Global surface temperatures in 2010 were tied with 2005 as the warmest on record as part of a continuing long-term trend, according to analyses released Wednesday by two separate U.S. government scientific institutions.
Figures from the NASA Goddard Institute for Space Studies (GISS) indicate that the difference between the two years was less than 0.018 degrees F—a statistical dead heat, because it was less than the uncertainty built into the year-to-year comparisons. The next warmest years since recordkeeping began in 1880--all tied--were 1998, 2002, 2003, 2006 and 2007. Global climate has warmed about a third of a degree Fahrenheit per decade since the late 1970s, and the last decade was the warmest ever, say the researchers. The full study appears in the journal Reviews of Geophysics.
A separate study released the same day by the National Oceanic and Atmospheric Administration (NOAA) agrees closely with the GISS analysis. Although it uses slightly different methods, it confirms the 2010-2005 tie, as well as the long-term trend. NOAA researchers said both years were 1.12 degrees F above the 20th century average. The two studies cover temperatures both on land at sea, but the NOAA study said that land temperatures taken alone were the hottest ever recorded, at 1.8 degrees F over the 20th-century average.
A great majority of earth scientists agree that the warming is being driven mainly by the release of human-generated gases into the atmosphere, including carbon dioxide. “If the warming trend continues, as expected, if greenhouse gases continue to increase, the 2010 record will not stand for long,” said James Hansen, director of GISS, which is an affiliate of Columbia University’s Earth Institute.
The GISS analysis is compiled from weather data from more than 1,000 meteorological stations around the world, satellite observations of sea-surface temperatures, and measurements made at polar research stations. A computer then calculates temperature anomalies—the difference between surface temperatures in a given month and the average temperature for the same period from 1951 to 1980, the baseline years for the analysis. GISS makes the analysis annually, and the resulting yearly figures have matched closely with those of NOAA, and a third group at the United Kingdom’s Met Office Hadley Centre (which has not yet released its 2010 figures).
The GISS researchers said the high overall average of 2010 was particularly noteworthy because the last half of the year was marked by a strong transition to cooler temperatures over vast areas of the tropical Pacific Ocean—part of a periodic natural cycle known as El Niño and La Niña. “Global temperature is rising as fast in the past decade as in the prior two decades, despite year-to-year fluctuations associated with the El Niño-La Niña,” the researchers reported in their paper.
In the contiguous United States, the year was not as exceptional as across the world as a whole, but some areas were marked by extreme weather. The East Coast saw record-breaking winter cold and snow, then record-breaking summer heat waves; there were floods in California and Tennessee; and an unusually high number of tornadoes in the Midwest and northern Plains.
Abroad, unprecedented summer heat drove wildfires in Russia; in December some parts of northeastern Canada were a full 18 degrees warmer than normal, according to the GISS figures; and catastrophic floods hit widespread places, from Pakistan to Australia. Climatologists connected some regional events, including the U.S. East Coast snows, to natural cycles, not climate change. However, many scientists project that extreme weather of all kinds will increase with global warming. Lately, some have begun to consider whether unusual cold last year in some places, including Europe, was, paradoxically, driven by dramatic warming in the arctic. They say that melting of sea ice may have shifted wind patterns, sending frigid polar air into the populated mid-latitudes during winter.
“One possibility is that the heat source due to open water in Hudson Bay affected arctic wind patterns, with a seesaw pattern that has arctic air downstream pouring into Europe,” Hansen said.