Duniya sanyaya
Zubar da hankali a duniya wani zato ne, musamman a cikin shekarun 1970s, na sanyaya mai zuwa na Duniya wanda ya ƙare a cikin wani lokaci mai zurfi, saboda tasirin sanyaya na aerosols ko tilastawar orbital. Wasu rahotanni na manema labarai a cikin shekarun 1970 sun yi hasashe game da ci gaba da sanyaya; waɗannan ba su nuna ainihin wallafe-wallafen kimiyya na lokacin ba, wanda gabaɗaya ya fi damuwa da dumama daga ingantaccen tasirin greenhouse.

A tsakiyar shekarun 1970s, iyakantaccen jerin zafin jiki da ake samu ya nuna cewa zafin jiki ya ragu na shekaru da yawa har zuwa lokacin. Yayin da jerin lokaci masu tsawo na inganci mafi girma suka kasance, ya zama bayyananne cewa zafin jiki na duniya ya nuna karuwa mai yawa gaba ɗaya.

Gabatarwa: wayar da kan jama'a da damuwa 
A cikin shekarun 1970s, masana kimiyya sun kara fahimtar cewa kimantawa na yanayin zafi na duniya ya nuna sanyaya tun 1945, da kuma yiwuwar babban dumama saboda fitar da iskar gas. A cikin takardun kimiyya waɗanda suka yi la'akari da yanayin yanayi na karni na 21, ƙasa da kashi 10% sun karkata zuwa sanyaya na gaba, yayin da yawancin takardun suka yi hasashen dumama na gaba. Jama'a ba su da masaniya game da tasirin carbon dioxide akan yanayi, amma Labaran Kimiyya a watan Mayu 1959 sun yi hasashen karuwar kashi 25% a cikin carbon dioxide na yanayi a cikin shekaru 150 daga 1850 zuwa 2000, tare da yanayin dumama. Ainihin karuwa a wannan lokacin ya kasance 29%. Paul R. Ehrlich ya ambaci dumamar duniya daga iskar gas a matsayin mai hanawa ga tasirin sanyaya na aerosols a shekarar 1968. A lokacin da ra'ayin sanyaya duniya ya kai ga manema labarai a tsakiyar shekarun 1970 yanayin zafi ya daina faduwa, kuma akwai damuwa a cikin al'ummar yanayin yanayi game da tasirin zafi na carbon dioxide. A mayar da martani ga irin waɗannan rahotanni, Hukumar Kula da Yanayi ta Duniya ta ba da gargadi a watan Yunin 1976 cewa "wani gagarumin zafi na yanayi na duniya" mai yiwuwa ne.

A halin yanzu, akwai wasu damuwa game da yiwuwar tasirin sanyaya na yanki na raguwa ko rufewar yaduwar thermohaline, wanda zai iya haifar da karuwar ruwa mai kyau da ke haɗuwa a cikin Arewacin Atlantic saboda narkewar glacial. Ana ganin yiwuwar wannan ya faru a matsayin ƙasa sosai, kuma IPCC ta lura, "ko da a cikin samfuran inda THC ke raunana, har yanzu akwai dumi a Turai. Misali, a cikin duk haɗin AOGCM inda tilasta radiative ke ƙaruwa, alamar canjin zafin jiki a arewa maso yammacin Turai tana da kyau.

Hanyoyin jiki 
Lokacin sanyaya yana sakewa ta hanyar tsarin yanayi na duniya na yanzu (1999 a kan) wanda ya haɗa da tasirin jiki na sulfate aerosols, kuma yanzu akwai yarjejeniya ta gaba ɗaya cewa tasirin aerosol shine babban dalilin sanyaya na tsakiyar karni na 20. A lokacin akwai hanyoyin jiki guda biyu waɗanda aka fi ci gaba da su akai-akai don haifar da sanyaya: aerosols da tilasta orbital.

Aerosols 
 
Ayyukan ɗan adam - galibi a matsayin samfur na ƙonewar man fetur, wani ɓangare ta hanyar canje-canje na amfani da ƙasa - yana ƙara yawan ƙananan barbashi (aerosols) a cikin yanayi. Wadannan suna da tasiri kai tsaye: suna kara yawan albedo na duniya, don haka suna sanyaya duniya ta hanyar rage hasken rana da ya kai saman; da kuma sakamako na kai tsaye: sun shafi kaddarorin girgije ta hanyar aiki a matsayin ƙwayoyin girgije. A farkon shekarun 1970 wasu sun yi hasashen cewa wannan tasirin sanyaya na iya mamaye tasirin dumama na sakin CO2: duba tattaunawar Rasool da Schneider (1971), a ƙasa. A sakamakon lura da sauyawa zuwa ƙone mai tsabta, wannan ba zai yiwu ba; aikin kimiyya na yanzu yana nuna cewa dumamar duniya ya fi dacewa. Kodayake raguwar zafin jiki da wannan tsarin ya hango yanzu an watsar da shi saboda mafi kyawun ka'idar da kuma yanayin zafi da aka lura, ana zaton aerosols sun ba da gudummawa ga yanayin sanyaya (wanda ya fi ƙarfin karuwar iskar gas) kuma sun ba da damar dimming na duniya.

