FOR IMMEDIATE RELEASE
A simulation suggests that slowing global warming may be more urgent than anyone has recognised: even halting greenhouse gas emissions could still leave the Earth’s average temperature rising.
LONDON, 25 November – A Swiss-American team of scientists has looked far into the future and calculated that the present lukewarm plans to limit climate change may involve too little action, applied too late.
Thomas Frölicher of ETH-Zurich and colleagues from Princeton report in Nature Climate Change that they tried to model the long-term planetary adjustment after carbon dioxide emissions from fossil fuel burning stopped altogether.
They simulated a planet in which greenhouse gas emissions continued to rise, until concentrations in the atmosphere had reached four times the pre-Industrial levels, and a total of 1,800 billion tons had been released into the atmosphere. And then the emissions stopped.
The consequences were unexpected. The carbon dioxide in the atmosphere would indeed gradually be absorbed by forests, crops, algae and other natural CO2 devourers; it would be incorporated into the calcium shells and corals and skeletons in the ocean and then slowly be tucked away as rock.
But after an initial period in which temperatures started to drop, something else happened. The simulated planet started to warm again, and go on warming for another 400 years or more.
Oceans’ influence dims
That is because although what scientists call “radiative forcing” – CO2 traps infra-red radiation and keeps the Earth’s temperature up – would begin to ease, the polar oceans that play such a powerful role in the climate machine would become less efficient at removing the surplus heat.
The logic of all this rests on the reasoning that life on Earth for the last 10,000 years has continued comfortably with a particular ratio of CO2 to other gases in the atmosphere. To increase carbon levels significantly – and this has already begun to happen – would therefore disturb this comfortable equilibrium, and then trigger a very long period of uncertainty.
Frölicher and colleagues found that 40% of the extra carbon in the atmosphere would have been been soaked up within 20 years, and 80% within 1,000 years. This would of course affect temperatures.
First, as the carbon dioxide levels reached a maximum, the world would warm sharply and then, after 15 or 20 years, start to cool. The cooling could continue for a century.
But in the simulation, after the initial 100-year cooling-off period the Earth started to warm again. It went on warming for 400 years, by 0.37°C. This doesn’t sound much – but the Earth has already warmed by 0.85°C over pre-Industrial averages.
The world’s governments have collectively agreed that it would be good if the rise in average global temperatures could be halted at 2°C, and they have accepted in principle – serious concerted action has yet to be agreed – that with 500 billion tons of CO2 already released into the atmosphere, the safe limit should be 1,000 billion. But this now looks less plausible.
“If our results are correct, the total carbon emissions required to stay below 2°C of warming would have to be three quarters of previous estimates, only 750 billion tons of carbon,” said Frölicher. “Thus, limiting the warming to 2°C would require keeping future cumulative carbon emissions below 250 billion tons, only half of the already emitted amount of 500 billion tons.”
The research is a simulation, and the real lesson is probably that researchers still have a lot of work to do to understand the subtle relationships between atmosphere and ocean. But it suggests that the climate problem is more urgent than anyone may have realised.
