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Connections between Climate Change and Ozone Depletion

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  • npat1@juno.com
    See post that follows called: OZONE HOLE IS LARGER AGAIN Connections between Climate Change and Ozone Depletion There are very important links between climate
    Message 1 of 1 , Dec 4, 2003
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      See post that follows called: OZONE HOLE IS LARGER AGAIN

      Connections between Climate Change and Ozone Depletion
      There are very important links between climate change and ozone depletion, and the first signs of these interactions might be occurring in the atmosphere.

      Climate change is caused by an increase in the amount of infrared radiation absorbed by the Earth�s atmosphere. Prior to the presence of greenhouse gases in the lower atmosphere (particularly water vapor, carbon dioxide, methane, nitrous oxide and ozone), infrared radiation, emitted by the Earth�s surface, would have been lost to space. There must be a balance between the energy received from the sun, mainly as visible radiation, and the energy radiated by the Earth back to space (infrared radiation) to maintain a steady climate. If the solar input exceeds the Earth�s output, the Earth�s surface would get warmer. This occurs as the abundance of greenhouse gases in the lower atmosphere increases, as is now occurring partly as a result of human activities. An increase of infrared absorption in the lower atmosphere also means that there is not as much of this infrared energy as before to be absorbed at higher altitudes in the atmosphere, particularly in the stratosphere.

      Ozone depletion is caused primarily by human-produced gases that contain chlorine and bromine, such as chlorofluorocarbons (CFCs) and halons. These gases have accumulated in the atmosphere over the last few decades following their release from products such as air conditioners or during their use as cleansing agents. CFCs and halons slowly move into the stratosphere where they are broken down by high-energy solar radiation, thereby releasing chlorine and bromine atoms that destroy ozone. The steady accumulation of chlorine- and bromine-containing chemicals in the atmosphere has increased the rate of ozone loss over the last few decades. However, in the last decade, the production of many halocarbons was regulated, and their abundances in the atmosphere, in many cases, have peaked and are now declining.

      Climate change and ozone change can interact because ozone itself is a greenhouse gas and because climate change can affect the chemistry of ozone depletion. The stratosphere is warmed when ozone absorbs either the incoming solar ultraviolet radiation or the upwelling infrared radiation from the Earth. If there is less energy coming from below, less is available to be absorbed and stratospheric temperatures drop. However, ozone depletion means less ozone is available to absorb both of these forms of radiation. This results in lower stratospheric temperatures, which in turn promote the further destruction of ozone. This is called a positive feedback loop. The stratosphere is also cooled as carbon dioxide and other greenhouse gases accumulate there and radiate more energy to space. Thus, enhanced greenhouse gas warming actually results in a colder stratosphere and, in some parts of the world, may increase ozone depletion.

      As mentioned above, ozone is a strong greenhouse gas and consequently, if stratospheric ozone is reduced, a cooling at the Earth�s surface occurs (a cooler and less ozone-rich stratosphere radiates less heat down to the surface). Once the stratospheric ozone layer recovers from the damage caused by man-made chemicals, there will be a small amount of surface warming. However, since such chlorine- and bromine-containing chemicals are also greenhouse gases, their decrease in the atmosphere will partially offset the warming caused by ozone increase.

      The interactions do not stop here. Climate change in the troposphere may be affecting large-scale weather systems that move from the troposphere into the stratosphere. A weakening of these weather systems will weaken winds in the stratosphere. These stratospheric winds transport ozone from the tropical latitudes, where it is produced, to higher latitudes, where it accumulates and where many of the chemical processes for ozone destruction exert their strongest effects. As this ozone transport slows, both ozone amounts and temperatures in the polar regions decline. This, again, feeds back to change air circulation.

      There is evidence that ozone change is affecting climate. Reductions of ozone in the stratosphere change the temperature distribution in the stratosphere, particularly in the Southern Hemisphere. This reduction strengthens the polar jet stream and the winter/spring polar vortex, delaying the transition to the summer circulation in the stratosphere. This delay also causes the Antarctic �ozone hole� phenomenon to extend into early summer. For the ozone hole to �heal,� the polar vortex needs to weaken so that ozone-rich air from lower latitudes can mix in with the depleted air over Antarctica.

