Foydalanuvchi:Anjaniy/qumloq

Soʻnggi global isish sabablari

Hozirgacha sodir bo'lgan global isishning jismoniy omillari. Karbonat angidrid emissiyasi kabi uzoq umr ko'rgan haydovchilar uchun kelajakdagi global isish potentsiali ko'rsatilmagan. Har bir satrdagi mo'ylovlar mumkin bo'lgan xato diapazonini ko'rsatadi. Physical drivers of global warming that has happened so far. Future global warming potential for long lived drivers like carbon dioxide emissions is not represented. Whiskers on each bar show the possible error range.

Iqlim tizimi o'z-o'zidan turli xil tsikllarni boshdan kechiradi, ular yillar, o'nlab yillar va hatto asrlar davom etishi mumkin. Misol uchun, El Niño hodisalari sirt haroratining qisqa muddatli ko'tarilishiga olib keladi, La Niña hodisalari esa qisqa muddatli sovutishga olib keladi.[1] Ularning nisbiy chastotasi o'n yillik vaqt oralig'ida global harorat tendentsiyalariga ta'sir qilishi mumkin.[2] Boshqa o'zgarishlar energiyaning tashqi ta'sirlardan kelib chiqadigan nomutanosibligidan kelib chiqadi.[3] Bunga issiqxona gazlari kontsentratsiyasining o'zgarishi, quyosh nuri, vulqon otilishi va Yerning Quyosh atrofidagi orbitasidagi o'zgarishlar misol bo'ladi.[4]

The climate system experiences various cycles on its own which can last for years, decades or even centuries. For example, El Niño events cause short-term spikes in surface temperature while La Niña events cause short term cooling. Their relative frequency can affect global temperature trends on a decadal timescale. Other changes are caused by an imbalance of energy from external forcings. Examples of these include changes in the concentrations of greenhouse gases, solar luminosity, volcanic eruptions, and variations in the Earth’s orbit around the Sun.

Insonning iqlim o'zgarishiga qo'shgan hissasini aniqlash uchun barcha mumkin bo'lgan sabablar uchun noyob "barmoq izlari" ishlab chiqiladi va kuzatilgan naqshlar va ma'lum ichki iqlim o'zgaruvchanligi bilan solishtiriladi.[5] Masalan, barmoq izi butun atmosferani isitishni o'z ichiga olgan quyosh quvvati inkor etiladi, chunki faqat atmosferaning pastki qismi isib ketgan.[6] Atmosfera aerozollari kichikroq, sovutish effektini hosil qiladi. Boshqa drayverlar, masalan, albedodagi o'zgarishlar kamroq ta'sir qiladi.[7]

To determine the human contribution to climate change, unique „fingerprints“ for all potential causes are developed and compared with both observed patterns and known internal climate variability. For example, solar forcing—whose fingerprint involves warming the entire atmosphere—is ruled out because only the lower atmosphere has warmed. Atmospheric aerosols produce a smaller, cooling effect. Other drivers, such as changes in albedo, are less impactful.

Issiqxona gazlari

Asosiy sahifa: Issiqxona gazlari va Issiqxona effekti

Andoza: so'nggi 800 000 yildagi CO2 kontsentratsiyasi muz yadrolari (ko'k/yashil) va to'g'ridan-to'g'ri (qora) Andoza:CO2 concentrations over the last 800,000 years as measured from ice cores (blue/green) and directly (black)

Issiqxona gazlari quyosh nurlari uchun shaffofdir va shuning uchun uning Yer yuzasini isitish uchun atmosferadan o'tishiga imkon beradi. Yer uni issiqlik sifatida chiqaradi va issiqxona gazlari uning bir qismini o'zlashtiradi. Bu yutilish issiqlikning koinotga chiqish tezligini sekinlashtiradi, issiqlikni Yer yuzasi yaqinida ushlab turadi va vaqt o'tishi bilan uni isitadi.[8]

Greenhouse gases are transparent to sunlight, and thus allow it to pass through the atmosphere to heat the Earth’s surface. The Earth radiates it as heat, and greenhouse gases absorb a portion of it. This absorption slows the rate at which heat escapes into space, trapping heat near the Earth’s surface and warming it over time.

Suv bug'lari (≈50%) va bulutlar (≈25%) issiqxona effektiga eng katta hissa qo'shsa-da, ular birinchi navbatda harorat funktsiyasi sifatida o'zgaradi va shuning uchun asosan iqlim sezgirligini o'zgartiruvchi teskari aloqalar hisoblanadi. Boshqa tomondan, Andoza:CO2 (≈20%), troposfera ozon, [9] CFC va azot oksidi kabi gazlarning kontsentratsiyasi haroratdan mustaqil ravishda qo'shiladi yoki chiqariladi va shuning uchun global haroratni o'zgartiruvchi tashqi ta'sirlar hisoblanadi. [10]

While water vapour (≈50%) and clouds (≈25%) are the biggest contributors to the greenhouse effect, they primarily change as a function of temperature and are therefore mostly considered to be feedbacks that change climate sensitivity. On the other hand, concentrations of gases such as Andoza:CO2 (≈20%), tropospheric ozone, CFCs and nitrous oxide are added or removed independently from temperature, and are therefore considered to be external forcings that change global temperatures.

Sanoat inqilobidan oldin, tabiiy ravishda paydo bo'lgan issiqxona gazlari miqdori yer yuzasiga yaqin havo ular yo'qligidan taxminan 33 °C issiqroq bo'lishiga olib keldi.[11][12] Sanoat inqilobidan keyin inson faoliyati, asosan, qazib olinadigan yoqilg'i (ko'mir, neft va tabiiy gaz) [13] qazib olish va yoqish atmosferadagi issiqxona gazlari miqdorini oshirdi. 2022 yilda Andoza:CO2 va metan kontsentratsiyasi 1750 yildan beri mos ravishda taxminan 50% va 164% ga oshgan.[14] Bu Andoza: CO2 darajalari so'nggi 14 million yil davomidagidan yuqori.[15] Metan kontsentratsiyasi oxirgi 800 000 yildagidan ancha yuqori.[16]

Before the Industrial Revolution, naturally-occurring amounts of greenhouse gases caused the air near the surface to be about 33 °C warmer than it would have been in their absence. Human activity since the Industrial Revolution, mainly extracting and burning fossil fuels (coal, oil, and natural gas), has increased the amount of greenhouse gases in the atmosphere. In 2022, the [[Carbon dioxide in Earth's atmosphere|concentrations of Andoza:CO2]] and methane had increased by about 50% and 164%, respectively, since 1750. These Andoza:CO2 levels are higher than they have been at any time during the last 14 million years. Concentrations of methane are far higher than they were over the last 800,000 years.

Global uglerod loyihasi 1880 yildan beri Andoza: CO2 ga qo'shilgan turli manbalar birin-ketin kuchayib borayotganini ko'rsatadi. The Global Carbon Project shows how additions to Andoza:CO2 since 1880 have been caused by different sources ramping up one after another.

2019-yilda inson tomonidan ishlab chiqarilgan issiqxona gazlarining global emissiyasi 59 milliard tonna Andoza:CO2 ga teng edi. Bu chiqindilarning 75% Andoza:CO2, 18% metan, 4% azot oksidi va 2% ftorli gazlar edi.[17] Andoza: CO2 emissiyasi asosan transport, ishlab chiqarish, isitish va elektr energiyasini ta'minlash uchun qazib olinadigan yoqilg'ilarni yoqishdan kelib chiqadi.[18] Qoʻshimcha Andoza:CO2 emissiyasi oʻrmonlarni kesish va sanoat jarayonlaridan kelib chiqadi, jumladan tsement, poʻlat, alyuminiy va oʻgʻit ishlab chiqarish uchun kimyoviy reaksiyalar natijasida ajralib chiqadigan Andoza:CO2.[19][20][21][22] Metan chiqindilari chorvachilik, goʻng, sholi yetishtirish, chiqindixonalar, oqava suvlar va koʻmir qazib olish, shuningdek, neft va gaz qazib olish natijasida hosil boʻladi[23][24]. Azot oksidi emissiyasi asosan oʻgʻitning mikrobial parchalanishidan kelib chiqadi.[25][26]

Global human-caused greenhouse gas emissions in 2019 were equivalent to 59 billion tonnes of Andoza:CO2. Of these emissions, 75% was Andoza:CO2, 18% was methane, 4% was nitrous oxide, and 2% was fluorinated gases. Andoza:CO2 emissions primarily come from burning fossil fuels to provide energy for transport, manufacturing, heating, and electricity. Additional Andoza:CO2 emissions come from deforestation and industrial processes, which include the Andoza:CO2 released by the chemical reactions for making cement, steel, aluminum, and fertilizer. Methane emissions come from livestock, manure, rice cultivation, landfills, wastewater, and coal mining, as well as oil and gas extraction. Nitrous oxide emissions largely come from the microbial decomposition of fertilizer.

