Countries world wide have controlled the production and use of ozone-eating chlorine compounds, and the Earth's atmosphere appears to be recovering from losses of "good" ozone in the upper reaches of the atmosphere. These findings were published in the journal Nature.
A paper by Betsy Weatherhead, a scientist working at the NOAA Earth System Research Laboratory in Boulder, Colo., and Signe Bech Andersen, of the Danish Meteorological Institute details an apparent leveling off of ozone loss as a result of the Montreal Protocol. This international agreement was first enacted in 1987 to control ozone-depleting chemicals in the atmosphere and was since signed by 180 countries.
"Ozone in the upper atmosphere protects life on Earth from harmful solar rays, and a thinning of ozone—even total depletion in some areas—has been a concern since the 1970s," said Weatherhead.
Upper-atmosphere ozone is sometimes referred to as "good" ozone in contrast to "bad" ozone at the Earth's surface that is associated with smog and poor air quality.
The paper is the first to show that the positive changes in the ozone layer are in general agreement with what is expected due to the changes in chlorine. Weatherhead said she and her colleagues are seeing signs of ozone recovery "in the right seasons, in the right latitudes and at the right altitudes." She called these positive signs a success story for international action to protect the environment. "Because the Montreal Protocol was enacted to control chlorine, the atmosphere is having a chance to recover," she said.
Weatherhead indicated that ozone is constantly created, destroyed and transported in the atmosphere. As the pollutants filter out of the atmosphere, the ozone layer naturally rebuilds. Data from NOAA, NASA and a global monitoring network have shown that chlorine has leveled off in the atmosphere, and now clearly show that ozone loss is leveling off, too.
"In these early stages of recovery, it can often be difficult to say what causes long-term changes because the atmosphere is so complex," said Weatherhead. "To be confident that the ozone layer is recovering, we need more than just an increase in ozone. We need the changes to agree with observations of the other factors that can influence ozone levels."
Weatherhead cautioned, however, that ozone remains at below-normal levels at all latitudes, and therefore, that ultra-violet (UV) rays from the sun are higher than they should be as well. People should continue to protect themselves from UV rays when they are outdoors.
These first signs are hopeful, but the recovery process is still in early stages. Unusual temperatures or a large volcanic eruption could trigger more ozone loss.
"We may still see very low ozone levels in the next few years, but the general tendency we're observing is that the atmosphere is starting to heal," said Weatherhead.
NOAA, an agency of the U.S. Department of Commerce, is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of the nation's coastal and marine resources.
Through the emerging Global Earth Observation System of Systems (GEOSS), NOAA is working with its federal partners, 61 countries and the European Commission to develop a global network that is as integrated as the planet it observes, predicts and protects.
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