Warm-up: Explain the differences between global warming and ozone depletion.
Global Warming and Ozone Depletion
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Global Warming and Ozone Depletion
Global warming is the increase in the average temperature of Earths near-surface air and
oceans since the mid-20th century and its projected continuation. According to the 2007 Fourth
Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), global surface
temperature increased 0.74 0.18 C (1.33 0.32 F) during the 20th century. Most of the
observed temperature increase since the middle of the 20th century was caused by increasing
concentrations of greenhouse gases, which results from human activity such as the burning
of fossil fuel and deforestation. Global dimming, a result of increasing concentrations of
atmospheric aerosols that block sunlight from reaching the surface, has partially countered the
effects of greenhouse gas induced warming.
Climate model projections summarized in the latest IPCC report indicate that the global surface
temperature is likely to rise a further 1.1 to 6.4 C(2.0 to 11.5 F) during the 21st century. The
uncertainty in this estimate arises from the use of models with differing sensitivity to
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greenhouse gas concentrations and the use of differing estimates of future greenhouse gas
emissions. An increase in global temperature will cause sea levels to rise and will change the
amount and pattern of precipitation, probably including expansion
of subtropical deserts. Warming is expected to be strongest in the Arctic and would be
associated with continuing retreat of glaciers, permafrost and sea ice. Other likely effects
include changes in the frequency and intensity of extreme weather events, species extinctions,
and changes in agricultural yields. Warming and related changes will vary from region to region
around the globe, though the nature of these regional variations is uncertain.
Temperature changes
Evidence for warming of the climate system includes observed increases in global average air
and ocean temperatures, widespread melting of snow and ice, and rising global average sealevel. The most common measure of global warming is the trend in globally averaged
temperature near the Earth's surface. Expressed as a linear trend, this temperature rose by
0.74 0.18 C over the period 19062005. The rate of warming over the last half of that period
was almost double that for the period as a whole (0.13 0.03 C per decade, versus 0.07 C
0.02 C per decade). The urban heat island effect is estimated to account for about 0.002 C of
warming per decade since 1900. Temperatures in the lower troposphere have increased
between 0.13 and 0.22 C (0.22 and 0.4 F) per decade since 1979, according to satellite
temperature measurements. Temperature is believed to have been relatively stable over
the one or two thousand years before 1850, with regionally varying fluctuations such as
the Medieval Warm Period and the Little Ice Age.
Estimates by NASAs Goddard Institute for Space Studies (GISS) and the National Climatic Data
Center show that 2005 was the warmest year since reliable, widespread instrumental
measurements became available in the late 1800s, exceeding the previous record set in 1998
by a few hundredths of a degree.
Estimates prepared by the World Meteorological
Organization and the Climatic Research Unit show 2005 as the second warmest year, behind
1998. Temperatures in 1998 were unusually warm because the strongest El Nio in the past
century occurred during that year. Global temperature is subject to short-term fluctuations that
overlay long term trends and can temporarily mask them. The relative stability in temperature
from 2002 to 2009 is consistent with such an episode.
Temperature changes vary over the globe. Since 1979, land temperatures have increased about
twice as fast as ocean temperatures (0.25 C per decade against 0.13 C per decade).Ocean
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temperatures increase more slowly than land temperatures because of the larger effective heat
capacity of the oceans and because the ocean loses more heat by evaporation. The Northern
Hemisphere warms faster than the Southern Hemisphere because it has more land and because it has
extensive areas of seasonal snow and sea-ice cover subject to ice-albedo feedback. Although
more greenhouse gases are emitted in the Northern than Southern Hemisphere this does not
contribute to the difference in warming because the major greenhouse gases persist long
enough to mix between hemispheres.
The thermal inertia of the oceans and slow responses of other indirect effects mean that
climate can take centuries or longer to adjust to changes in forcing. Climate
commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a
further warming of about 0.5 C (0.9 F) would still occur.
External forcings
External forcing refers to processes external to the climate system (though not necessarily
external to Earth) that influence climate. Climate responds to several types of external forcing,
such asradiative forcing due to changes in atmospheric composition (mainly greenhouse
gas concentrations), changes in solar luminosity, volcanic eruptions, and variations in Earth's
orbit around the Sun.Attribution of recent climate change focuses on the first three types of
forcing. Orbital cycles vary slowly over tens of thousands of years and thus are too gradual to
have caused the temperature changes observed in the past century.
