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科技報道
Climate change in the Arctic
北極氣候變化
Beating a retreat
倉惶撤退
Arctic sea ice is melting far faster than climate models predict. Why?
北極海冰正在以比氣候模型所預測的快得多的速度融化，為什么？
ON SEPTEMBER 9th, at the height of its summertime shrinkage, ice covered 4.33m square km, or 1.67m square miles, of the Arctic Ocean, according to America's National Snow and Ice Data Centre.
據美國國家冰雪中心監測，今年的9月9日，處于夏季收縮極值的北極海冰僅僅覆蓋了433萬平方公里，或相當于167萬平方英里的北冰洋洋面。
That is not a record low—not quite.
這雖未創下最低記錄，但也已相去不遠。
But the actual record, 4.17m square km in 2007, was the product of an unusual combination of sunny days, cloudless skies and warm currents flowing up from mid-latitudes.
2007年的417萬平方公里的最低記錄是受到當時艷陽高照，萬里無云的天空以及從中緯度上來的暖流這種異常組合的影響的產物。
This year has seen no such opposite of a perfect storm, yet the summer sea-ice minimum is a mere 4% bigger than that record.
而盡管并沒有觀測到如此不利的情況，今年海冰的極小值也僅僅比那年的記錄大了4%。
Add in the fact that the thickness of the ice, which is much harder to measure, is estimated to have fallen by half since 1979, when satellite records began, and there is probably less ice floating on the Arctic Ocean now than at any time since a particularly warm period 8,000 years ago, soon after the last ice age.
除此以外，較難測量的冰面厚度預計比首次有衛星觀測記錄的1979年降低了一半。現在，漂浮在北冰洋上面的冰塊很可能是8000千年前最后一個冰河期結束后的那個極暖期以來最少的。
That Arctic sea ice is disappearing has been known for decades.
數十年前，人們已經認識到北極海冰正在消亡一事。
The underlying cause is believed by all but a handful of climatologists to be global warming brought about by greenhouse-gas emissions.
除了少數人以外，幾乎所有氣候學家都將其歸咎于溫室氣體排放所帶來的全球變暖。
Yet the rate the ice is vanishing confounds these climatologists' models.
然而海冰消失的速率使這些氣象學家建立的氣候模型陷入混亂。
These predict that if the level of carbon dioxide, methane and so on in the atmosphere continues to rise, then the Arctic Ocean will be free of floating summer ice by the end of the century.
按照他們的預計，若大氣中的二氧化碳、甲烷以及其他溫室氣體持續增加，到本世紀末夏季的北極海冰將完全消失。
At current rates of shrinkage, by contrast, this looks likely to happen some time between 2020 and 2050.
但是相較之下，依現在的消融速率，這一情況將可能在2020年到2050年之間發生。
The reason is that Arctic air is warming twice as fast as the atmosphere as a whole.
其原因是由于北極的空氣正在以大氣整體的兩倍速度暖化。
Some of the causes of this are understood, but some are not.
其中部分根源已經被了解，但仍有一些未能解開。
The darkness of land and water compared with the reflectiveness of snow and ice means that when the latter melt to reveal the former, the area exposed absorbs more heat from the sun and reflects less of it back into space.
與強反射的冰雪表面相比，當其融化后露出下面深色的陸地或水體時，這部分區域將從太陽吸收到更多的熱量而僅僅反射更少的部分到空中。
The result is a feedback loop that accelerates local warming. Such feedback, though, does not completely explain what is happening.
結果造成了一個局部暖化加速的惡性循環，盡管這種反饋機制未能完全解釋當下正在發生的事情。
Hence the search for other things that might assist the ice's rapid disappearance.
今后對其他事物的研究可能會對解釋海冰的快速消失帶來幫助。
Forcing the issue
解決問題
One is physical change in the ice itself.
另一個原因是海冰自身的物理結構發生了改變。
Formerly a solid mass that melted and refroze at its edges, it is now thinner, more fractured, and so more liable to melt.