Metan atmosferada o'rtacha 12 yil davom etsa-da,[27] Andoza:CO2 ancha uzoqroq turadi. Er yuzasi uglerod aylanishining bir qismi sifatida Andoza: CO2 ni o'zlashtiradi. Quruqlikdagi va okeandagi o'simliklar har yili Andoza:CO2 ning ortiqcha emissiyasini o'zlashtirsa-da, biologik moddalar hazm bo'lganda, yonganda yoki parchalanib ketganda, o'sha Andoza:CO2 atmosferaga qaytadi.[28] Tuproqda uglerod fiksatsiyasi va fotosintez kabi quruqlikdagi uglerodning cho'kishi jarayonlari yillik global Andoza: CO2 emissiyasining taxminan 29% ni olib tashlaydi.[29] Okean so'nggi yigirma yil ichida chiqarilgan Andoza:CO2 ning 20-30% ni o'zlashtirgan.[30] Andoza: CO2 atmosferadan faqat Yer qobig'ida saqlanganida uzoq muddatga chiqariladi, bu jarayon millionlab yillar davom etishi mumkin.[28]

While methane only lasts in the atmosphere for an average of 12 years, Andoza:CO2 lasts much longer. The Earth’s surface absorbs Andoza:CO2 as part of the carbon cycle. While plants on land and in the ocean absorb most excess emissions of Andoza:CO2 every year, that Andoza:CO2 is returned to the atmosphere when biological matter is digested, burns, or decays. Land-surface carbon sink processes, such as carbon fixation in the soil and photosynthesis, remove about 29% of annual global Andoza:CO2 emissions. The ocean has absorbed 20 to 30% of emitted Andoza:CO2 over the last two decades. Andoza:CO2 is only removed from the atmosphere for the long term when it is stored in the Earth’s crust, which is a process that can take millions of years to complete.

Yer yuzasidagi oʻzgarishlar

2001 yildan beri global daraxt qoplamini yo'qotish darajasi taxminan ikki baravar ko'paydi va yillik yo'qotish Italiyaning kattaligiga yaqinlashdi.[31] The rate of global tree cover loss has approximately doubled since 2001, to an annual loss approaching an area the size of Italy.

Yer yuzidagi yer maydonining 30% ga yaqini odamlar uchun yaroqsiz (muzliklar, choʻllar va boshqalar), 26% oʻrmonlar, 10% butazorlar va 34% qishloq xoʻjaligi yerlaridir.[32] O'rmonlarning kesilishi global isishning asosiy er o'zgarishiga hissa qo'shadigan asosiy omildir[33], chunki vayron qilingan daraxtlar Andoza:CO2 ni chiqaradi va ularning o'rniga yangi daraxtlar qolmaydi, bu esa uglerod cho'kmasini olib tashlaydi.[34] 2001 yildan 2018 yilgacha bo'lgan davrda o'rmonlarning kesilishining 27 foizi qishloq xo'jaligini ekinlar va chorvachilik uchun kengaytirishga imkon berish uchun doimiy tozalash natijasida sodir bo'ldi. Yana 24% o'zgaruvchan qishloq xo'jaligi tizimlarida vaqtincha tozalash uchun yo'qolgan. 26% yog'och va undan tayyorlangan mahsulotlar uchun daraxt kesish bilan bog'liq bo'lsa, qolgan 23% o'rmon yong'inlari hissasiga to'g'ri keldi.[35] Ba'zi o'rmonlar to'liq tozalanmagan, ammo bu ta'sirlar tufayli allaqachon buzilgan. Bu o'rmonlarni qayta tiklash ularning uglerod cho'kmasi sifatidagi salohiyatini ham tiklaydi.[36]

Around 30% of Earth’s land area is largely unusable for humans (glaciers, deserts, etc.), 26% is forests, 10% is shrubland and 34% is agricultural land. Deforestation is the main land use change contributor to global warming, as the destroyed trees release Andoza:CO2, and are not replaced by new trees, removing that carbon sink. Between 2001 and 2018, 27% of deforestation was from permanent clearing to enable agricultural expansion for crops and livestock. Another 24% has been lost to temporary clearing under the shifting cultivation agricultural systems. 26% was due to logging for wood and derived products, and wildfires have accounted for the remaining 23%. Some forests have not been fully cleared, but were already degraded by these impacts. Restoring these forests also recovers their potential as a carbon sink.

Mahalliy o'simliklar qoplami quyosh nurlarining qancha qismi kosmosga qaytarilishiga (albedo) va bug'lanish natijasida qancha issiqlik yo'qolishiga ta'sir qiladi. Misol uchun, qorong'i o'rmondan o'tloqqa o'tish sirtni engilroq qiladi va quyosh nurini ko'proq aks ettiradi. Oʻrmonlarni kesish bulutlarga taʼsir etuvchi kimyoviy birikmalarning chiqarilishini ham oʻzgartirishi mumkin va shamol shakllarini oʻzgartirishi mumkin.[37] Tropik va motadil hududlarda aniq ta'sir sezilarli darajada isishni keltirib chiqaradi va o'rmonlarni qayta tiklash mahalliy haroratni salqinlashi mumkin.[36] Qutblarga yaqinroq boʻlgan kengliklarda oʻrmonlar oʻrnini qor bilan qoplangan (va koʻproq aks ettiruvchi) tekisliklar egallaganligi sababli sovutish effekti mavjud.[37] Global miqyosda, yer usti albedosining bu o'sishi erdan foydalanishning o'zgarishi natijasida haroratga bevosita ta'sir ko'rsatadi. Shunday qilib, hozirgi kunga qadar erdan foydalanishning o'zgarishi biroz sovutish effektiga ega bo'lishi taxmin qilinmoqda.[38]

Local vegetation cover impacts how much of the sunlight gets reflected back into space (albedo), and how much heat is lost by evaporation. For instance, the change from a dark forest to grassland makes the surface lighter, causing it to reflect more sunlight. Deforestation can also modify the release of chemical compounds that influence clouds, and by changing wind patterns. In tropic and temperate areas the net effect is to produce significant warming, and forest restoration can make local temperatures cooler. At latitudes closer to the poles, there is a cooling effect as forest is replaced by snow-covered (and more reflective) plains. Globally, these increases in surface albedo have been the dominant direct influence on temperature from land use change. Thus, land use change to date is estimated to have a slight cooling effect.