Matsi na Orbital 

Orbital tilasta yana nufin jinkirin, canje-canje na cyclical a cikin karkatawar axis na Duniya da kuma siffar ta. Wadannan sake zagayowar suna canza jimlar hasken rana da ke isa Duniya da karamin adadi kuma suna shafar lokaci da tsananin yanayi. Wannan hanyar ana zaton tana da alhakin lokacin sake zagayowar zamanin kankara, kuma fahimtar hanyar tana ƙaruwa cikin sauri a tsakiyar shekarun 1970.

Takardar Hays, Imbrie, da Shackleton "Variations in the Earth's Orbit: Pacemaker of the Ice Ages" sun cancanci tsinkayinsu tare da cewa "dole ne a cancanta hasashen ta hanyoyi biyu. Na farko, suna amfani ne kawai ga bangaren halitta na yanayin yanayi na gaba - kuma ba ga tasirin ɗan adam ba kamar waɗanda ke haifar da ƙone burbushin burbushin halittu. Na biyu, suna bayyana yanayin dogon lokaci ne kawai, saboda suna da alaƙa da bambance-bambance na orbital tare da lokutan shekaru 20,000 da tsayi. Ba a yi hasashen sauye-sauyen yanayi a mafi girma ba ... sakamakon ya nuna cewa yanayin dogon lokaci a cikin shekaru 20,000 masu zuwa yana zuwa ga babban glaciation na Arewacin Hemisphere da yanayin sanyi. "

Ra'ayin cewa za'a iya hango yanayin shekarun kankara da ra'ayin cewa wani ya kasance saboda "ba da daɗewa ba" - watakila saboda yawancin wannan binciken ya faru ne daga masana kimiyyar ƙasa, waɗanda suka saba da ma'amala da ma'auni na dogon lokaci kuma suna amfani da "ba da sauri" don komawa ga lokutan dubban shekaru. Aikace-aikacen ƙa'idar Milankovitch ba ya ba da damar tsinkaya na farkon shekarun kankara "da sauri" (watau, ƙasa da ƙarni ɗaya ko biyu) tunda lokacin da ya fi sauri ya kai kimanin shekaru 20,000. [ana buƙatar ƙa'ida] An sami wasu hanyoyin kirkirar wannan, musamman wanda Nigel Calder ya goyi bayan shi a ƙarƙashin sunan "snowblitz", amma waɗannan ra'ayoyin ba su sami karɓa sosai ba.

Ya zama ruwan dare a ga ya tabbatar da cewa tsawon yawan zafin jiki na yanzu yana kama da tsawon saman interglacial da ya gabata (Sangamon / Eem), kuma daga wannan kammalawa cewa muna iya kusantar ƙarshen wannan lokacin dumi. Wannan kammalawa ba daidai ba ne. Da farko, saboda tsawon interglacials na baya ba na yau da kullun ba ne; duba adadi. Petit et al. sun lura cewa "interglacials 5.5 da 9.3 sun bambanta da Holocene, amma suna kama da juna a tsawon lokaci, siffar da faɗin. A lokacin kowane ɗayan waɗannan abubuwan biyu, akwai lokacin dumi na 4 kyr wanda ya biyo bayan sanyaya mai sauri. " Abu na biyu, bambance-bambance na gaba ba za su yi kama da na baya ba.

Damuwa kafin shekarun 1970 
A cikin 1923, akwai damuwa game da sabon zamanin kankara kuma Kyaftin Donald Baxter MacMillan ya tashi zuwa Arctic wanda National Geographical Society ta tallafawa don neman shaidar ci gaba da kankara.

A cikin 1926, wani masanin taurari na Berlin yana hasashen sanyaya duniya amma cewa "tsufa" ne.

Damuwa cewa sabon zamanin kankara yana gabatowa an farfado da shi a cikin shekarun 1950. A lokacin Yakin Cold, Harry Wexler ya damu da cewa kashe bama-bamai na atom na iya hanzarta sabon zamanin kankara daga yanayin hunturu na nukiliya.