Greenhouse gases
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Recent atmospheric carbon dioxide(CO2) increases. Monthly CO2measurements display
seasonal oscillations in overall yearly uptrend; each year's maximum occurs during the
Northern Hemispheres late spring, and declines during its growing season as plants remove
some atmospheric CO2.
The greenhouse effect is the process by which absorption and emission of infrared radiation bygases in the atmosphere warm a planet's lower atmosphere and surface. It was proposed
by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in
1896. The question in terms of global warming is how the strength of the presumed
greenhouse effect changes when human activity increases the concentrations of greenhouse
gases in the atmosphere.
Naturally occurring greenhouse gases have a mean warming effect of about 33 C (59 F). The
major greenhouse gases are water vapor, which causes about 3670 percent of the greenhouse
effect; carbon dioxide (CO2), which causes 9
26 percent; methane (CH4), which causes 4
9percent; and ozone (O3), which causes 37 percent. Clouds also affect the radiation balance,
but they are composed of liquid water or ice and so have different effects on radiation from
water vapor.
Human activity since the Industrial Revolution has increased the amount of greenhouse gases in
the atmosphere, leading to increased radiative forcing from CO2,methane,
tropospheric ozone, CFCs and nitrous oxide. The concentrations of CO2 and methane have
increased by 36% and 148% respectively since 1750.These levels are much higher than at any
time during the last 650,000 years, the period for which reliable data has been extracted
from ice cores. Less direct geological evidence indicates that CO2 values higher than this were
last seen about 20 million years ago. Fossil fuel burning has produced about three-quarters of
the increase in CO2 from human activity over the past 20 years. Most of the rest is due to land-
use change, particularly deforestation.
Over the last three decades of the 20th
century, GDP per capita and population growth were the
main drivers of increases in greenhouse gas emissions. CO2emissions are continuing to rise due
to the burning of fossil fuels and land-use change. Emissions scenarios, estimates of changes in
future emission levels of greenhouse gases, have been projected that depend upon uncertain
economic, sociological, technological, and natural developments. In most scenarios, emissions
continue to rise over the century, while in a few, emissions are reduced. These emission
scenarios, combined with carbon cycle modelling, have been used to produce estimates of how
atmospheric concentrations of greenhouse gases will change in the future. Using the six
IPCC SRES"marker" scenarios, models suggest that by the year 2100, the atmospheric
concentration of CO2 could range between 541 and 970 ppm.This is an increase of 90-250%
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above the concentration in the year 1750. Fossil fuel reserves are sufficient to reach these
levels and continue emissions past 2100 if coal, tar sands or methane clathrates are extensively
exploited.
The destruction of stratospheric ozone by chlorofluorocarbons is sometimes mentioned in
relation to global warming. Although there are a few areas of linkage, the relationship between
the two is not strong. Reduction of stratospheric ozone has a cooling influence on the entire
troposphere, but a warming influence on the surface. Substantial ozone depletion did not occur
until the late 1970s. Ozone in the troposphere (the lowest part of the Earth's atmosphere) does
contribute to surface warming.
Aerosols and soot
Global dimming, a gradual reduction in the amount of global direct irradiance at the Earth'ssurface, has partially counteracted global warming from 1960 to the present. The main cause of
this dimming is aerosols produced by volcanoes and pollutants. These aerosols exert a cooling
effect by increasing the reflection of incoming sunlight. The effects of the products of fossil fuel
combustionCO2 and aerosolshave largely offset one another in recent decades, so that net
warming has been due to the increase in non-CO2 greenhouse gases such as methane. Radiative
forcing due to aerosols is temporally limited due to wet deposition which causes aerosols to
have an atmospheric lifetime of one week. Carbon dioxide has a lifetime of a century or more,
and as such, changes in aerosol concentrations will only delay climate changes due to carbon
dioxide.
In addition to their direct effect by scattering and absorbing solar radiation, aerosols have
indirect effects on the radiation budget. Sulfate aerosols act ascloud condensation nuclei and
thus lead to clouds that have more and smaller cloud droplets. These clouds reflect solar
radiation more efficiently than clouds with fewer and larger droplets.[This effect also causes
droplets to be of more uniform size, which reduces growth of raindrops and makes the cloud
more reflective to incoming sunlight.[Indirect effects are most noticeable in marine stratiform
clouds, and have very little radiative effect on convective clouds. Aerosols, particularly indirect
effects, represent the largest uncertainty in radiative forcing.[
Soot may cool or warm the surface, depending on whether it is airborne or deposited.
