NOAA: Greenhouse gases continue climbing
2012 a record year; Arctic reaches milestone level of carbon dioxide
NOAA’s updated Annual Greenhouse Gas Index (AGGI), which measures the direct climate influence of many heat-trapping gases like carbon dioxide and methane, shows 2012 continued the steady upward trend that began with the Industrial Revolution of the 1880s.
Driven in good part by rising levels of carbon dioxide (CO2), the AGGI reached 1.32 in 2012, meaning the combined heating effect of long-lasting, human-caused emissions with that of existing gases trapped in the atmosphere has increased by 32 percent since 1990, the baseline year for the index.
Although no other gas currently contributes to warming more than carbon dioxide, the AGGI includes measurements of methane and nitrous oxide, gases emitted by both human activities and natural sources. It also includes several chemicals known to deplete Earth’s protective ozone layer, which are also active as greenhouse gases.
"2012 was not a surprise. This Index—a highly-sought and respected tool for researchers—shows that the world is getting warmer because of our continued emissions of these long-living, heat trapping gases," said Jim Butler, director of the Global Monitoring Division of NOAA’s Boulder-based Earth System Research Laboratory (ESRL). "This Index provides scientists and decision makers alike with information useful for understanding climate change and it’s present-day and potential future impacts on our communities.”
Scientists at ESRL calculate the AGGI each year from atmospheric data collected through an international cooperative air-sampling network of about 80 sites around the world. Researchers from CIRES, the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder, are involved at many stages: from shipping flasks around the world to air sampling and data analysis.
Last year, CO2 at the peak of its cycle reached 400 ppm for one month at all eight Arctic sites for the first time. (This year, peak CO2 values at Mauna Loa—considered our “global benchmark” site— exceeded 400 ppm)
The AGGI is analogous to the dial on an electric blanket. Just as the dial does not tell you exactly how hot you will get, the AGGI does not predict how much Earth’s climate will warm. You do know, however, that if the dial is turned up a little, the blanket will get warmer—and not immediately. If you turn it up a lot, you know the blanket will get a lot warmer—eventually.
“At this rate of emissions, the global average will shortly reach 400 ppm and, within 4 to 5 years, the South Pole,” added Butler. “We anticipate this number will steadily rise with continued emissions in the 21st century, with the remote Arctic sites likely to be the last to see CO2 values in the 300s, as plants in high latitudes scale back on natural emissions of CO2 emissions earlier in summertime. This steady rise of CO2, along with contributions from other gases, will continue to drive the AGGI upward.”
NOAA researchers developed the AGGI in 2004 and have updated it annually since. Although it currently is calculated for years starting in 1978, atmospheric composition data from ice core and other records could allow the record to be extended back centuries. To learn more about the index, visit: http://www.esrl.noaa.gov/gmd/aggi/.
CIRES is a joint institute of the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado Boulder.
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