EXCERPTS: A new study by NASA researchers shows that a key ozone-depleting compound named carbon tetrachloride (CCl4) is surprisingly abundant in the ozone layer.
"We are not supposed to be seeing this at all," says NASA atmospheric scientist Qing Liang.
Between 2007 and 2012, countries around the world reported zero emissions of CCl4, yet measurements by satellites, weather balloons, aircraft, and surface-based sensors tell a different story. A study led by Liang shows worldwide emissions of CCl4 average 39 kilotons per year, approximately 30 percent of peak emissions prior to the international treaty going into effect.
In the 1980s, chlorofluorocarbons became well-known to the general public. As the ozone hole widened, "CFC" became a household word. Fewer people, however, have heard of CCl4, once used in applications such as dry cleaning and fire-extinguishers.
"Nevertheless," says Liang, "CCl4 is a major ozone-depleting substance. It is the 3rd most important anthropogenic ozone-depleting compound behind CFC-11 and CFC-12."
Levels of CCl4 have been declining since the Montreal Protocol was signed, just not as rapidly as expected. With zero emissions, abundances should have dropped by 4% per year. Instead, the decline has been closer to 1% per year.
READ MORE WATCH VIDEO ->
- ·
- Report
- ·
- September 8, 2014 1:12 am