J. Murray Mitchell ya nuna tun farkon 1963 sanyaya da yawa tun daga 1940. A wani taro kan canjin yanayi da aka gudanar a Boulder, Colorado a shekarar 1965, shaidar da ke tallafawa sake zagayowar Milankovitch ta haifar da hasashe kan yadda aka lissafa ƙananan canje-canje a hasken rana na iya haifar da shekarun kankara. A cikin 1966, Cesare Emiliani ya yi hasashen cewa "sabon ƙanƙara zai fara cikin 'yan dubban shekaru". A cikin littafinsa na 1968 The Population Bomb, Paul R. Ehrlich ya rubuta "An inganta tasirin greenhouse yanzu ta hanyar karuwar matakin carbon dioxide ... [wannan] ana magance shi da girgije mai ƙarancin matakin da aka samar da ƙura, ƙura, da sauran gurɓataccen abu. A halin yanzu ba za mu iya hango abin da sakamakon yanayi zai kasance na amfani da yanayi a matsayin zubar da shara ba.

Damuwa a cikin shekarun 1970

Sanarwar shekarun 1970 
Damuwa ta kai kololuwa a farkon shekarun 1970s, kodayake " yiwuwar dumama ta mutum ta mamaye wallafe-wallafen da aka sake dubawa har ma a lokacin" (lokacin sanyaya ya fara a 1945, kuma shekaru ashirin na yanayin sanyaya ya nuna cewa an kai ga rami bayan shekaru da yawa na dumama). Wannan damuwa mai yawa ya kasance a wani bangare saboda gaskiyar cewa ba a san shi sosai ba game da yanayin duniya da abubuwan da ke haifar da shekarun kankara. Masana kimiyya na yanayi sun san cewa tsinkaya bisa ga wannan yanayin ba zai yiwu ba - saboda ba a yi nazarin yanayin sosai ba kuma ba a fahimta ba (alal misali duba bayanin). Duk da haka, a cikin shahararrun manema labarai an bayar da rahoton yiwuwar sanyaya gabaɗaya ba tare da gargadi da ke cikin rahotanni na kimiyya ba, kuma "ƙananan hunturu a Asiya da sassa na Arewacin Amurka a cikin 1972 da 1973 ... sun tura batun cikin sanin jama'a".

A cikin shekarun 1970s, tattara bayanan don samar da bayanan hemispheric, ko na duniya, sun fara.

Tarihin Spencer R. Weart na The Discovery of Global Warming ya ce: "Yayin da ba masana kimiyya ko jama'a ba za su iya tabbatarwa a cikin shekarun 1970s ko duniya tana da zafi ko sanyaya, mutane sun kara karkata suyi imani cewa yanayin duniya yana kan tafiya, kuma a kowace hanya ba" [an kara da hankali].

A ranar 11 ga watan Janairun shekara ta 1970, The Washington Post ta ruwaito cewa "Colder Winters Held Dawn of New Ice Age".

A shekara ta 1972, Emiliani ya yi gargadi cewa "Ayyukan Mutum na iya haifar da wannan sabon zamanin kankara ko kuma haifar da narkewar kankara".

Har ila yau, a cikin 1972, wani rukuni na masana na lokacin glacial a wani taro sun amince da cewa "ƙarshen yanayi na zamaninmu mai dumi tabbas yana kusa"; amma ƙarar Quaternary Research da ke bayar da rahoto game da taron ya ce "mahimmanci da za a samu daga tattaunawar a wannan sashe shi ne cewa ilimin da ake buƙata don fahimtar tsarin canjin yanayi har yanzu bai isa ba". George Kukla da Robert Matthews, a cikin rubuce-rubucen Kimiyya na wani taro, sun tambayi lokacin da kuma yadda interglacial na yanzu zai ƙare; sun kammala cewa, sai dai idan akwai tasiri daga ayyukan ɗan adam na gaba, "Zamara ta duniya da canje-canje masu sauri na muhalli, wanda ya wuce sauye-sauyen da mutum ya samu a lokutan tarihi, dole ne a sa ran su kasance a cikin 'yan dubban shekaru ko ma ƙarni masu zuwa", amma wasu masana kimiyya da yawa sun yi shakkar waɗannan ƙaddamarwa.

Rahoton SCEP na 1970 
Nazarin Matsalar Muhalli na 1970 ya ba da rahoton yiwuwar dumama daga karuwar carbon dioxide, amma babu damuwa game da sanyaya, yana saita ƙananan iyaka a farkon sha'awa a cikin "sanyi na duniya".

1971 zuwa 1975: takardu kan abubuwan dumi da sanyaya 
A shekara ta 1971, binciken ya nuna cewa gurɓataccen iska da mutum ya haifar yana yaduwa, amma akwai rashin tabbas game da ko aerosols zai haifar da dumi ko sanyaya, da kuma ko sun fi girma fiye da hauhawar matakan CO2. J. Murray Mitchell har yanzu yana kallon mutane a matsayin "masu kallo marasa laifi" a cikin sanyaya daga shekarun 1940 zuwa 1970, amma a cikin 1971 lissafinsa ya ba da shawarar cewa karuwar hayaki na iya haifar da sanyaya mai mahimmanci bayan 2000, kodayake ya kuma yi jayayya cewa hayaki na zai iya haifar da dumama dangane da yanayi. Ƙididdigar ta kasance mai mahimmanci a wannan lokacin don a amince da ita don ba da sakamako mai aminci.

