment where the focus of attention on whether climate change is linked to human activity, whether the science is sufficient, to what on earth are we going to do about it."

The panel's report says temperatures may continue rising over the coming centuries, even if we take steps to fight global warming. It notes the world has already seen more intense storms and hurricanes, and will likely see more of them in the coming years. And, it says climatic changes could create "environmental refugees" in Africa and Asia.

The panel was more cautious in projecting other changes, such as the melting of the ice sheet covering Greenland. Senior U.S. scientist Susan Solomon, a co-chair of the panel, says such an event could take thousands of years.

"And, I must insist, the word, 'eventually,' is carefully chosen, and the word, 'millennia,' is carefully chosen," she said. "It takes a long time, to our best understanding of the moment, that would raise sea levels by seven meters."

The U.N. report is aimed at pressing governments and leading companies around the world to adopt policies that will curb the emission of greenhouse gases.