Northern Hemisphere Temperature Shatters July Record

NASA released data today (11 August 2010) showing that the average surface temperature in July 2010 in the Northern Hemisphere shattered the previous record set in 2005.  According to NASA's  Goddard Institute for Space Studies, the Northern Hemisphere was 1.04oC above the long-term mean, well above the previous record set in 2005 when July temperatures were 0.93oC above the mean.  The anomaly was in sharp contrast to 2009, when July was 0.66oC above the mean.

As the figure above indicates, the largest departures from the mean in the Northern Hemisphere were in Europe, East Asia (especially northeast Siberia), eastern North America, North Africa and the Middle East. 

In the Southern Hemisphere, where it now is winter, the average temperature in July was above normal.  But at 0.41oC above the mean, it was far from breaking the record high for July of 0.86oC above the mean set in 1990.  Large areas of Antarctica saw temperatures below the mean with one notable exception: the Antarctic Peninsula where temperatures were well above the mean.

Globally, average surface temperatures were 0.72oC above the mean, making July 2010 the 4th warmest on record. The warmest July on record globally was 1998 when temperatures were 0.84oC above the mean.

NASA also indicates in its Comparison of [January-July] 2010 Temperature to the Two Other Years with the Warmest Annual Means [PDF], that globally, the year to date is the warmest on record (i.e. in 131 years).  The warmth was especially pronounced in the Arctic.

In a special page posted by NASA on July 2010 — What Global Warming Looks Like, the agency provides the graph below showing the dramatic increase in the 12-month running mean temperature anomaly for the globe.

The NASA page says:

"Climate anomalies in the Northern Hemisphere summer of 2010, including the heat in Eastern Europe and unusually heavy rainfall and floods in several regions, have received much attention. Are these climate anomalies an example of what we can expect global warming to look like? ... The location of extreme events in any particular month depends on specific weather patterns, which are unpredictable except on short time scales. The weather patterns next summer will be different than this year. It could be a cooler than average summer in Moscow in 2011.

But note ... that the area warmer than climatology already (with global warming of 0.55°C relative to 1951-1980) is noticeably larger than the area cooler than climatology. Also the magnitude of warm anomalies now usually exceeds the magnitude of cool anomalies.

What we can say is that global warming has an effect on the probability and intensity of extreme events. This is true for precipitation as well as temperature, because the amount of water vapor that the air carries is a strong function of temperature. So the frequency of extremely heavy rain and floods increases as global warming increases. But at times and places of drought, global warming can increase the extremity of temperature and associated events such as forest fires.

Online Resources:

NASA Goddard Institute for Space Studies:

•  Northern Hemisphere Land-Ocean Temperature Index
• Southern Hemisphere Land-Ocean Temperature Index
• Global Land-Ocean Temperature Index

WWF Climate Blog:

• The World Meteorological Organization on "Unprecedented sequence of extreme weather events.  08/12/2010.
• For Sixth Consecutive Month, Record High Sea Surface Temperatures in Tropical Atlantic .  08/09/2010.
• Much Above Normal July Temperatures Help Make May-July 2010 the Hottest on Record for Eastern U.S.  08/09/2010
• Arctic Sea Ice in July is Second Lowest on Record, Maintaining Rapid Longer Term Decline.  08/08/2010.
• Greenland Glacier Calves the Arctic's Largest Ice Chunk in Nearly a Half-Century. 08/08/2010.
• Russian President Dmitry Medvedev: "Everyone is talking about climate change now."  08/05/2010. 
• Peter Sinclair's "Crock of the Week" Video: Heatwave Edition (and Denialist Smackdown).  08/03/2010.
• Ukraine Sees Hottest Temperature Ever as 2010 Tops the Record Books for National Temperature Extremes. 08/03/2010.

• 2010 Now Tied With 2007 For Number of Countries Breaking All Time High Temperature Records .   08/02/2010.