The summer of 2012 brought Greenland far more extensive melt than anything observed in the satellite record: in July 2012, surface melt extended over nearly the entire ice sheet. The standardized melt index was nearly double the previous record.
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A scorching July contributed to the third hottest summer on record for the contiguous United States. Most of the U.S. was also drier than average. Rains from Isaac did little to relieve drought.
Imagine heat waves like the one last July coming more often & lasting longer: that’s the projection from climate models for the middle of this century based on one future emissions path.
A series of unusually strong, long-lasting high pressure systems has parked over Greenland this summer. As many a weather forecaster has explained, high pressure generally leads to calm winds and sunny skies, both of which boost temperatures during the all-day sunshine of mid-summer at high latitudes. The conditions contributed to widespread melting of the ice sheet.
The lead character in the 2011 climate story was La Niña—the cool phase of the El Niño-Southern Oscillation—which chilled the central and eastern tropical Pacific at both the start and the end of the year. These natural cooling events have a long reach: many of the big climate events of 2011, including famine-inducing drought in East Africa, an above-average hurricane season in the Atlantic, and record rainfall in many parts of Australia, are common “side effects” of La Niña.
In September 2011, Arctic sea ice reached its second-lowest minimum extent in the satellite record.
In 2011, global sea levels fell below the long-term trend of sea level rise, but as La Niña waned late in the year, global ocean levels began rising rapidly.
Despite the double-dip La Nina that occurred throughout the year, 2011 was still among the 15 warmest years on record. Including the 2011 temperature, the rate of warming since 1971 is now between 0.14° and 0.17° Celsius per decade (0.25°-0.31° Fahrenheit), and 0.71-0.77° Celsius per century (1.28°-1.39° F) since 1901.
In 2011, Earth’s atmosphere was cooler and drier than it had been the previous year, but it was more humid than the long-term average.
Except for some La Niña-cooled regions of the tropical Pacific and a few other cool spots, the upper ocean held more heat than average in 2011 in the Pacific, Atlantic, Indian, and Southern Oceans.