      UV radiation at the ground increases with decreasing stratospheric ozone. However, there are other important factors that determine UV radiation levels. The most prominent are cloud cover, aerosol content, and surface albedo. All of these parameters are changing as a consequence of climate change. Furthermore, there are a number of possible feedbacks between an increase of UV radiation and climate change. For example, increases in UV radiation � e.g., as a consequence of stratospheric ozone decline � affect ocean phytoplankton, which may lead to an enhanced greenhouse effect by reducing carbon dioxide uptake in the oceans.

      In summary, the enhanced greenhouse effect is likely to delay the recovery of the ozone layer, and the ozone layer strongly influences the wind regime in the stratosphere that, in turn, affects the global climate. Therefore, an understanding of the composition of the stratosphere, its chemistry and dynamics, and the changes that are occurring, is even more relevant than in the past if we are to make meaningful predictions about the future climate and surface UV radiation levels.
      http://www.ndsc.ncep.noaa.gov/climchng.html

      > Subject: OZONE HOLE IS LARGER AGAIN
      > It's back to the record year-2000 size:
      > http://www.aig.asn.au/resurgent_ozone_hole.htm
      > How it's affecting the southern hemisphere (Australia etc):
      > http://www.melbourne.indymedia.org/news/2003/11/57187.php
      > one respondent,
      >
      > Ozone/ Global Warming
      > by Anne O'Brien, Monday November 10, 2003 at 10:23 PM
      >
      > writes,
      >
      > "I was shocked last Tuesday, when I sat out in the sun, and my
      > shoulders got burnt in TWENTY MINUTES!!!"
      >
      > There are important connections
      >
      > http://www.ndsc.ncep.noaa.gov/climchng.html
      >
      > between global warming (really: "climate change") and ozone
      > depletion.
      >
      > Notice how loud the media stories were in 2002 when
      > the Ozone hole was somewhat smaller? How much
      > have you heard (those of you outside Australia/region) about
      > this? Thanks to Australia IMC.
      >
      > = = = =
      > STILL FEELING LIKE THE MAINSTREAM U.S. CORPORATE MEDIA
      > IS GIVING A FULL HONEST PICTURE OF WHAT'S GOING ON?
      > = = = =
      >
      The Australian Institute of Geoscientists

      The latest ESA Earth Observation data show (snip).

      The ozone hole is normally at its largest in September, but 2002 saw it at its smallest extent for more than a decade: 40% down on previous years. And a year ago yesterday ongoing satellite measurements of ozone - gathered by the Royal Dutch Meteorological Institute (KNMI) from the Global Ozone Monitoring Experiment (GOME) instrument on ESA�s ERS-2 satellite - showed it splitting in two.
      �Using GOME we have gathered global stratospheric ozone data over the last eight years,� said Henk Eskes of KNMI. �And last year we were actually able to accurately predict the split a few days before it happened, as we were operating an ozone forecasting service.�

      This dramatic reverse came just two years after the ozone hole had reached a record size � more than 30 million sq km in 2000.

      There was speculation that last year�s shrinking hole showed the ozone layer was recovering from damage caused by man-made chemicals including chlorofluorocarbons (CFCs) - in the past used in aerosol cans and refrigerators. But the bad news is that this year�s ozone hole looks much more like the 2000 than the 2002 version.

      Chlorine activation measured by MIPAS over the South Pole during 25 September 2003, shown by volume mixing ratio.
      Credits: BIRA-IASB

      The latest ozone measurements acquired yesterday by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument aboard Envisat - ESA�s latest Earth Observation spacecraft � show this year�s ozone hole is in no danger of splitting this time, and, with an area of 26 million sq km, is almost as big as the 2000 ozone hole. The Belgian Institute for Space Aeronomy (BIRA-IASB) generated this value-adding MIPAS data based on level 2 products provided by ESA.
      MIPAS is a German-built instrument that works by measuring infrared emissions from the Earth�s 'limb' � the band of atmosphere between planetary surface and empty space, as observed from behind Envisat. Working through day and night, MIPAS can map the atmospheric concentrations of more than 20 trace gases, including ozone as well as the pollutants that attack it. This makes the instrument invaluable in the study of atmospheric chemistry.

