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Humans are driving climate change, federal scientists say

New U.S. report tallies impacts from hottest-ever years to extreme weather threats

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6:19pm, November 3, 2017
Jakobshavn Glacier in western Greenland

RETREATING ICE  Jakobshavn Glacier in western Greenland (its front edge, where ice is calving into the ocean, shown here in 2012) is one of the world’s fastest-shrinking glaciers. A new U.S. report increases projections of average global sea level rise due to accelerating ice sheet melting if greenhouse gas emissions continue unabated.

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It is “extremely likely” that humans are driving warming on Earth since the 1950s. That statement — which indicates a 95 to 100 percent confidence in the finding — came in a report released November 3 by the U.S. Global Change Research Program. This interagency effort was established in 1989 by presidential initiative to help inform national science policy.

The 2017 Climate Science Special Report, which lays out the current state of scientific knowledge on climate change, will be rolled into the fourth National Climate Assessment, set to be released in late 2018.

The last national climate assessment, released in 2014, also concluded that recent warming was mostly due to humans, but didn’t give a confidence level (SN Online: 5/6/14). Things haven’t gotten better. Ice sheet melting has accelerated, the 2017 report finds. As a result, projections of possible average global sea level rise by 2100 under a high greenhouse gas emissions scenario (in which emissions rise unabated throughout the 21st century) have increased from 2 meters to as much as 2.6 meters.

In addition, the report notes that three of the warmest years on record — 2014, 2015 and 2016 — occurred since the last report was released; those years also had record-low sea ice extent in the Arctic Ocean in the summer.

The report also notes some still-unresolved questions that have become increasingly active areas of research. One big one: How will climate change alter atmospheric circulation in the mid-latitude areas? Scientists are wrangling with whether and how these changes will affect storm patterns and contribute to extreme weather events, including blizzards and drought.

Citations

D.J. Wuebbles et al (eds.).  Climate Science Special Report: Fourth National Climate Assessment, Volume I. U.S. Global Change Research Program. November 3, 2017. doi: 10.7930/J0J964J6.

Further Reading

T. Sumner. 195 nations approve historic climate accord. Science News. Vol. 189, January 9, 2016, p. 6.

T. Sumner. Global warming ‘hiatus’ just an artifact, study finds. Science News. Vol. 187, June 27, 2015, p. 6.

B. Mole. Year in review: Climate warnings heat up. Science News. Vol. 186, December 27, 2014, p. 29.

A. Yeager. Federal report details climate change in U.S. Science News Online, May 6, 2014.

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