Climate change is already being felt in every region of the United States, resulting in hotter summers, shorter winters, extreme precipitation, even worsening allergies that will change the way Americans live, according to a government report released Tuesday.
The National Climate Assessment, mandated by Congress and published every four years to guide policymakers, offers sobering details of climate change's immediate effects.
"The overall message is that climate change is happening right now — we can't think of this as an issue for future generations," said Radley Horton, one of the lead authors and a climate scientist at the Earth Institute's Center for Climate Systems Research at Columbia University. "We know that the effects on ecosystems, infrastructure, economics and public health are going to gro! w."
The report sketches out grim scenarios for different regions. The Northeast and Midwest, for instance, would see many more heavy downpours that could lead to flooding and erosion. The Southwest, including California, would be more prone to extreme heat, drought and wildfire, while the Northwest could see a widespread tree die-off because of wildfire, insect outbreaks and disease.
"Evidence of climate change appears in every region and impacts are visible in every state," the report asserts, saying that a national infrastructure built to withstand "historical conditions" already is being overwhelmed by prolonged rains, rapid snowmelt and extreme heat.
The assessment tackles head-on humanity's contribution to climate change, the thorniest question tied to the issue and the heart of the debate that has deadlocked efforts to cut greenhouse gas emissions. A variety of evidence confirms human activities have driven global warming over the last 50 years, the report concludes, citing specifically the emissions of heat-trapping gases from the burning of coal, oil and natural gas.
Arguments often used to deny that man-made climate change is occurring are dismissed in decisive language. The idea that warming temperatures have been caused by greater solar activity or volcanic eruptions, for example, is not supported by satellite data, the report states. A recent pause in the rise of global average land temperatures "appears to be related to cyclic changes in the oceans and in the sun's energy output," it says.
The report's message tracks closely with the Obama administration's vow to push climate change near the top o! f the president's agenda, after being criticized by supporters for neglecting it in his first term.
Surveys show that most Americans trust their television weather guides as reliable sources on climate change.kathleen.hennessey@latimes.comneela.banerjee@latimes.com
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