Tipping Points in the Climate System
Iqlim tizimidagi burilish nuqtalari
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Iqlimning qaytarib bo‘lmas o‘zgarishlari xavfi va ijobiy “burilish nuqtalari” haqida.
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Much public discussion of climate change imagines a gradual process: each additional tonne of carbon dioxide adds a little more warming, and the consequences worsen steadily and predictably. For many aspects of the climate, this picture is broadly accurate. But scientists have long been concerned that some parts of the Earth system may behave very differently, responding to gradual warming with sudden, self-reinforcing and potentially irreversible change. These thresholds are known as tipping points.
Iqlim o‘zgarishi haqidagi jamoatchilik muhokamalarining aksariyati asta-sekin jarayonni tasavvur qiladi: har bir qo‘shimcha tonna karbonat angidrid biroz ko‘proq isishni qo‘shadi va oqibatlar barqaror va oldindan aytib bo‘ladigan tarzda yomonlashadi. Iqlimning ko‘p jihatlari uchun bu manzara umuman to‘g‘ri. Lekin olimlar uzoq vaqtdan beri Yer tizimining ba’zi qismlari tubdan boshqacha harakat qilishi, asta-sekin isishga to‘satdan, o‘zini o‘zi kuchaytiradigan va ehtimol qaytarib bo‘lmaydigan o‘zgarish bilan javob berishi mumkinligidan xavotirda. Bu chegaralar burilish nuqtalari deb ataladi.
The basic idea can be illustrated with the ice sheets of Greenland and West Antarctica. As an ice sheet melts, its surface sinks to lower altitudes where the air is warmer, which accelerates melting further. Similarly, as bright ice gives way to darker land or ocean, less sunlight is reflected and more is absorbed, causing additional warming. Beyond a certain point, such feedbacks may make the loss of the ice sheet unstoppable, even if global temperatures were later stabilised. The complete loss of the Greenland ice sheet would raise global sea levels by around seven metres, although this would take centuries or millennia to unfold.
Asosiy g‘oyani Grenlandiya va G‘arbiy Antarktidaning muz qatlamlari misolida ko‘rsatish mumkin. Muz qatlami eriganda, uning sirti havo issiqroq bo‘lgan pastroq balandliklarga cho‘kadi, bu esa erishni yanada tezlashtiradi. Xuddi shunday, yorqin muz qoraroq quruqlik yoki okeanga o‘rin bo‘shatganda, quyosh nuri kamroq qaytariladi va ko‘proq yutiladi, bu esa qo‘shimcha isishga sabab bo‘ladi. Ma’lum bir nuqtadan keyin bunday qayta aloqalar muz qatlamining yo‘qolishini to‘xtatib bo‘lmas qilib qo‘yishi mumkin, hatto keyinchalik global harorat barqarorlashtirilsa ham. Grenlandiya muz qatlamining to‘liq yo‘qolishi dunyo okeani sathini taxminan yetti metrga ko‘taradi, garchi bu asrlar yoki ming yilliklar davomida sodir bo‘lsa ham.
Other potential tipping points involve living systems. The Amazon rainforest generates much of its own rainfall by recycling moisture through its trees. Scientists fear that a combination of deforestation and warming could reduce this moisture recycling to the point where large parts of the forest can no longer sustain themselves and gradually turn into drier savannah, releasing vast quantities of stored carbon. Thawing permafrost in the Arctic, which contains roughly twice as much carbon as the atmosphere currently does, could release carbon dioxide and methane as it decomposes, adding to the warming that caused it to thaw.
Boshqa ehtimoliy burilish nuqtalari tirik tizimlarni o‘z ichiga oladi. Amazon tropik o‘rmoni daraxtlari orqali namlikni qayta aylantirib, o‘z yog‘ingarchiligining katta qismini o‘zi hosil qiladi. Olimlar o‘rmonlarning kesilishi va isishning birgalikdagi ta’siri bu namlik aylanishini o‘rmonning katta qismlari o‘zini o‘zi ta’minlay olmaydigan va asta-sekin quruqroq savannaga aylanib, ulkan miqdordagi saqlangan uglerodni chiqaradigan darajagacha kamaytirishi mumkinligidan qo‘rqishadi. Atmosferadagidan taxminan ikki baravar ko‘p uglerodni o‘z ichiga olgan Arktikadagi erib borayotgan abadiy muzlik parchalanar ekan, karbonat angidrid va metan chiqarishi mumkin, bu esa uning erishiga sabab bo‘lgan isishga qo‘shiladi.
Perhaps the most dramatic concern relates to the Atlantic Meridional Overturning Circulation, a system of ocean currents that carries warm water northwards and plays a major role in the relatively mild climate of north-western Europe. Fresh water from melting ice and increased rainfall could weaken this circulation, and some studies suggest it has already slowed. A collapse, which most scientists consider unlikely this century but cannot rule out, would cause severe cooling in parts of Europe, shift rainfall patterns in Africa and Asia and raise sea levels along the coast of North America.