Boshqa omillar

Aerozol va bulutlar

Aerozollar shaklida havoning ifloslanishi iqlimga keng miqyosda ta'sir qiladi.[39] Aerozollar quyosh nurlarini sochadi va yutadi. 1961 yildan 1990 yilgacha Yer yuzasiga keladigan quyosh nuri miqdorining bosqichma-bosqich kamayishi kuzatildi. Bu hodisa xalq orasida global karartma sifatida tanilgan [40] va birinchi navbatda ko'mir va bunker yoqilg'isi kabi og'ir oltingugurt kontsentratsiyasiga ega bo'lgan qazib olinadigan yoqilg'ining yonishi natijasida hosil bo'lgan sulfat aerozollari bilan bog'liq.[41] Kichikroq hissalar qora ugleroddan (qazib olinadigan yoqilg'i va biomassaning yonishidan) va changdan keladi.[42][43][44] Global miqyosda aerozollar 1990 yildan beri ifloslanish nazorati tufayli kamayib bormoqda, ya'ni ular endi issiqxona gazlarining isishini unchalik yashirmaydilar.[45][41]

Air pollution, in the form of aerosols, affects the climate on a large scale. Aerosols scatter and absorb solar radiation. From 1961 to 1990, a gradual reduction in the amount of sunlight reaching the Earth’s surface was observed. This phenomenon is popularly known as global dimming, and is primarily attributed to sulfate aerosols produced by the combustion of fossil fuels with heavy sulfur concentrations like coal and bunker fuel. Smaller contributions come from black carbon (from combustion of fossil fuels and biomass), and from dust. Globally, aerosols have been declining since 1990 due to pollution controls, meaning that they no longer mask greenhouse gas warming as much.

Aerozollar Yerning energiya byudjetiga ham bilvosita ta'sir ko'rsatadi. Sulfat aerozollari bulutli kondensatsiya yadrolari rolini o'ynaydi va ko'proq va kichikroq bulut tomchilari bo'lgan bulutlarga olib keladi. Bu bulutlar quyosh nurlanishini kamroq va kattaroq tomchilar bilan bulutlarga qaraganda samaraliroq aks ettiradi.[46] Ular, shuningdek, yomg'ir tomchilarining o'sishini kamaytiradi, bu esa bulutlarni kiruvchi quyosh nurini ko'proq aks ettiradi.[47] Aerozollarning bilvosita ta'siri radiatsiyaviy majburlashdagi eng katta noaniqlikdir.[48]

Aerosols also have indirect effects on the Earth's energy budget. Sulfate aerosols act as cloud condensation nuclei and lead to clouds that have more and smaller cloud droplets. These clouds reflect solar radiation more efficiently than clouds with fewer and larger droplets. They also reduce the growth of raindrops, which makes clouds more reflective to incoming sunlight. Indirect effects of aerosols are the largest uncertainty in radiative forcing.

Aerozollar odatda quyosh nurini aks ettirish orqali global isishni cheklasa-da, qor yoki muzga tushgan qora uglerod global isishga hissa qo'shishi mumkin. Bu nafaqat quyosh nurlarining yutilishini oshiradi, balki erish va dengiz sathining ko'tarilishini ham oshiradi.[49] Arktikadagi yangi qora uglerod konlarini cheklash 2050 yilga kelib global isishni 0,2 °C ga kamaytirishi mumkin.[50] 2020 yildan beri kemalar uchun mazut tarkibidagi oltingugurt miqdorining pasayishi [51] taʼsiri 2050 yilga kelib global oʻrtacha haroratning qoʻshimcha 0,05 °C oshishiga olib kelishi taxmin qilinmoqda.[52]

While aerosols typically limit global warming by reflecting sunlight, black carbon in soot that falls on snow or ice can contribute to global warming. Not only does this increase the absorption of sunlight, it also increases melting and sea-level rise. Limiting new black carbon deposits in the Arctic could reduce global warming by 0.2 °C by 2050. The effect of decreasing sulfur content of fuel oil for ships since 2020 is estimated to cause an additional 0.05 °C increase in global mean temperature by 2050.

Quyosh va vulqon harakati

Toʻrtinchi Milliy iqlim bahosi (“NCA4”, USGCRP, 2017) na quyosh, na vulqon faolligi kuzatilgan isishni tushuntira olmasligini koʻrsatadigan jadvallarni oʻz ichiga oladi.[53][54] The Fourth National Climate Assessment („NCA4“, USGCRP, 2017) includes charts illustrating that neither solar nor volcanic activity can explain the observed warming.

Quyosh Yerning asosiy energiya manbai bo'lgani uchun, kiruvchi quyosh nurlarining o'zgarishi iqlim tizimiga bevosita ta'sir qiladi.[48] Quyosh nurlanishi to'g'ridan-to'g'ri sun'iy yo'ldoshlar tomonidan o'lchangan[55] va bilvosita o'lchovlar 1600-yillarning boshidan boshlab mavjud.[48]. 1880 yildan beri atmosferaning quyi qatlamlari (troposfera) isishidan farqli o'laroq, Quyosh energiyasining Yerga yetib borishida o'sish tendentsiyasi kuzatilmadi.[56] Agar Quyosh Yerga ko'proq energiya yuborgan bo'lsa, atmosferaning yuqori qatlami (stratosfera) ham isinar edi, lekin buning o'rniga u soviydi.[6] Bu issiqlikning Yer atmosferasini tark etishiga to'sqinlik qiladigan issiqxona gazlari bilan mos keladi.[57]

As the Sun is the Earth’s primary energy source, changes in incoming sunlight directly affect the climate system. Solar irradiance has been measured directly by satellites, and indirect measurements are available from the early 1600s onwards. Since 1880, there has been no upward trend in the amount of the Sunʼs energy reaching the Earth, in contrast to the warming of the lower atmosphere (the troposphere). The upper atmosphere (the stratosphere) would also be warming if the Sun was sending more energy to Earth, but instead, it has been cooling. This is consistent with greenhouse gases preventing heat from leaving the Earth’s atmosphere.

Portlovchi vulqon otilishi quyosh nurini qisman to‘sib qo‘yadigan va haroratni pasaytiradigan gazlar, chang va kullarni chiqarishi yoki atmosferaga issiqxona gazlarini qo‘shib, haroratni oshiradigan suv bug‘ini yuborishi mumkin.[58] Haroratga bu ta'sirlar faqat bir necha yil davom etadi, chunki suv bug'lari ham, vulkanik moddalar ham atmosferada past chidamlilikka ega.[59] Vulkanik Andoza:CO2 emissiyalari barqarorroqdir, lekin ular hozirgi insoniyat tomonidan ishlab chiqarilgan Andoza:CO2 emissiyasining 1% dan kamiga teng.[60] Vulqon faolligi hali ham sanoat davridagi haroratga eng katta tabiiy ta'sirni (majburiy) ifodalaydi. Biroq, boshqa tabiiy majburlashlar singari, u sanoat inqilobidan beri global harorat tendentsiyalariga ahamiyatsiz ta'sir ko'rsatdi.[59]

Explosive volcanic eruptions can release gases, dust and ash that partially block sunlight and reduce temperatures, or they can send water vapour into the atmosphere, which adds to greenhouse gases and increases temperatures. These impacts on temperature only last for several years, because both water vapour and volcanic material have low persistence in the atmosphere. [[Volcanic gas|volcanic Andoza:CO2 emissions]] are more persistent, but they are equivalent to less than 1% of current human-caused Andoza:CO2 emissions. Volcanic activity still represents the single largest natural impact (forcing) on temperature in the industrial era. Yet, like the other natural forcings, it has had negligible impacts on global temperature trends since the Industrial Revolution.

Iqlim oʻzgarishi yuzasidan fikr-mulohazalar

Dengiz muzlari kiruvchi quyosh nurlarining 50% dan 70% gacha, okean esa qorong'i bo'lib, faqat 6% ni aks ettiradi. Dengiz muzlari hududi erishi va okeanni ko'proq ochishi sababli, okean tomonidan ko'proq issiqlik so'riladi va harorat ko'tariladi, bu esa ko'proq muzni eritadi. Bu ijobiy fikr bildirish jarayonidir.[61] Sea ice reflects 50% to 70% of incoming sunlight, while the ocean, being darker, reflects only 6%. As an area of sea ice melts and exposes more ocean, more heat is absorbed by the ocean, raising temperatures that melt still more ice. This is a positive feedback process.

