Ozone Layer Solid Research Essay Example For Students

Ozone Layer Solid Research Essay Subject: TABLE OF CONTENTSHow to get this FAQCopyright StatementGeneral remarksCaveats, Disclaimers, and Contact InformationTABLE OF CONTENTS1. THE STRATOSPHERE1.1) What is the stratosphere?1.2) How is the composition of air described? 1.3) How does the composition of the atmosphere change with2. THE OZONE LAYER2.1) How is ozone created?2.2) How much ozone is in the layer, and what is a2.3) How is ozone distributed in the stratosphere?2.4) How does the ozone layer work?2.5) What sorts of natural variations does the ozone layer show?2.5.a) Regional and Seasonal Variation2.5.b) Year-to-year variations. 2.6) What are CFCs?2.7) How do CFCs destroy ozone?2.8) What is an Ozone Depletion Potential?2.9) What about HCFCs and HFCs? Do they destroy ozone?2.10) *IS* the ozone layer getting thinner?2.11) Is the middle-latitude ozone loss due to CFC emissions?2.12) If the ozone is lost, wont the UV light just penetrate 2.13) Do Space Shuttle launches damage the ozone layer?2.14) Will commercial supersonic aircraft damage the ozone layer?2.15) What is being done about ozone depletion?3. REFERENCES FOR PART IIntroductory ReadingBooks and Review ArticlesMore Specialized ReferencesInternet ResourcesSubject: 1. THE STRATOSPHERESubject: 1.1) What is the stratosphere?The stratosphere extends from about 15 km to 50 km. In thestratosphere temperature _increases_ with altitude, due to theabsorption of UV light by oxygen and ozone. This creates a globalinversion layer which impedes vertical motion into and within the stratosphere since warmer air lies above colder air, convectionis inhibited. The word s tratosphere is related to the wordstratification or layering. The stratosphere is often compared to the troposphere, which isthe atmosphere below about 15 km. The boundary called the tropopause between these regions is quite sharp, but itsprecise location varies between ~9 and ~18 km, depending upon latitude and season. The prefix tropo refers to change: the troposphere is the part of the atmosphere in which weather occurs. This results in rapid mixing of tropospheric air. Above the stratosphere lie the mesosphere, ranging from ~50 to~100 km, in which temperature decreases with altitude; the thermosphere, ~100-400 km, in which temperature increaseswith altitude again, and the exosphere, beyond ~400 km, whichfades into the background of interplanetary space. In the uppermesosphere and thermosphere electrons and ions are abundant, sothese regions are also referred to as the ionosphere. In technicalliterature the term lower atmosphere is synonymous with thetroposphere, middle atmosphere refers to the stratosphereand mesosphere, while upper atmo sphere is usually reserved for thethermosphere and exosphere. This usage is not universal, however,and one occasionally sees the term upper atmosphere used todescribe everything above the troposphere (for example, in NASAsUpper Atmosphere Research Satellite, UARS.)Subject: 1.2) How is the composition of air described? (Or, what is a mixing ratio?)The density of the air in the atmosphere depends upon altitude, andin a complicated way because the temperature also varies withaltitude. It is therefore awkward to report concentrations ofatmospheric species in units like g/cc or molecules/cc. Instead,it is convenient to report the mole fraction, the relativenumber of molecules of a given type in an air sample. Atmosphericscientists usually call a mole fraction a mixing ratio. Typicalunits for mixing ratios are parts-per-million, billion, ortrillion by volume, designated as ppmv, ppbv, and pptvrespectively. (The expression by volume reflects Avogadros Law for an ideal gas mixture, equal v olumes contain equal numbers of molecules and serves to distinguish mixing ratios from mass fractions which are given as parts-per-million by weight.) Thuswhen someone says the mixing ratio of hydrogen chloride at 3 kmis 0.1 ppbv, he means that 1 out of every 10 billion molecules inan air sample collected at that