Atmospheric soot aerosols directly absorb solar radiation, which heats the atmosphere and
cools the surface. In isolated areas with high soot production, such as rural India, as much as
50% of surface warming due to greenhouse gases may be masked by atmospheric brown
clouds.]Atmospheric soot always contributes additional warming to the climate system. When
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deposited, especially on glaciers or on ice in arctic regions, the lower surface albedo can also
directly heat the surface. The influences of aerosols, including black carbon, are most
pronounced in the tropics and sub-tropics, particularly in Asia, while the effects of greenhouse
gases are dominant in the extratropics and southern hemisphere.
Solar variation
Variations in solar output have been the cause of past climate changes. The consensus among
climate scientists is that changes in solar forcing probably had a slight cooling effect in recent
decades. This result is less certain than some others, with a few papers suggesting a warming
effect.
Greenhouse gases and solar forcing affect temperatures in different ways. While both increased
solar activity and increased greenhouse gases are expected to warm the troposphere, anincrease in solar activity should warm the stratosphere while an increase in greenhouse gases
should cool the stratosphere.]Observations show that temperatures in the stratosphere have
been cooling since 1979, when satellite measurements became available Radiosonde. (weather
balloon) data from the pre-satellite era show cooling since 1958, though there is greater
uncertainty in the early radiosonde record.
A related hypothesis, proposed by Henrik Svensmark, is that magnetic activity of the sun
deflects cosmic rays that may influence the generation of cloud condensation nuclei and
thereby affect the climate. Other research has found no relation between warming in recentdecades and cosmic rays The influence of cosmic rays on cloud cover is about a factor of 100
lower than needed to explain the observed changes in clouds or to be a significant contributor
to present-day climate change.
Attributed and Expected Effects
Global warming may be detected in natural ecological or social systems as a change having statistical
significance.Attribution of these changes e.g., to natural or human activities, is the next step following
detection
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Natural systemsRising sea levels and observed decreases in snow and ice extent are consistent with warming.
Most of the increase in global average temperature since the mid-20th
century is, with high
probability,is atttributable to human-induced changes in greenhouse gas concentrations.
Changes in regional climate are expected to include greater warming over land, with most
warming at high northern latitudes, and least warming over theSouthern Ocean and parts of
the North Atlantic Ocean.
Even with current policies to reduce emissions, global emissions are still expected to continue
to grow over the coming decades.[82]
Over the course of the 21st
century, increases in emissions
at or above their current rate would very likely induce changes in the climate system larger
than those observed in the 20th
century.
In the IPCC Fourth Assessment Report, across a range of future emission scenarios, model-based estimates of sea level rise for the end of the 21
stcentury (the year 2090-2099, relative to
1980-1999) range from 0.18 to 0.59 m. These estimates, however, were not given a likelihood
due to a lack of scientific understanding, nor was an upper bound given for sea level rise. Over
the course of centuries to millennia, the melting of ice sheets could result in sea level rise of 4
6 m or more
Snow cover area and sea ice extent are expected to decrease. The frequency of hot extremes,
heat waves, and heavy precipitation will very likely increase.
Ecological systems
In terrestrial ecosystems, the earlier timing of spring events, and poleward and upward shifts in
plant and animal ranges, have been linked with high confidence to recent warming. Future
climate change is expected to particularly affect certain ecosystems
including tundra, mangroves, and coral reefs. It is expected that most ecosystems will be
affected by higher atmospheric CO2 levels, combined with higher global temperatures. Overall,
it is expected that climate change will result in the extinction of many species and reduced
diversity of ecosystems.
Social systems
There is some evidence of regional climate change affecting systems related to human
activities, including agricultural and forestry management activities at higher latitudes in the
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Northern Hemisphere. Future climate change is expected to particularly affect some sectors
and systems related to human activities. Water resources may be stressed in some dry regions
at mid-latitudes, the dry tropics, and areas that depend on snow and ice melt. Reduced water
availability may affect agriculture in low latitudes. Low-lying coastal systems are vulnerable to
sea level rise and storm surge. Human health in populations with limited capacity to adapt to
climate change. It is expected that some regions will be particularly affected by climate change,
including the Arctic, Africa, small islands, and Asian and African megadeltas. Some people, such
as the poor, young children, and the elderly, are particularly at risk, even in high-income areas.
