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Last year I showed these two slides so that demonstrate that the arctic ice cap,
去年我給各位展示了兩個(gè)關(guān)于北極冰帽的演示，
which for most of the last three million years has been the size of the lower 48 states, has shrunk by 40 percent.
在過去三百萬(wàn)年中，其面積由相當(dāng)于美國(guó)南方48州面積總和縮減了40%。
But this understates the seriousness of this particular problem because it doesn't show the thickness of the ice.
但這些沒能完全說明這個(gè)問題的嚴(yán)重性，因?yàn)檫@沒有表示出冰帽的厚度。
The arctic ice cap is, in a sense, the beating heart of the global climate system.
感覺上，北極冰帽就好象全球氣候系統(tǒng)中跳動(dòng)的心臟。
It expands in winter and contracts in summer.
冬天心臟舒張，夏天心臟收縮。
The next slide I show you will be a rapid fast-forward of what's happened over the last 25 years.
下面我要展示的是在過去25年里的極劇變化。
The permanent ice is marked in red.
紅色的是永凍冰。
As you see, it expands to the dark blue -- that's the annual ice in winter, and it contracts in summer.
你看，它正在變成深藍(lán)色，這是每年冬天形成的年度冰，在夏天永凍冰收縮。
The so-called permanent ice, five years old or older, you can see is almost like blood, spilling out of the body here.
所謂的“永凍”，是指形成五年或更久的冰，你看，這也像血液一樣輸送到身體各部位。
In 25 years it's gone from this, to this.
在25年的時(shí)間里，它從這里到了這里。
This is a problem because the warming heats up the frozen ground around the Arctic Ocean,
值得注意的是，溫室效應(yīng)使得北冰洋周圍的凍土層受熱，
where there is a massive amount of frozen carbon which, when it thaws, is turned into methane by microbes.
而這里有大量被凍封的碳（干冰），解凍時(shí)，微生物降解碳形成甲烷。
Compared to the total amount of global warming pollution in the atmosphere,
如果突破頂點(diǎn)，溫室氣體排放量
that amount could double if we cross this tipping point.
將是現(xiàn)有大氣層中的全球溫室污染總量。
Already in some shallow lakes in Alaska, methane is actively bubbling up out of the water.
在阿拉斯加的一些淺湖里已經(jīng)可以看到水中探頭的沼氣泡。
Professor Katey Walter from the University of Alaska went out with another team to another shallow lake last winter.
去年冬天，阿拉斯加大學(xué)的Katey Walter教授結(jié)隊(duì)去了一個(gè)淺湖。
