US advisory group sees climate change well under way

A new assessment of climate change in the US paints a bleak picture for the years ahead that includes increasing incidences of coastal flooding and heat waves in the Northeast; growing water shortages in the Southwest, Southeast, and Great Plains; and declining crop yields across all regions. The draft report from the National Climate Assessment and Development Advisory Committee attributes most of the temperature rise that has occurred in the past 50 years to human activities, mainly the burning of fossil fuels.

The 60-member federal advisory committee reports to the National Science and Technology Council, the interagency coordinating entity that under the 1990 Global Change Research Act is required to periodically present such reports to the president and Congress. According to the draft report, the effects of climate change are being felt in the US via increasing extreme weather events, droughts, rising seas, warmer winters, and hotter summers. The assessment of current scientific research on the observed and projected impacts of climate change on the US relies heavily on the findings of the US Global Change Research Program. That 13-agency collaboration observes, monitors, models, researches, and manages data on global change impacts and proposes options for adaptation and mitigation. More than 240 authors contributed to the report, which will be reviewed by the National Academies and made available for public comment, then will be revised and published as the third National Climate Assessment. The previous assessment was finalized in 2009.

Since 1992 the rate of global sea-level rise measured by satellites has been roughly twice the rate observed over the past century. Nearly 5 million Americans live within four feet of the local high-tide level, the report notes, and sea level is projected to rise by another 0.3–1.2 meters in this century, with some scenarios suggesting as much as a 2-meter rise by 2100. Winter storms along the West Coast and the coast of New England have increased slightly in frequency and intensity. Heavy rains have increased over the past century in many parts of the country, especially in the Northeast, Midwest, and Great Plains, where downpours have exceeded the capacity of infrastructure such as storm drains and have led to flooding events and accelerated erosion. There is some evidence that the dramatic loss of sea ice in the Arctic has affected weather patterns in the southern US, the report says.

Historic droughts, floods, and heat waves

The US contributes about 20% of worldwide emissions of carbon dioxide. Although US emissions have declined in recent years due to the recession and other factors, they are expected to grow as economic growth continues.

‘This draft report confirms what millions of Americans have been seeing right outside their window,’ Gene Karpinski, president of the League of Conservation Voters, said in a statement. ‘Hurricane Sandy and the historic droughts, floods and heat waves happening across the country aren’t a fluke, but the result of a climate warming much faster than previously thought.’

‘The findings in the report are a three-alarm fire,’ commented Representative Henry Waxman (D-CA), ranking minority member of the Committee on Energy and Commerce. ‘Climate change is already causing widespread disruption across the nation. We are in deep trouble if we don’t act forcefully this year.’ Echoed Senator Barbara Boxer (D-CA), chairman of the Committee on Environment and Public Works, ‘This draft report sends a warning to all of us: We must act in a comprehensive fashion to reduce carbon pollution or expose our people and communities to continuing devastation from extreme weather events and their aftermath.’

‘This could help restart a national conversation about climate change,’ said Todd Sanford, a climate scientist at the Union of Concerned Scientists. ‘It gives us a roadmap for climate change. And the road is much bumpier if we continue along a higher emissions pathway.’