altitude will be an HCl molecule. Subject: 1.3) How does the composition of the atmosphere change withaltitude? (Or, how can CFCs get up to the stratosphere when they are heavier than air?) In the earths troposphere and stratosphere, most _stable_ chemicalspecies are well-mixed their mixing ratios are independent ofaltitude. If a species mixing ratio changes with altitude, somekind of physical or chemical transformation is taking place. That last statement may seem surprising one might expect the heavier molecules to dominate at lower altitudes. The mixing ratio of Krypton (mass 84), then, would decrease with altitude, while that of Helium (mass 4) would increase. In reality, however, molecules do not segregate by weight in the troposphere or stratosphere. The relative proportions of Helium, Nitrogen, and Krypton are unchanged up to about 100 km. Why is this? Vertical transport in the troposphere takes place byconvection and turbulent mixing. In the stratosphere and in themesosphere, it takes place by eddy diffusi on the gradual mechanical mixing of gas by motions on small scales. These mechanisms do not distinguish molecular masses. Only at much higher altitudes do mean free paths become so large that _molecular_ diffusion dominates and gravity is able to separate the different species, bringing hydrogen and helium atoms to the top. The lower and middle atmosphere are thussaid to be well mixed. Experimental measurements of the fluorocarbon CF4 demonstrate thishomogeneous mixing. CF4 has an extremely long lifetime in thestratosphere probably many thousands of years. The mixing ratioof CF4 in the stratosphere was found to be 0.056-0.060 ppbv from 10-50 km, with no overall trend. An important trace gas that is *not* well-mixed is water vapor. Thelower troposphere contains a great deal of water as much as 30,000ppmv in humid tropical latitudes. High in the troposphere, however,the water condenses and falls to the earth as rain or snow, so thatthe stratosphere is extremely dry, typical mixing ratios being about5 ppmv. Indeed, the transport of water vapor from troposphere to stratosphere is even less efficient than this would suggest, since much of the small amount of water in the stratosphere is actuallyproduced _in situ_ by the oxidation of stratospheric methane. Sometimes that part of the atmosphere in which the chemicalcomposition of stable species does not change with al titude iscalled the homosphere. The homosphere includes the troposphere,stratosphere, and mesosphere. The upper regions of the atmosphere the thermosphere and the exosphere are then referred to as the heterosphere. Subject: 2. THE OZONE LAYER Subject: 2.1) How is ozone created?Ozone is formed naturally in the upper stratosphere by shortwavelength ultraviolet radiation. Wavelengths less than ~240nanometers are absorbed by oxygen molecules (O2), which dissociate togive O atoms. The O atoms combine with other oxygen molecules to make ozone: O2 + hv -* O + O (wavelength * 240 nm)O + O2 -* O3Subject: 2.2) How much ozone is in the layer, and what is aDobson Unit ?A Dobson Unit (DU) is a convenient scale for measuring the totalamount of ozone occupying a column overhead. If the ozone layerover the US were compressed to 0 degrees Celsius and 1 atmospherepressure, it would be about 3 mm thick. So, 0.01 mm thickness at 0 C and 1 at is defined to be 1 DU; this makes the average thicknessof the ozone layer over the US come out to be about 300 DU. In absolute terms, 1 DU is about 2.7 x 10^16 molecules/cm^2. The unit is named after G.M.B. Dobson, who carried out pioneering studies of atmospheric ozone between ~1920-1960. Dobson designedthe standard instrument used to measure ozone from the ground. TheDobson spectrophotometer measures the intensity solar UV radiation atfour wavelengths, two of which are absorbed by ozone and two ofwhich are not . These instruments are still in usein many places, although they are gradually being replaced by the more elaborate Brewer spectrophotometers. Today ozone is measured in many ways, from