Linkage Between Climate Change and Stratospheric Ozone Depletion
Ozone depletion and climate change have usually been thought of as environmental issues with little in common other than their global scope. Download a PDF of "Ozone Depletion, Greenhouse Gases, and Climate Change" by the National Research Council for free. This is the first time that ozone depletion, an upper atmospheric phenomenon confined to the polar regions, has been linked to climate change.
One example of ozone depletion is the annual ozone "hole" over Antarctica that has occurred during the Antarctic spring since the early s. This is not really a hole through the ozone layer, but rather a large area of the stratosphere with extremely low amounts of ozone. It is important to understand that ozone depletion is not limited to the area over the South Pole.
Research has shown that ozone depletion occurs over the latitudes that include North America, Europe, Asia, and much of Africa, Australia, and South America. What is the connection between ozone depletion and climate change? ODSs and many of their non-ozone depleting substitutes are potent greenhouse gases that contribute to climate change. Some ODSs and ODS substitutes have global warming potentials that are several thousand times greater than that of carbon dioxide. Recently, ODS alternatives that have lower global warming potentials have become available.
How do we know that natural sources are not responsible for ozone depletion? CFCs and halons cause chemical reactions that break down ozone molecules, reducing ozone's ultraviolet radiation-absorbing capacity. How ozone works How ozone is distributed in the atmosphere. NOAA The sun emits electromagnetic radiation at different wavelengths, meaning energy at different intensities.
The atmosphere acts like a multi-layer shield that protects Earth from dangerous solar radiation. Ozone is found in two different parts of our atmosphere. It is found in the lower atmosphere troposphere and has nothing to do with the "ozone hole.
The stratospheric ozone layer absorbs ultraviolet UV radiation, preventing dangerous UV rays from hitting Earth's surface and harming living organisms.
UV rays cannot be seen or felt, but they are very powerful and change the chemical structure of molecules. UV radiation plays a small role in global warming because its quantity is not enough to cause the excess heat trapped in the atmosphere. UV radiation represents a small percentage of the energy from the sun, and is not highly absorbed or scattered in the atmosphere—especially when compared with other wavelengths, like infrared. But, ozone depletion is also concerning because it directly impacts the health of humans, and other living organisms.
The ozone hole The ozone hole. People, plants, and animals living under the ozone hole are harmed by the solar radiation now reaching the Earth's surface—where it causes health problems, from eye damage to skin cancer.EPA Section 608 Ozone Depletion and Global Warming
Stratospheric ozone is constantly produced by the action of the sun's ultraviolet radiation on oxygen molecules known as photochemical reactions. Although ozone is created primarily at tropical latitudes, large-scale air circulation patterns in the lower stratosphere move ozone toward the poles, where its concentration builds up.
Frequently Asked Questions about the Ozone Layer
In addition to this global motion, strong winter polar vortices are also important to concentrating ozone at the poles.
During the continuously dark polar winter, the air inside the polar vortices becomes extremely cold, a necessary condition for polar stratospheric cloud formation. Polar stratospheric clouds create the conditions for drastic ozone destruction, providing a surface for chlorine to change into ozone-destroying form.
Currently, CFC production and consumption are increasing due at least in part to the involvement of newly industrialized and lesser developed countries in CFC use.
Ozone depletion and climate change - 572233.info
In addition to breaking down ozone through the action of chlorine radicals, chlorofluorocarbons contribute to the greenhouse effect. Estimates put the CFC contribution to global temperature change at percent, although under the Montreal Protocol it would be reduced to percent.
Nitrous oxide in the atmosphere originates from both natural and man-made sources, including many bacterial processes involved in the nitrification or denitrification cycles. Recently, nitrous oxide has been increasing at a rate of V about 0. In the atmosphere N20 is partly converted into nitrogen oxides NOx. Nitrous oxide N20 plays a role in both ozone depletion and global climate change. The N20 functions as a greenhouse gas contributing to global warming. Converted to nitrogen oxides NOx it destroys stratospheric ozone in a catalytic cycle similar to that of chlorine radicals.
On the other hand, nitrogen oxides can serve as a temporary sink for the ozone depleting chlorine monoxide CIOso the net effect is uncertain. NOx also is a precursor to acid deposition. The concentration of C02 has been increasing in recent years by an average of about 0. Carbon dioxide links the issue of stratospheric ozone depletion to that of the global climate change issue primarily because of its role as a greenhouse gas.
- Can ozone depletion and global warming interact to produce rapid climate change?
- Is There a Connection Between the Ozone Hole and Global Warming?