An buga lissafin lambobi na farko na tasirin yanayi a cikin mujallar Science a watan Yulin 1971 a matsayin takarda ta S. Ichtiaque Rasool da Stephen H. Schneider, mai taken "Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate".
Takardar ta yi amfani da bayanai da daidaitattun bayanai don lissafin yiwuwar tasirin gaba na karuwa mai yawa a cikin yanayin nau'ikan hayakin muhalli guda biyu:

 iskar gas kamar carbon dioxide;
 gurɓataccen ƙwayoyin kamar su smog, wasu daga cikinsu sun kasance an dakatar da su a cikin yanayi a cikin nau'in aerosol na shekaru.

Rahoton hukumar na 1974, Kimiyya da kalubalen da ke gaba, ya ci gaba da wannan jigon. "A cikin shekaru 20-30 da suka gabata, yanayin zafin duniya ya ragu, ba bisa ka'ida ba a farko amma ya fi girma a cikin shekaru goma da suka gabata."  Tattaunawar lokutan dusar ƙanƙara ba ta bayyana a cikin wannan rahoton ba. A maimakon haka, rawar da mutane ke takawa ce ke kan gaba wajen nazarin rahoton. "Ba a san dalilin da yasa yanayin sanyaya ya kasance da tabbas ba. Amma ana ƙara nuna damuwa cewa mutum da kansa yana da hannu a ciki, ba wai kawai a yanayin sanyi na baya-bayan nan ba, har ma da yanayin zafi a ƙarnin da ya gabata.”  Rahoton bai kammala ba ko carbon dioxide a cikin dumamar yanayi, ko gurɓataccen aikin gona da masana'antu a cikin sanyaya, sune abubuwan da ke cikin sauye-sauyen yanayi na baya-bayan nan, lura da cewa; "Kafin a iya warware irin waɗannan tambayoyi kamar waɗannan, dole ne a sami babban ci gaba a cikin fahimtar sinadarai da kimiyyar lissafi na yanayi da teku, da kuma aunawa da gano abubuwan da ke cikin tsarin."

1972 da 1974 Hukumar Kimiyya ta Kasa 
Rahoton Hukumar Kimiyya ta Kasa da Perspectives a cikin Kimiyya ta Muhalli na 1972 sun tattauna game da halayyar yanayi, da kuma fahimtar lokacin da duniyar ke shiga wani lokaci na sanyaya bayan lokacin dumi. "A yin hukunci daga rikodin shekarun interglacial da suka gabata, lokacin yanzu na yanayin zafi ya kamata ya ƙare, don a bi shi da dogon lokaci na yanayin sanyi wanda ke haifar da zamanin glacial na gaba kimanin shekaru 20,000 daga yanzu. " Amma kuma ya ci gaba; "Duk da haka, yana yiwuwa, ko ma mai yiwuwa, cewa tsangwama ta mutum ta riga ta canza yanayin da ke kusa da nan gaba zai bi wata hanya daban. "

Rahoton hukumar na 1974, Kimiyya da kalubalen da ke gaba, ya ci gaba da wannan jigon. "A cikin shekaru 20-30 da suka gabata, yanayin zafin duniya ya ragu, ba bisa ka'ida ba a farko amma ya fi girma a cikin shekaru goma da suka gabata."  Tattaunawar lokutan dusar ƙanƙara ba ta bayyana a cikin wannan rahoton ba. A maimakon haka, rawar da mutane ke takawa ce ke kan gaba wajen nazarin rahoton. "Ba a san dalilin da yasa yanayin sanyaya ya kasance da tabbas ba. Amma ana ƙara nuna damuwa cewa mutum da kansa yana da hannu a ciki, ba wai kawai a yanayin sanyi na baya-bayan nan ba, har ma da yanayin zafi a ƙarnin da ya gabata.”  Rahoton bai kammala ba ko carbon dioxide a cikin dumamar yanayi, ko gurɓataccen aikin gona da masana'antu a cikin sanyaya, sune abubuwan da ke cikin sauye-sauyen yanayi na baya-bayan nan, lura da cewa; "Kafin a iya warware irin waɗannan tambayoyi kamar waɗannan, dole ne a sami babban ci gaba a cikin fahimtar sinadarai da kimiyyar lissafi na yanayi da teku, da kuma aunawa da gano abubuwan da ke cikin tsarin."

Rahoton Cibiyar Kimiyya ta Kasa ta 1975 
There also was a Report by the U.S. National Academy of Sciences (NAS) entitled, "Understanding Climate Change: A Program for Action".
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