Ozone Depletion
Ozone depletion describes two distinct, but related observations: a slow, steady decline of
about 4 percent per decade in the total volume ofozone in Earth'sstratosphere (the ozone
layer) since the late 1970s, and a much larger, but seasonal, decrease in stratospheric ozone
over Earth's polar regions during the same period. The latter phenomenon is commonlyreferred to as the ozone hole. In addition to this well-known stratospheric ozone depletion,
there are alsotropospheric ozone depletion events, which occur near the surface in polar
regions during spring.
The detailed mechanism by which the polar ozone holes form is different from that for the mid-
latitude thinning, but the most important process in both trends iscatalytic destruction of ozone
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by atomic chlorine and bromine.[1]
The main source of these halogen atoms in the stratosphere
is photodissociation ofchlorofluorocarbon (CFC) compounds, commonly called freons, and
ofbromofluorocarbon compounds known as halons. These compounds are transported into the
stratosphere after being emitted at the surface.[2]
Both ozone depletion mechanisms
strengthened as emissions of CFCs and halons increased.
CFCs and other contributory substances are commonly referred to as ozone-depleting
substances (ODS). Since the ozone layer prevents most harmful UVB wavelengths (270
315 nm) ofultraviolet light (UV light) from passing through the Earth's atmosphere, observed
and projected decreases in ozone have generated worldwide concern leading to adoption of
the Montreal Protocol that bans the production of CFCs and halons as well as related ozone
depleting chemicals such as carbon tetrachloride and trichloroethane. It is suspected that a
variety of biological consequences such as increases in skin cancer, cataracts,[3]
damage to
plants, and reduction ofplankton populations in the ocean's photic zone may result from theincreased UV exposure due to ozone depletion.
Ozone Hole and its Causes
The Antarctic ozone hole is an area of the Antarctic stratosphere in which the recent ozone
levels have dropped to as low as 33% of their pre-1975 values. The ozone hole occurs during
the Antarctic spring, from September to early December, as strong westerly winds start to
circulate around the continent and create an atmospheric container. Within this polar vortex,over 50% of the lower stratospheric ozone is destroyed during the Antarctic spring.
As explained above, the primary cause of ozone depletion is the presence of chlorine-
containing source gases (primarily CFCs and related halocarbons). In the presence of UV light,
these gases dissociate, releasing chlorine atoms, which then go on to catalyze ozone
destruction. The Cl-catalyzed ozone depletion can take place in the gas phase, but it is
dramatically enhanced in the presence ofpolar stratospheric clouds (PSCs).
These polar stratospheric clouds(PSC) form during winter, in the extreme cold. Polar winters are
dark, consisting of 3 months without solar radiation (sunlight). The lack of sunlight contributes
to a decrease in temperature and the polar vortex traps and chills air. Temperatures hover
around or below -80 C. These low temperatures form cloud particles. There are three types of
PSC clouds; nitric acid trihydrate clouds, slowly cooling water-ice clouds, and rapid cooling
water-ice(nacerous) clouds; that provide surfaces for chemical reactions that lead to ozone
destruction.[21]
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The photochemical processes involved are complex but well understood. The key observation is
that, ordinarily, most of the chlorine in the stratosphere resides in stable "reservoir"
compounds, primarily hydrochloric acid (HCl) and chlorine nitrate (ClONO 2). During the
Antarctic winter and spring, however, reactions on the surface of the polar stratospheric cloud
particles convert these "reservoir" compounds into reactive free radicals (Cl and ClO). The
clouds can also remove NO2 from the atmosphere by converting it to nitric acid, which prevents
the newly formed ClO from being converted back into ClONO2.
The role of sunlight in ozone depletion is the reason why the Antarctic ozone depletion is
greatest during spring. During winter, even though PSCs are at their most abundant, there is no
light over the pole to drive the chemical reactions. During the spring, however, the sun comes
out, providing energy to drive photochemical reactions, and melt the polar stratospheric
clouds, releasing the trapped compounds. Warming temperatures near the end of spring breakup the vortex around mid-December. As warm, ozone-rich air flows in from lower latitudes, the
PSCs are destroyed, the ozone depletion process shuts down, and the ozone hole closes.
