SCIENCE VISUALIZED
U.S. temps keep on rising
1901–1930
1911–1940
1921–1950
1931–1960
1941–1970
1951–1980
1961–1990
1971–2000
1981–2010
1991–2020
Temperature change (degrees Fahrenheit) –1.0
–0.5
0
0.5
1.0
MAPS: NOAA CLIMATE.GOV; ANALYSIS: JARED RENNIE/NCEI AND NORTH CAROLINA INSTITUTE FOR CLIMATE STUDIES
There’s a new normal for U.S. weather. On May 4, the National Oceanic and Atmospheric Administration announced an official change to its reference values for temperature and precipitation. Instead of using the average values from 1981 to 2010, NOAA’s new “climate normals” will be the averages from 1991 to 2020. This new period is the warmest on record for the country. Compared with the previous 30-year span, for example, the average temperature across the contiguous United States rose from 52.8° Fahrenheit to 53.3°. Some of the largest increases were in the South as well as the Southwest, which also showed a dramatic decrease in precipitation. The United States and other members of the World Meteorological Organization are required to update their climate normals every 10 years. These data put daily weather events in historical context and also help track changes in drought conditions, energy use and freeze risks for farmers. That moving window of averages for the United States also tells a stark story about the accelerating pace of climate change. When each 30-year period (right) is compared with the average 1901–2000 temperature, no part of the United States is cooler now than that 20th century average. And temperatures in large swaths of the country are 1 to 2 degrees higher. — Carolyn Gramling
U.S. 30-year temperature averages compared with 20th century average
32 SCIENCE NEWS | June 19, 2021
sci vis.indd 32
6/2/21 11:20 AM
