The Economist
ON FEBRUARY 26th James Inhofe, a senator from Oklahoma, threw a snowball at another senator inside America’s upper chamber. He did it to back up his contention that man-made climate change is not the threat President Barack Obama (and many others) say it is. Mr Inhofe is chairman of the Senate’s environment committee and his argument has a simple and persuasive logic: much of the United States has experienced four unusually freezing winters in succession. Surely that contradicts the notion that the Earth’s climate is warming up?
Not necessarily, for two reasons. First, the climate and the weather are not the same: they are related, but weather patterns develop and change over hours, days and weeks; the climate changes over years and decades. And second, the American landmass is just one small part of the surface of the globe. While temperatures have been well below average across much of the United States, other parts of the world have been abnormally warm. And indeed, there may be a connection between climate change and colder winters in parts of the northern hemisphere. The link is the Arctic region. Because the poles are colder than the equator, air streams north and south in order to equalise temperatures. In the northern hemisphere, this flow is called the jet stream. Because of the rotation of the Earth, the stream turns right as the planet spins, and flows in a wavy line around the pole, like a badly cut monk's tonsure. In the northern hemisphere the jet stream brings up warmer air from the south, producing more temperate weather in the northern regions over which it flows.
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