Iqlim tizimining dastlabki kuchga bo'lgan munosabati o'zgarishlarni kuchaytiradigan yoki susaytiradigan qayta aloqa orqali shakllanadi. O'z-o'zini mustahkamlovchi yoki ijobiy fikr-mulohazalar javobni oshiradi, muvozanatlashtiruvchi yoki salbiy fikr-mulohazalar esa uni kamaytiradi.[62] Asosiy mustahkamlovchi fikr-mulohazalar suv-bugʻi, muz-albedo teskari aloqasi va bulutlarning aniq taʼsiridir.[63][64] Muvozanatning asosiy mexanizmi radiatsion sovutishdir, chunki Yer yuzasi haroratning oshishiga javoban kosmosga ko'proq issiqlik beradi.[65] Harorat bilan bog'liq fikr-mulohazalar bilan bir qatorda, uglerod aylanishida Andoza:CO2 ning o'simliklarning o'sishiga o'g'itlash ta'siri kabi fikrlar mavjud.[66] Iqlim sezgirligini oshirib, issiqxona gazlari emissiyasi davom etar ekan, fikr-mulohazalar ijobiy tomonga o'zgarishi kutilmoqda.[67]

The climate system’s response to an initial forcing is shaped by feedbacks, which either amplify or dampen the change. Self-reinforcing or positive feedbacks increase the response, while balancing or negative feedbacks reduce it. The main reinforcing feedbacks are the water-vapour feedback, the ice–albedo feedback, and the net effect of clouds. The primary balancing mechanism is radiative cooling, as Earth’s surface gives off more heat to space in response to rising temperature. In addition to temperature feedbacks, there are feedbacks in the carbon cycle, such as the fertilizing effect of Andoza:CO2 on plant growth. Feedbacks are expected to trend in a positive direction as greenhouse gas emissions continue, raising climate sensitivity.

Ushbu qayta aloqa jarayonlari global isish tezligini o'zgartiradi. Misol uchun, issiqroq havo suv bug'i shaklida ko'proq namlikni ushlab turishi mumkin, bu o'zi kuchli issiqxona gazidir.[63] Issiqroq havo bulutlarni balandroq va ingichka qilib qo'yishi mumkin, shuning uchun ham iqlim isishini oshiradi.[68] Arktikadagi qor qoplami va dengiz muzlarining qisqarishi yana bir muhim fikr bo'lib, bu mintaqadagi Yer yuzasining aks ettirish qobiliyatini pasaytiradi va Arktikaning isishini tezlashtiradi.[69][70] Bu qo'shimcha isish atmosferaga metan va Andoza:CO2 ni chiqaradigan abadiy muzlik erishiga ham hissa qo'shadi.[71]

These feedback processes alter the pace of global warming. For instance, warmer air can hold more moisture in the form of water vapour, which is itself a potent greenhouse gas. Warmer air can also make clouds higher and thinner, and therefore more insulating, increasing climate warming. The reduction of snow cover and sea ice in the Arctic is another major feedback, this reduces the reflectivity of the Earth’s surface in the region and accelerates Arctic warming. This additional warming also contributes to permafrost thawing, which releases methane and Andoza:CO2 into the atmosphere.

Andoza: CO2 emissiyasining qariyb yarmi quruqlikdagi oʻsimliklar va okeanlar tomonidan soʻriladi. quruqlikda va tuproqlar issiqroq bo'lganda o'lik o'simliklardan ko'proq uglerod chiqaradi.[72][73] Okeanlarning atmosfera uglerodini yutish tezligi pasayadi, chunki ular ko'proq kislotali bo'lib, termohalin aylanishi va fitoplankton taqsimotida o'zgarishlar yuz beradi.[74][75][76] Fikr-mulohazalarga nisbatan noaniqlik, xususan, bulut qoplami [77], turli iqlim modellari ma'lum miqdordagi emissiya uchun har xil issiqlik kattaliklarini loyihalashining asosiy sababidir.[78]

Around half of human-caused Andoza:CO2 emissions have been absorbed by land plants and by the oceans. This is because climate change increases droughts and heat waves that eventually inhibit plant growth on land, and soils will release more carbon from dead plants when they are warmer. The rate at which oceans absorb atmospheric carbon will be lowered as they become more acidic and experience changes in thermohaline circulation and phytoplankton distribution. Uncertainty over feedbacks, particularly cloud cover, is the major reason why different climate models project different magnitudes of warming for a given amount of emissions.

Modelling

Energy flows between space, the atmosphere, and Earth’s surface. Most sunlight passes through the atmosphere to heat the Earth’s surface, then greenhouse gases absorb most of the heat the Earth radiates in response. Adding to greenhouse gases increases this insulating effect, causing an energy imbalance that heats the planet up.

A climate model is a representation of the physical, chemical and biological processes that affect the climate system. Models include natural processes like changes in the Earth’s orbit, historical changes in the Sunʼs activity, and volcanic forcing. Models are used to estimate the degree of warming future emissions will cause when accounting for the strength of climate feedbacks. Models also predict the circulation of the oceans, the annual cycle of the seasons, and the flows of carbon between the land surface and the atmosphere.

The physical realism of models is tested by examining their ability to simulate current or past climates. Past models have underestimated the rate of Arctic shrinkage and underestimated the rate of precipitation increase. Sea level rise since 1990 was underestimated in older models, but more recent models agree well with observations. The 2017 United States-published National Climate Assessment notes that „climate models may still be underestimating or missing relevant feedback processes“. Additionally, climate models may be unable to adequately predict short-term regional climatic shifts.

A subset of climate models add societal factors to a physical climate model. These models simulate how population, economic growth, and energy use affect—and interact with—the physical climate. With this information, these models can produce scenarios of future greenhouse gas emissions. This is then used as input for physical climate models and carbon cycle models to predict how atmospheric concentrations of greenhouse gases might change. Depending on the socioeconomic scenario and the mitigation scenario, models produce atmospheric Andoza:CO2 concentrations that range widely between 380 and 1400 ppm.

Impacts

Asosiy sahifa: Effects of climate change

The sixth IPCC Assessment Report projects changes in average soil moisture at 2.0 °C of warming, as measured in standard deviations from the 1850 to 1900 baseline.

Environmental effects

The environmental effects of climate change are broad and far-reaching, affecting oceans, ice, and weather. Changes may occur gradually or rapidly. Evidence for these effects comes from studying climate change in the past, from modelling, and from modern observations. Since the 1950s, droughts and heat waves have appeared simultaneously with increasing frequency. Extremely wet or dry events within the monsoon period have increased in India and East Asia. Monsoonal precipitation over the Northern Hemisphere has increased since 1980. The rainfall rate and intensity of hurricanes and typhoons is likely increasing, and the geographic range likely expanding poleward in response to climate warming. Frequency of tropical cyclones has not increased as a result of climate change.

Historical sea level reconstruction and projections up to 2100 published in 2017 by the U. S. Global Change Research Program

Global sea level is rising as a consequence of thermal expansion and the melting of glaciers and ice sheets. Sea level rise has increased over time, reaching 4.8 cm per decade between 2014 and 2023. Over the 21st century, the IPCC projects 32–62 cm of sea level rise under a low emission scenario, 44–76 cm under an intermediate one and 65–101 cm under a very high emission scenario. Marine ice sheet instability processes in Antarctica may add substantially to these values, including the possibility of a 2-meter sea level rise by 2100 under high emissions.

Climate change has led to decades of shrinking and thinning of the Arctic sea ice. While ice-free summers are expected to be rare at 1.5 °C degrees of warming, they are set to occur once every three to ten years at a warming level of 2 °C. Higher atmospheric Andoza:CO2 concentrations cause more Andoza:CO2 to dissolve in the oceans, which is making them more acidic. Because oxygen is less soluble in warmer water, its concentrations in the ocean are decreasing, and dead zones are expanding.

Tipping points and long-term impacts

Different levels of global warming may cause different parts of Earth’s climate system to reach tipping points that cause transitions to different states.

