How old is ozone layer

The stratosphere gets warmer at higher altitudes. In fact, this warming is caused by ozone absorbing ultraviolet radiation. Warm air remains in the upper stratosphere, and cool air remains lower, so there is much less vertical mixing in this region than in the troposphere.

Most commercial airplanes fly in the lower part of the stratosphere. Health and Environmental Effects of Ozone Depletion. Ozone Layer Research and Technical Resources. Information for students about the Ozone Layer. Addressing Ozone Layer Depletion.

Adapting to a Changed Ozone Layer. Phasing Out Ozone-Depleting Substances. Managing Refrigerant Emissions. Most atmospheric ozone is concentrated in a layer in the stratosphere, about 9 to 18 miles 15 to 30 km above the Earth's surface see the figure below. Ozone is a molecule that contains three oxygen atoms. At any given time, ozone molecules are constantly formed and destroyed in the stratosphere.

The total amount has remained relatively stable during the decades that it has been measured. The ozone layer in the stratosphere absorbs a portion of the radiation from the sun, preventing it from reaching the planet's surface.

UVB is a kind of ultraviolet light from the sun and sun lamps that has several harmful effects. It is a cause of melanoma and other types of skin cancer. It has also been linked to damage to some materials, crops, and marine organisms. The ozone layer protects the Earth against most UVB coming from the sun.

It is always important to protect oneself against UVB, even in the absence of ozone depletion, by wearing hats, sunglasses, and sunscreen. However, these precautions will become more important as ozone depletion worsens.

UVB has been linked to many harmful effects , including skin cancers, cataracts, and harm to some crops and marine life. Scientists have established records spanning several decades that detail normal ozone levels during natural cycles.

Ozone concentrations in the atmosphere vary naturally with sunspots, seasons, and latitude. These processes are well understood and predictable. Each natural reduction in ozone levels has been followed by a recovery. Scientists found out that chlorofluorocarbons CFCs —long-lived chemicals that had been used in refrigerators and aerosol sprays since the s—had a dark side. In the layer of the atmosphere closest to Earth the troposphere , CFCs circulated for decades without degrading or reacting with other chemicals.

When they reached the stratosphere, however, their behavior changed. In the upper stratosphere beyond the protection of the ozone layer , ultraviolet light caused CFCs to break apart, releasing chlorine, a very reactive atom that repeatedly catalyzes ozone destruction.

The global recognition of the destructive potential of CFCs led to the Montreal Protocol , a treaty phasing out the production of ozone-depleting chemicals. Scientists estimate that about 80 percent of the chlorine and bromine, which has a similar ozone-depleting effect in the stratosphere over Antarctica today comes from human, not natural, sources.

Models suggest that the concentration of chlorine and other ozone-depleting substances in the stratosphere will not return to pre levels until the middle decades of the 21st century. Scientists have already seen the first definitive proof of ozone recovery, observing a 20 percent decrease in ozone depletion during the winter months from to For example, in , hydrofluorocarbons were added to the list of controlled substances, because these gases have been identified as potent greenhouse gases.

The treaty is considered to be one of the most successful protocols to tackle an environmental challenge caused by humans. Yes and no. As a result of the Montreal Protocol, concentrations of ozone-depleting gases in the atmosphere have significantly declined. But according to Laura Revell, an environmental physics professor at the University of Canterbury, the issue isn't solved yet.

Stephen Montzka, a research chemist at the National Oceanic and Atmospheric Administration, says they've detected possible illegal CFCs in the atmosphere.

In , Montzka coauthored a report in Nature that showed unexpected levels of CFC, a type of chlorofluorocarbons, were present. This concentration of CFC was perhaps the result of unauthorized industrial production, going against the Montreal Protocol. Further research by Montzka showed that the recovery of the ozone hole could be delayed because of these emissions. As countries continue to abide by the Montreal Protocol, climate models show that ozone levels should return to standard measures by the end of the 21st century.

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