Summit County Citizens Voice

Northern hemisphere snow cover well below average for the month

Red indicates above-average temperatures in this global map of April 2012 temperature anomalies. IMAGE COURTESY NOAA/NCDC.

Northern hemisphere snow cover extent has been trending below normal in April.

By Summit Voice

SUMMIT COUNTY — Very warm land-surface temperatures around the world helped propel April 2012 into the top five warmest Aprils on record for the planet, marking the largest departure from 20th century averages since Nov. 2010, at the beginning of a two-year La Niña episode.

The combined global average land and sea surface temperature for the month was 57.87 degrees, more than one degree above the long-term norm, according the National Climatic Data Center monthly summary. It was the 36th April in a row with above-average readings. The last time April temps were below average was in 1976.

Despite the remnant effects of a fading La Niña, the global average sea surface temperature was .68 degrees above the 20th century average, the 11-warmest on record.

Land surface temperature anomalies were particularly pronounced in April, at 2.5 degrees above average, making it the second-warmest April on record, behind 2007. Readings were warmer than average across nearly all the world’s land masses, with the warmest temperatures reported from Alaska and the Lower 48 states and Mexico and most of Russia.

Exceptions were in northern Australia and parts of Europe, where Norway and Sweden reported the coolest April readings since 1968.

For the year to date (January to April) land and sea surface temps combined where the 15th-warmest on record and the coolest since 2008. Arctic sea ice in April was slightly below average, while sea ice around Antarctica was 9.2 percent above average, making it the sixth-largest sea ice extent in the 34-year satellite record.
For the ninth year in a row, April snow cover in the northern hemisphere was well below average — the fourth-smallest in the 46-year record. April snow cover extent has been below average every year since 1999 except for 2003.

Compiled from the NOAA National Climatic Data Center State of the Climate: Global Analysis for April 2012, published online May 2012, retrieved on May 15, 2012 from http://www.ncdc.noaa.gov/sotc/global/2012/4.

Filed under: climate and weather, Environment, global warming Tagged: | climate, Environment, global temperatures April 2012, global warming, National Climatic Data Center, National Oceanic and Atmospheric Administration, State of the Climate