Asosiy sahifa: Tipping points in the climate system

Greater degrees of global warming increase the risk of passing through 'tipping points'—thresholds beyond which certain major impacts can no longer be avoided even if temperatures return to their previous state. For instance, the Greenland ice sheet is already melting, but if global warming reaches levels between 1.7 °C and 2.3 °C, its melting will continue until it fully disappears. If the warming is later reduced to 1.5 °C or less, it will still lose a lot more ice than if the warming was never allowed to reach the threshold in the first place. While the ice sheets would melt over millennia, other tipping points would occur faster and give societies less time to respond. The collapse of major ocean currents like the Atlantic meridional overturning circulation (AMOC), and irreversible damage to key ecosystems like the Amazon rainforest and coral reefs can unfold in a matter of decades.

The long-term effects of climate change on oceans include further ice melt, ocean warming, sea level rise, ocean acidification and ocean deoxygenation. The timescale of long-term impacts are centuries to millennia due to Andoza:CO2's long atmospheric lifetime. The result is an estimated total sea level rise of 2.3 metr / degree Celsius (4.2 ft/°F) after 2000 years. Oceanic Andoza:CO2 uptake is slow enough that ocean acidification will also continue for hundreds to thousands of years. Deep oceans (below 2,000 metr (6,600 ft)) are also already committed to losing over 10% of their dissolved oxygen by the warming which occurred to date. Further, the West Antarctic ice sheet appears committed to practically irreversible melting, which would increase the sea levels by at least 3.3 m (10 ft 10 in) over approximately 2000 years.

Nature and wildlife

Recent warming has driven many terrestrial and freshwater species poleward and towards higher altitudes. For instance, the range of hundreds of North American birds has shifted northward at an average rate of 1.5 km/year over the past 55 years. Higher atmospheric Andoza:CO2 levels and an extended growing season have resulted in global greening. However, heatwaves and drought have reduced ecosystem productivity in some regions. The future balance of these opposing effects is unclear. A related phenomenon driven by climate change is woody plant encroachment, affecting up to 500 million hectares globally. Climate change has contributed to the expansion of drier climate zones, such as the expansion of deserts in the subtropics. The size and speed of global warming is making abrupt changes in ecosystems more likely. Overall, it is expected that climate change will result in the extinction of many species.

The oceans have heated more slowly than the land, but plants and animals in the ocean have migrated towards the colder poles faster than species on land. Just as on land, heat waves in the ocean occur more frequently due to climate change, harming a wide range of organisms such as corals, kelp, and seabirds. Ocean acidification makes it harder for marine calcifying organisms such as mussels, barnacles and corals to produce shells and skeletons; and heatwaves have bleached coral reefs. Harmful algal blooms enhanced by climate change and eutrophication lower oxygen levels, disrupt food webs and cause great loss of marine life. Coastal ecosystems are under particular stress. Almost half of global wetlands have disappeared due to climate change and other human impacts. Plants have come under increased stress from damage by insects.

Climate change impacts on the environment

Ecological collapse. Coral bleaching from thermal stress has damaged the Great Barrier Reef and threatens coral reefs worldwide. Extreme weather. Drought and high temperatures worsened the 2020 bushfires in Australia. Arctic warming. Permafrost thaws undermine infrastructure and release methane, a greenhouse gas. An emaciated polar bear stands atop the remains of a melting ice floe. Habitat destruction. Many arctic animals rely on sea ice, which has been disappearing in a warming Arctic. Pest propagation. Mild winters allow more pine beetles to survive to kill large swaths of forest.

Humans

Asosiy sahifa: Effects of climate change

Extreme weather will be progressively more common as the Earth warms.

The effects of climate change are impacting humans everywhere in the world. Impacts can be observed on all continents and ocean regions, with low-latitude, less developed areas facing the greatest risk. Continued warming has potentially „severe, pervasive and irreversible impacts“ for people and ecosystems. The risks are unevenly distributed, but are generally greater for disadvantaged people in developing and developed countries.

Health and food

Asosiy sahifa: Effects of climate change on agriculture#Global food security and undernutrition va Effects of climate change on human health

The World Health Organization calls climate change one of the biggest threats to global health in the 21st century. Scientists have warned about the irreversible harms it poses. Extreme weather events affect public health, and food and water security. Temperature extremes lead to increased illness and death. Climate change increases the intensity and frequency of extreme weather events. It can affect transmission of infectious diseases, such as dengue fever and malaria. According to the World Economic Forum, 14.5 million more deaths are expected due to climate change by 2050. 30% of the global population currently live in areas where extreme heat and humidity are already associated with excess deaths. By 2100, 50% to 75% of the global population would live in such areas.

While total crop yields have been increasing in the past 50 years due to agricultural improvements, climate change has already decreased the rate of yield growth. Fisheries have been negatively affected in multiple regions. While agricultural productivity has been positively affected in some high latitude areas, mid- and low-latitude areas have been negatively affected. According to the World Economic Forum, an increase in drought in certain regions could cause 3.2 million deaths from malnutrition by 2050 and stunting in children. With 2 °C warming, global livestock headcounts could decline by 7–10% by 2050, as less animal feed will be available. If the emissions continue to increase for the rest of century, then over 9 million climate-related deaths would occur annually by 2100.

Livelihoods and inequality

Economic damages due to climate change may be severe and there is a chance of disastrous consequences. Severe impacts are expected in South-East Asia and sub-Saharan Africa, where most of the local inhabitants are dependent upon natural and agricultural resources. Heat stress can prevent outdoor labourers from working. If warming reaches 4 °C then labour capacity in those regions could be reduced by 30 to 50%. The World Bank estimates that between 2016 and 2030, climate change could drive over 120 million people into extreme poverty without adaptation.

Inequalities based on wealth and social status have worsened due to climate change. Major difficulties in mitigating, adapting to, and recovering from climate shocks are faced by marginalized people who have less control over resources. Indigenous people, who are subsistent on their land and ecosystems, will face endangerment to their wellness and lifestyles due to climate change. An expert elicitation concluded that the role of climate change in armed conflict has been small compared to factors such as socio-economic inequality and state capabilities.

While women are not inherently more at risk from climate change and shocks, limits on womenʼs resources and discriminatory gender norms constrain their adaptive capacity and resilience. For example, womenʼs work burdens, including hours worked in agriculture, tend to decline less than menʼs during climate shocks such as heat stress.

Climate migration

Asosiy sahifa: Climate migration

Low-lying islands and coastal communities are threatened by sea level rise, which makes urban flooding more common. Sometimes, land is permanently lost to the sea. This could lead to statelessness for people in island nations, such as the Maldives and Tuvalu. In some regions, the rise in temperature and humidity may be too severe for humans to adapt to. With worst-case climate change, models project that almost one-third of humanity might live in Sahara-like uninhabitable and extremely hot climates.

These factors can drive climate or environmental migration, within and between countries. More people are expected to be displaced because of sea level rise, extreme weather and conflict from increased competition over natural resources. Climate change may also increase vulnerability, leading to „trapped populations“ who are not able to move due to a lack of resources.

Climate change impacts on people

Environmental migration. Sparser rainfall leads to desertification that harms agriculture and can displace populations. Shown: Telly, Mali (2008). Agricultural changes. Droughts, rising temperatures, and extreme weather negatively impact agriculture. Shown: Texas, US (2013). Tidal flooding. Sea-level rise increases flooding in low-lying coastal regions. Shown: Venice, Italy (2004). Storm intensification. Bangladesh after Cyclone Sidr (2007) is an example of catastrophic flooding from increased rainfall. Heat wave intensification. Events like the 2022 Southern Cone heat wave are becoming more common.

Reducing and recapturing emissions

Asosiy sahifa: Climate change mitigation

Global greenhouse gas emission scenarios, based on policies and pledges as of November 2021

Climate change can be mitigated by reducing the rate at which greenhouse gases are emitted into the atmosphere, and by increasing the rate at which carbon dioxide is removed from the atmosphere. To limit global warming to less than 1.5 °C global greenhouse gas emissions needs to be net-zero by 2050, or by 2070 with a 2 °C target. This requires far-reaching, systemic changes on an unprecedented scale in energy, land, cities, transport, buildings, and industry.

