(CBS/AP) The warning from a top panel of international scientists was blunt and dire: "warming of the climate system is unequivocal," the cause is "very likely" man-made, and the menace will "continue for centuries."

Authors of the 21-page report released Friday on why the planet is warming by the Intergovernmental Panel on Climate Change placed the onus on governments to stop prevaricating and take action.

The report highlighted "increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level," the report said.

The best climate scientists on the planet say it is clear the earth is getting warmer and greenhouse gases produced since the industrial revolution are to blame, reports CBS News correspondent Mark Phillips from Paris.

The report said man-made emissions of greenhouse gases can already be blamed for fewer cold days, hotter nights, killer heat waves, floods and heavy rains, devastating droughts and an increase in hurricane and tropical storm strength — particularly in the Atlantic Ocean.

A top U.S. government scientist, Susan Solomon, said "there can be no question that the increase in greenhouse gases are dominated by human activities."

The message to be taken from the report is "it's later than we think," Solomon said from the U.S. National Oceanic and Atmospheric Administration during an interview with The Associated Press.

A White House science advisor praised the report, saying it "captures and summarizes the current state of client change research." A statement released Friday said the study reflects "the robust body of knowledge" on climate change science.

The statement, however, makes no mention of any forthcoming changes in the administration's policy on climate change. The statement also mirrors much of what was said by U.S. officials at the climate change meeting, CBS News correspondent Peter Maer reports.

The report and the scientists who wrote it called the document conservative — only using peer-reviewed published science, edited by representatives of 113 governments that also had to agree to every word. It is a snapshot of where the world is with global warming and where it is heading, but does not tell government officials what to do.

Yet if nothing is done, the world is looking at more than 1 million dead and hundreds of billions of dollars in costs adapting to a warmer world with more extreme weather, study co-author Kevin Trenberth said in an interview.

The next step is up to public officials, scientists said. "I want to see action — not messages," said Swiss scientist Thomas Stocker, a co-author.

"It is critical that we look at this report ... as a moment where the focus of attention will shift from whether climate change is linked to human activity, whether the science is sufficient, to what on earth are we going to do about it," U.N. Environment Program Executive Director Achim Steiner said.

"The public should not sit back and say 'There's nothing we can do'," Steiner said. "Anyone who would continue to risk inaction on the basis of the evidence presented here will one day in the history books be considered irresponsible."

Another report by the panel later this year will address the most effective measures for slowing global warming.

If it looks bad now, the harmful effects during the 21st century "would very likely be larger than those observed during the 20th century," the report said.

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