- Ozone depletion and climate change
As such, it will absorb solar radiation being radiated from the surface of the earth and re-radiate it in all directions increasing the global warming. Because it is a greenhouse gas C02 modifies the temperature structure of the atmosphere, cooling the stratosphere Less ozone is destroyed if the stratosphere is cooler, so the effect of C02 acting alone is to decrease ozone depletion in the stratosphere. Resulting from both natural and man-made processes, methane is involved in several important reactions in the atmosphere.
Through its effect on the amounts of water vapor in the stratosphere methane can lead to destruction of stratospheric ozone. Water droplets may act as a surface upon which the reactions that destroy ozone occur. The increase or decrease of ozone depletion will depend upon where the water vapor is produced.
Ozone depletion will increase if water vapor increases in the stratosphere. A further effect of methane occurs in the troposphere. Here, when methane is oxidized, it will produce an increase in the amount of tropospheric ozone. This reaction occurs in the presence of nitrogen oxide. Natural sources of methane include natural wetlands, arctic tundra, agricultural crops such as rice paddies, and ruminate animals. Man-made sources of CH4 include the production of fossil fuels such as natural gas and oil, and cement production.
The natural processes contribute about half of the total methane production. Carbon monoxide is not a radiatively important trace gas, but it is involved indirectly in both stratospheric ozone destruction and global warming. Carbon monoxide controls the concentration of the hydroxy1 radical OH in the troposphere, which has a direct effect on the concentration of methane.
The concentration of methane, as described earlier, plays a role in the amount of tropospheric ozone as well as stratospheric ozone.
Methane is also a very important contributor to the greenhouse effect. Based on current scenarios, the stratospheric component of the total ozone column is calculated to decrease over time, whereas the tropospheric constituents of the total ozone column will increase. Whether or not there will be an overall increase in the level of ultraviolet radiation reaching the surface of the earth is still uncertain.
Even if the levels of ultraviolet radiation at the earth's surface were not to change, the photochemical reactions involving ultraviolet radiation and the interaction of ozone with various other atmospheric gases would alter the distribution of ozone in the atmospheric column. Changes in the concentration and altitude of ozone will play a major role in altering temperature and atmospheric processes affecting current climate and perhaps add to long-term global climate change.
Increased levels of ultraviolet radiation reaching the earth's surface also will increase the production of ozone at ground level through photochemical reactions. These conditions affect regional air quality. Tropospheric ozone formation takes place in the presence of nitrogen oxide. In addition, hydrogen peroxide H is produced, which is a strong oxidant and a catalyst in the production of sulfuric acid from sulfur dioxide.
These two processes illustrate the linkage between stratospheric ozone depletion and acid deposition. Sulfur dioxide and nitrogen oxides are the two major precursors to acid deposition. Trace gases affecting ozone also contribute to global climate change. Any efforts by humans to address the potential problems in either area will influence the other. If global warming were to begin, efforts to address the rise in greenhouse gases could increase ozone depletion.
Restraints imposed on the buildup of carbon dioxide, methane, and nitrous oxide to control their contribution to global warming, might reduce their role as moderators of potential ozone depletion in high CFC emission scenarios .
Scientists have identified many potentially serious effects on the environment and on human health from increased exposure to UV-B radiation. These include damage to: Changes associated with an altered global climate, such as increased C02 levels, interact with the effects of UV-B radiation. In assessing the impact of increased exposure of crops and terrestrial ecosystems to UV-B radiation it must be recognized that existing knowledge is in many ways deficient.
The effects of enhanced levels of UV-B radiation have been studied in species from only a few representatives of the major terrestrial ecosystems. We derive most of our knowledge from studies focused upon agricultural crops and conducted at mid- latitudes.
Despite uncertainties due to the complexities of field experiments, the data presently available suggest that plant photosynthesis is vulnerable to increased levels of solar UV-B radiation . Unlike drought or other geographically isolated stresses, stratospheric ozone depletion would affect all areas of the world, including ecosystems whose UV-B sensitivity has not been investigated.
Less photosynthesis decreases the amount of C02 fixed by plants and exacerbates the rise in C02 levels. Higher C02 may lead to global warming. This shows a direct link from an effect of stratospheric ozone depletion through terrestrial ecosystems to climate change. Increased levels of UV-B radiation also may affect forest productivity. Only limited data are available on coniferous species, but about one-half of the species of seedlings studied were adversely affected by UV-B radiation .
Existing data also suggest that increased UV-B radiation will modify the distribution and abundance of plants.