What's more, says David Keith who directs the University of Calgary's Energy and Environmental Systems Group, it would be pretty easy to do.

而且，卡尔加里大学能源和环境系统小组的负责人大卫·基思说，要这么做很容易。

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The team also featured David Beckham, Ryan Giggs and Nicky Butt, while Robbie Savage and Keith Gillespie were on the bench.

当时球队阵容中还包括贝克汉姆，吉格斯，而野人萨维奇，吉莱斯皮是球队的替补。

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David Keith was in the audience with Caldeira that day in Aspen.

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And if all else fails, Harvard professor David Keith, proposes geo-engineering as a way to combat global warming with his plan to refreeze the Arctic.

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"Carbon dioxide is the one thing that we've done nothing about so far, from really any of our economy aside by from increasing efficiency, and its the one thing that will substantially change the climate on time scales of 100 years or so, " said David Keith, an engineering professor at Carnegie Mellon University in Pittsburgh.

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