Ehtimol eng dramatik xavotir Atlantika meridional aylanma oqimiga tegishli — bu iliq suvni shimolga olib boradigan va shimoli-g‘arbiy Yevropaning nisbatan mo‘’tadil iqlimida katta rol o‘ynaydigan okean oqimlari tizimi. Erigan muzdan chiqqan chuchuk suv va ko‘paygan yog‘ingarchilik bu aylanishni zaiflashtirishi mumkin va ba’zi tadqiqotlar u allaqachon sekinlashganini ko‘rsatadi. Ko‘pchilik olimlar bu asrda ehtimoldan yiroq deb hisoblaydigan, lekin istisno qila olmaydigan qulash Yevropaning ba’zi qismlarida keskin sovishga olib keladi, Afrika va Osiyoda yog‘ingarchilik naqshlarini o‘zgartiradi va Shimoliy Amerika qirg‘oqlari bo‘ylab dengiz sathini ko‘taradi.
There is considerable scientific uncertainty about where these thresholds lie and how they interact. A widely discussed assessment published in 2022 concluded that several tipping points, including the collapse of the Greenland and West Antarctic ice sheets and the widespread death of tropical coral reefs, could become likely if warming exceeded one and a half degrees. Other scientists caution that some systems may respond more gradually than the tipping point metaphor implies. What is clear is that the risk increases with every increment of warming, which strengthens the case for limiting it as much as possible.
Bu chegaralar qayerda joylashgani va ular qanday o‘zaro ta’sir qilishi haqida jiddiy ilmiy noaniqlik bor. 2022-yilda nashr etilgan va keng muhokama qilingan baholash isish bir yarim darajadan oshsa, bir nechta burilish nuqtalari, jumladan Grenlandiya va G‘arbiy Antarktida muz qatlamlarining qulashi va tropik marjon riflarining keng ko‘lamli nobud bo‘lishi ehtimoli yuqori bo‘lishi mumkin degan xulosaga kelgan. Boshqa olimlar ba’zi tizimlar burilish nuqtasi metaforasi nazarda tutganidan ko‘ra asta-sekinroq javob berishi mumkinligidan ogohlantirishadi. Aniq narsa shuki, xavf isishning har bir ulushi bilan ortadi, bu esa uni iloji boricha cheklash zarurligini kuchaytiradi.
Some researchers have recently drawn attention to the possibility of positive tipping points in human society. The cost of solar panels has fallen by around ninety percent in little more than a decade, and once clean technologies become cheaper than fossil fuels, their adoption can accelerate rapidly, as investment, infrastructure and social norms reinforce one another. Electric vehicles, for instance, rose from a tiny share of new car sales to a substantial proportion in several countries within a few years.
Ba’zi tadqiqotchilar yaqinda insoniyat jamiyatidagi ijobiy burilish nuqtalari ehtimoliga e’tibor qaratishdi. Quyosh panellarining narxi o‘n yildan sal ko‘proq vaqt ichida taxminan to‘qson foizga tushdi va toza texnologiyalar qazilma yoqilg‘ilardan arzonroq bo‘lgach, investitsiyalar, infratuzilma va ijtimoiy me’yorlar bir-birini mustahkamlar ekan, ularning qabul qilinishi tez tezlashishi mumkin. Masalan, elektromobillar bir necha yil ichida bir nechta mamlakatda yangi avtomobil sotuvining kichik ulushidan sezilarli qismigacha ko‘tarildi.
The concept of tipping points, then, cuts both ways. It warns that the climate may not wait patiently for us to act, but it also reminds us that change in human systems, too, can be sudden and self-reinforcing once the right conditions are in place.
Shunday qilib, burilish nuqtalari tushunchasi ikki tomonlama. U iqlim biz harakat qilishimizni sabr bilan kutmasligi mumkinligidan ogohlantiradi, lekin u shuningdek, to‘g‘ri sharoitlar yaratilgach, inson tizimlaridagi o‘zgarish ham to‘satdan va o‘zini o‘zi kuchaytiruvchi bo‘lishi mumkinligini eslatadi.
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Javob topa olmasangiz, «O‘qish» bosqichiga qaytib, matnga qarang — bu ham mashq.
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Asosiy g‘oya
1 What is the main idea of the article?
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2 Why does melting ice sheets’ surface lowering speed up melting?
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3 How could the Amazon reach a tipping point?
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4 What is the Atlantic Meridional Overturning Circulation?
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5 What is a “positive tipping point” in society?
True / False / Not Given
True — matnda aynan shunday deyilgan. False — matn aksini aytadi. Not Given — matnda bu haqda ma’lumot yo‘q.
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1 Electric vehicles now make up most new car sales worldwide.
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2 Some studies suggest the Atlantic circulation has already slowed.
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3 The 2022 assessment linked several tipping points to warming above 1.5 degrees.
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4 For many aspects of the climate, gradual change is a broadly accurate picture.
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5 Parts of the Amazon have already turned into savannah.
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6 The cost of solar panels fell by around ninety percent in just over a decade.
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7 Darker surfaces absorb more sunlight than ice.
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8 A collapse of the circulation would bring cooling to Central Asia.
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9 Permafrost contains about twice as much carbon as the atmosphere.
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10 All scientists agree on exactly where tipping points lie.
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11 Losing the Greenland ice sheet would raise sea levels within a few years.
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12 Most scientists think a collapse of the circulation is very likely this century.
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