For the planet as a whole, 2010 was one of the two warmest years on record, according to three independent datasets detailed in the latest State of the Climate report, released today by the National Oceanic and Atmospheric Administration and the American Meteorological Society.
The year 2005 tops the list of warmest years since temperature recordkeeping began in 1880.
The annual State of the Climate report is a detailed update on global climate indicators, notable climate events and other climate information from every continent. The 2010 report was compiled by 368 scientists from 45 countries.
The year 2010 was notable for its globally-averaged warmth, the report states.
The peer-reviewed report tracks 41 climate indicators, four more than last year.
Indicators include temperature of the lower and upper atmosphere, precipitation, greenhouse gases, humidity, cloud cover, ocean temperature and salinity, sea ice, glaciers, and snow cover.
The data show that annual average temperatures in the Arctic continued to rise at about twice the rate of the lower latitudes.
Arctic sea ice shrank to the third smallest area on record, and the Greenland ice sheet melted at the highest rate since at least 1958. The Greenland ice sheet melt area was eight percent greater than the previous record set in 2007.
While several well-known cyclical weather patterns influenced weather and climate events throughout the year, the analysis of indicators shows "a continuation of the long-term trends consistent with global climate change that scientists have seen over the last 50 years," the report states.
Last year was marked by climate oscillations like the El Niño-Southern Oscillation and the Arctic Oscillation, which affected regional climates and contributed to many of the world's significant weather events in 2010.
Even with a moderate-to-strong La Niña in place during the second half of the year, which is associated with cooler equatorial waters in the tropical Pacific, the 2010 average global sea surface temperature was third warmest on record and sea level continued to rise.
Oceans were saltier than average in areas of high evaporation and fresher than average in areas of high precipitation, suggesting that the water cycle is intensifying.
Several major cyclical weather patterns played a key role in weather and climate in 2010:
- El Niño-Southern Oscillation: A strong warm El Niño climate pattern at the beginning of 2010 transitioned to a cool La Niña by July, contributing to some unusual weather patterns around the world and impacting global regions in different ways.
Tropical cyclone activity was below normal in nearly all basins around the globe, especially in much of the Pacific Ocean. The Atlantic basin was the exception, with near-record high North Atlantic basin hurricane activity.
Heavy rains led to a record wet spring (September - November) in Australia, ending a decade-long drought.
- Arctic Oscillation: In its negative phase for most of 2010, the Arctic Oscillation affected large parts of the Northern Hemisphere, causing frigid arctic air to plunge southward and warm air to surge northward. Canada had its warmest year on record while Britain had its coldest winter at the beginning of the year and coldest December at the end of the year. The Arctic Oscillation reached its most negative value in February, the same month several cities along the U.S. East Coast had their snowiest months ever.
- Southern Annular Mode: An atmospheric pattern related to the strength and persistence of the storm track circling the Southern Hemisphere and the Antarctic led to an all-time maximum in 2010 of average sea ice volume in the Antarctic.