“This is illustrative of how difficult it may be to reverse climate change – we stop the emissions but we still get an increase in the global mean temperature,” says Frölicher. – Climate News Network
Simulation inaonyesha kwamba kupunguza joto la dunia inaweza kuwa muhimu zaidi kuliko mtu yeyote amekubali: hata kusimamisha uzalishaji wa gesi chafu bado inaweza kuacha joto la wastani duniani kuongezeka. Timu ya wanasayansi wa Uswisi na Marekani imeangalia mbali katika siku zijazo na kuhesabu kwamba mipango ya sasa ya kupunguza mabadiliko ya hali ya hewa inaweza kuhusisha hatua kidogo sana, kutumika marehemu sana. Thomas Fröller, Mtaalamu wa Utafiti wa ETH Zurich na wenzake kutoka Princeton, walijaribu kuunda mfano wa marekebisho ya muda mrefu ya sayari baada ya uzalishaji wa kaboni dioksidi kutoka kwa kuchoma mafuta ya visukuku kukoma kabisa. Wanasayansi hao walifanya simulizi ya sayari ambayo uzalishaji wa gesi za chafu uliendelea kuongezeka hadi viwango vya gesi za chafu katika angahewa vilipofikia kiwango cha mara nne cha kiwango cha kabla ya viwanda, na jumla ya tani bilioni 1,800 zilitolewa angahewa. Kisha uzalishaji ukakoma. Matokeo yalikuwa yasiyotazamiwa. Kaboni dioksidi katika angahewa bila shaka itanyunyizwa hatua kwa hatua na misitu, mazao, mwani na wengine wa asili CO2 devourers; itakuwa kuingizwa katika magamba ya kalsiamu na matumbawe na mifupa katika bahari na kisha polepole tucked mbali kama mwamba. Lakini baada ya kipindi cha kwanza ambapo halijoto ilianza kushuka, jambo jingine lilitokea. Mwili wa mwanadamu ulipopungua joto, ulipungua joto kwa miaka 400 au zaidi. "Hiyo ni kwa sababu ingawa kile wanasayansi wanaita ""radiative forcing"" - CO2 hufunga mionzi ya infrared na inahifadhi joto la Dunia juu - itaanza kupungua, bahari za polar ambazo zina jukumu kubwa sana katika mashine ya hali ya hewa zitakuwa chini ya ufanisi katika kuondoa joto la ziada." "Logika ya yote haya inategemea hoja kwamba maisha duniani kwa miaka 10,000 iliyopita yameendelea vizuri na uwiano maalum wa CO2 na gesi nyingine katika anga. """ Kuongeza viwango vya kaboni kwa kiasi kikubwa - na hii tayari imeanza kutokea - kwa hivyo ingevuruga usawa huu wa starehe, na kisha kusababisha kipindi kirefu sana cha kutokuwa na uhakika. Frölicher na wenzake walipata kwamba asilimia 40 ya kaboni iliyokuwa imeongezeka katika angahewa ingekuwa imevutwa ndani ya miaka 20, na asilimia 80 ndani ya miaka 1000. Bila shaka hilo lingeathiri halijoto. "Kwanza, kiwango cha kaboni dioksidi kilipofikia kiwango cha juu, dunia ingepanda joto kwa kasi na kisha, baada ya miaka 15 au 20, kuanza baridi.""" Baridi hiyo yaweza kuendelea kwa karne moja. Katika simulation, baada ya miaka 100 ya baridi, dunia ilianza kupasha joto tena. Kwa miaka 400, joto la dunia liliongezeka kwa 0.37C. Hii haisikiki sana lakini Dunia tayari imepanda joto kwa 0.85 ° C juu ya wastani wa kabla ya Viwanda. Serikali za dunia zimekubaliana kwa pamoja kuwa itakuwa nzuri ikiwa ongezeko la wastani wa joto la dunia linaweza kusimamishwa kwa 2 ° C, na wamekubaliana kwa kanuni - hatua kubwa ya pamoja bado haijakubaliwa - kwamba na tani bilioni 500 za CO2 tayari kutolewa katika anga, kikomo salama kinapaswa kuwa bilioni 1. Lakini sasa hilo halionekani kuwa jambo linalowezekana. "Ikiwa matokeo yetu ni sahihi, jumla ya uzalishaji wa kaboni unaohitajika kukaa chini ya joto la 2 ° C ingekuwa na theluthi tatu ya makadirio ya awali, tani bilioni 750 tu ya kaboni. """ "Kwa hivyo, kupunguza ongezeko la joto kwa 2 ° C itahitaji kuweka uzalishaji wa kaboni wa baadaye chini ya tani bilioni 250 - nusu tu ya kiasi cha tani bilioni 500 tayari iliyotolewa. ""Utafiti ni simulation, na somo halisi ni pengine kwamba watafiti bado wana kazi nyingi ya kufanya kuelewa mahusiano ya subtle kati ya anga na bahari." Lakini inaonyesha kwamba tatizo la hali ya hewa ni muhimu zaidi kuliko mtu yeyote anaweza kuwa alitambua. "Hii inaonyesha jinsi inaweza kuwa vigumu kugeuza mabadiliko ya hali ya hewa - tunasimamisha uzalishaji lakini bado tunapata ongezeko la joto la wastani la ulimwengu, "Frolicher anasema.  Mtandao wa Habari za Hali ya Hewa