The United Nations Environment Programme estimates that countries need to triple their pledges under the Paris Agreement within the next decade to limit global warming to 2 °C. An even greater level of reduction is required to meet the 1.5 °C goal. With pledges made under the Paris Agreement as of 2024, there would be a 66% chance that global warming is kept under 2.8 °C by the end of the century (range: 1.9–3.7 °C, depending on exact implementation and technological progress). When only considering current policies, this raises to 3.1 °C. Globally, limiting warming to 2 °C may result in higher economic benefits than economic costs.

Although there is no single pathway to limit global warming to 1.5 or 2 °C, most scenarios and strategies see a major increase in the use of renewable energy in combination with increased energy efficiency measures to generate the needed greenhouse gas reductions. To reduce pressures on ecosystems and enhance their carbon sequestration capabilities, changes would also be necessary in agriculture and forestry, such as preventing deforestation and restoring natural ecosystems by reforestation.

Other approaches to mitigating climate change have a higher level of risk. Scenarios that limit global warming to 1.5 °C typically project the large-scale use of carbon dioxide removal methods over the 21st century. There are concerns, though, about over-reliance on these technologies, and environmental impacts. Solar radiation modification (SRM) is also a possible supplement to deep reductions in emissions. However, SRM raises significant ethical and legal concerns, and the risks are imperfectly understood.

Clean energy

Asosiy sahifa: Sustainable energy va Sustainable transport

Coal, oil, and natural gas remain the primary global energy sources even as renewables have begun rapidly increasing.

Wind and solar power, Germany

Renewable energy is key to limiting climate change. For decades, fossil fuels have accounted for roughly 80% of the world’s energy use. The remaining share has been split between nuclear power and renewables (including hydropower, bioenergy, wind and solar power and geothermal energy). Fossil fuel use is expected to peak in absolute terms prior to 2030 and then to decline, with coal use experiencing the sharpest reductions. Renewables represented 86% of all new electricity generation installed in 2023. Other forms of clean energy, such as nuclear and hydropower, currently have a larger share of the energy supply. However, their future growth forecasts appear limited in comparison.

While solar panels and onshore wind are now among the cheapest forms of adding new power generation capacity in many locations, green energy policies are needed to achieve a rapid transition from fossil fuels to renewables. To achieve carbon neutrality by 2050, renewable energy would become the dominant form of electricity generation, rising to 85% or more by 2050 in some scenarios. Investment in coal would be eliminated and coal use nearly phased out by 2050.

Electricity generated from renewable sources would also need to become the main energy source for heating and transport. Transport can switch away from internal combustion engine vehicles and towards electric vehicles, public transit, and active transport (cycling and walking). For shipping and flying, low-carbon fuels would reduce emissions. Heating could be increasingly decarbonized with technologies like heat pumps.

There are obstacles to the continued rapid growth of clean energy, including renewables. Wind and solar produce energy intermittently and with seasonal variability. Traditionally, hydro dams with reservoirs and fossil fuel power plants have been used when variable energy production is low. Going forward, battery storage can be expanded, energy demand and supply can be matched, and long-distance transmission can smooth variability of renewable outputs. Bioenergy is often not carbon-neutral and may have negative consequences for food security. The growth of nuclear power is constrained by controversy around radioactive waste, nuclear weapon proliferation, and accidents. Hydropower growth is limited by the fact that the best sites have been developed, and new projects are confronting increased social and environmental concerns.

Low-carbon energy improves human health by minimizing climate change as well as reducing air pollution deaths, which were estimated at 7 million annually in 2016. Meeting the Paris Agreement goals that limit warming to a 2 °C increase could save about a million of those lives per year by 2050, whereas limiting global warming to 1.5 °C could save millions and simultaneously increase energy security and reduce poverty. Improving air quality also has economic benefits which may be larger than mitigation costs.

Energy conservation

Asosiy sahifa: Efficient energy use va Energy conservation

Reducing energy demand is another major aspect of reducing emissions. If less energy is needed, there is more flexibility for clean energy development. It also makes it easier to manage the electricity grid, and minimizes carbon-intensive infrastructure development. Major increases in energy efficiency investment will be required to achieve climate goals, comparable to the level of investment in renewable energy. Several COVID-19 related changes in energy use patterns, energy efficiency investments, and funding have made forecasts for this decade more difficult and uncertain.

Strategies to reduce energy demand vary by sector. In the transport sector, passengers and freight can switch to more efficient travel modes, such as buses and trains, or use electric vehicles. Industrial strategies to reduce energy demand include improving heating systems and motors, designing less energy-intensive products, and increasing product lifetimes. In the building sector the focus is on better design of new buildings, and higher levels of energy efficiency in retrofitting. The use of technologies like heat pumps can also increase building energy efficiency.

Agriculture and industry

Yana qarang: Sustainable agriculture va Green industrial policy

Taking into account direct and indirect emissions, industry is the sector with the highest share of global emissions. Data as of 2019 from the IPCC.

Agriculture and forestry face a triple challenge of limiting greenhouse gas emissions, preventing the further conversion of forests to agricultural land, and meeting increases in world food demand. A set of actions could reduce agriculture and forestry-based emissions by two-thirds from 2010 levels. These include reducing growth in demand for food and other agricultural products, increasing land productivity, protecting and restoring forests, and reducing greenhouse gas emissions from agricultural production.

On the demand side, a key component of reducing emissions is shifting people towards plant-based diets. Eliminating the production of livestock for meat and dairy would eliminate about 3/4ths of all emissions from agriculture and other land use. Livestock also occupy 37% of ice-free land area on Earth and consume feed from the 12% of land area used for crops, driving deforestation and land degradation.

Steel and cement production are responsible for about 13% of industrial Andoza:CO2 emissions. In these industries, carbon-intensive materials such as coke and lime play an integral role in the production, so that reducing Andoza:CO2 emissions requires research into alternative chemistries. Where energy production or Andoza:CO2-intensive heavy industries continue to produce waste Andoza:CO2, technology can sometimes be used to capture and store most of the gas instead of releasing it to the atmosphere. This technology, carbon capture and storage (CCS), could have a critical but limited role in reducing emissions. It is relatively expensive and has been deployed only to an extent that removes around 0.1% of annual greenhouse gas emissions.

Carbon dioxide removal

Asosiy sahifa: Carbon dioxide removal va Carbon sequestration

Most Andoza:CO2 emissions have been absorbed by carbon sinks, including plant growth, soil uptake, and ocean uptake (2020 Global Carbon Budget).

Natural carbon sinks can be enhanced to sequester significantly larger amounts of Andoza:CO2 beyond naturally occurring levels. Reforestation and afforestation (planting forests where there were none before) are among the most mature sequestration techniques, although the latter raises food security concerns. Farmers can promote sequestration of carbon in soils through practices such as use of winter cover crops, reducing the intensity and frequency of tillage, and using compost and manure as soil amendments. Forest and landscape restoration yields many benefits for the climate, including greenhouse gas emissions sequestration and reduction. Restoration/recreation of coastal wetlands, prairie plots and seagrass meadows increases the uptake of carbon into organic matter. When carbon is sequestered in soils and in organic matter such as trees, there is a risk of the carbon being re-released into the atmosphere later through changes in land use, fire, or other changes in ecosystems.

The use of bioenergy in conjunction with carbon capture and storage (BECCS) can result in net negative emissions as Andoza:CO2 is drawn from the atmosphere. It remains highly uncertain whether carbon dioxide removal techniques will be able to play a large role in limiting warming to 1.5 °C. Policy decisions that rely on carbon dioxide removal increase the risk of global warming rising beyond international goals.

Adaptation

Asosiy sahifa: Climate change adaptation

Adaptation is „the process of adjustment to current or expected changes in climate and its effects“. Without additional mitigation, adaptation cannot avert the risk of „severe, widespread and irreversible“ impacts. More severe climate change requires more transformative adaptation, which can be prohibitively expensive. The capacity and potential for humans to adapt is unevenly distributed across different regions and populations, and developing countries generally have less. The first two decades of the 21st century saw an increase in adaptive capacity in most low- and middle-income countries with improved access to basic sanitation and electricity, but progress is slow. Many countries have implemented adaptation policies. However, there is a considerable gap between necessary and available finance.

