"If it were ever shut off, Europe would see an average temperature drop of 15 degrees, " says Jeff Schultz, the center's chief climatologist.

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This is true especially when the temperature begins to drop as a pile of blankets will always be more inviting than sitting in a chilly chair.

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"So-called 'sceptics' should now drop their thoroughly discredited claims that the increase in global average temperature could be attributed to the impact of growing cities, " he said.

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Inside the greenhouse, lines of bright sodium lights shine down on the growing tomato plants, and the temperature remains a constant, warm 23C -- even in the depths of winter when outside temperatures drop well below freezing.

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