The draft report comes as world leaders are meeting in Sharm el Sheikh, Egypt, this week for the annual United Nations climate change summit. This year’s talks are focused on the harm that global warming is inflicting on the world’s poorest nations and the question of what rich countries should do to help. But the forthcoming U.S. assessment will offer a stark reminder that even wealthy nations will face serious consequences if temperatures keep rising.
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The United States has warmed 68 percent faster than Earth as a whole over the past 50 years, according to the draft report, with average temperatures in the lower 48 states rising 2.5 degrees Fahrenheit (1.4 degrees Celsius) during that time period. That reflects a global pattern in which land areas are warming faster than oceans are, and higher latitudes are warming faster than lower latitudes are as humans heat up the planet, primarily by burning fossil fuels like oil, gas and coal for energy.
Americans can now feel the effects of climate change in their everyday lives, the draft says. In coastal cities like Miami Beach, Fla., the frequency of disruptive flooding at high tide has quadrupled over the last 20 years as sea levels have risen. In Alaska, 14 major fishery disasters have been linked to changes in climate, including an increase in marine heat waves. In Colorado, ski industries have lost revenue because of declining snowfall.
Across the country, deadly and destructive extreme weather events such as heat waves, heavy rainfall, droughts and wildfires have already become more frequent and severe.
In the 1980s, the nation suffered an extreme weather disaster that caused at least $1 billion in economic damage about once every four months, on average, after adjusting for inflation. “Now,” the draft says, “there is one every three weeks on average.” Some extreme events, like the Pacific Northwest heat wave last year that killed at least 229 people, would have been virtually impossible without global warming.
Bigger hazards are on the way if global temperatures keep rising, the draft report says, although the magnitude of those risks will largely depend on how quickly humanity can get its fossil fuel emissions under control.