Adaptation to sea level rise consists of avoiding at-risk areas, learning to live with increased flooding, and building flood controls. If that fails, managed retreat may be needed. There are economic barriers for tackling dangerous heat impact. Avoiding strenuous work or having air conditioning is not possible for everybody. In agriculture, adaptation options include a switch to more sustainable diets, diversification, erosion control, and genetic improvements for increased tolerance to a changing climate. Insurance allows for risk-sharing, but is often difficult to get for people on lower incomes. Education, migration and early warning systems can reduce climate vulnerability. Planting mangroves or encouraging other coastal vegetation can buffer storms.

Ecosystems adapt to climate change, a process that can be supported by human intervention. By increasing connectivity between ecosystems, species can migrate to more favourable climate conditions. Species can also be introduced to areas acquiring a favourable climate. Protection and restoration of natural and semi-natural areas helps build resilience, making it easier for ecosystems to adapt. Many of the actions that promote adaptation in ecosystems, also help humans adapt via ecosystem-based adaptation. For instance, restoration of natural fire regimes makes catastrophic fires less likely, and reduces human exposure. Giving rivers more space allows for more water storage in the natural system, reducing flood risk. Restored forest acts as a carbon sink, but planting trees in unsuitable regions can exacerbate climate impacts.

There are synergies but also trade-offs between adaptation and mitigation. An example for synergy is increased food productivity, which has large benefits for both adaptation and mitigation. An example of a trade-off is that increased use of air conditioning allows people to better cope with heat, but increases energy demand. Another trade-off example is that more compact urban development may reduce emissions from transport and construction, but may also increase the urban heat island effect, exposing people to heat-related health risks.

Examples of adaptation methods

Mangrove planting and other habitat conservation can reduce coastal flooding. Seawalls to protect against storm surge worsened by sea level rise Green roofs to provide cooling in cities Selective breeding for drought-resistant crops Selective breeding for drought-resistant crops

Policies and politics

Yana qarang: Politics of climate change va Climate change mitigation#Policies

The Climate Change Performance Index ranks countries by greenhouse gas emissions (40% of score), renewable energy (20%), energy use (20%), and climate policy (20%).

High

Medium

Low

Very low

Countries that are most vulnerable to climate change have typically been responsible for a small share of global emissions. This raises questions about justice and fairness. Limiting global warming makes it much easier to achieve the UNʼs Sustainable Development Goals, such as eradicating poverty and reducing inequalities. The connection is recognized in Sustainable Development Goal 13 which is to „take urgent action to combat climate change and its impacts“. The goals on food, clean water and ecosystem protection have synergies with climate mitigation.

The geopolitics of climate change is complex. It has often been framed as a free-rider problem, in which all countries benefit from mitigation done by other countries, but individual countries would lose from switching to a low-carbon economy themselves. Sometimes mitigation also has localized benefits though. For instance, the benefits of a coal phase-out to public health and local environments exceed the costs in almost all regions. Furthermore, net importers of fossil fuels win economically from switching to clean energy, causing net exporters to face stranded assets: fossil fuels they cannot sell.

Policy options

A wide range of policies, regulations, and laws are being used to reduce emissions. As of 2019, carbon pricing covers about 20% of global greenhouse gas emissions. Carbon can be priced with carbon taxes and emissions trading systems. Direct global fossil fuel subsidies reached $319 billion in 2017, and $5.2 trillion when indirect costs such as air pollution are priced in. Ending these can cause a 28% reduction in global carbon emissions and a 46% reduction in air pollution deaths. Money saved on fossil subsidies could be used to support the transition to clean energy instead. More direct methods to reduce greenhouse gases include vehicle efficiency standards, renewable fuel standards, and air pollution regulations on heavy industry. Several countries require utilities to increase the share of renewables in power production.

Climate justice

Policy designed through the lens of climate justice tries to address human rights issues and social inequality. According to proponents of climate justice, the costs of climate adaptation should be paid by those most responsible for climate change, while the beneficiaries of payments should be those suffering impacts. One way this can be addressed in practice is to have wealthy nations pay poorer countries to adapt.

Oxfam found that in 2023 the wealthiest 10% of people were responsible for 50% of global emissions, while the bottom 50% were responsible for just 8%. Production of emissions is another way to look at responsibility: under that approach, the top 21 fossil fuel companies would owe cumulative climate reparations of $5.4 trillion over the period 2025–2050. To achieve a just transition, people working in the fossil fuel sector would also need other jobs, and their communities would need investments.

International climate agreements

Since 2000, rising Andoza:CO2 emissions in China and the rest of world have surpassed the output of the United States and Europe.

Per person, the United States generates Andoza:CO2 at a far faster rate than other primary regions.

Nearly all countries in the world are parties to the 1994 United Nations Framework Convention on Climate Change (UNFCCC). The goal of the UNFCCC is to prevent dangerous human interference with the climate system. As stated in the convention, this requires that greenhouse gas concentrations are stabilized in the atmosphere at a level where ecosystems can adapt naturally to climate change, food production is not threatened, and economic development can be sustained. The UNFCCC does not itself restrict emissions but rather provides a framework for protocols that do. Global emissions have risen since the UNFCCC was signed. Its yearly conferences are the stage of global negotiations.

The 1997 Kyoto Protocol extended the UNFCCC and included legally binding commitments for most developed countries to limit their emissions. During the negotiations, the G77 (representing developing countries) pushed for a mandate requiring developed countries to „[take] the lead“ in reducing their emissions, since developed countries contributed most to the accumulation of greenhouse gases in the atmosphere. Per-capita emissions were also still relatively low in developing countries and developing countries would need to emit more to meet their development needs.

The 2009 Copenhagen Accord has been widely portrayed as disappointing because of its low goals, and was rejected by poorer nations including the G77. Associated parties aimed to limit the global temperature rise to below 2 °C. The Accord set the goal of sending $100 billion per year to developing countries for mitigation and adaptation by 2020, and proposed the founding of the Green Climate Fund. -Missing required parameter 1=''month''!, 2020-yil(2020-Missing required parameter 1=month!-00) holatiga koʻra, only 83.3 billion were delivered. Only in 2023 the target is expected to be achieved.

In 2015 all UN countries negotiated the Paris Agreement, which aims to keep global warming well below 2.0 °C and contains an aspirational goal of keeping warming under 7002274649999999999♠1.5 °C. The agreement replaced the Kyoto Protocol. Unlike Kyoto, no binding emission targets were set in the Paris Agreement. Instead, a set of procedures was made binding. Countries have to regularly set ever more ambitious goals and reevaluate these goals every five years. The Paris Agreement restated that developing countries must be financially supported. -Missing required parameter 1=''month''!, [[-yil]](October 2021-Missing required parameter 1=month!-00) holatiga koʻra, 194 states and the European Union have signed the treaty and 191 states and the EU have ratified or acceded to the agreement.

The 1987 Montreal Protocol, an international agreement to phase out production of ozone-depleting gases, has had benefits for climate change mitigation. Several ozone-depleting gases like chlorofluorocarbons are powerful greenhouse gases, so banning their production and usage may have avoided a temperature rise of 0.5 °C–1.0 °C, as well as additional warming by preventing damage to vegetation from ultraviolet radiation. It is estimated that the agreement has been more effective at curbing greenhouse gas emissions than the Kyoto Protocol specifically designed to do so. The most recent amendment to the Montreal Protocol, the 2016 Kigali Amendment, committed to reducing the emissions of hydrofluorocarbons, which served as a replacement for banned ozone-depleting gases and are also potent greenhouse gases. Should countries comply with the amendment, a warming of 0.3 °C–0.5 °C is estimated to be avoided.

