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The world's climate scientists are charged with a difficult task:
世界氣候科學家肩負著一項艱巨的任務：
to create a crystal ball with which to skry a future that promises to be hotter than today.
創造一個水晶球，用它來預示一個比現在更熱的未來。
But exactly how much hotter depends on innumerable factors, both natural and human.
但到底有多熱，這取決于無數的因素，有自然也有人類因素。
Creating the crystal ball is thus a two-stage process. First, you have to build a simulacrum of how Earth's climate works.
因此，創建水晶球是一個兩階段的過程。首先，你需要建立一個地球氣候運行的模擬模型。
Then, you try to perturb this simulacrum with plausible future human actions, to see what picture appears.
然后，你要嘗試用未來可能的人類行為擾亂這個擬像，看看會出現什么情況。
Modern magic being what it is, the crystal balls are actually supercomputers running programs with 1m or more lines of code.
現代魔法就是這樣，水晶球其實是超級計算機，運營著擁有百萬或更多代碼的程序。
These programs are models that divide the planet's atmosphere, ocean and land surface into grids of cells—many millions of them.
這些程序就是模型，將地球的大氣、海洋和陸地分成網格細胞—有數百萬個。
Land cells are flat. Atmosphere and ocean cells are three-dimensional
陸地細胞是平的。大氣和海洋細胞時三維的
and are stacked in columns to account for the effects of altitude and depth.
并被堆疊在列中，以解釋高度和深度的影響。
A model calculates what is going on, physically and chemically, inside each cell,
這是一個計算每個細胞中物理和化學變化的模型
and how this will affect that cell's neighbours, both sideways and, if appropriate, above and below.
一個全方位計算這將如何影響這個細胞鄰居的模型。
Then it does it again. And again. And again. That is a complicated process.
然后再重復一遍。重復再重復，這是一個復雜的過程。
A model's code has to represent everything from the laws of thermodynamics to the intricacies of how air molecules interact with one another.
一個模型的代碼必須代表一切，從熱力學定律到空氣分子相互作用的復雜性。
Running it means performing quadrillions of mathematical operations a second—hence the need for supercomputers.
運行這個模型意味著每秒要執行千萬億次數學運算——因此需要超級計算機。
And using it to make predictions means doing this thousands of times,
用它來進行預測意味著要執行數千次
with slightly different inputs on each run, to get a sense of which outcomes are likely,
每次運行的輸入略有不同，這樣才能了解哪些結果有可能
which unlikely but possible, and which implausible in the extreme.
哪些不太可能，但有希望以及哪些在極端情況下是不可信的。
Even so, such models are crude. Millions of grid cells might sound a lot,
即便如此，這樣的模型也很粗糙。數以百萬計的網格單元可能聽起來很多，
but it means that an individual cell's area, seen from above, is about 10,000 square kilometres,
但這意味著從上面看，單個細胞領域約有一萬平方公里，
while an air or ocean cell may have a volume of as much as 100,000 cubic kilometers.
而一個空氣或海洋細胞的體積可能高達10萬立方千米。
Treating these enormous areas and volumes as points misses much detail.
把這些巨大的區域和體量當作點來處理會忽略很多細節。
Clouds, for instance, present a particular challenge to modellers.
例如，云層是分析員面臨的一個特殊挑戰。
Depending on how they form and where, they can either warm or cool the climate.
根據它們的形成方式和地點，它們可以使氣候變暖或變冷。
But a cloud is far smaller than even the smallest grid-cells, so its individual effect cannot be captured.
但是云甚至比最小的網格單元都要小得多，因此它的個體效應無法被捕捉到。
The same is true of regional effects caused by things like topographic features or islands.
地形特征或島嶼等因素造成的區域效應也是如此。
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