Global Temperature Trend Update —August 2009

Every month University of Alabama climatologists John Christy and Roy Spencer report the latest global temperature trends from satellite data. Below are the newest data updated through July, 2009.

The press release from the University reports:

Global climate trend since Nov. 16, 1978: +0.13 C per decade  

July temperatures (preliminary)

Global composite temp.: +0.41 C (about 0.74 degrees Fahrenheit) above 20-year average for July.

Northern Hemisphere: +0.21 C (about 0.38 degrees Fahrenheit) above 20-year average for July.

Southern Hemisphere: +0.61 C (about 1.10 degrees Fahrenheit) above 20-year average for July.

The global average temperature jumped 0.41 C from June to July, the largest one-month jump in the 31-year global temperature record, according to Dr. John Christy, director of UAHuntsville's Earth System Science Center. The global average went from normal in June to the second hottest July on record.

"Part of that is an artificial artifact of where we put the calendar boundaries," Christy said. "Warmth from the new El Nino was not felt at all in June but really got going almost from the first day of July."

At 0.41 C warmer than seasonal norms, July 2009 was second only to July 1998 (+0.51 C). July 1998 was on the back end of the most powerful El Nino Pacific Ocean warming event of the 20th century. That El Nino also caused the warmest monthly average temperature in the climate record: +0.77 in April 1998.

At 0.61 C warmer than seasonal norms, temperatures in the Southern Hemisphere in July tied May 1998 (during that big El Nino) as the second warmest month south of the equator. It was also the second warmest month on record in the Antarctic, where the average temperature was 3.11 C (about 5.60 degrees Fahrenheit) warmer than seasonal norms for the Antarctic winter. The warmest (compared to seasonal norms) was May 2002, when the continent's average temperature was 3.30 C warmer than normal.