National responses

[[File:Annual-co2-emissions-by-region-2022.png|thumb|260px|Annual [[List of countries by carbon dioxide emissions|Andoza:CO2 emissions by region]]. This measures fossil fuel and industry emissions. Land use change is not included.]] In 2019, the United Kingdom parliament became the first national government to declare a climate emergency. Other countries and jurisdictions followed suit. That same year, the European Parliament declared a „climate and environmental emergency“. The European Commission presented its European Green Deal with the goal of making the EU carbon-neutral by 2050. In 2021, the European Commission released its „Fit for 55“ legislation package, which contains guidelines for the car industry; all new cars on the European market must be zero-emission vehicles from 2035.

Major countries in Asia have made similar pledges: South Korea and Japan have committed to become carbon-neutral by 2050, and China by 2060. While India has strong incentives for renewables, it also plans a significant expansion of coal in the country. Vietnam is among very few coal-dependent, fast-developing countries that pledged to phase out unabated coal power by the 2040s or as soon as possible thereafter.

As of 2021, based on information from 48 national climate plans, which represent 40% of the parties to the Paris Agreement, estimated total greenhouse gas emissions will be 0.5% lower compared to 2010 levels, below the 45% or 25% reduction goals to limit global warming to 1.5 °C or 2 °C, respectively.

Society

Denial and misinformation

Data has been cherry picked from short periods to falsely assert that global temperatures are not rising. Blue trendlines show short periods that mask longer-term warming trends (red trendlines). Blue rectangle with blue dots shows the so-called global warming hiatus.

Public debate about climate change has been strongly affected by climate change denial and misinformation, which originated in the United States and has since spread to other countries, particularly Canada and Australia. Climate change denial has originated from fossil fuel companies, industry groups, conservative think tanks, and contrarian scientists. Like the tobacco industry, the main strategy of these groups has been to manufacture doubt about climate-change related scientific data and results. People who hold unwarranted doubt about climate change are called climate change „skeptics“, although „contrarians“ or „deniers“ are more appropriate terms.

There are different variants of climate denial: some deny that warming takes place at all, some acknowledge warming but attribute it to natural influences, and some minimize the negative impacts of climate change. Manufacturing uncertainty about the science later developed into a manufactured controversy: creating the belief that there is significant uncertainty about climate change within the scientific community to delay policy changes. Strategies to promote these ideas include criticism of scientific institutions, and questioning the motives of individual scientists. An echo chamber of climate-denying blogs and media has further fomented misunderstanding of climate change.

Public awareness and opinion

The public substantially underestimates the degree of scientific consensus that humans are causing climate change. Studies from 2019 to 2021 found scientific consensus to range from 98.7 to 100%.

Climate change came to international public attention in the late 1980s. Due to media coverage in the early 1990s, people often confused climate change with other environmental issues like ozone depletion. In popular culture, the climate fiction movie The Day After Tomorrow (2004) and the Al Gore documentary An Inconvenient Truth (2006) focused on climate change.

Significant regional, gender, age and political differences exist in both public concern for, and understanding of, climate change. More highly educated people, and in some countries, women and younger people, were more likely to see climate change as a serious threat. College biology textbooks from the 2010s featured less content on climate change compared to those from the preceding decade, with decreasing emphasis on solutions. Partisan gaps also exist in many countries, and countries with high CO₂ emissions tend to be less concerned. Views on causes of climate change vary widely between countries. Concern has increased over time, and a majority of citizens in many countries now express a high level of worry about climate change, or view it as a global emergency. Higher levels of worry are associated with stronger public support for policies that address climate change.

Climate movement

Asosiy sahifa: Climate movement va Climate change litigation

Climate protests demand that political leaders take action to prevent climate change. They can take the form of public demonstrations, fossil fuel divestment, lawsuits and other activities. Prominent demonstrations include the School Strike for Climate. In this initiative, young people across the globe have been protesting since 2018 by skipping school on Fridays, inspired by Swedish activist and then-teenager Greta Thunberg. Mass civil disobedience actions by groups like Extinction Rebellion have protested by disrupting roads and public transport.

Litigation is increasingly used as a tool to strengthen climate action from public institutions and companies. Activists also initiate lawsuits which target governments and demand that they take ambitious action or enforce existing laws on climate change. Lawsuits against fossil-fuel companies generally seek compensation for loss and damage.

History

Early discoveries

This 1912 article succinctly describes the greenhouse effect, how burning coal creates carbon dioxide to cause global warming and climate change.

Scientists in the 19th century such as Alexander von Humboldt began to foresee the effects of climate change. In the 1820s, Joseph Fourier proposed the greenhouse effect to explain why Earth’s temperature was higher than the Sunʼs energy alone could explain. Earth’s atmosphere is transparent to sunlight, so sunlight reaches the surface where it is converted to heat. However, the atmosphere is not transparent to heat radiating from the surface, and captures some of that heat, which in turn warms the planet.

In 1856 Eunice Newton Foote demonstrated that the warming effect of the Sun is greater for air with water vapour than for dry air, and that the effect is even greater with carbon dioxide (Andoza:Co2). She concluded that „An atmosphere of that gas would give to our earth a high temperature…“

Studying what would become known as the greenhouse effect, Tyndall’s pre-1861 ratio spectrophotometer measured how much various gases in a tube absorb and emit infrared radiation—which humans experience as heat.

Starting in 1859, John Tyndall established that nitrogen and oxygen—together totalling 99% of dry air—are transparent to radiated heat. However, water vapour and gases such as methane and carbon dioxide absorb radiated heat and re-radiate that heat into the atmosphere. Tyndall proposed that changes in the concentrations of these gases may have caused climatic changes in the past, including ice ages.

Svante Arrhenius noted that water vapour in air continuously varied, but the Andoza:Co2 concentration in air was influenced by long-term geological processes. Warming from increased Andoza:Co2 levels would increase the amount of water vapour, amplifying warming in a positive feedback loop. In 1896, he published the first climate model of its kind, projecting that halving Andoza:Co2 levels could have produced a drop in temperature initiating an ice age. Arrhenius calculated the temperature increase expected from doubling Andoza:Co2 to be around 5–6 °C. Other scientists were initially sceptical and believed that the greenhouse effect was saturated so that adding more Andoza:Co2 would make no difference, and that the climate would be self-regulating. Beginning in 1938, Guy Stewart Callendar published evidence that climate was warming and Andoza:Co2 levels were rising, but his calculations met the same objections.

Development of a scientific consensus

Yana qarang: Scientific consensus on climate change

Scientific consensus on causation: Academic studies of scientific agreement on human-caused global warming among climate experts (2010–2015) reflect that the level of consensus correlates with expertise in climate science. A 2019 study found scientific consensus to be at 100%, and a 2021 study concluded that consensus exceeded 99%. Another 2021 study found that 98.7% of climate experts indicated that the Earth is getting warmer mostly because of human activity.

In the 1950s, Gilbert Plass created a detailed computer model that included different atmospheric layers and the infrared spectrum. This model predicted that increasing Andoza:Co2 levels would cause warming. Around the same time, Hans Suess found evidence that Andoza:Co2 levels had been rising, and Roger Revelle showed that the oceans would not absorb the increase. The two scientists subsequently helped Charles Keeling to begin a record of continued increase, which has been termed the „Keeling Curve“. Scientists alerted the public, and the dangers were highlighted at James Hansenʼs 1988 Congressional testimony. The Intergovernmental Panel on Climate Change (IPCC), set up in 1988 to provide formal advice to the world’s governments, spurred interdisciplinary research. As part of the IPCC reports, scientists assess the scientific discussion that takes place in peer-reviewed journal articles.

There is a near-complete scientific consensus that the climate is warming and that this is caused by human activities. As of 2019, agreement in recent literature reached over 99%. No scientific body of national or international standing disagrees with this view. Consensus has further developed that some form of action should be taken to protect people against the impacts of climate change. National science academies have called on world leaders to cut global emissions. The 2021 IPCC Assessment Report stated that it is „unequivocal“ that climate change is caused by humans.