Lapho Konakaliswa Umoya Osemkhathini Wethu
NGO-1971, lapho eya enyangeni egibele u-Apollo 14, u-Edgar Mitchell wathi lapho ebuka umhlaba: “Ubukeka njengetshe eliyigugu elikhazimulayo eliluhlaza nokumhlophe.” Kodwa yini umuntu abengayibona lapho esemkhathini namuhla?
Ukuba ubenezibuko ezikhethekile ezimvumela ukuba abone amagesi angabonakali omoya osemkhathini, ubeyobona umfanekiso ohluke ngempela. Kumagazini i-India Today, uRaj Chengappa wabhala: “Ubeyobona izimbobo ezinkulukazi ezingqimbeni ezivikelayo ze-ozone phezu kwe-Antarctica neNyakatho Melika. Kunokuba abone itshe eliyigugu elikhazimulayo eliluhlaza nokumhlophe ubeyobona umhlaba ofiphele, ongcolile ogcwele amafu amnyama, ayaluzayo esikhutha ne-sulphur dioxide.”
Yini evule izimbobo ongqimbeni olungaphezulu lwe-ozone yomoya osemkhathini wethu? Ingabe ukwanda kwezinto ezingcolisa umoya kuyingozi kangako ngempela?
Indlela I-ozone Ebhujiswa Ngayo
Eminyakeni engaphezu kwengu-60 edlule, ososayensi bamemezela ukuthi bathole isiqandisi esiphephile esasingathatha indawo yezinye ezazinoshevu nephunga elibi. Lelikhemikhali elisha lalinama-molecule ane-athomu elilodwa le-carbon, amabili e-chlorine, namabili e-fluorine (CCl2F2). Lona kanye namanye anjengalo enziwe umuntu abizwa ngokuthi ama-chlorofluorocarbon (ama-CFC).
Ekuqaleni kwawo-1970, ama-CFC ayesekhiqizwa kabanzi ezimbonini zomhlaba wonke. Ayengasetshenziswa nje kuphela eziqandisini kodwa nasezifuthweni ezisemathinini, kuziphephetha-moya, kumakhemikhali okuhlanza, nasekwenzeni izitsha zokuphatha ukudla neminye imikhiqizo elula yepulasitiki.
Nokho, ngo-September 1974, ososayensi ababili, uSherwood Rowland noMario Molina, bachaza ukuthi ama-CFC kancane kancane akhuphukela kuyi-stratosphere lapho efika ayikhiphele khona i-chlorine ayiqukethe. Labososayensi balinganisela ukuthi i-athomu ngalinye le-chlorine lalingabhubhisa izinkulungwane zama-molecule e-ozone. Kodwa kunokuba i-ozone ibhujiswe ngokulinganayo kulo lonke ungqimba olungaphezulu lomoya osemkhathini, iye yaphela kakhulu ezindaweni ezibandayo zasenyakatho naseningizimu.
Njalo entwasahlobo kusukela ngo-1979, e-Antarctic kuye kwanyamalala i-ozone eningi yaphinde yavela. Lokhu kuncipha kwe-ozone ngezikhathi ezithile kubizwa ngokuthi imbobo ye-ozone. Ngaphezu kwalokho, eminyakeni yamuva lokho okubizwa ngokuthi imbobo bekukhula futhi kuhlala isikhathi eside ngokwengeziwe. Ngo-1992, izilinganiso zesiphuphutheki zembula imbobo ye-ozone eqopha umlando—enkulu kuneNyakatho Melika. Futhi kwakusele i-ozone encane kuyo. Izilinganiso ezathathwa emoyeni zembula ukwehla ngamaphesenti angaphezu kuka-60—ukwehla okukhulu kunakho konke okwake kwabikwa.
