The effects of climate change already are occurring on all continents and across the oceans, and the world in many cases is unprepared, says the latest report from the U.N. Intergovernmental Panel on Climate Change.
"Nobody on this planet is going to be untouched by the impacts of climate change,'' says IPCC chairman Rajendra Pachauri.
Dr Saleemul Huq, a convening lead author on one of the chapters, says, "Before this we thought we knew this was happening, but now we have overwhelming evidence that it is happening and it is real."
The report is based on more than 12,000 peer-reviewed scientific studies.
It's "the most solid evidence you can get in any scientific discipline," says Michel Jarraud, secretary-general of the World Meteorological Organization.
There are opportunities to respond to the risks of climate change, but the risks will be hard to manage with high levels of warming, the report says.