Sunday, April 11, 2010

"The Ozone Layer."

The ozone layer is a layer of gas in the upper atmosphere which protects humans and other living things from the harmful ultraviolet (UV-B) rays of the sun. In the 1970´s scientists discovered that certain man-made chemicals could destroy ozone and deplete the ozone layer. Further research found that the growing production and use of chemicals like chlorofluorocarbons (CFCs) in aerosol sprays, refrigeration, insulation and air conditioning was contributing to the accumulation of ozone-depleting substances (ODS) in the atmosphere. They also observed that an "ozone hole" was developing above the ANTARCTIC.
A thinning ozone layer leads to a number of serious health risks for humans. It causes greater incidences of skin cancer and eye cataracts, with children being particularly vulnerable. There are also serious impacts for biodiversity. Increased UV-B rays reduce levels of plankton in the oceans and subsequently diminish fish stocks. It can also have adverse effects on plant growth, thus reducing agricultural productivity. A direct negative economic impact is the reduced lifespan of certain materials like plastic.
Severe depletion of the Antarctic ozone layer was first observed in the early 1980´s. The international response embodied in the Montreal Protocol. Today 196 parties worldwide have signed the Montreal Protocol which is widely regarded as the most successful Multinational Environmental Agreement, and it is the first treaty achieving universal ratification. Furthermore, the phasing out of ozone depleting substances (ODS) has helped to fight climate change since many ODS are also powerful greenhouse gases.
Ozone is a gas that occurs naturally in our atmosphere. Most of it is concentrated in the ozone layer, a region located in the stratosphere several miles above the surface of the Earth. Although ozone represents only a small fraction of the gas present in the atmosphere, it plays a vital role by shielding humans and other life from harmful ultraviolet light from the Sun. Human activities in the last several decades have produced chemicals, such as chlorofluorocarbons (CFCs), which have been released into atmosphere and have contributed to the depletion of this important protective layer. When scientists realized the destructive effect these chemicals could have on the ozone layer, international agreements were put in place to limit such emissions. As a result, it is expected that the ozone layer will recover in the coming decades.
Ozone is also a greenhouse gas in the upper atmosphere and, therefore, plays a role in Earth´s climate. The increases in primary greenhouse gases, such as carbon dioxide, may effect how the ozone layer recovers in coming years. Understanding precisely how ozone abundances will change in a future with diminished chlorofluorocarbon emissions and increased emissions of greenhouse gases remains an important challenge for atmospheric scientists in NOAA and other research centers.
Ozone depletion occurs in many places in the Earth´s ozone layer, most severely in the polar regions. NOAA scientists have traveled to Antarctica to study the ozone hole that has been occurring there since the late 1970s. In 1986, soon after the reported discovery of the ozone hole, Aeronomy Lab (now ESRL) scientist Dr. Susan Solomon led a team of 16 scientists, the National Ozone Expedition
(NOZE I) to Antarctica. The scientists took measurements of various trace gases and physical properties of the atmosphere. The data, along with additional findings from the NOZE II mission the following year, showed conclusively that human-produced trace gases that contain chlorine and bromine were causing the ozone hole. The Global Monitoring Division of ESRL has monitored the yearly Antarctic ozone hole since 1986 by using instruments located on the ground and by launching balloon-borne ozonesondes, onboard aircraft and satellites, from the South Pole station and measuring total column ozone from a ground based Dobson spectrophotometer since 1963. This unique record from the South Pole station clearly shows the annual development of the springtime Antarctic ozone hole over the past two decades.
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