Ngesikhathi esifanayo, amazinga e-ozone abelokhu encipha nasongqimbeni olungaphezulu lomoya osemkhathini kwezinye izingxenye zomhlaba. “Izilinganiso ezithathwe muva nje,” kubika umagazini i-New Scientist, “zibonisa ukuthi . . . kwakunezilinganiso ze-ozone eziphansi ngokungavamile ngo-1992 ezindaweni eziphakathi kuka-50° eNyakatho no-60° eNyakatho, okuhlanganisa iNyakatho Yurophu, iRussia neCanada. Izinga le-ozone lalehle ngamaphesenti angu-12 kulokho okuvamile, liphansi kunanoma isiphi isikhathi eminyakeni engu-35 yokugcinwa kwemibhalo okuqhubekayo.”
“Ngisho nezibikezelo ezimbi kakhulu,” kusho iphephabhuku i-Scientific American, “manje kuboniswa ukuthi ziye zalulaza ukuphela kwe-ozone okubangelwa ama-chlorofluorocarbon. . . . Kodwa ngalesosikhathi, izikhulu zohulumeni nezezimboni zamelana ngokuqinile nokubekwa kwemingcele, ngesisekelo sokuntuleka kobufakazi obuphelele obungokwesayensi.”
Kulinganiselwa ukuthi kakade kuye kwakhishelwa ama-CFC angamathani angu-20 emoyeni. Njengoba kuthatha iminyaka eminingi ukuba ama-CFC akhuphukele kuyi-stratosphere, izigidi zamathani azikafinyeleli ongqimbeni olungaphezulu lomoya osemkhathini lapho zenza khona umonakalo. Nokho, akuwona ama-CFC kuphela akhipha i-chlorine ebhubhisa i-ozone. “I-NASA ilinganisela ukuthi amathani angaba ngu-75 e-chlorine akhishelwa ongqimbeni lwe-ozone isikhathi ngasinye lapho kucitshwa umkhumbi-mkhathi,” kubika umagazini i-Popular Science.
Kunamiphi Imiphumela?
Imiphumela ye-ozone encane ongqimbeni olungaphezulu lomoya osemkhathini ayikaqondakali ngokuphelele. Nokho, into eyodwa ebonakala iqinisekile ukuthi izinga lokukhishwa kwemisebe ye-UV (ultraviolet) eyingozi efika emhlabeni liyanda, okubangela ukwanda komdlavuza wesikhumba. “Phakathi neminyaka eyishumi edlule,” kubika iphephabhuku i-Earth, “isilinganiso saminyaka yonke semisebe ye-UV eyingozi efika enyakatho nenkabazwe siye sanda ngamaphesenti angaba mahlanu.”
Ukwanda kwama-UV ngephesenti elilodwa nje kuphela kulinganiselwa ukuthi kubangela ukwanda komdlavuza wesikhumba ngamaphesenti amabili kuya kwamathathu. Umagazini wase-Afrika i-Getaway uthi: “Kunabantu abasha abangaphezu kuka-8 000 abangenwa umdlavuza wesikhumba eNingizimu Afrika minyaka yonke . . . Sinelinye lamazinga aphansi kakhulu esivikelo se-ozone nokwanda okukhulu kakhulu komdlavuza wesikhumba (lokhu kuhlobana akubanga khona ngengozi).”
Ukuthi ukubhujiswa kwe-ozone ongqimbeni olungaphezulu lomoya osemkhathini kwakuyobangela ukwanda komdlavuza wesikhumba kwabikezelwa eminyakeni eminingi edlule ososayensi uRowland noMolina. Batusa ukuba kuvinjelwe ngokushesha ukusetshenziswa kwama-CFC ezifuthweni e-United States. Eqaphela lengozi, amazwe amaningi avumile ukuyeka ukukhiqiza ama-CFC ngo-January 1996. Nokho, okwamanje, ukusetshenziswa kwawo kuyaqhubeka kusongela ukuphila emhlabeni.