aircraft, balloons, satellites, and space shuttle missions,but the worldwide Dobson network is the only source of long-term data. A station at Arosa in Switzerland has been measuring ozone since the1920s (see http://www The Salem Community by Miller Essay _Aside_: One sometimes hears that the US government killed the SSTproject in 1971 because of concerns raised by H. S. Johnstons work on NOx. This is not true. The US House of Representatives had alreadyvoted to cut off Federal funding for the SST when Johnston beganhis calculations. The House debate had centered around economics and the effects of noise, especially sonic booms, although there were some vague concerns about pollution and one physicist had testifiedabout the possible effects of water vapor on ozone. About 6 weeks after both houses had voted to cancel the SST, its supporters succeeded in reviving the project in the House. In the meantime, Johnston had sent a preliminary report to several professional colleagues and submitted a paper to _Science_. A preprint of Johnstons report leaked to a small California newspaper which published a highly sensationalized account. The story hit the press a few days before the Senate voted, 58-37, not to revive the SST. (The previous Senate vote had been 51-46 to cancel the project. The reason for the larger majority in the second vote was probably the statement by Boeings chairman that at least $500 million more would be needed to revive the program.).. Subject: 2.15) What is being done about ozone depletion?The 1987 Montreal Protocol (full text available on the world-wide web athttp://www.unep.org/unep/secretar/ozone/treaties.htm) specified thatCFC emissions should be reduced by 50% by the year 2000 (they had been _increasing_ by 3% per year.) This agreement was amended inLondon in 1990, to state that production of CFCs, CCl4, and halons should cease entirely by the year 2000. Restrictions were also appliedapplied to other Cl sources such as methylchloroform. (The details ofthe protocols are complicated, involving different schedules for differentcompounds, delays for developing nations, etc.) The phase-out schedulewas accelerated by four years by the 1992 Copenhagen agreements. A great deal of effort has been devoted to recovering and recycling CFCs that arecurrently being used in closed-cycle systems. For more information about legal and policy issues, see the books by and , and the following web sites:http://www.unep.org/unep/se cretar/ozone/home.htm http://www.unep.ch/ozone/ (European mirror site for above)http://www.epa.gov/docs/ozone/index.htmlhttp://www.ciesin.org/TG/OZ/ozpolic.htmlRecent NOAA measurements show that the _rate of increase_ of halocarbon concentrations in the atmosphere has decreased markedly since 1987. It appears that theProtocols are being observed. Under these conditions total stratospheric chlorine is predicted to peak at 3.8 ppbv in the year 1998, 0.2 ppbv above 1994 levels, and to slowly decline thereafter. Extrapolation of current trends suggests that the maximum ozone losses will be :Northern Mid-latitudes in winter/Spring: 12-13% below late 1960s levels, ~2.5% below current levels. Northern mid-latitudes in summer/fall: 6-7% below late 1960s levels,~1.5% below current levels. Southern mid-latitudes, year-round: ~ 11% below late 1960s levels,~2.5% below current levels. Very little depletion has been seen in the tropics and little isexpected there. After the year 2000, the ozone layer will slowly recover over a period of 50 years or so. The antarctic ozone hole is expected to last until about 2045. Some scientists are investigating ways to replenish stratosphericozone, either by removing CFCs from the troposphere or by tying upthe chlorine in inactive compounds. This is discussed in Part III. Subject: 3. REFERENCES FOR PART IA remark on references: they are neither representative norcomprehensive. There are _hundreds_ of people working on theseproblems. Where possible I have limited myself to articles thatare (1) available outside of University libraries (e.g. _Science_ or _Nature_ rather than archival journals such as _J. Geophys. Res._) and (2) directly related to the frequently asked questions. I have not listed papers whose importance is primarily historical. (I make an exception for the Nobel-Prize winning work of Crutzen,Molina and Rowland.) Readers who want to see who did what shouldconsult the review articles listed below, or, if they can get them,the WMO reports which are extensively documented. Subject: Introductory Reading R. R. Garcia, Causes of Ozone Depletion, _Physics World_April 1994 pp 49-55. T. E. Graedel and P. J. Crutzen, _Atmospheric Change: an Earth System Perspective_, Freeman, NY 1993. F.S. Rowland, Chlorofluorocarbons and the depletionof stratospheric ozone, _American Scientist_ _77_, 36, 1989. F. S. Rowland and M. J. Molina, Ozone depletion: 20 years after the alarm, _Chemical and Engineering News_, 15 Aug. 1994, pp. 8-13. P. S. Zurer, Ozone Depletions Recurring SurprisesChallenge Atmospheric Scientists, _Chemical and Engineering News_,24 May 1993, pp. 9-18. Subject: Books and Review Articles R. Bene*censored*, _Ozone Diplomacy_, Harvard, 1991. G. Brasseur and S. Solomon, _Aeronomy of the Middle Atmosphere_, 2nd. Edition, D. Reidel, 1986 J. W. Chamberlain and D. M. Hunten,_Theory of Planetary Atmospheres_, 2nd Edition, Academic Press, 1987 G. M. B. Dobson, _Exploring the Atmosphere_, 2nd Edition, Oxford, 1968. G. M. B. Dobson, Forty Years research on atmosphericozone at Oxford, _Applied Optics_, _7_, 387, 1968. Climate Impact Committee, National Research Council,_Environmental Impact of Stratospheric Flight_, National Academy of Sciences, 1975. H. S. Johnston, Atmospheric Ozone, _Annu. Rev. Phys. Chem._ _43_, 1, 1992. M. K. W. Ko, N.-D. Sze, and M. J. Prather, BetterProtection of the Ozone Layer, _Nature_ _367_, 505, 1994. K. T. Litvin, _Ozone Discourses_, Columbia 1994. M. McElroy and R. Salawich, Changing Composition of the Global Stratosphere, _Science_ _243, 763, 1989. F. S. Rowland and M. J. Molina,Chlorofluoromethanes in the Environment, Rev. Geophys. Space Phys. _13_, 1, 1975. F. S. Rowland, Stratospheric Ozone Depletion, _Ann. Rev. Phys. Chem._ _42_, 731, 1991. M. L. Salby and R. R. Garcia, Dynamical Perturbationsto the Ozone Layer, _Physics Today_ _43_, 38, March 1990. S. Solomon, Progress towards a quantitative understandingof Antarctic ozone depletion, _Nature_ _347_, 347, 1990. J. M. Wallace and P. V. Hobbs,_Atmospheric Science: an Introductory Survey_, Academic Press, 1977. R. P. Wayne, _Chemistry of Atmospheres_, 2nd. Ed., Oxford, 1991. World Meteorological Organization, _Report of the International Ozone Trends Panel_, Global Ozone Research and Monitoring Project Report #18. World Meteorological Organization, _Scientific Assessment of Stratospheric Ozone: 1991_Global Ozone Research and Monitoring Project Report #20. World Meteorological Organization, _Scientific Assessment of Ozone Depletion: 1991_Global Ozone Research and Monitoring Project Report #25. World Meteorological Organization, _Scientific Assessment of Ozone Depletion: 1994_Global Ozone Research and Monitoring Project Report #37. The Executive Summary of this report is available on theWorld-Wide Web at http://www.al.noaa.gov/WWWHD/pubdocs/WMOUNEP94.htmlSubject: More Specialized References R. D. Bojkov, V. E. Fioletov, D. S. Balis,C. S. Zerefos, T. V. Kadygrova, and A. M. Shalamjansky, Further ozone decline during the northern hemisphere winter-springof 1994-95 and the new record low ozone over Siberia,Geophys. Res. Lett. _22_, 2729, 1995. G. Brasseur and C. Granier, Mt. Pinatuboaerosols, chlorofluorocarbons, and ozone depletion, _Science__257_, 1239, 1992. P. J. Crutzen, The influence of nitrogen oxides on theatmospheric ozone content, _Quart. J. R. Met. Soc._ _90_, 320, 1970. J. W. Elkins, T. M. Thompson, T. H. Swanson,J. H. Butler, B. D. Hall, S. O. Cummings, D. A. Fisher, and A. G. Raffo, Decrease in Growth Rates of Atmospheric Chlorofluorocarbons 11 and 12, _Nature_ _364_, 780, 