A new reality

新現(xiàn)實

The IPCC delivers its starkest warning yet about climate change

IPCC發(fā)出迄今最嚴峻的氣候變化警告

The effects of a hotter planet are visible around the world

地球變熱的影響到處可見【深度】

AT A KEY moment in the film “Jaws”, police chief Martin Brody, having known that a shark attack was possible, witnesses one actually happen. The director, Steven Spielberg, underlines the transformative nature of Brody’s shock with a shot which makes inspired use of a camera technique called a “dolly zoom”. Nothing on screen actually moves. But Brody’s guilty face seems to rush towards the audience, taking up more and more of the frame. At the same time his surroundings, rather than being displaced, are revealed more fully.

在電影《大白鯊》中，警察局長馬丁·布羅迪（Martin Brody）事先就知道可能發(fā)生鯊魚襲擊事件。在片中一個關鍵場景中，他親眼目睹了一次襲擊真實發(fā)生。導演史蒂文·斯皮爾伯格在這里巧妙運用了名為“推軌變焦”的拍攝手法來突顯布羅迪的震驚，預示著這個角色的行為將發(fā)生巨大的轉(zhuǎn)變。畫面中其實什么都沒動，但布羅迪愧疚的臉龐卻似乎在向觀眾沖來，在畫面中不斷放大，同時背景不但沒有被遮蓋，反而更寬廣地展現(xiàn)出來。

The report released on August 9th by the Intergovernmental Panel on Climate Change, the first part of the IPCC’s sixth assessment report (AR6), presents the spectacle of the possible becoming real in a similarly unnerving way, mixing close-up alarm with wide-angle context. It is a starker and blunter document than its predecessor in AR5, which was published in 2013. The statements in the summary expressing “high confidence” handily outnumber those that offer only “medium confidence”. Last time around the two categories were roughly level pegging.

政府間氣候變化專門委員會（以下簡稱IPCC）在8月9日發(fā)布了第六次評估報告（以下簡稱AR6）的第一部分，以同樣令人不安的方式呈現(xiàn)了可能成真的前景：既用特寫發(fā)出警示，也從廣角展現(xiàn)背景。相比2013年發(fā)表的第五次評估報告（以下簡稱AR5），這份報告的語氣更加冷峻直白。概述中表達出“高度可信”的陳述數(shù)量大大超過“比較可信”的次數(shù)。而在上一份報告中，兩者大致持平。

Part of that higher confidence is down to better science, which is welcome. Another part is down to bitter experience, which is not. The report stresses that the world is living through climate change, not watching it draw near. Its 234 authors base their conclusions, in a phrase that acts as something of a refrain, on 'multiple lines of evidence'. Some of that evidence comes from computer models, and some from improved physical understanding of various planetary processes. Crucially, an increasing proportion comes from direct observations of the way in which the world has changed so far.

可信度提升的一方面要歸功于科學進步， 這是好事。而另_方面是因為苦果已經(jīng)顯 現(xiàn)，這很糟糕。該報告強調(diào)，地球已經(jīng)在經(jīng)歷氣候變化了，而不是看著它逐步逼近。234名科學家參與撰寫該報告，他們的結論基于'多方面的證據(jù)”，這個說法反復出現(xiàn)在報告中。其中一些證據(jù)來自計算機模型，另一些源于對各種行星演化過程的物理研究的進展。重要的是，越來越多 的證據(jù)來自對迄今世界變化的直接觀察。

Start with the predictions of what lies dead ahead. Over the past decade the Earth has been between 0.95°C and 1.2°C (1.7-2.2°F) hotter than it was in the second half of the 19th century; the best estimate is 1.1°C. That is more than 0.2°C higher than the change that AR5 found when it made the same comparison in the previous decade. Though some of the difference is now put down to AR5 having underestimated the then current temperatures, most is seen as being due to continued heating.