Most of the ozone that is destroyed is in the lower stratosphere, in contrast to the much
smaller ozone depletion through homogeneous gas phase reactions, which occurs primarily in
the upper stratosphere.
Consequences of Ozone layer depletionSince the ozone layer absorbs UVB ultraviolet light from the Sun, ozone layer depletion is
expected to increase surface UVB levels, which could lead to damage, including increases in skin
cancer. This was the reason for the Montreal Protocol. Although decreases in stratospheric
ozone are well-tied to CFCs and there are good theoretical reasons to believe that decreases in
ozone will lead to increases in surface UVB, there is no direct observational evidence linking
ozone depletion to higher incidence of skin cancer in human beings. This is partly due to the
fact that UVA, which has also been implicated in some forms of skin cancer, is not absorbed by
ozone, and it is nearly impossible to control statistics for lifestyle changes in the populace.
Increased UV
Ozone, while a minority constituent in the Earth's atmosphere, is responsible for most of the
absorption of UVB radiation. The amount of UVB radiation that penetrates through the ozone
layerdecreases exponentially with the slant-path thickness/density of the layer.
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Correspondingly, a decrease in atmospheric ozone is expected to give rise to significantly
increased levels of UVB near the surface.
Increases in surface UVB due to the ozone hole can be partially inferred by radiative
transfer model calculations, but cannot be calculated from direct measurements because of the
lack of reliable historical (pre-ozone-hole) surface UV data, although more recent surface UV
observation measurement programmes exists.
Because it is this same UV radiation that creates ozone in the ozone layer from O2 (regular
oxygen) in the first place, a reduction in stratospheric ozone would actually tend to increase
photochemical production of ozone at lower levels (in the troposphere), although the overall
observed trends in total column ozone still show a decrease, largely because ozone produced
lower down has a naturally shorter photochemical lifetime, so it is destroyed before the
concentrations could reach a level which would compensate for the ozone reduction higher up.
Biological effects
The main public concern regarding the ozone hole has been the effects of increased surface UV
and microwave radiation on human health. So far, ozone depletion in most locations has been
typically a few percent and, as noted above, no direct evidence of health damage is available in
most latitudes. Were the high levels of depletion seen in the ozone hole ever to be common
across the globe, the effects could be substantially more dramatic. As the ozone hole over
Antarctica has in some instances grown so large as to reach southern parts of Australia, New
Zealand, Chile, Argentina, and South Africa, environmentalists have been concerned that the
increase in surface UV could be significant.
Effects on humans
UVB (the higher energy UV radiation absorbed by ozone) is generally accepted to be a
contributory factor to skin cancer. In addition, increased surface UV leads to increased
tropospheric ozone, which is a health risk to humans.
1. Basal and Squamous Cell Carcinomas The most common forms of skin cancer inhumans, basal and squamous cell carcinomas, have been strongly linked to UVB exposure. The
mechanism by which UVB induces these cancers is well understoodabsorption of UVB
radiation causes the pyrimidine bases in the DNA molecule to form dimers, resulting in
transcription errors when the DNA replicates. These cancers are relatively mild and rarely fatal,
although the treatment of squamous cell carcinoma sometimes requires extensive
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reconstructive surgery. By combining epidemiological data with results of animal studies,
scientists have estimated that a one percent decrease in stratospheric ozone would increase
the incidence of these cancers by 2%.
2. Malignant Melanoma Another form of skin cancer, malignant melanoma, is much less
common but far more dangerous, being lethal in about 1520% of the cases diagnosed. The
relationship between malignant melanoma and ultraviolet exposure is not yet well understood,
but it appears that both UVB and UVA are involved. Experiments on fish suggest that 90 to 95%
of malignant melanomas may be due to UVA and visible radiation whereas experiments on
opossums suggest a larger role for UVB. Because of this uncertainty, it is difficult to estimate
the impact of ozone depletion on melanoma incidence. One study showed that a 10% increase
in UVB radiation was associated with a 19% increase in melanomas for men and 16% for
women. A study of people in Punta Arenas, at the southern tip ofChile, showed a 56% increase
in melanoma and a 46% increase in nonmelanoma skin cancer over a period of seven years,along with decreased ozone and increased UVB levels.