1993. D. W. Fahey, E. R. Keim, K. A. Boering,C. A. Brock, J. C. Wilson, H. H. Jonsson, S. Anthony, T. F. Hanisco,P. O. Wennberg, R. C. Miake-Lye, R. J. Salawich, N. Louisnard, E. L. Woodbridge, R. S. Gao, S. G. Donnelly, R. C. Wamsley,L. A. Del Negro, S. Solomon, B. C. Daube, S. C. Wofsy, C. R. Webster,R. D. May, K. K. Kelly, M. Loewenstein, J. R. Podolske, and K. R. Chan,Emission Measurements of the Concorde Supersonic Aircraft in theLower Stratosphere, _Science_ _270_, 70, 1995. J. Gleason, P. Bhatia, J. Herman, R. McPeters, P. Newman, R. Stolarski, L. Flynn, G. Labow, D. Larko, C. Seftor, C. Wellemeyer, W. Komhyr, A. Miller, and W. Planet, Record Low GlobalOzone in 1992, _Science_ _260_, 523, 1993. K. Henriksen and V. Roldugin, Total ozonevariations in Middle Asia and dynamics meteorological processesin the atmosphere, _Geophys. Res. Lett._ _22_, 3219, 1995. K. Henriksen, T. Svenoe, and S. H. H. Larsen,On the stability of the ozone layer at Tromso, J. Atmos. Terr. Phys. _55_, 1113, 1992. J. R. Herman, R. McPeters, and D. Larko,Ozone depletion at northern and southern latitudes derivedfrom January 1979 to December 1991 TOMS data,J. Geophys. Res. _98_, 12783, 1993. D. J. Hofmann and S. Solomon, Ozone destruction through heterogeneous chemistry following the eruption of El Chichon, J. Geophys. Res. _94_, 5029, 1989. D. J. Hofmann, S. J. Oltmans, W. D. Komhyr, J. M. Harris, J. A. Lathrop, A. O. Langford, T. Deshler, B. J. Johnson, A. Torres, and W. A. Matthews,Ozone Loss in the lower stratosphere over the United States in1992-1993: Evidence for heterogeneous chemistry on the Pinatuboaerosol, Geophys. Res. Lett. _21_, 65, 1994. D. J. Hofmann, S. J. Oltmans, J. M. Harris,J. A. Lathrop, G. L. Koenig, W. D. Komhyr, R. D. Evans, D. M. Quincy,T. Deshler, and B. J. Johnson,Recovery of stratospheric ozone over the United States in the winterof 1993-94, Geophys. Res. Lett. _21_, 1779, 1994. D. J. Hofmann, S. J. Oltmans, G. L. Koenig,B. A. Bodhaine, J. M. Harris, J. A. Lathrop, R. C. Schnell, J. Barnes,J. Chin, D. Kuniyuki, S. Ryan, R. Uchida, A. Yoshinaga, P. J. Neale,D. R. Hayes, Jr., V. R. Goodrich, W. D. Komhyr, R. D. Evans, B. J. Johnson,D. M. Quincy, and M. Clark, Record low ozone at Mauna Loa Observatoryduring winter 1994-95: A consequence of chemical and dynamicalsynergism?, Geophys. Res. Lett. _23_, 1533, 1996. J. B. Kerr, D. I. Wardle, and P. W. Towsick,Record low ozone values over Canada in early 1993,Geophys. Res. Lett. _20_, 1979, 1993. M. A. K. Khalil and R. Rasmussen, The GlobalSources of Nitrous Oxide, _J. Geophys. Res._ _97_, 14651, 1992. S. H. H. Larsen and T. Henriksen, Persistent Arctic ozone layer, _Nature_ _343_, 134, 1990. M. P. McCormick, L. W. Thomason, and C. R. Trepte, Atmospheric effects of the Mt Pinatubo eruption,_Nature_ _373_, 399, 1995. R. D. McPeters, S. M. Hollandsworth, andC. J. Seftor, Long-term ozone trends derived from the 16-year combinedNimbus 7/Meteor 3 TOMS Version 7 record, Geophys. Res. Lett. _23_,3699, 1996. M. J. Molina and F. S. Rowland,Stratospheric sink for chlorofluoromethanes: chlorineatom-catalyzed destruction of ozone, _Nature_ _249_, 810, 1974. S. A. Montzka, J. H. Butler, R. C. Myers,T. M. Thompson, T. H. Swanson, A. D. Clarke, L. T. Lock, and J. W. Elkins, Decline in the Tropospheric Abundance of Halogenfrom Halocarbons: Implications for Stratospheric Ozone Depletion,_Science_ _272_, 1318, 1996. M. J. Prather, M.M. Garcia, A.R. Douglass, C.H. Jackman, M.K.W. Ko, and N.D. Sze, The Space Shuttles impact onthe stratosphere, J. Geophys. Res. _95_, 18583, 1990. M. J. Prather, P. Midgley, F. S. Rowland,and R. Stolarski, The ozone layer: the road not taken,_Nature_ _381_, 551, 1996. A. R. Ravishankara, A. A. Turnipseed,N. R. Jensen, S. Barone, M. Mills, C. J. Howard, and S. Solomon,Do Hydrofluorocarbons Destroy Stratospheric Ozone?,_Science_ _263_, 71, 1994. Special Section on the Stratospheric Aerosol and Gas Experiment II, _J. Geophys. Res._ _98_, 4835-4897, 1993. S. Solomon and D.L. Albritton,Time-dependent ozone depletion potentials for short- and long-termforecasts, _Nature_ _357_, 33, 