Key findings

From the United Nations report:

Global warming is “unequivocal”: Eleven of the last 12 years are among the warmest since 1850. Sea levels have risen by an average seven-hundredths of an inch per year since 1961.

Extinction: About 20 percent to 30 percent of all plant and animal species face the risk of extinction if temperatures increase by 2.7 degrees Fahrenheit.

Causes: Human activity is largely responsible for warming. Global emissions of greenhouse gases grew 70 percent from 1970 to 2004.

Weather: Tropical storms will be more frequent and intense. Heat waves and heavy rains will raise the risk of wildfires and the spread of diseases.

Solutions: A wide array of tools exist, or will soon be available, to adapt to climate change and reduce its potential effects. One is to put a price on carbon emissions.