The assessment draws from scientific peer-reviewed research and technical input reports that demand immediate action in no uncertain terms. As the report begins, “Climate change, once considered an issue for a distant future, has moved firmly into the present.” Further, the human element in global warming is no longer in doubt: “The amount of warming projected beyond the next few decades [is] directly linked to the cumulative global emissions of heat-trapping gases and particles.”
The trend is no less apparent in America. Since 1895, average United States temperatures have increased between 1.3 and 1.9 degrees Fahrenheit, with most of that increase occurring in the last 40 years. In the coming decades, average temperatures are projected to rise even higher, by as much as 4 degrees.
The assessment breaks down the effects and consequences of climate change by U.S. region, projecting heat waves and extreme precipitation events for the northeast; water shortages for the Great Plains, Southeast, Southwest and Hawaii; damaged infrastructure and ecosystems due to receding glaciers in Alaska; and the benefits of the Midwest’s longer carbon-induced growing season being offset by alternating droughts and floods. Overall, America’s agriculture and economy will be negatively impacted if compensatory measures are not adopted countrywide.
A team of 300 experts was assembled to provide input on the NCA, with stakeholders including policymakers from the public and private sectors, resource and environmental managers, researchers and representatives from business and non-governmental organizations. An interactive website has been launched to allow the public to interact with the findings. The highlights and overview of the report can be downloaded here.