The world's leading climate scientists said in a United Nations report that there was no longer room for doubt that climate change was occuring, and the dominant cause has been human actions in pouring greenhouse gases into the atmosphere.
The IPCC declared today in the “Summary for Policymakers” of its Fifth Assessment Report on climate science, from hundreds of the world’s top scientists, there is a 95 to 100 percent chance global warming is caused by humans. “Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes,” the Intergovernmental Panel on Climate Change wrote in the report that also called on governments to “step up” their responses.
Climate-change deniers have promoted the fact that temperatures have risen more slowly in the past 15 years as a refutation of man’s responsibility for global warming. Scientists say this explanation is oversimple and doesn’t take into account a long-term warming trend.
Warming of the climate system is "unequivocal," states the report, and since the 1950s, many of the observed changes are "unprecedented over decades to millennia." The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.