以前融化和凍結僅發生在冰塊的邊緣，但是它現在變得更薄，更易破裂，并且更傾向融化。
But that is a marginal effect. Filling the gap between model and reality may need something besides this.
但這只是名副其實的邊際效應。要彌合模型與現實的差距，還需要其他原因。
The latest candidates are short-term climate forcings.
最后一個候選者是所謂的短期氣候強迫物質。
These are pollutants, particularly ozone and soot, that do not hang around in the atmosphere as carbon dioxide does, but have to be renewed continually if they are to have a lasting effect.
即是大氣污染物，尤其是臭氧和煤煙。盡管它們不能像二氧化碳那樣在大氣中停留，以至于需要不斷補充以持續發揮作用。
If they are so renewed, though, their impact may be as big as CO2's.
但是假如它們得到足夠的補充，將對全球變暖帶來不亞于二氧化碳的影響。
At the moment, most eyes are on soot.
當前，絕大多數眼球都注目于煤煙。
In the Arctic, soot is a double whammy.
煤煙給北極帶來了雙重打擊。
First, when released into the air as a result of incomplete combustion, soot particles absorb sunlight, and so warm up the atmosphere. Then, when snow or rain wash them onto an ice floe, they darken its surface and thus cause it to melt faster.
首先，當作為非充分燃燒的產物被排放到空中后，煤煙顆粒吸收陽光，加熱了大氣。其次，當雨雪將煤煙帶到冰面上后，使冰面顏色變深，并導致加速消融。
Reducing soot would not stop the summer sea ice disappearing, but it might delay the process by a decade or two.
盡管減少煤煙排放不能阻止夏季海冰的消失，但或許能減緩這一過程十到二十年。
According to a recent report by the United Nations Environment Programme,
聯合國環境規劃署的一份最新報告顯示，
reducing black carbon and ozone in the lower part of the atmosphere, especially in the Arctic countries of America, Canada, Russia and Scandinavia, could cut warming in the Arctic by two-thirds over the next three decades.
減少低層大氣中的黑炭以及臭氧，尤其是北極圈國家，如美國，加拿大，俄羅斯，斯堪的納維亞諸國，能夠在未來三十年里降低北極地區的暖化速度達三分之二。
Indeed, the report suggests, if such measures—preventing crop burning and forest fires, cleaning up diesel engines and wood stoves, and so on—were adopted everywhere they could halve the wider rate of warming by 2050.
事實上，如果能如此份報告所說，到處都采取諸如防止焚燒作物和森林火災，清理柴油發動機以及火爐等措施，到2050年止能將當下較大的暖化速率減半。
Without corresponding measures to cut CO2 emissions, this would be but a temporary fix.
如果沒有相應的削減二氧化碳排放的措施，這將只是一個臨時性解決方法。
Nonetheless, it is an attractive idea because it would have other benefits and would not require the wholesale rejigging of energy production which reducing CO2 emissions implies.
盡管如此，這仍是一個有足夠吸引力的主意，因為它還能帶來其他利益，也不會像削減二氧化碳排放那樣需要大規模調整能源產業。
Not everyone agrees it would work, though. Gunnar Myhre of the Centre for International Climate and Environmental Research in Oslo, for example, notes that the amount of black carbon in the Arctic is small and has been falling in recent decades. He does not believe it is the missing factor in the models.
然而，不是每個人都認為它將很有效。例如位于奧斯陸的國際氣候與環境研究中心的岡納·邁爾表示，他注意到北極的黑炭的量微乎其微，并且已經在最近的數十年里沉降下來。他不相信這會是模型中確實的影響因子。
Carbon dioxide, in his view, is the main culprit. Black carbon deposited on the Arctic snow and ice, he says, will have only a minimal effect on its reflectivity.
在他眼中，二氧化碳才是罪魁禍首。他說，落到北極冰雪上面的黑炭，只會對其反射率帶來微小的影響。
The rapid melting of the Arctic sea ice, then, illuminates the difficulty of modelling the climate—but not in a way that brings much comfort to those who hope that fears about the future climate might prove exaggerated.