      Stratospheric ozone absorbs up to 98% of the Sun�s harmful ultraviolet light. But human production of CFCs and other pollutants has led to thinning of this protective ozone layer. The discovery of this fact in the 1980s came as a shock.

      �Nobody expected such an outcome,� said Eskes. �The very reason these classes of compounds were used by industry was because they were chemically inert � they did not react with other materials. Now we have learned to expect surprises, and we monitor accordingly.�

      An image of the ozone hole over the South Pole after splitting in two on 25 September 2002, acquired from GOME data. Ozone 'thickness' is measured in Dobson Units.

      The latest ozone measurements acquired yesterday by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument aboard Envisat - ESA�s latest Earth Observation spacecraft � show this year�s ozone hole is in no danger of splitting this time, and, with an area of 26 million sq km, is almost as big as the 2000 ozone hole. The Belgian Institute for Space Aeronomy (BIRA-IASB) generated this value-adding MIPAS data based on level 2 products provided by ESA.

      MIPAS is a German-built instrument that works by measuring infrared emissions from the Earth�s 'limb' � the band of atmosphere between planetary surface and empty space, as observed from behind Envisat. Working through day and night, MIPAS can map the atmospheric concentrations of more than 20 trace gases, including ozone as well as the pollutants that attack it. This makes the instrument invaluable in the study of atmospheric chemistry.

      Stratospheric ozone absorbs up to 98% of the Sun�s harmful ultraviolet light. But human production of CFCs and other pollutants has led to thinning of this protective ozone layer. The discovery of this fact in the 1980s came as a shock.

      �Nobody expected such an outcome,� said Eskes. �The very reason these classes of compounds were used by industry was because they were chemically inert � they did not react with other materials. Now we have learned to expect surprises, and we monitor accordingly.�

      What was not anticipated was that when these compounds reach a sufficiently high altitude they are split apart by contact with high-energy UV light, releasing more reactive chemicals � chief among them chlorine. In the presence of high-altitude clouds in the cold air above the South Pole these reactive chemicals break ozone down to form oxygen molecules.

      �The result of this discovery was the international Montreal Protocol, which has been very successful,� said Eskes. �Emissions of ozone-destroying compounds have been reduced and their concentration in the atmosphere has stabilised. But they are very long-lived and will stay in place for a long time.�
      A single molecule of chlorine can degrade more than 100,000 molecules of ozone. And there are large amounts of them in the air � largely stored within intermediate and inactive 'reservoir' compounds, but activated by particular meteorological conditions, notably those found above the South Pole in winter.

      Current data from MIPAS do show a high level of chlorine activation over Antarctica. The ozone layer is most prone to thinning here because the extreme low temperatures of the long polar night form ice clouds containing chlorine compounds. Then sunshine from the polar spring splits the chlorine into ultra-reactive radicals, which depletes the ozone.

      Comparative ozone hole areas for the years 2000 to present, using GOME data and MIPAS data for this year. Note the sudden decline of the blue 2002 line in late September, corresponding to the ozone hole split.

      Small ozone holes have also been known to form over the Arctic, but meteorological conditions there prevent the stratospheric temperature dropping enough to cause thinning on an Antarctic scale. The small size of the 2002 Antarctic ozone hole was due to the same reason � unusual wind patterns and warm weather prevented more ice cloud formation. But this year�s measurements show there is little room for complacency on this issue.

      �The result of this discovery was the international Montreal Protocol, which has been very successful,� said Eskes. �Emissions of ozone-destroying compounds have been reduced and their concentration in the atmosphere has stabilised. But they are very long-lived and will stay in place for a long time.�

      A single molecule of chlorine can degrade more than 100,000 molecules of ozone. And there are large amounts of them in the air � largely stored within intermediate and inactive 'reservoir' compounds, but activated by particular meteorological conditions, notably those found above the South Pole in winter.

      Current data from MIPAS do show a high level of chlorine activation over Antarctica. The ozone layer is most prone to thinning here because the extreme low temperatures of the long polar night form ice clouds containing chlorine compounds. Then sunshine from the polar spring splits the chlorine into ultra-reactive radicals, which depletes the ozone.

