Good news on ozone, bad news on greenhouse gasses

The Montreal Protocol, created in response to the decline in the Earth's ozone layer, called for a world-wide phase out in the production of chemicals that were responsible for the ozone's decline. It is perhaps the greatest global environmental achievement to date. And, this week, the World Meteorological Organization and the United Nations Environmental Programme announced it was working. Unfortunately, this week also saw the WMO release its annual greenhouse gas bulletin, and here the news was nowhere near as promising, as emissions returned to levels not seen since the 1980s.

First, the good news. In the 2014 version of the Scientific Assessment of Ozone Depletion, the WMO finds that the atmospheric concentrations of most of the chemicals covered by the Montreal Protocol are in decline. The exceptions are hydrochlorofluorocarbons, which are used in refrigeration, and halon, used in fire suppression. The WMO also noted that there must be some unidentified source of carbon tetrachloride to explain its persistence in the atmosphere.

In sum, however, the effect has been positive. Chlorine and bromine levels in the stratosphere were down 10-15 percent over the past 15 years. And, after having declined over the course of the 1980s and 90s, the ozone concentrations have been stable since about 2000. If everything continues to go as expected, ozone will return to levels seen in 1980 by the middle of this century.