Across the World this winter is biting hard--harder than it has been for years. And with a new cold snap  threatening much of the U.S, it looks like it's going to get chillier. But don't you go thinking Global Warming is rubbish.
That's the message from scientists who are keen to dispel some of the public misunderstanding on the matter. This is a misunderstanding which stems from what the average Joe would call a common sense argument: "If it's such a cold Winter, how come you guys are scared the Earth's warming up?" The problem, of course, is that there's no such thing as common sense, and the poor logic of this argument is in collision with some very hard-won scientific facts.
And it's also about a misunderstanding on the difference between climate and weather. The fact that man is influencing the climate to warm it up is now pretty much beyond question, but the term "climate" applies to the entire atmosphere and its complex interplay of chemistry, physics, fluid dynamics, solar flux variations, and a trillion other features on a global scale. On the other hand the term "weather", which is often mistakenly interchanged with "climate," refers to exactly how the local atmospheric conditions are behaving from a human observer's point of view. Though climate influences weather, the link is obscenely complex and unpredictable.
To boil that down to plain English, look at it like this: The entire atmosphere is being messed around with by human activity, and seems to be warming up a infinitesimal amount each year. But that isn't going to stop events like the huge chunk of cold Arctic air currently sliding down over the U.S. and Europe and making it snow. In fact, global warming may even, in the short term, make that sort of event more likely, not less.
As senior scientist at the National Center for Atmospheric Research in Boulder, Gerald Meehl, notes "It's part of natural variability." And he's being careful with his words: The climate and weather are actually mathematically chaotic, and one of the early pioneers in Chaos theory, Edward Lorenz , built up his understanding of the math by studying the way air masses move through the atmosphere. Though Chaos theory is extremely difficult to explain, one way to think about it is to look at the beautiful clouds on Jupiter.
These are pretty familiar, and we all know those rough bands of reddish color that are an apparently predictable trademark of the planet, along with the persistent hurricane of the Great Red Spot. This behavior of Jupiter is like our climate's predictable patterns: Seasonal changes, the Gulf Stream, and so on. But if you zoom in to look at the detail of any of Jupiter's bands of cloud, it's impossibly changeable and complex and definitely unpredictable. Think of Earth's local weather as equivalent to those unpredictable small details, and you'll get why some days it rains in summer and the sun blazes bright in winter.
And there's a bigger upshot of Chaos for the issue of global warming, which is simpler to explain and tied in to the debate about the current weather conditions: Nature is an unpredictable beast. We know we're warming the climate up as a whole, which is going to have long term impact on the patterns of our climate. But that doesn't mean Mother Nature isn't going to dump a mountain of snow on you from time to time.