3. Cortical Cataracts Studies are suggestive of an association between ocular
cortical cataracts and UV-B exposure, using crude approximations of exposure and various
cataract assessment techniques. A detailed assessment of ocular exposure to UV-B was carried
out in a study on Chesapeake Bay Watermen, where increases in average annual ocular
exposure were associated with increasing risk of cortical opacity. In this highly exposed group of
predominantly white males, the evidence linking cortical opacities to sunlight exposure was the
strongest to date. However, subsequent data from a population-based study in Beaver Dam, WIsuggested the risk may be confined to men. In the Beaver Dam study, the exposures among
women were lower than exposures among men, and no association was seen. Moreover, there
were no data linking sunlight exposure to risk of cataract in African Americans, although other
eye diseases have different prevalences among the different racial groups, and cortical opacity
appears to be higher in African Americans compared with whites.
4. Increased Tropospheric Ozone Increased surface UV leads to
increased tropospheric ozone. Ground-level ozone is generally recognized to be a health risk, as
ozone is toxic due to its strong oxidant properties. At this time, ozone at ground level is
produced mainly by the action of UV radiation on combustion gases from vehicle exhausts.
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Ozone Hole and Global Warming
There are five areas of linkage between ozone depletion and global warming:
The same CO2 radiative forcing that produces global warming is expected to cool
the stratosphere. This cooling, in turn, is expected to produce
relative increase in ozone (O3) depletion in polar area and the frequency of ozone holes.
Conversely, ozone depletion represents a radiative forcing of the climate system. There
are two opposing effects: Reduced ozone causes the stratosphere to absorb less solar
radiation, thus cooling the stratosphere while warming the troposphere; the resulting
colder stratosphere emits less long-wave radiation downward, thus cooling the
troposphere. Overall, the cooling dominates; the IPCC concludes that "observed
stratospheric O3losses over the past two decades have caused a negative forcing of the
surface-troposphere system" of about 0.15 0.10 watts per square meter (W/m). One of the strongest predictions of the greenhouse effect is that the stratosphere will
cool. Although this cooling has been observed, it is not trivial to separate the effects of
changes in the concentration ofgreenhouse gases and ozone depletion since both will
lead to cooling. However, this can be done by numerical stratospheric modeling. Results
from the National Oceanic and Atmospheric Administration's Geophysical Fluid
Dynamics Laboratory show that above 20 km (12.4 miles), the greenhouse gases
dominate the cooling.
Ozone depleting chemicals are also greenhouse gases. The increases in concentrations
of these chemicals have produced 0.34 0.03 W/m of radiative forcing, corresponding
to about 14% of the total radiative forcing from increases in the concentrations of well-
mixed greenhouse gases.
The long term modeling of the process, its measurement, study, design of theories and
testing take decades to document, gain wide acceptance, and ultimately become the
dominant paradigm. Several theories about the destruction of ozone were hypothesized
in the 1980s, published in the late 1990s, and are currently being proven. Dr Drew
Schindell, and Dr Paul Newman, NASA Goddard, proposed a theory in the late 1990s,
using a SGI Origin 2000 supercomputer, that modeled ozone destruction, accounted for78% of the ozone destroyed. Further refinement of that model accounted for 89% of the
ozone destroyed, but pushed back the estimated recovery of the ozone hole from 75
years to 150 years.
http://en.wikipedia.org/wiki/Global_warminghttp://en.wikipedia.org/wiki/Stratospherehttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Tropospherehttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Watthttp://en.wikipedia.org/wiki/Greenhouse_gashttp://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administrationhttp://en.wikipedia.org/wiki/Geophysical_Fluid_Dynamics_Laboratoryhttp://en.wikipedia.org/wiki/Geophysical_Fluid_Dynamics_Laboratoryhttp://en.wikipedia.org/wiki/SGI_Origin_2000http://en.wikipedia.org/wiki/SGI_Origin_2000http://en.wikipedia.org/wiki/Geophysical_Fluid_Dynamics_Laboratoryhttp://en.wikipedia.org/wiki/Geophysical_Fluid_Dynamics_Laboratoryhttp://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administrationhttp://en.wikipedia.org/wiki/Greenhouse_gashttp://en.wikipedia.org/wiki/Watthttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Tropospherehttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Stratospherehttp://en.wikipedia.org/wiki/Global_warming