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Global climate change

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presents us with unprecedented challenges.

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Since climate science can do no more than

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estimate a broad set of possible outcomes

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ranging from the concerning to the catastrophic,

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society must treat the problem as one of

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risk assessment and management.

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At one extreme, we could elect to do nothing

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and gamble on an only

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moderately challenging outcome.

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But if we are wrong

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we will saddle children and their descendants

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with enormous problems.

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At the other extreme,

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we could make serious economic and

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tangible sacrifices that

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might prove unnecessary.

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Unfortunately, waiting much longer to see

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which way things go is not a viable option

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since it takes thousands of years

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for CO2 levels in our atmosphere

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to decline once emissions stop.

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In fact, even if we were to magically cut

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all emissions today,

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we would still see CO2 levels

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of over 400 ppm

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until the year 3000.

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By the time the consequences of

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climate change become unequivocally clear,

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it will almost certainly be too late to do much about it.

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We must decide – and act.