Understanding Climate

Winter storms in February improved drought in the Southeast and Midwest, but well below average precipitation in parts of the West in recent months has worsened drought in other places.

As the whole ocean gets warmer, NOAA scientists must redefine what they consider “average” temperature in the central tropical Pacific, where they keep watch for El Niño and La Niña.

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.

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.

Data from 2010 indicate that mountain glaciers predominantly lost mass, and preliminary data from 2011 indicate a continuation of the same long-term trend.

In early 2011, stratospheric temperatures rose over the tropics due to La Nina while temperatures over the poles fell below the long-term average.

In 2011, annual snow cover extent over Northern Hemisphere continents (including the Greenland ice sheet) averaged 24.7 million square kilometers, which is 0.3 million square kilometers less than the long-term average.

In 2011, La Niña and the Pacific Decadal Oscillation cooled parts of the Pacific Ocean, but unusually warm temperatures predominated elsewhere.