2012 among 10 warmest years on record

WASHINGTON - The year of 2012 was among the 10 warmest on record for global land and ocean surface temperature, showed an annual State of the Climate report released Tuesday by the American Meteorological Society.

The study, led by researchers from the US National Oceanic and Atmospheric Administration-led (NOAA) and also compiled by scientists from many other countries, said that 2012 ranked as the eighth or ninth warmest year since records began in the mid-to-late 1800s, depending upon the dataset used.

The year was 0.14 to 0.17 degrees Celsius above the 1981 to 2010 average and the United States and Argentina had their warmest year on record, it said.

"Many of the events that made 2012 such an interesting year are part of the long-term trends we see in a changing and varying climate - carbon levels are climbing, sea levels are rising, Arctic sea ice is melting, and our planet as a whole is becoming a warmer place," Acting NOAA Administrator Kathryn Sullivan said in a statement.  

The study found that the Arctic continued to warm at about twice the rate compared with lower latitudes, with sea ice shrinking to its smallest "summer minimum" extent (3.42 million square kilometers) since satellite records began 34 years ago.

Meanwhile, the Antarctic maximum sea ice extent reached a record high of 19.45 million square kilometers in September, the study said.

Globally, sea surface temperature for 2012 was among the 11 warmest on record, while average sea level reached a record high. It is estimated that sea level has been increasing at an average rate of 3.2 millimeters per year over the past two decades.

Continuing a trend that began in 2004, oceans were saltier than average in areas of high evaporation, including the central tropical North Pacific, and fresher than average in areas of high precipitation, including the north central Indian Ocean, suggesting that rainfall is increasing in already rainy areas and evaporation is intensifying in drier locations.

Major greenhouse gas concentrations, including carbon dioxide, methane, and nitrous oxide, continued to rise during 2012, the report said.

Following a slight decline in manmade emissions associated with the global economic downturn, global carbon dioxide emissions from fossil fuel combustion and cement production reached a record high in 2011 of about 9.5 billion tons of carbon, and a new record of about 9.7 billion tons of carbon is estimated for 2012.

Atmospheric carbon dioxide concentrations increased by 2.1 parts per million (ppm) in 2012, reaching a global average of 392. 6 ppm for the year, it said. In spring 2012, for the first time, the atmospheric carbon dioxide concentration exceeded 400 ppm at several Arctic observational sites.

The 2012 State of the Climate report is peer-reviewed and published annually as a special supplement to the Bulletin of the American Meteorological Society. This year marks the 23rd edition of the report.