北極海冰的快速消融揭示了建立氣候模型的困難，只不過，與那些認為對未來氣候的恐懼可能被過分夸大的人的想法背道而馳。
When reality is changing faster than theory suggests it should, a certain amount of nervousness is a reasonable response.
當事實上的變化快于紙面理論時，一定量的情緒不安是合理的反應。
It's an ill wind
一利百弊
The direct consequences of changes in the Arctic are mixed.
北極的變化將帶來的各種后果。
They should not bring much rise in the sea level, since floating ice obeys Archimedes's principle and displaces its own mass of water.
它并不會使海平面上升許多，因為浮冰遵循阿基米德原理排開了相當于它自身的水。
A darker—and so more heat-absorbent—Arctic, though, will surely accelerate global warming and may thus encourage melting of the land-bound Greenland ice sheet.
然而一個相對深色的—也會吸收更多熱量—北極，毫無疑問會加速全球變暖，并且可能促使連接在陸地上的格陵蘭島冰蓋加快融化。
That certainly would raise sea levels.
而這將一定導致海平面上升。
Wildlife will also suffer.
野生動物也將深受其害。
Polar bears, which hunt for seals along the ice's edge, and walruses, which fish there, will both be hard-hit.
沿著浮冰邊緣狩獵海豹的北極熊，以及在此捕魚的海象，都將受到沉重打擊。
The effects on the wider climate are tricky to assess.
它給更廣范圍的氣候所帶來的影響難以評估。
Some meteorologists suspect unseasonal snow storms off the east coast of America in 2010 were partly caused by Arctic warming shifting wind patterns.
一些氣象學家推測北極變暖造成的氣流模式改變是造成2010年襲擊美國東海岸的那場非季節性暴風雪的部分原因。
One feedback loop that does seems certain, though, is that the melting Arctic will enable the extraction of more fossil fuel, with all that that implies for greenhouse-gas emissions.
然而，有一個惡性循環似乎是真的—一個融化中的北極將會使得更多化石燃料被抽取，這與溫室氣體排放直接關聯。
The Arctic is reckoned to hold around 15% of the world's undiscovered oil reserves and 30% of those of natural gas.
北極被估計保有全球石油儲量的15%以及天然氣儲量的30%。
Hence a growing polar enthusiasm among energy companies—as witnessed last month in an Arctic tie-up between Exxon Mobil, of America, and Rosneft, Russia's state-controlled oil giant.
因此，在能源公司中掀起了一股極地熱潮—上個月美國的埃克森美孚公司與俄羅斯國有石油巨頭俄羅斯石油公司達成北極大陸架戰略伙伴關系協議就是明證。
Recent plankton blooms suggest a warmer Arctic will provide a boost to fisheries there, too.
而浮游生物的大量繁殖預示著一個較溫暖的北極也將推動此處的漁業發展。
And the vanishing ice has begun to allow a trickle of shipping across the Arctic's generally frozen north-west and north-east passages, thus linking the Atlantic and Pacific oceans.
消失的冰面也開始允許船只緩慢通過通常封凍的北極西北和東北通道，從而連接了大西洋和太平洋。
In August a Russian supertanker, the Vladimir Tokohonov, aided by two nuclear icebreakers, became the first such vessel to cross the north-east route, hugging the Siberian coast.
在今年八月，一艘俄羅斯籍超級油輪，弗拉基米爾·蒂克霍諾夫號在兩艘核能破冰船的幫助下成為了第一艘通過東北路徑的同類船只。
So far, despite some posturing by Canada and Russia, there are few territorial disputes in the region and the Arctic Council, the club of Arctic nations, has functioned reasonably well.
迄今為止，除了加拿大和俄羅斯所擺出的一些姿勢外，在該地區鮮少有領土爭端問題。
Whether the interests of these countries coincide with those of the wider world, though, is moot.
北極理事會—北極圈國家的俱樂部，也運行良好。
A warming Arctic will bring local benefits to some.
盡管有待討論，無論這些國家的利益是否與其他國家重合，一個正在變暖的北極只會給當地帶來利益，
The rest of the world may pay the cost.
而世界上其他地方將不得不為之埋單。