      Small ozone holes have also been known to form over the Arctic, but meteorological conditions there prevent the stratospheric temperature dropping enough to cause thinning on an Antarctic scale. The small size of the 2002 Antarctic ozone hole was due to the same reason � unusual wind patterns and warm weather prevented more ice cloud formation. But this year�s measurements show there is little room for complacency on this issue.
      �Since the end of the 1990s, there is experimental evidence that the total chlorine loading in the stratosphere is decreasing, but this is a slow process,� observed Dominique Fonteyn of BIRA-IASB. �Superimposed on this is the meteorological variability which this year still allows sufficient chlorine activation over a large area and for a longer period than last year.�

      MIPAS will continue to monitor the condition of the ozone layer for the life of the Envisat spacecraft, together with the spacecraft�s other atmospheric instruments: Global Ozone Monitoring by Occultation of Stars (GOMOS) and Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY). KNMI has plans to resume its ozone forecasting service using the latter instrument.

      MetOp-1 will be Europe's first operational polar-orbiting weather satellite. When it is launched towards the middle of this decade, it will replace one of two satellite services operated by the United States National Oceanic and Atmospheric Administration (NOAA).

      Credits: ESA

      And in 2005 the first of the three-spacecraft MetOp operational meteorology system will be launched into polar orbit. MetOp will include a next-generation ozone-monitoring instrument called GOME-2, intended to guarantee continuity of observation of this vital environmental factor well into the following decade.

      European Space Agency Media Release

      24-Oct-2003

      The Australian Institute of Geoscientists
      Telephone: 08 9427 0820 Facsimile: 08 9427 0821 e-mail: aig@...

      Copyright � The Australian Institute of Geoscientists 1999 - 2003
      http://www.aig.asn.au/resurgent_ozone_hole.htm

      Ozone Hole Warning - Southern Australia
      by Bob Howard, Wednesday November 05, 2003 at 12:36 PM
      rmhoward@... Albany W.A.

      Residents of Southern Australia and New Zealand should be aware of the imminent passage of the remnants from the break up of the largest ever seen ozone hole.

      Residents of Southern Australia and New Zealand should be aware of the
      imminent passage of the remnants from the break up of the largest ever seen ozone hole. Ozone levels around 250DU are likely compared to the normal of around 300DU for this time of the year.

      Over the last week or so the ozone hole has begun to elongate into a dumb- bell shape. In the Indian Ocean this has reached almost to the Tropic of Capricorn. Although this break up pattern is similar to previous years the size of the hole and the subsequent northward extent of the ozone depleted air is unprecedented.

      Temperatures in Perth are expected to be in the mid 30's within the next 5 days. Whilst substantially depleted air may not reach that far north. These temperatures (which will be replicated across southern australia), will bring people out in their droves to beaches and pools.

      We could see an increase in severe sunburn cases with noticeable affects upon emergency departments In many areas, increased susceptibility to fungal diseases, increased dessication of plants and potential for detrimental affects on seed setting in currently flowering species may be long term affects. imho there is a definite risk here which no government agency appears to be aware of nor is there any dicussion of this issue (beyond bland press releases about
      'getting on top of the problem')

      Interested parties should view the South pole ozone images for the 2 and 3 November available at this site.
      http://toms.gsfc.nasa.gov/eptoms/ep.html

      Please repost and distribute this warning as widely as you see fit.
      Bob Howard

      LATEST COMMENTS ABOUT THIS ARTICLE
      Listed below are the 10 latest comments of 5 posted about this article.

      TITLE AUTHOR DATE
      Going to Hell in a Handbasket Agent Karlos 13/11/2003 at 01:13 PM
      Ozone/ Global Warming Anne O'Brien 10/11/2003 at 10:23 PM
      correct AP 08/11/2003 at 02:03 AM
      Cause for concern Takver 07/11/2003 at 01:43 AM
      Thanks Bob Already Published (turing) 06/11/2003 at 03:02 PM

      http://www.melbourne.indymedia.org/news/2003/11/57187.php




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