1992. R. Stolarski, R. Bojkov, L. Bishop, C. Zerefos,J. Staehelin, and J. Zawodny, Measured Trends in StratosphericOzone, Science _256_, 342 (17 April 1992) J. Waters, L. Froidevaux, W. Read, G. Manney, L. Elson, D. Flower, R. Jarnot, and R. Harwood, Stratospheric ClO andozone from the Microwave Limb Sounder on the Upper AtmosphereResearch Satellite, _Nature_ _362_, 597, 1993. R. Zander, M. R. Gunson, C. B. Farmer, C. P. Rinsland, F. W. Irion, and E. Mahieu, The 1985 chlorine andfluorine inventories in the stratosphere based on ATMOSobservations at 30 degrees North latitude, J. Atmos. Chem. _15_,171, 1992. Subject: Internet ResourcesThis list is preliminary and by no means comprehensive; it includes a few sites that I have found particularly useful and which providegood starting points for further exploration. Probably the most extensive collection of online resources is that providedby the Consortium for International Earth Science Information Network:http://sedac.ciesin.org/ozone/It includes links to many other documents, including on-line versionsof some of the original research papers. At the present time portionsof the site are very much under construction. Lenticular Press publishes a multimedia CD-ROM (for Apple Macintosh)containing ozone data and images, as well as a hypertext document similarto this FAQ. For sample images and information about ordering the CD,see http://www.lenticular.com/ Note that these samples are copyrightedand may not be further distributed. The NOAA Aeronomy Lab: http://www.al.noaa.gov/ , has the text of the Executive Summary of the 1994 WMO ScientificAssessment, http://www.al.noaa.gov/WWWHD/pubdocs/WMOUNEP94.htmlThe United Nations Environmental Program (UNEP) Ozone Secretariat:Main page http://www.unep.org/unep/secretar/ozone/home.htm (Nairobi, Kenya). Mirror site http://www.unep.ch/ozone/ (Geneva, Switzerland). The US Environmental Protection Agency has an ozone page that includeslinks to both science and policy resources:http://www.epa.gov/docs/ozone/index.htmlSome of the more interesting scientific web pages include:The Centre for Antarctic Information and Research (ICAIR) in New Zealand:http://icair.iac.org.nz/ozone/index.html Environment Canada: http://www.doe.ca/ozone/index.htmThe TOMS home page: http://jwocky.gsfc.nasa.gov/The EASOE home page: http://www.atm.ch.cam.ac.uk/images/easoe/The UARS Project Definition page:http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/UARS_project.htmlThe HALOE home page: http://haloedata.larc.nasa.gov/home.htmlThe British Antarctic Survey:http://www.nbs.ac.uk/public/icd/jds/ozone/The ETH Zuerich Institute for Atmospheric Sciencehttp://www.umnw.ethz.ch/LAPETH/lapeth.htmlThe Institute for Meteorology at the Free University of Berlin:http://strat-www.met.fu-berlin.de/The Climate Prediction Centers TOVS Total Ozone Analysis page:http://nic.fb4.noaa.gov:80/products/st ratosphere/tovsto/The USDA UV-B Radiation Monitoring Program Climate Network,http://uvb.nrel.colostate.edu/UVB/uvb_climate_network.html Send corrections/additions to the FAQ Maintainer: Last Update September 28 2000 @ 04:24 AM Ozone Depletion FAQ Part IV: UV Radiation and its EffectsFrom: (Robert Parson)Newsgroups: sci.environment,sci.answers,news.answersSubject: Ozone Depletion FAQ Part IV: UV Radiation and its EffectsFollowup-To: posterDate: 24 Dec 1997 20:51:43 GMTOrganization: University of Colorado, BoulderExpires: Sun, 1 Jan 1998 00:00:00 GMTMessage-ID: **Reply-To: Summary: This is the fourth of four files dealing with stratosphericozone depletion. It describes the properties of solar UVradiation and some of its biological effects. Keywords: ozone layer depletion UVB UVA skin cancer phytoplanktonArchive-name: ozone-depletion/uvLast-modified: 16 Dec 1997Version: 5.9Subject: How to get this FAQThese files are posted to the newsgroups sci.environment, sci.answers,and news.answers. They are also archived at a variety of sites. Thesearchives work by automatically downloading the faqs from the newsgroupsand reformatting them in site-specific ways. They usually update tothe latest