National Climate Assessment: Better Science Means Better Data - Appalachian Mountain Club

National Climate Assessment: Better Science Means Better Data

October 25, 2017
National Climate Assessment
The National Climate Assessment shows minimal net change in global temperature due to natural factors alone.

The fourth edition of the United States’ National Climate Assessment (NCA), a periodic report on the latest in climate science, currently awaits approval from the White House. In the meantime, the collaborative report between leading scientists and 13 federal agencies, from the National Oceanic and Atmospheric Administration to the Department of Defense, was released for public review.

Congress enacted the NCA in 1990 to inform policy makers about climate trends. The latest edition highlights how much this science has developed since then. Thanks to more research and improved technology, such as satellite photography, scientists are increasingly confident in their ability to parse and measure individual contributors to climate change. According to studies cited in the NCA, human activity—greenhouse gas emissions, in particular—increased the global mean temperature between 1.1 and 1.4 degrees Fahrenheit from 1951 to 2010. Natural factors, such as solar radiation and volcanic eruptions, had an impact between -0.2 to 0.2 degrees.

The chart above shows the change in global mean temperature based on 36 climate models combined. The orange line represents the change in temperature attributed to natural and human-caused factors, while the blue line represents natural factors alone. The shaded areas show 2 standard deviations to either side of those measurements. 

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Marc Chalufour

Marc Chalufour, a former senior editor of AMC Outdoors, writes the trail-running blog Running Wild.