Worldwide, 2012 was among the 10 warmest years on record according to the 2012 State of the Climate report released online on August 2 by the American Meteorological Society (AMS).
Conditions in the Arctic were a major story of 2012, with the region experiencing unprecedented change and breaking several records. Sea ice shrank to its smallest “summer minimum” extent since satellite records began 34 years ago. In addition, more than 97 percent of the Greenland ice sheet showed some form of melt during the summer, four times greater than the 1981–2010 average melt extent.
“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,” said acting NOAA Administrator Kathryn D. Sullivan, Ph.D.
NOAA’s peer-reviewed annual State of the Climate report is published as a special supplement to the Bulletin of the American Meteorological Society. This year marks its 23rd edition. The full report was compiled by 384 scientists from 52 countries. 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.
The summary you are reading is condensed from State of the Climate in 2012: Highlights, so it is a summary of a summary; clicking the link to read (at least) the complete Highlights is worthwhile. All inline links, except one obvious one, are to the Report.
- Warm temperature trends continue near Earth’s surface: Four major independent datasets show 2012 was among the 10 warmest years on record, ranking either 8th or 9th, depending upon the dataset used. The United States and Argentina had their warmest year on record. Including the 2012 temperature, Earth is warming at a rate of 0.06°C (0.11°F) per decade since 1880 and a more rapid 0.16°C (0.28°F) per decade since 1970.
- La Niña dissipates into neutral conditions: For the first time in several years, neither El Niño nor La Niña, which can dominate regional weather and climate conditions around the globe, prevailed for the majority of the year.
- The Arctic continues to warm; sea ice extent reaches record low: The Arctic continued to warm at about twice the rate compared with lower latitudes. Minimum Arctic sea ice extent in September and Northern Hemisphere snow cover extent in June each reached new record lows. Arctic sea ice minimum extent (1.32 million square miles, September 16) was 18 percent lower than the previous record low extent that occurred in 2007.
- Antarctica sea ice extent reaches record high: The Antarctic maximum sea ice extent reached a record high of 7.51 million square miles on September 26. This is 0.5 percent higher than the previous record high extent that occurred in 2006.
- Sea surface temperatures increase: The globally averaged sea surface temperature for 2012 was among the 11 warmest on record.
- Ocean heat content remains near record levels: Heat content in the upper 2,300 feet, or a little less than one-half mile, of the ocean remained near record high levels in 2012. Overall increases from 2011 to 2012 occurred between depths of 2,300 to 6,600 feet and even in the deep ocean.
- Sea level reaches record high: Following sharp decreases in global sea level in the first half of 2011 that were linked to the effects of La Niña, sea levels rebounded to reach record highs in 2012. Globally, sea level has been increasing at an average rate of 3.2 ± 0.4 mm per year over the past two decades. [Coincidentally, a good item on sea level rise has just appeared on RealClimate.]
- Ocean salinity trends continue: 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 precipitation is increasing in already rainy areas and evaporation is intensifying in drier locations.
- Tropical cyclones near average: Global tropical cyclone activity during 2012 was near average, with a total of 84 storms. The North Atlantic was the only hurricane basin that experienced above-normal activity.
- Greenhouse gases climb: Major greenhouse gas concentrations, including carbon dioxide, methane, and nitrous oxide, continued to rise during 2012. Atmospheric CO2 concentrations increased by 2.1 ppm in 2012, reaching a global average of 392.6 ppm for the year. In spring 2012, for the first time, the atmospheric CO2 concentration exceeded 400 ppm at several Arctic observational sites.
- Following a slight decline in manmade emissions associated with the global economic downturn, global CO2 emissions from fossil fuel combustion and cement production reached a record high in 2011 of 9.5 ± 0.5 petagrams of carbon, and a new record of 9.7 ± 0.5 petagrams is estimated for 2012.