NOAA’s updated Annual Greenhouse Gas Index, which measures the direct climate influence of many greenhouse gases such as carbon dioxide and methane, shows a continued steady upward trend that began with the Industrial Revolution of the 1880s.
Started in 2004, the Index reached 1.29 in 2010. That means the combined heating effect of long-lived greenhouse gases added to the atmosphere by human activities has increased by 29 percent since 1990, the year used as a baseline for comparison. This is slightly higher than in 2009 when the combined heating effect of those additional greenhouse gases was 27 percent higher than in 1990.
The good news is that there has been a continued recent drop in two chlorofluorocarbons, CFC11 and CFC12: Levels of these two compounds – which are ozone-depleting chemicals in addition to greenhouse gases – have been dropping at about one percent per year since the late 1990s, because of an international agreement, the Montreal Protocol, to protect the ozone layer.
Carbon dioxide, methane and nitrous oxide are all rising. Global carbon dioxide levels rose to an average of 389 parts per million in 2010, compared with 354 in the index or comparison year of 1990. Before the Industrial Revolution of the 1880s, carbon dioxide concentration in the atmosphere was about 280 ppm.
Methane is 25 times more potent as a greenhouse gas than carbon dioxide, and this has risen for the fourth consecutive year.