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I began teaching with the idea of giving back; I received more than I gave. This brings me to the final movement of this speech. It begins with a story about an extraordinary scientific discovery and a new dilemma that it poses. It’s a call to arms and about making a difference.
我懷著回報社會的想法，開始了教學生涯。我的一生中，得到的多于我付出的，所以我要回報社會。這就引出了這次演講的最后一個樂章。首先我要講一個了不起的科學發現，以及由此帶來的新挑戰。它是一個戰斗的號令，到了做出改變的時候了。
In the last several decades, our climate has been changing. Climate change is not new: the Earth went through six ice ages in the past 600,000 years. However, recent measurements show that the climate has begun to change rapidly. The size of the North Polar Ice Cap in the month of September is only half the size it was a mere 50 years ago. The sea level which been rising since direct measurements began in 1870 at a rate that is now five times faster than it was at the beginning of recorded measurements. Here’s the remarkable scientific discovery. For the first time in human history, science is now making predictions of how our actions will affect the world 50 and 100 years from now. These changes are due to an increase in carbon dioxide put into the atmosphere since the beginning of the Industrial Revolution. The Earth has warmed up by roughly 0.8 degrees Celsius since the beginning of the Revolution. There is already approximately a 1 degree rise built into the system, even if we stop all greenhouse gas emissions today. Why? It will take decades to warm up the deep oceans before the temperature reaches a new equilibrium.
過去幾十年中，我們的氣候一直在發生變化。氣候變化并不是現在才有的，過去60萬年中就發生了6次冰河期。但是，現在的測量表明氣候變化加速了。北極冰蓋在9月份的大小，只相當于50年前的一半。1870年起，人們開始測量海平面上升的速度，現在的速度是那時的5倍。一個重大的科學發現就這樣產生了?？茖W第一次在人類歷史上，預測出我們的行為對50~100年后的世界有何影響。這些變化的原因是，從工業革命開始，人類排放到大氣中的二氧化碳增加 了。這使得地球的平均氣溫上升了0.8攝氏度。即使我們立刻停止所有溫室氣體的排放，氣溫仍然將比過去上升大約1度。因為在氣溫達到均衡前，海水溫度的上升將持續幾十年。
If the world continues on a business-as-usual path, the Intergovernmental Panel on Climate Change predicts that there is a fifty-fifty chance the temperature will exceed 5 degrees by the end of this century. This increase may not sound like much, but let me remind you that during the last ice age, the world was only 6 degrees colder. During this time, most of Canada and the United States down to Ohio and Pennsylvania were covered year round by a glacier. A world 5 degrees warmer will be very different. The change will be so rapid that many species, including Humans, will have a hard time adapting. I’ve been told for example, that, in a much warmer world, insects were bigger. I wonder if this thing buzzing around is a precursor.
如果全世界保持現在的經濟模式不變，聯合國政府間氣候變化專門委員會（IPCC）預測，本世紀末將有50%的可能，氣溫至少上升5度。這聽起來好像不多，但是讓我來提醒你，上一次的冰河期，地球的氣溫也僅僅只下降了6度。那時，俄亥俄州和賓夕法尼亞州以北的大部分美國和加拿大的土地，都終年被冰川覆蓋。氣溫上升5度的地球，將是一個非常不同的地球。由于變化來得太快，包括人類在內的許多生物，都將很難適應。比如，有人告訴我，在更溫暖的環境中，昆蟲的個頭將變大。我不知道現在身旁嗡嗡叫的這只大蒼蠅，是不是就是前兆。
We also face the specter of nonlinear “tipping points” that may cause much more severe changes. An example of a tipping point is the thawing of the permafrost. The permafrost contains immense amounts of frozen organic matter that have been accumulating for millennia. If the soil melts, microbes will spring to life and cause this debris to rot. The difference in biological activity below freezing and above freezing is something we are all familiar with. Frozen food remains edible for a very long time in the freezer, but once thawed, it spoils quickly. How much methane and carbon dioxide might be released from the rotting permafrost? If even a fraction of the carbon is released, it could be greater than all the greenhouse gases we have released to since the beginning of the industrial revolution. Once started, a runaway effect could occur.
我們還面臨另一個幽靈，那就是非線性的“氣候引爆點”，這會帶來許多嚴重得多的變化?！皻夂蛞c”的一個例子就是永久凍土層的融化。永久凍土層經 過千萬年的累積形成，其中包含了巨量的凍僵的有機物。如果凍土融化，微生物就將廣泛繁殖，使得凍土層中的有機物快速腐爛。冷凍后的生物和冷凍前的生物，它 們在生物學特性上的差異，我們都很熟悉。在冷庫中，冷凍食品在經過長時間保存后，依然可以食用。但是，一旦解凍，食品很快就腐爛了。一個腐爛的永久凍土層，將釋放出多少甲烷和二氧化碳？即使只有一部分的碳被釋放出來，可能也比我們從工業革命開始釋放出來的所有溫室氣體還要多。這種事情一旦發生，局勢就失控了。
The climate problem is the unintended consequence of our success. We depend on fossil energy to keep our homes warm in the winter, cool in the summer, and lit at night; we use it to travel across town and across continents. Energy is a fundamental reason for the prosperity we enjoy, and we will not surrender this prosperity. The United States has 3 percent of the world population, and yet, we consume 25 percent of the energy. By contrast, there are 1.6 billion people who don’t have access to electricity. Hundreds of millions of people still cook with twigs or dung. The life we enjoy may not be within the reach of the developing world, but it is within sight, and they want what we have.
氣候問題是我們的經濟發展在無意中帶來的后果。我們太依賴化石能源，冬天取暖，夏天制冷，夜間照明，長途旅行，環球觀光。能源是經濟繁榮的基礎，我 們不可能放棄經濟繁榮。美國人口占全世界的3%，但是我們消耗全世界25%的能源。與此形成對照，全世界還有16億人沒有電，數億人依靠燃燒樹枝和動物糞便來煮飯。發展中國家的人民享受不到我們的生活，但是他們都看在眼里，他們渴望擁有我們擁有的東西。
