"A new report from the United Nations' panel on climate change says major action is needed, and fast, if policy makers want to limit global warming to acceptable levels."

"There's an international target to control climate change: keeping the global temperature rise to just two degrees Celsius above pre-industrial levels—that's 3.6 degrees Fahrenheit. The Intergovernmental Panel on Climate Change now says it's technically possible to meet that goal. But doing so will require rapid, large-scale shifts in energy production and use."

"Greenhouse gas emissions will have to drop 40 to 70 percent by 2050 — and then drop even more, to nearly zero by the end of this century — the report says."