version within a few days of its being posted, although inthe past there have been some lapses; if the Last-Modified date inthe FAQ seems old, you may want to see if there is a more recent versionin a different archive. Many individuals have archived copies on their own servers, but theseare often seriously out of date and in general are not recommended. A. World-Wide Web(Limited) hypertext versions, with embedded links to some of the on-lineresources cited in the faqs, can be found at:http://www.faqs.org/faqs/ozone-depletion/ http://www.cis.ohio-state.edu/hypertext/faq/usenet/ozone-depletion/top.htmlhttp://www.lib.ox.ac.uk/internet/news/faq/sci.environment.html http://www.cs.ruu.nl/wais/html/na-dir/ozone-depletion/.htmlPlaintext versions can be found at:ftp://rtfm.mit.edu/pub/usenet/news.answers/ozone-depletion/ftp://ftp.uu.net/usenet/news.answers/ozone-depletion/-B. Anonymous ftpTo rtfm.mit.edu, in the directory /pub/usenet/news.answers/ozone-depletionTo ftp.uu.net, in the directory /usenet/news.answers/ozone-depletionLook for the four files named intro, stratcl, antarctic, and uv. -C. Regular emailSend the following messages to :send usenet/news.answers/ozone-depletion/introsend usenet/news.answers/ozone-depletion/stratclsend usenet/news.answers/ozone-depletion/antarcticsend usenet/news.answers/ozone-depletion/uvLeave the subject line blank. If you want to find out more about the mail server, send amessage to it containing the word help. Subject: Copyright Notice************************************************************************ Copyright 1997 Robert Parson ** ** This file may be distributed, copied, and archived. All such ** copies must include this notice and the paragraph below entitled ** Caveat. Reproduction and distribution for personal profit is ** not permitted. If this document is transmitted to other networks or ** stored on an electronic archive, I ask that you inform me. I also ** ask you to keep your archive up to date; in the case of world-wide ** web pages, this is most easily done by linking to the master at the ** ohio-state http URL instead of storing local copies. Finally, I ** request that you inform me before including any of this information ** in any publications of your own. Students should note that this ** is _not_ a peer-reviewed publication and may not be acceptable as ** a reference for school projects; it should instead be used as a ** pointer to the published literature. In particular, all scientific ** data, numerical estimates, etc. should be accompanied by a citation ** to the original published source, not to this document. ************************************************************************Subject: General RemarksThis file deals with the physical properties of ultravioletradiation and its biological consequences, emphasizing thepossible effects of stratospheric ozone depletion. It frequentlyrefers back to Part I, where the basic properties of the ozonelayer are described; the reader should look over that file first. The overall approach I take is conservative. I concentrate on whatis known and on most probable, rather than worst-case, scenarios. For example, I have relatively little to say about theeffects of UV radiation on plants this does not mean that theeffects are small, it means that they are as yet not wellquantified (and moreover, I am not well qualified to interpret theliterature.) Policy decisions must take into account not only themost probable scenario, but also a range of less probable ones. will probably do, but also the worst that he could possibly do. There have been surprises, mostly unpleasant, in this field in thepast, and there are sure to be more in the future. In general,_much_ less is known about biological effects of UV-B than aboutthe physics and chemistry of the ozone layer. Subject: Caveats, Disclaimers, and Contact Information| _Caveat_: I am not a specialist. In fact, I am not an atmospheric| scientist at all I am a physical chemist studying gas-phase| reactions who talks to atmospheric scientists. In this part