Every month for the past 25 years the global temperature has been above the 20th Century average. And the rate of increase is speeding up.
The world’s climate is not only continuing to warm, it’s adding heat-trapping greenhouse gases faster, researchers said yesterday. The global temperature has been warmer than the 20th century average every month for more than 25 years, they said at a teleconference. “The indicators show unequivocally that the world continues to warm,’’ Thomas R. Karl, director of the National Climatic Data Center, said. –Associated Press news report, June 29, 2011.
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Excerpts from State of the Climate in 2010: Highlights, published this week by the National Climatic Data Center, a division of the U.S. Department of Commerce.
Levels of greenhouse gases in the atmosphere continued to rise. Carbon dioxide levels increased at a faster rate in 2010 than in 2009 and also faster than the average rate over the past 30 years. Greenhouse gases trap heat in Earth’s lower atmosphere.
Snow cover during February was high over the Northern Hemisphere, but by May warm surface temperatures reduced it to the lowest area ever recorded by satellites. The decrease in snow cover from December to May was the largest in more than 40 years. The amount of snow and timing of melt affects the water cycle and water supply.
Air temperature above land was the second warmest on record. The Arctic continued to warm at about twice the rate of lower latitudes. Locally and regionally, changes in temperature can influence the distribution of expected weather, alter precipitation patterns, and affect trends in many other climate indicators.
Stratospheric temperature, air in the upper layers of the atmosphere, continued to be colder than average. This is expected, given increased greenhouse gases and decreased ozone levels.
The world’s mountain glaciers lost mass for the 20th consecutive year. Greenland glaciers lost more mass in 2010 than any other year on record. Water from melting glaciers and ice sheets around the world contributes to acceleration of the water cycle and sea-level rise.
Antarctic sea ice grew to record levels during the South Pole’s winter, affected by an air circulation pattern that locked in the cold. Sea ice responds to colder temperatures by growing more. In turn, more sea ice leads to less sunlight absorption in the water and thus less warming.
Arctic sea ice shrank to its third smallest area on record. The area was so small in September that for the first time in modern history, both the Northwest Passage and the Northern Sea Route were open for navigation. Sea ice responds to warmer temperatures by shrinking more. In turn, less sea ice leads to more sunlight absorption in the water and thus more warming.
Sea level continued to rise across the world’s oceans on average. Water expands as it warms and thus ocean heating is responsible for much of the sea-level rise; melting glaciers and ice sheets are responsible for the rest.
Sea surface temperature in the eastern tropical Pacific Ocean cooled almost 2 degrees Fahrenheit from 2009 to 2010, reflecting the transition from an El Niño to La Niña climate pattern. Even so, the average sea surface temperature for 2010 of all the oceans around the world was the third warmest on record. These warmer temperatures contribute to more evaporation from the ocean into the atmosphere and to changes in sea level.
Ocean heat content in 2010 was similar to 2009 and was among the highest values in the record. Oceans store a large portion of the heat that is trapped by increasing greenhouse gases. Changes in heat content contribute to changes in sea level.
Ocean salinity – The world’s oceans were saltier than average in areas where evaporation is high and fresher than average where precipitation is high, suggesting that the water cycle is intensifying. Heavier downpours and snows can be expected with a faster water cycle.
Ocean heat content in 2010 was similar to 2009 and was among the highest values in the record. Oceans store a large portion of the heat that is trapped by increasing greenhouse gases. Changes in heat content contribute to changes in sea level.