A team of scientists overseen by the federal government has concluded that human-induced climate change is already having an impact on weather patterns, though the types of impacts vary from one region to another.
The Northeast, for example, has seen more extreme precipitation than elsewhere in the country, with more than 70 percent increase in these events between 1958 and 2010. The average temperature has increased in the region by almost 2 degrees Fahrenheit between 1895 and 2011, compared to increases of 1.3-1.9 degrees across the U.S. The report also found above-average sea level rise in the Northeast. Coastal waters have risen almost a foot since 1900, compared to a global average of 8 inches. Warmer temperatures are expanding the oceans, and in addition, in the Northeast, the land mass is sinking.
"A warmer atmosphere can hold more moisture," said Radley Horton, an associate research scientist at Columbia University's Earth Institute. "We've also seen average rainfall go up somewhat in the Northeast. And some portion of why the Northeast could be getting more than other areas — some of that could be natural variability."
The report, the National Climate Assessment, predicts that coastal flooding from hurricanes and other storms will be worse because of sea level rise, and that increased temperatures will lead to more heat waves. It is the third such report since 1990, when Congress called for a team of experts to regularly review published research on climate change.
"Globally, natural variations can be as large as human-induced climate change over timescales of up to a few decades," the authors write. "However, changes in climate at the global scale observed over the past 50 years are far larger than can be accounted for by natural variability."
The White House released the report Tuesday as the Obama administration is battling Congressional Republicans over proposed regulations that would limit emissions from new power plants.
In a response, two staff members of the conservative Cato Institute called the report biased. While the researchers, Chip Knappenberger and Patrick Michaels, acknowledged that climate change is increasing the frequency of heat waves, they argued that society has been able to adapt and that heat-related mortality has actually decreased. One of the articles they cite, however, predicts that 1,907 additional people would nonetheless die each summer across the country because increases in temperature will outpace the ability of vulnerable populations to adapt.