Back-to-back La Niñas cooled globe and influenced extreme weather in 2011

NOAA: Worldwide, 2011 was the coolest year on record since 2008, yet temperatures remained above the 30 year average, according to the 2011 State of the Climate report released online today by NOAA. The peer-reviewed report, issued in coordination with the American Meteorological Society (AMS), was compiled by 378 scientists from 48 countries around the world. It provides a detailed update on global climate indicators, notable weather events and other data collected by environmental monitoring stations and instruments on land, sea, ice and sky.

“2011 will be remembered as a year of extreme events, both in the United States and around the world,” said Deputy NOAA Administrator Kathryn D. Sullivan, Ph.D. “Every weather event that happens now takes place in the context of a changing global environment. This annual report provides scientists and citizens alike with an analysis of what has happened so we can all prepare for what is to come.”

Two back-to-back La Niñas, each characterized by cooler-than-average water temperatures in the eastern equatorial Pacific, affected regional climates and influenced many of the world’s significant weather events throughout the year. These included historic droughts in East Africa, the southern United States and northern Mexico. La Niña conditions contributed to an above-average tropical cyclone season in the North Atlantic hurricane basin and a below-average season in the Eastern North Pacific. It was also associated with the wettest two-year period (2010–2011) on record in Australia, which was particularly remarkable as the wet conditions followed a decade-long dry spell.

The Arctic continued to show more rapid changes than the rest of the planet. Sea ice shrank to its second smallest “summer minimum” extent on record during 2011, as older ice (four to five years old) reached a new record minimum at more than 80 percent below average. Overall, glaciers around the world continued to lose mass. Loss from Canadian Arctic glaciers and ice caps were the greatest since measurements began in 2002.

The report used 43 climate indicators to track and identify changes and overall trends to the global climate system. These indicators include greenhouse gas concentrations, temperature of the lower and upper atmosphere, cloud cover, sea surface temperature, sea level rise, ocean salinity, sea ice extent and snow cover. Each indicator includes thousands of measurements from multiple independent datasets....

The lead character of the 2011 climate story was a double dip La Niña, which chilled the Pacific at the start and end of the year. Many of the 2011 seasonal climate patterns around the world were consistent with common side effects of La Niña. Graphic from the NOAA Climate Portal