Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 01:30 PM GMT em 25 de Abril de 2012
March 2012 was the globe's 16th warmest March on record, but the coolest March since 1999, according to the National Oceanic and Atmospheric Administration's National Climatic Data Center (NCDC). March 2012 was the 17th warmest on record, according to NASA. March 2012 global land temperatures were the 18th warmest on record, and ocean temperatures were the 14th warmest on record. The relatively cool global temperatures were due, in part, to the lingering effects of the La Niña event in the Eastern Pacific that is now ending. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were near average, the 17th or 11th warmest in the 34-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH). March temperatures in the stratosphere were the 1st or 2nd coldest on record. We expect cold temperatures there due to the greenhouse effect and to destruction of ozone due to CFC pollution. Northern Hemisphere snow cover during March was near average, ranking 23rd largest (24th smallest) in the 46-year record. Wunderground's weather historian, Christopher C. Burt, has a comprehensive post on the notable weather events of March in his March 2012 Global Weather Extremes Summary. Notably, Norway, Iceland, and Scotland all recorded their hottest March temperatures on record, and it was the warmest March in U.S. history. Portions of Italy received no measurable precipitation whatsoever, and for most of southern Europe, it was the driest March on record. In the U.K. it was the driest March since 1953.
Figure 1. Departure of temperature from average for March 2012. The U.S. and Canada experienced the most extreme warmth of anywhere in the globe during March. Image credit: National Climatic Data Center (NCDC) .
La Niña conditions no longer present
La Niña conditions are no longer present in the equatorial Pacific, where sea surface temperatures were approximately 0.4°C below average during March and the the first half of April. The threshold for a La Niña is for these temperatures to be 0.5°C below average or cooler. NOAA's Climate Prediction Center forecasts that La Niña will be gone by the end of April. The majority of the El Niño computer models (48%) predict neutral conditions for this fall, during the August - September - October peak of hurricane season, though 35% of the models predict an El Niño will develop. El Niño conditions tend to decrease Atlantic hurricane activity, by increasing wind shear over the tropical Atlantic.
Figure 2. Ice age data show that first-year ice made up 75% of the Arctic sea ice cover this March. Thicker multi-year ice used to make up around a quarter of the Arctic sea ice cover. Now it constitutes only 2%. Image credit: National Snow and Ice Data Center (NSIDC).
March Arctic sea ice extent ninth lowest on record
Arctic sea ice extent was at its ninth lowest extent on record in March, according to the National Snow and Ice Data Center (NSIDC). This was the highest since 2008 and one of the highest March extents in the past decade. Ice extent as of April 23 was close to average, one of the few times during the past decade that has occurred. However, ice in the Arctic is increasingly young, thin ice, which will make it easy for this year's ice to melt away to near-record low levels this summer, if warmer than average weather occurs in the Arctic. During the 1980s, more than 20% of the Arctic ice was more than 4 years old; this March, that fraction was just 2%. Satellite sea ice records date back to 1979.
I'll have a new post by Friday.
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