By: Kathleen Guo
The hole in the ozone layer is the smallest it has been since its discovery in 1985, NASA says. While the ozone hole has been recovering at a steady pace, its smaller size this year is due to abnormal weather and wind patterns.
During normal weather patterns, the hole in the ozone above Antarctica grows to a maximum area of about 8 million square miles in late September or early October, according to NASA. However, this year it reached a maximum of 6.3 million square miles on September 6, but then fell to fewer than 3.9 million square miles later that month, where it has stayed.
The ozone layer, located 25 miles above earth in a part of the atmosphere called the stratosphere, reflects ultraviolet radiation that can cause skin cancer, cataracts and other hazardous conditions. It keeps the radiation from reaching the surface of the planet.
“It’s great news for ozone in the Southern Hemisphere,” said Paul Newman, chief scientist for Earth Sciences at NASA, in a report on the ozone released this week. “But it’s important to recognize that what we’re seeing this year is due to warmer stratospheric temperatures. It’s not a sign that atmospheric ozone is suddenly on a fast track to recovery.”
This limited ozone depletion due to weather systems has happened 3 times in the past 40 years. Smaller ozone holes were also observed in September 1988 and 2002 due to similar weather patterns, said Susan Strahan, an atmospheric scientist with Universities Space Research Association, who works at NASA Goddard in the NASA report.
“It’s a rare event that we’re still trying to understand,” she said.
When the hole was first discovered, scientists linked it to man-made substances such as chlorofluorocarbons, commonly found in refrigerators and other coolants. In 1987, nearly 200 countries signed a treaty regulating the production of such ozone-depleting compounds, and over time the hole began to slowly recover.
However, despite the gradual decline in the size of the hole, emissions of the prohibited chemicals have risen in some regions.
Earlier this year, an international research team reported in the journal Nature that, despite a world-wide ban, emissions of an ozone-scarring chemical from eastern mainland China is jeopardizing the ozone layer at mid-latitudes where much of the world’s population is concentrated. Emissions of the banned CFC-11 have increased in China by around 7,000 tons each year.
Scientists using air-monitoring equipment have also detected steady emissions of a chlorofluorocarbon known as trichlorofluoromethane (CFC-11) coming from Japan and Korea of which the world had agreed to terminate beginning in 2010.
[SOURCES]