Man-made climate change is already altering the way Americans live and work, according to a new federal report that projects the country could warm another 5-10 degrees Fahrenheit by the end of this century if emissions of heat-trapping gases continue to rise.
"Evidence for climate change abounds, from the top of the atmosphere to the depths of the oceans," says the report, the third national assessment of climate change impacts in the United States. "The sum total of this evidence tells an unambiguous story: The planet is warming."
Average temperatures in the United States have risen by 1.5 degrees Fahrenheit since 1895, but 80 percent of that increase has occurred since 1980, the analysis says, laying much of the blame on greenhouse gas emissions produced by human activities.
Across the nation, oceans, rivers and lakes have warmed; the number of frost-free days and heavy downpours has increased; sea level has risen; and the area covered by snow, glaciers, permafrost and sea ice has significantly decreased, concludes the report, which was compiled by an independent panel of experts.
Those shifts threaten human health and well-being, the report says, citing "impacts from increased extreme weather events, wildfire, decreased air quality, diseases transmitted by insects, food and water and threats to mental health."
"As climate change and its impacts are becoming more prevalent, Americans face choices as a result of past emissions of heat-trapping gases," the report says. "Some amount of additional climate change and related impacts is now unavoidable."
But decisions made by leaders in the United States and other countries could significantly limit climate change's toll, the report adds.
"Beyond the next few decades, the amount of climate change will still largely be determined by choices society makes about emissions," it says.
Making significant reductions in greenhouse gas emissions by 2050 could limit warming to an additional 3-5 degrees Fahrenheit by the end of the century, while allowing emissions to continue rising would lead to a 5-10-degree increase, the report says.
The document, a draft analysis released today by the U.S. Global Change Research Program, will undergo a three-month public comment period and a separate, independent review by the National Academy of Sciences.
It was authored under a 1990 law that requires the White House to produce regular status updates on climate change in the United States.