I-Our Living World ibika ukuthi ukuncipha kwe-ozone phezu kwe-Antarctica “kuye kwavumela imisebe ye-ultraviolet ukuba ingene olwandle ngokujulé kakhulu kunalokho okwakucatshangwa ngaphambili. . . . Lokhu kuye kwabangela ukuncipha okukhulu ekuzalaneni kwezinto eziphilayo ezinengqamuzana elilodwa eziyisisekelo somjikelezo wokudla wasolwandle.” Ukuhlola kubonisa nokuthi ukwanda kwama-UV kunciphisa isivuno sezitshalo eziningi, okusongela ukutholakala kokudla embulungeni yonke.
Ngempela, ukusetshenziswa kwama-CFC kuyinhlekelele enkulu. Kodwa umoya osemkhathini wethu uhlaselwa nangezinye izinto eziningi ezingcolisayo. Enye yigesi esemoyeni osemkhathini ebaluleke kakhulu ekuphileni okusemhlabeni uma itholakala ngamazinga aphansi.
Umphumela Wokungcola
Maphakathi nekhulu le-19, abantu baqala ukubasa amalahle, igesi, nowoyela omningi ngokwandayo, benezela isikhutha esiningi emoyeni osemkhathini. Ngalesosikhathi izinga lalegesi etholakala ngesilinganiso esincane esemoyeni lalingaba izingxenye ezingu-285 kweziyisigidi. Kodwa ngenxa yokusebenzisa komuntu ngokwandayo izinto zokubasa, izinga lesikhutha selifinyelela ezingxenyeni ezingaphezu kwezingu-350 kweziyisigidi. Uye waba yini umphumela wokwanda kwalegesi ebamba ukushisa esemoyeni osemkhathini?
Abaningi bakholelwa ukuthi ukwanda kwamazinga esikhutha yikhona okuye kwabangela ukunyuka kwamazinga okushisa emhlabeni. Nokho, abanye abacwaningi bathi ukufudumala kwembulunga kubangelwa ikakhulukazi ukushintsha kwelanga—bathi ilanga belikhipha ukushisa okukhulu ezikhathini zamuva.
Kungakhathaliseki ukuthi ikuphi, ishumi leminyaka lawo-1980 lalishisa kakhulu ukudlula wonke selokhu kwaqalwa ukugcina imibhalo maphakathi nekhulu le-19. “Lokhu kuthambekela kwaqhubekela kulelishumi leminyaka,” kubika iphephandaba laseNingizimu Afrika i-Star, “njengoba u-1990 aba unyaka oshisa kunayo yonke embhalweni ogciniwe, u-1991 waba unyaka wesithathu, kwathi u-1992 . . . waba unyaka weshumi oshisa kunayo yonke embhalweni ogciniwe weminyaka engu-140.” Ukwehla kancane kwezinga lokushisa eminyakeni emibili edlule kuthiwa kwabangelwa uthuli olwaphumela emoyeni lapho kuqhuma iMount Pinatubo ngo-1991.
Ukuthi esikhathini esizayo iyoba yini imiphumela yokukhuphuka kwamazinga okushisa emhlabeni kuseyimpikiswano eshubile. Kodwa into eyodwa ngokusobala eye yabangelwa ukufudumala kwembulunga iye yaba ukuwenza ube inkimbinkimbi ngokwengeziwe umsebenzi onzima kakade wokubikezela isimo sezulu. I-New Scientist iphawula ukuthi izibikezelo zezulu ezinephutha “zingase zande njengoba ukufudumala kwembulunga kushintsha isimo sezulu.”
Izinkampani eziningi zomshuwalense zinovalo lokuthi ukufudumala kwembulunga kuyobhuntshisa izinkambiso zazo. “Njengoba zibhekene nezinhlekelele eziningi,” kuvuma i-Economist, “ezinye izinkampani ezixhasa umshuwalense zinciphisa imali eziyikhokha ngenxa yezinhlekelele ezingokwemvelo. Ezinye zikhuluma ngokushiya phansi ngokuphelele. . . . Zisaba ukungaqiniseki.”
