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 (July 10, 2012) 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."
- Warm temperature trends continue: Four independent datasets show 2011 among the 15 warmest since records began in the late 19th century, with annually-averaged temperatures above the 1981-2010 average, but coolest on record since 2008. The Arctic continued to warm at about twice the rate compared with lower latitudes. On the opposite pole, the South Pole station recorded its all-time highest temperature of 9.9°F on December 25, breaking the previous record by more than 2 degrees.
- Greenhouse gases climb: Major greenhouse gas concentrations, including carbon dioxide, methane, and nitrous oxide, continued to rise. Carbon dioxide steadily increased in 2011 and the yearly global average exceeded 390 parts per million (ppm) for the first time since instrumental records began. This represents an increase of 2.10 ppm compared with the previous year. There is no evidence that natural emissions of methane in the Arctic have increased significantly during the last decade.
- Arctic sea ice extent decreases: Arctic sea ice extent was below average for all of 2011 and has been since June 2001, a span of 127 consecutive months through December 2011. Both the maximum ice extent (5.65 million square miles, March 7) and minimum extent (1.67 million square miles, September 9) were the second smallest of the satellite era.
- Ozone levels in Arctic drop: In the upper atmosphere, temperatures in the tropical stratosphere were higher than average while temperatures in the polar stratosphere were lower than average during the early 2011 winter months. This led to the lowest ozone concentrations in the lower Arctic stratosphere since records began in 1979 with more than 80 percent of the ozone between 11 and 12 miles altitude destroyed by late March, increasing UV radiation levels at the surface.
- Sea surface temperature & ocean heat content rise:Even with La Niña conditions occurring during most of the year, the 2011 global sea surface temperature was among the 12 highest years on record. Ocean heat content, measured from the surface to 2,300 feet deep, continued to rise since records began in 1993 and was record high.
- Ocean salinity trends continue: Continuing a trend that began in 2004 and similar to 2010, oceans were saltier than average in areas of high evaporation, including the western and central tropical Pacific, and fresher than average in areas of high precipitation, including the eastern tropical South Pacific, suggesting that precipitation is increasing in already rainy areas and evaporation is intensifying in drier locations.
- Determining the causes of extreme events remains difficult. While scientists cannot trace specific events to climate change with absolute certainty, new and continued research help scientists understand how the probability of extreme events change in response to global warming.
- La Niña-related heat waves, like that experienced in Texas in 2011, are now 20 times more likely to occur during La Niña years today than La Niña years fifty years ago.
- The UK experienced a very warm November 2011 and a very cold December 2010. In analyzing these two very different events, UK scientists uncovered interesting changes in the odds. Cold Decembers are now half as likely to occur now versus fifty years ago, whereas warm Novembers are now 62 times more likely.
- Climate change cannot be shown to have played any role in the 2011 floods on the Chao Phraya River that flooded Bangkok, Thailand. Although the flooding was unprecedented, the amount of rain that fell in the river "catchment" area was not very unusual. Other factors, such as changes in reservoir policies and increased construction on the flood plain, were found most relevant in setting the scale of the disaster.