先看有關眼前變化的那些預測。過去十年，地球氣溫比19世紀后半葉高了 0.95°C 至1.2°C ,最佳估計值為1.1°C。這比AR5對它發(fā)布前的十年所做的同一比較發(fā)現(xiàn)的變化高了0.2°C不止。這一差異雖然有一部分被歸結為AR5低估了當時的溫度，但主要還是地球不斷變暖的緣故。

The total amount by which the planet will heat up depends pretty closely on cumulative greenhouse-gas emissions. That allows the 'carbon budgets' associated with various levels of worldwide temperature rise to be calculated. For AR6 this exercise in climate accounting has been gone through all over again.

地球?qū)淼目偵郎睾艽蟪潭壬先Q于累積的溫室氣體排放。因此，與各種全球升溫程度對應的“碳預算”是可以計算出來的。AR6也再一次完成了這項氣候核算工作。

Worldwide greenhouse-gas emissions since 1850 are now put at 2,400bn tonnes of carbon dioxide, give or take 10%. Every subsequent 1,000bn tonnes is likely to cause between 0.27°C and 0.63°C more warming. If that seems quite imprecise, it is a much tighter estimate than was previously possible. Such calculations rely ultimately on how sensitive global temperatures are to rising carbon-dioxide levels. That crucial number is one of those things which is easier to estimate now that there is more experience to go on. The error range is notably smaller now than it was in AR5.

目前估計，自1850年以來，全球溫室氣體排放量約為2.4萬億噸二氧化碳當量，上下誤差在10%以內(nèi)。之后每增加一萬億噸排放就可能導致氣溫上升0.27°C至0.63°C。這雖然看起來不算精確，但相比以往能得出的估計已經(jīng)嚴謹?shù)枚?。這類計算最終取決于全球氣溫對二氧化碳水平上升的敏感程度。如今有了更多經(jīng)驗可循， 要估計包括這個關鍵數(shù)字在內(nèi)的一些事情變得更容易了。現(xiàn)在的誤差范圍明顯要比AR5時小。

The budget associated with a 50% chance of keeping warming below 1.5°C—the more ambitious of the two goals laid out in the Paris agreement of 2015—allows just 500bn more tonnes to be emitted. That is about 15 years of industrial emissions at current rates. To avoid busting that budget would require the whole world, not just rich countries, to get net emissions of carbon dioxide down to zero before 2050. That is a tall order, to put it mildly. Even the most ambitious of the various emissions scenarios modelled by the IPCC's experts offers less than a 50% chance of staying below 1.5°C of heating.

要有50%的機會把全球升溫幅度控制在 1.5°C以下（2015年《巴黎協(xié)定》的兩個目標中較宏偉的那個），溫室氣體的排放預算就只剩5000億噸。按目前的排放速 度，這大約是15年的工業(yè)排放量。要避免超出這一預算，不僅是富裕國家，整個世界都必須在2050年之前把二氧化碳凈排放量降至零。說得客氣點，這很難辦。即使是IPCC專家模擬的各種排放情境中最具減排野心的那種，把升溫幅度控制在 1.5°C以下的幾率也不到50%。  

The very-low-emission scenarios do offer a fighting chance of keeping warming below 2°C. But the emission cuts they require go far beyond what the nations of the world have currently promised. What is more, those scenarios mandate not just heroic emission cuts but also 'negative emissions'—techniques that actively remove carbon dioxide from the atmosphere, thus paying back some of the carbon budget spent previously. It is just about conceivable that, if emissions fall very quickly and carbon-dioxide removal scales up really well, warming may exceed 1.5°C during the coming decades but fall back below that level by the end of the century.

在那些排放水平很低的情境下，確實還有可能經(jīng)過努力把升溫控制在2°C以下，但所需減排量遠遠超出世界各國目前的承諾。更重要的是，這些情境不僅要求急劇減排，還需要實施'負排放”，即運用技術主動清除大氣中的二氧化碳，以抵消之前消耗掉的一些碳預算。勉強可以想象一下，如果排放量迅速下降，二氧化碳得到大幅清除，在未來幾十年升溫幅度可能超過1.5°C，但到本世紀末會回落至該水平以下。

Happily, the report confirms that removing carbon dioxide from the atmosphere might be a plausible way of reducing temperatures. Since such removals now offer the only way of reconciling the modest near-term cuts currently enshrined in national policies with the much more dramatic long-term ambitions those same countries proclaim, this is just as well. If the IPCC had found large-scale carbon-dioxide removal untenable that would have put the kibosh on the whole idea of reaching net-zero emissions.