Ngokuphawulekayo, ngo-1990, okuwunyaka owawushisa kunayo yonke emlandweni ogciniwe, ingxenye enkulu yeqhwa lase-Arctic yancibilika ngezinga elalingakaze libonwe ngaphambili. Lokhu kwabangela ukuba amakhulukhulu amabhele asezindaweni ezibandayo asale dengwane esiQhingini saseWrangell isikhathi esingaphezu kwenyanga. “Ngenxa yokufudumala kwembulunga,” kuxwayisa umagazini i-BBC Wildlife, “lezizimo . . . zingase zibe insakavukela.”
Iphephandaba elithile lase-Afrika labika ngo-1992: “Ochwepheshe besimo sezulu basola ukufudumala kwembulunga ngokwanda okumangalisayo kwenani lezintaba zeqhwa ezikhukhulekela enyakatho zisuka e-Antarctica futhi eziyingozi emikhunjini eningizimu Atlantic.” Ngokwe-Earth ka-January 1993, ukukhuphuka okuqhubekayo kolwandle ngasogwini oluseningizimu yeCalifornia ngokwengxenye kubangelwa ukufudumala kwamanzi.
Ngeshwa, abantu bayaqhubeka bekhiphela emoyeni osemkhathini izinga elishaqisayo lamagesi anoshevu. “E-United States,” kusho incwadi ethi The Earth Report 3, “umbiko ka-1989 we-Environmental Protection Agency walinganisela ukuthi kukhishelwa amathani angaphezu kuka-900 000 amakhemikhali anoshevu emoyeni minyaka yonke.” Lesisibalo sibhekwa njengesilinganiso nje ngenxa yokuthi asisihlanganisi isisi esikhishwa izigidigidi zezimoto.
Kunemibiko eshaqisayo yokungcoliswa komoya evela nakwamanye amazwe amaningi ezezimboni. Okwesabisa nakakhulu kuye kwaba ukwembulwa kwamuva nje kokungcoliswa komoya okwakungalawulwa emazweni aseMpumalanga Yurophu phakathi namashumi eminyaka okubusa kobuKhomanisi.
Izihlahla zomhlaba, ezithatha isikhutha zikhiphe umoya-mpilo, ziphakathi kwezisulu zomoya onoshevu. I-New Scientist yabika: “Izihlahla zaseJalimane ziyaqhubeka ziba buthaka, ngokusho . . . kukangqongqoshe wezolimo [owathi] ukungcoliswa komoya kusengesinye sezizathu eziyinhloko zokuwohloka kwempilo yamahlathi.”
Isimo siyefana eHighveld yaseNtilasifali eNingizimu Afrika. “Izimpawu zokuqala zomonakalo obangelwa imvula ye-acid manje seziyavela eMpumalanga Ntilasifali lapho amacembe ephayini eshintsha khona ekubeni luhlaza cwé eba nombala omhloshana ophaphathekile,” kubika uJames Clarke encwadini yakhe ethi Back to Earth.
Imibiko enjalo ivela emhlabeni wonke. Alikho izwe elivikelekile. Njengoba enoshimula abafinyelela phezulu esibhakabhakeni, amazwe ezezimboni angcolisa amazwe angomakhelwane. Umlando womuntu wentuthuko yezezimboni ezinobugovu awunikezi themba.
Nokho, sikhona isisekelo sethemba. Singaqiniseka ngokuthi umoya oyigugu osemkhathini wethu uzovikelwa ekubhujisweni. Funda esihlokweni esilandelayo ukuthi lokhu kuyofezwa kanjani.
[Isithombe ekhasini 7]
Ukubhujiswa kwe-“ozone” ongqimbeni olungaphezulu lomoya osemkhathini kuye kwabangela ukwanda komdlavuza wesikhumba
[Isithombe ekhasini 9]
Iyini imiphumela yokungcola okunjena?