Why the Arctic is climate change's canary in the coal mine - William Chapman

為什麼北極是氣候變遷的「煤礦中的金絲雀」—威廉‧查普曼 (William Chapman)

譯者: Regina Chu 審譯者: Geoff Chen

The area surrounding the North Pole

北極四周的環境

may seem like a frozen and desolate environment where nothing ever changes.

看似一片冰凍荒蕪，亙古不變

But it is actually a complex and finely balanced natural system,

但它其實是複雜 又微妙平衡的自然系統

and its extreme location makes it vulnerable to feedback processes

它極端的地理位置 使其很容易受回饋過程影響

that can magnify even tiny changes in the atmosphere.

即使是大氣中極小的變化 也會放大

In fact, scientists often describe the Arctic as the canary in the coal mine

事實上，科學家經常描述北極 為煤礦坑中的金絲雀

when it comes to predicting the impact of climate change.

以此來形容北極對 氣候變遷影響的預測力

One major type of climate feedback involves reflectivity.

氣候回饋主要型態之一是反射率

White surfaces, like snow and ice,

白色的表面，如雪或冰

are very effective at reflecting the sun's energy back into space,

能高效反射太陽的能量回到太空

while darker land and water surfaces absorb much more incoming sunlight.

但較深色的陸地及水面 則會吸收更多射入的陽光

When the Arctic warms just a little, some of the snow and ice melts,

當北極變暖一點點 部分的雪及冰會融化

exposing the ground and ocean underneath.

暴露出其下的地面及海洋

The increased heat absorbed by these surfaces causes even more melting,

地面及海面因此吸收更多的熱量

又加劇了融化 諸如此類不斷循環

and so on.

And although the current situation in the Arctic follows the warming pattern,

雖然北極目前的情況 與暖化週期相符

the opposite is also possible.

反向操作也是可能的

A small drop in temperatures would cause more freezing,

稍稍下降的溫度可能形成更多冰

increasing the amount of reflective snow and ice.

增加能反射的雪量及冰量

This would result in less sunlight being absorbed,

結果是陽光吸收量降低

and lead to a cycle of cooling, as in previous ice ages.

導致冷卻循環 如同前一個冰河時期

Arctic sea ice is also responsible for another feedback mechanism

北極海冰則是另一種回饋機制

through insulation.

靠的是絕緣

By forming a layer on the ocean's surface,

在海洋表面形成的一層冰

the ice acts as a buffer between the frigid arctic air

可作為寒冷的北極空氣

and the relatively warmer water underneath.

與冰下相對溫暖的水之間的緩衝

But when it thins, breaks, or melts in any spot,

但是當海冰上任何一點 變薄、破裂甚或融化

heat escapes from the ocean,

熱氣就從海洋逸出

warming the atmosphere and causing more ice to melt in turn.

溫暖大氣，導致更多冰融化

Both of these are examples of positive feedback loops,

這兩者都是正回饋迴圈的例子

not because they do something good,

不是因為它們做了什麼好事

but because the initial change is amplified in the same direction.

而是因為初始變動以相同趨勢放大

A negative feedback loop, on the other hand,

另一方面，負回饋迴圈

is when the initial change leads to effects

則是初使變動

that work in the opposite direction.

在相反趨勢產生效應

Melting ice also causes a type of negative feedback

融化的冰也會引發負回饋

by releasing moisture into the atmosphere.

因為融冰釋放了水氣進入大氣

This increases the amount and thickness of clouds present,

這會使雲增量及增厚

which can cool the atmosphere by blocking more sunlight.

遮蔽更多的陽光，冷卻大氣

But this negative feedback loop is short-lived,

但這種負回饋迴圈很短命

due to the brief Arctic summers.

原因是北極的夏天很短

For the rest of the year, when sunlight is scarce,

夏天以外的時間，陽光稀少

the increased moisture and clouds

增加的水氣及雲量

actually warm the surface by trapping the Earth's heat,

會捕捉地球的熱氣，暖化地表

turning the feedback loop positive for all but a couple of months.

使回饋迴圈除了夏天幾個月外 幾乎都轉正向

While negative feedback loops encourage stability

儘管負回饋迴圈促進穩定

by pushing a system towards equilibrium,

因為它讓系統趨向平衡

positive feedback loops destabilize it by enabling larger and larger deviations.

正回饋迴圈卻破壞平衡 因其產生的偏差愈來愈大

And the recently increased impact of positive feedbacks

而最近增加的正回饋影響

may have consequences far beyond the Arctic.

其後果可能不僅影響北極

On a warming planet,

在暖化的星球上

these feedbacks ensure that the North Pole warms at a faster rate than the equator.

這些回饋確保北極 暖化的速度比赤道快一點

The reduced temperature differences between the two regions

這兩個區域間的溫度差

may lead to slower jet stream winds

可能導致噴射氣流減慢

and less linear atmospheric circulation in the middle latitudes,

減少線性的中緯度環流

where most of the world's population lives.

而中緯度區是全球人口最多的地方

Many scientists are concerned that shifts in weather patterns

許多科學家擔心天氣型態改變

will last longer and be more extreme,

會持續更久且更異常

with short term fluctuations becoming persistent cold snaps,

本來是短暫的變異 卻變成持續的冷鋒

heat waves, droughts and floods.

熱浪、乾旱及水災

So the Arctic sensitivity doesn't just serve as an early warning alarm

所以北極的敏感度

不只對地球其餘地區的 氣候變遷有早期預警的效果

for climate change for the rest of the planet.

Its feedback loops can affect us in much more direct and immediate ways.

它的回饋迴路還以更直接 更立即的方式影響我們

As climate scientists often warn,

如同氣候科學家常警告的

what happens in the Arctic doesn't always stay in the Arctic.

在北極發生的事不會只影響北極