所幸，該報告證實從大氣中清除二氧化碳也許是可行的降溫方法。這是個好消息， 畢竟，要調(diào)和各國目前已寫入政策中的較保守的近期減排目標、和這些國家宣稱的更宏大的長期目標，當前唯一的辦法就是清除二氧化碳。假如IPCC發(fā)現(xiàn)大規(guī)模清除二氧化碳行不通，凈零排放這個想法也就會徹底泡湯。

But the report also notes that such removals could affect more than just temperatures. They could also have an impact on food production, biodiversity and water availability and quality, especially if they are carried out through the use of huge forestry plantations. And it has nothing to say about how those systems might operate or how much they would cost—that work is left to the reports on impacts and on mitigation, which are due out next year.

但報告也指出，這種清除行動影響的也許不止是溫度，還可能沖擊糧食生產(chǎn)、生物多樣性以及水資源的供應和質(zhì)量，特別是通過大規(guī)模造林來清除二氧化碳的話。報告第一部分沒有提及這些系統(tǒng)的運作方式 或成本，預計明年公布的關于影響和緩解效果的報告將對此做出解釋。

You're going to need a cleaner boat

Meanwhile, in wide-angle, the predicted consequences of a warming world are becoming clearer and more fine-grained. Again, this is partly the product of better scientific understanding, and partly the product of direct experience. In 2013 AR5 referred to just three studies linking extreme weather events to rising temperatures. The authors of the latest report were able to assess hundreds of such event-attribution papers. Those allow it to make the clear statement that climate change is already affecting every inhabited region of the planet, with human influence contributing to many observed changes in weather and climate extremes.

你需要一條更清潔的船

同時，從更廣闊的角度看，全球變暖的后果預測變得更清晰、細致。同樣，這既是科學研究發(fā)展的結果，也是直接經(jīng)驗的產(chǎn)物。2013年發(fā)布的AR5只援引了三項有關極端天氣事件與變暖關聯(lián)的研究。AR6的作者則評估了數(shù)百份這樣的天氣事件歸因文獻。這使得報告能夠明確指出氣候變化已經(jīng)在影響地球上每個有人居住的地區(qū)， 而人類的影響是許多可觀測到的天氣變化和極端氣候事件的原因之一。

The current trend towards more frequent and intense heavy rainfall will continue, but not monotonically; rain and snowfall will become more variable within seasons and, probably, from year to year. The authors are thus fairly certain that flooding will be more frequent and intense in most of Asia and Africa if the world warms by 1.5°C, and pretty sure the same changes will be seen in North America and Europe. Earlier melting of mountain snow-packs will add to the flood risk in some areas; in others, higher sea levels will raise the risk, as will the greater frequency of the most intense tropical cyclones.

如今強降雨更頻繁猛烈的趨勢將持續(xù)下去，但不是簡單的重復：降雨和降雪的季節(jié)內(nèi)變化會加大，而且可能每年的情況都不一樣。因此，報告的作者們相當肯定地指出，如果全球變暖1.5°C，在亞洲和非洲的大部分地區(qū)，洪災會更頻繁、更兇猛，北美和歐洲也很可能出現(xiàn)同樣的情況。山區(qū)積雪提前融化將加劇一些地區(qū)的 洪災風險，而在其他地區(qū)，威脅將來自海平面上升以及更頻繁的超強熱帶氣旋。

Heatwaves will climb in number and severity. Extreme 'wet-bulb” temperatures —a measure which includes the degree to which humidity makes it harder for the human body to shed heat—will become more common more quickly than unadjusted high temperatures do. Temperatures on the hottest days in some mid-latitude regions, including parts of Europe, will rise 1.5 to 2 times as fast as global warming more generally.

