Global Warming Reports

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Executive Summary

Scientists expect that global warming will cause a variety of changes to precipitation patterns in the United States. Many areas will receive increased amounts of rain and snow over the course of a year; some areas will receive less. But scientists expect that, all across the country, the rainstorms and snowstorms that do occur will be more intense – increasing the risk of flooding and other impacts.

In this report, we evaluate trends in the frequency of storms with extreme levels of rainfall or snowfall across the contiguous United States over the last 60 years. We analyze daily precipitation records spanning from 1948 through 2006 at more than 3,000 weather stations in 48 states. We then examine patterns in the timing of heavy precipitation relative to the local climate at each weather station. We find that storms with extreme amounts of rain or snowfall are happening more often across most of America, consistent with the predicted impact of global warming.

Scientists expect global warming to increase the frequency of heavy precipitation.

By halting the increase in total U.S. global warming emissions now and reducing emissions by at least 80 percent by mid-century, we can limit the increase in major storm frequency – and thus reduce future risks of flooding and other serious consequences of extreme rainstorms.

To address global warming, America should limit emissions of global warming pollution, while improving energy efficiency and increasing the use of renewable energy.

· To protect future generations, the United States should adopt a mandatory cap on global warming pollution that reduces total U.S. emissions by at least 15 to 20 percent by 2020 and by at least 80 percent by 2050.

· If policymakers choose a cap-and-trade program to achieve this goal, it should include auctioning 100 percent of emission allowances, rather than giving allowances away to polluters. By auctioning allowances, we can reduce the cost of achieving emission reduction goals, making it more likely that America will succeed.

· The United States should also adopt complementary policies to improve energy efficiency and increase the use of clean, renewable energy.