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Article for Investigation 4.1: 2010

The New Normal?: Average Global Temperatures Continue to Rise
2010 may prove to be the hottest year since
record keeping began in 1880
By David Biello  | July 22, 2010 | 65 | Scientific American

Hot summers (and balmier winters) may simply be the new normal, thanks to carbon dioxide lingering in the atmosphere for centuries.

This trend reaches back further than a couple of years. There have been exactly zero months, since February 1985, with average temperatures below those for the entire 20th century. (And those numbers are not as dramatic as they could be, because the last 15 years of the 20th century included in this period raised its average temperature, thereby lessening the century-long heat differential.) That streak—304 months and counting—was certainly not broken in June 2010, according to the U.S. National Oceanic and Atmospheric Administration (NOAA). Last month saw average global surface temperatures 0.68 degree Celsius warmer than the 20th-century average of 15.5 degrees C for June—making it the warmest June at ground level since record-keeping began in 1880. [See explanation of temperature scales.]

Not only that, June continued another streak—this year, it was the fourth warmest month on record in a row globally, with average combined land and sea surface temperatures for the period at 16.2 degrees C. The high heat in much of Asia and Europe as well as North and South America more than counterbalanced some local cooling in southern China, Scandinavia and the northwestern U.S.—putting 2010 on track to surpass 2005 as the warmest year on record. Even in the higher reaches of the atmosphere—where cooling of the upper levels generally continues thanks to climate change below—June was the second warmest month since satellite record-keeping began in 1978, trailing only 1998.

"Warmer than average global temperatures have become the new normal," says Jay Lawrimore, chief of climate analysis at NOAA's National Climatic Data Center, which tracks these numbers. "The global temperature has increased more than 1 degree Fahrenheit [0.7 degree C] since 1900 and the rate of warming since the late 1970s has been about three times greater than the century-scale trend."

. . . The short-term is fairly clear to climatologist James Hansen of the NASA Goddard Institute for Space Studies. "A new record global temperature, for the period with instrumental measurements, should be set within the next few months," he wrote in an unpublished paper in March.