熱浪出現(xiàn)的次數(shù)和嚴重程度都會攀升。極端“濕球”溫度（這一指標計入了高濕度讓人體難以散熱的程度）相比未經(jīng)調(diào)整的高溫將更快成為更普遍的現(xiàn)象。在包括歐洲部分地區(qū)的中緯度地帶，最熱季節(jié)的升溫速度將會是全球變暖速度的1.5至2倍。

The oceans will heat up more slowly than the land. But as they do so they will expand and rise, a trend exacerbated by the melting of glaciers and ice caps. The warming will not be even. The Arctic will heat up more than other seas; in every one of the IPCC’s scenarios there will be sea-ice-free days in the Arctic by the middle of the century. There will be local aberrations, too. Marine heatwaves— short-lived bursts of hot water which have only recently become a topic of concern-are expected to continue to become more common, especially in the tropics and the Arctic.

海洋升溫會比陸地慢。但當海洋升溫時， 海水會膨脹，海面會上升，而冰川和冰蓋融化更加劇了這一趨勢。變暖將不會均勻地發(fā)生。北冰洋的變暖程度將高于其他海洋；在IPCC推演的每種情境中，到本世紀中葉，北冰洋每年都將出現(xiàn)沒有海冰的曰子。還會出現(xiàn)局部反?，F(xiàn)象。預計海洋熱浪（暫時性的海水高溫現(xiàn)象，近些年才引起關注）將不斷變得更普遍，特別是在熱帶地區(qū)和北冰洋。

Ocean warming will also suppress the tendency of waters from different depths to mix. Both the heatwaves and the increased stratification will have ecological effects that may be profound, both in the Arctic and beyond.

海洋變暖也將抑制不同深度的海水混合的傾向。熱浪及海水分層加劇都可能對北冰洋和其他地區(qū)的生態(tài)環(huán)境產(chǎn)生深遠影響。

Generally speaking, what is wet becomes wetter, what is dry, drier, and what is uncommon more common. The rarer the event, the higher the likelihood that it will become more frequent. Even at 1.5°C of heating the report warns there will be some events—heatwaves, droughts and such—that are more severe than any that have been observed before. This is true at a global level as well as a regional one. 'Low-likelihood, high-impact” events are, by their nature, hard to be specific about. It is a good bet they become more likely with higher temperatures. But even at comparatively modest levels of warming such calamities as widespread forest dieback or a collapsing Antarctic ice sheet are hard to completely rule out.

總的來說就是，澇的愈澇，旱的愈旱，稀奇變尋常。越是罕見的氣候現(xiàn)象越有可能更頻繁地出現(xiàn)。報告警告稱，即使只升溫 1.5°C，熱浪、旱災等氣候事件也可能比以往所見更嚴重，在全球和區(qū)域?qū)用娑际侨绱恕?低可能性、高沖擊性”的事件本身就是很難具體預測的。八九不離十的是， 隨著溫度升高，這些事件將更可能出現(xiàn)。但即使變暖程度相對輕微，森林大范圍梢枯或南極冰蓋崩塌等災難也難以完全排除。

Recommendations about what to do are not part of this report’s remit. But nevertheless it pushes hard for more and stronger action on methane. In terms of its contribution to warming so far, methane is second only to carbon dioxide (see chart 2). Atmospheric levels of the stuff, like those of carbon dioxide, are higher than at any other point in human history. But unlike carbon dioxide, atmospheric methane is transient—it has an atmospheric half-life of less than a decade. This means that cuts in methane emissions pay off much faster than cuts in carbon dioxide. If the world is really serious about trying to keep below 2°C of warming, let alone 1.5°C, doubling down on attempts to cut methane emissions, both from industry and agriculture, should be a high priority.

