If the world doesn't cut the levels of greenhouse gases in the atmosphere, the already noticeable harms of global warming could spiral "out of control", according to a 32-volume, 2,610-page report released by the Intergovernmental Panel on Climate Change.
Recent disasters such as droughts in Australia and deadly flooding in Mozambique, Thailand and Pakistan show how vulnerable we are to extreme weather. The dangers are going to worsen as the climate changes even more, the report's authors said.
While global warming will hit everyone in some way, it will be worse for the people who can least afford it, the report says. It will increase the gaps between the rich and poor, healthy and sick, young and old, and men and women.
The report echoes an earlier UN climate science panel that said if greenhouse gases continue to rise, the world is looking at about 3.5 or 4 degrees Celsius of warming by 2100. The difference, Princeton's Oppenheimer said, "is the difference between driving on an icy road at 30 mph versus 90 mph. It's risky at 30, but deadly at 90."
Global warming is triggered by heat-trapping gases, such as carbon dioxide, that stay in the atmosphere for a century. Much of the gases still in the air and trapping heat came from the United States and other industrial nations. China is now by far the number one carbon dioxide polluter, followed by the United States and India.