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    February 11, 2014 | 10:00 AM

    Don’t Let the Polar Vortex Freeze the Climate Conversation

    A chilling prospect, that. But take heart. The cold doesn’t threaten your accurate understanding of (and concern for) what’s happening to our planet’s climate system. In fact, it’s a weapon in your arsenal of climate facts. Here’s why.

    First things first: there is a difference between climate and weather. Weather always has—and always will—fluctuate. There are warm days, mild days, and cool days. There are dry periods and wet periods. And this will continue to be the case.

    But while weather is short-term, momentary, and often localized, the climate system is longer-term, global, and greater than the sum of all current weather events. It doesn’t swing wildly from one extreme to the other, and – since human beings have been around – it’s been largely stable. We have a pretty good general idea of what will happen broadly with temperatures each season because we saw it happen about this time last year. And the year before that and the year before that.

    As we warm the climate, though, we can see the long-term temperature trend change. Think of it like the stock market. We still have short periods in time when the market climbs rapidly, setting new daily or weekly highs. And we still have short periods when the market tanks, setting new daily or weekly lows. On those days, should you sell every bit of a blue-chip stock you own, just because it lost some value? Why not? On that day, it’s a bad investment after all! But we know that medium and long-term trends are really what matter for market value. We also know that, on the whole, the value of stock markets has grown over time. In other words, even with the bad days and low points, the overall trend is upward.

    It’s the same with the weather and climate: we have short-term cold spells, but the long-term trend for global temperatures is still warming. Like our friends at Grist tell it, you could also think of weather and climate like mood and personality. We’re making a fairly pleasant person more grouchy. They still have happy days when they’re super sweet and adorable, but on the whole they’re more bitter and irritable than they used to be... and over time they’re having many more bad days than normal or good days.

    Want yet another simple analogy? As this video explains, the difference between a fluctuation or variation and a trend is similar to the pattern made by a dog being walked by his owner. Video credit: Siffer, produced by TeddyTV for NRK. Animation by Ole Christoffer Haga

    If your relative gets the distinction between weather and climate, that’s an end to the debate right there. Ta da. Of course, if you want to really show that the bone-chilling weather isn’t a cause for you to back down, there’s more. To borrow a rhetorical flourish, ask not how the polar vortex impairs your ability to explain climate change. Ask how you can explain climate change better, using the polar vortex. Aha! But be warned, what follows is tricky.

    Ready? Ok: the polar vortex is just a catchy name for a pattern of circulating air that occurs over both poles, high up in the stratosphere. The northern hemisphere polar vortex tends to sit over cold Arctic air. As NOAA explains, as you move north to south from the Arctic towards the equator, this air gets warmer, with the warming becoming most rapid at the mid latitudes. At that strong point of transition, the Jetstream – a high-velocity air current in the middle to upper levels of the atmosphere (i.e. where jet airplanes fly) – is formed. Which means the Jetstream is basically the outer edge of the polar vortex.

    Arctic oscillation, another term you may have heard recently, is a measure of the Jetstream’s irregularity, and “a surface expression of the polar vortex.” In simple terms, when Arctic oscillation is weak, or negative, the Jetstream is slower. When the Jetstream moves more slowly from west to east, frigid Arctic air is trapped underneath the polar vortex for longer periods, making cold snaps more lengthy. Scientists have noticed a negative trend in the Arctic oscillation since the 1990s.

    Why is this happening? The short answer: it’s all about the Jetstream. While the scientific community doesn’t yet know for certain, some peer-reviewed studies (PDF )  indicate that as global temperatures rise, a warming Arctic is contributing to this slowing of the Jetstream. Some scientists have even suggested that a warmer Arctic may be pushing cold air from the region farther south than usual, due to an increasingly wavy Jetstream.

    Case in point: at the same time that the polar vortex was being blamed for bringing Arctic air farther south than typical, the opposite (i.e. warmer-than-usual air circulating farther north than typical) was happening in other locations around the globe. This is linked to the wavy Jetstream pattern, which moves in peaks and troughs with cold air found within the troughs and warmer air found south of the ridges. Recently, while repeated dips or troughs in the Jetstream brought the eastern two-thirds of the U.S. bone-chilling cold snaps this January, ridges in the pattern over the northern Pacific Ocean extended farther north than usual, leading to record high temperatures in Alaska. Greenland also became unusually warm as the Jetstream shifted far north.

    Like we said, it’s tricky and there’s a lot of detail here, but we found this short video to be helpful in understanding this phenomenon. Check it out: Video credit: Yahoo EarthNow CIMMS, January 4, 2013

    So there’s the science. Now what do we do about it? First we need to understand climate change better and explain it better to dispel any confusion about what’s happening. Second, we need to support actions that reduce carbon pollution, the root of the problem. In the U.S. right now, this means we need to unite behind the Environmental Protection Agency’s historic action to reduce carbon pollution from power plants, America’s biggest source of carbon pollution. A temporary dip in temperature means nothing in the face of ongoing climate change. As we start to understand what’s really happening, we need to stand up and support the EPA as it seeks to limit the carbon pollution from power plants changing our climate. Let’s keep our eye on the prize, and not let a polar vortex or two distract us!

    Shravya Reddy is the science and solutions director at Climate Reality. Ryan Towell is Climate Reality’s climate science advisor. They both excel at explaining complex science over a burrito and a beer at the bar.

    Image  © 2010 glasses eyes view/Flickr cc by 2.0

     

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