提出對策不在這份報告的范圍之內(nèi)。盡管如此，報告還是大力敦促加強限制甲烷排放。論迄今對氣候變暖的推動作用，甲烷僅次于二氧化碳（見圖表2)。和二氧化碳一樣，目前大氣中的甲烷水平比人類史上任何時期都要高。但不同于二氧化碳， 甲烷在大氣中的存留時間短，半衰期不到 十年。這意味著減少甲烷排放比減少二氧化碳排放收效快得多。如果世界真想把升溫控制在2°C以下（更別說1.5°C)，一大要務應是加倍努力減少工業(yè)和農(nóng)業(yè)甲烷排放。

As the report points out, this is particularly important because of the effects of another pollutant. Sulphates are given off mostly by coal plants and the sorts of heavy fuel oils that power big ships. They have the opposite effect to methane and carbon dioxide: by reflecting sunlight back into space, they cool the planet. The IPCC reckons sulphate pollution keeps the world about 0.5°C cooler than it would otherwise be. Without it, the world would probably have already breached the Paris aspiration of limiting temperature rises to 1.5°C.

正如報告指出的，甲烷減排非常重要，因 為還有另一種污染物的影響。硫化物排放主要由火電廠和大型船舶使用的那類重燃油造成，其影響與甲烷和二氧化碳相反：它把陽光反射回太空，令地球變冷。IPCC認為，硫化物污染使全球升溫減少了0.5°C。如果沒有硫化物污染，全球升溫幅度可能已經(jīng)超出了《巴黎協(xié)定》所期望的1.5°C。

The problem is that sulphates are deadly. Over the past few decades they have contributed a great deal to the particulate air pollution that has killed tens of millions. Clean-air laws have seen them increasingly scrubbed out of fuels and smoke stacks. The IPCC report finds that continuing this good work on air pollution would contribute to global warming in all the emission scenarios it studied. That is another reason, it says, to promote quick and lasting cuts in methane emissions. Without increased ambition on methane, cleaner, clearer air will add to the challenge of rising temperatures.

問題是，硫化物污染會致人死亡。過去幾十年，硫化物已成為導致數(shù)千萬人死亡的顆粒物空氣污染的一個重要因素。清潔空氣法規(guī)的實施使燃料和煙囪的硫化物排放曰益減少。IPCC報告發(fā)現(xiàn)，在其研究的所有排放情境中，繼續(xù)推進這項有益于控制空氣污染的工作都會加劇全球變暖。報告指出，這是提倡快速且持久地減排甲烷的另一個原因。不加大甲烷的減排力度，空氣變得更干凈清澈只會令全球變暖的挑戰(zhàn)越發(fā)棘手。

Mr Spielberg’s coup de cinema in “Jaws” marks the moment when the police chief realises that the opportunity to avert calamity is gone; his inaction has led to a covert threat becoming a blood-in-the-water reality. As a result the chief is seized by a new fervour for action—one which brings him into direct conflict with the mayor, who prefers to minimise the risks so as not to scare off the tourists.

斯皮爾伯格在《大白鯊》里那個神來之筆的鏡頭標志著那一刻警察局長意識到災難已無可避免，他之前的無所作為令潛藏的威脅變成了血淋淋的現(xiàn)實。結果，局長轉(zhuǎn)而決意采取行動，這讓他和主張盡量淡化風險以免嚇跑游客的市長產(chǎn)生了直接沖突。

When it comes to climate change the realisation has hardly been instantaneous; it has been dawning for at least a decade or so. But coming as it does in a summer of shattered temperature records and terrifying fires and floods, an IPCC report in which predictions of future global warming are, more than ever before, backed up with observations should offer a similar punctuation. Deciding how much action to take on climate change is politically hard, because it means imposing high costs today for largely hidden benefits tomorrow. But when, in November, the world's governments get together in Glasgow to discuss how they can improve on the insufficient action they have taken to date, they need to think like people who have seen the blood in the water.

談到氣候變化，人們并沒有即刻認識到問題：危機在至少約十年前便已顯現(xiàn)苗頭。但是，隨著這個夏天破紀錄的焦灼高溫、 可怕的山火與洪災涌現(xiàn)，IPCC報告對未來全球變暖的預測獲得了前所未有的直觀證據(jù)支持，應該能起到與電影中那一幕類似的警醒作用。決定究竟采取多少行動來應對氣候變化要面對政治上的阻力，因為這需要在當下投入高成本，而收益卻大部分潛藏于未來。但是，當各國代表在11月聚首格拉斯哥討論改善至今力度不足的行動時，他們需要像那些親眼看到水里泛起血色的人那樣思考。