Fewer Frigid Days

It’s hardly news that it’s really cold right now across much of the contiguous U.S. The reason? The polar vortex, a rotating mass of bitterly cold air that usually remains confined to the Arctic, has veered off and moved unusually far south. It's bringing us some of the coldest air that we’ve felt in nearly two decades, sparing only the West Coast and Southwest. Even in a warming world, seasons and year-to-year temperatures will always be influenced by natural variation, so it can take time for the overall climate trend to break through the noise of these annual swings. That got us wondering how extreme cold events like this are being affected by climate change in your market.

In this week’s graphic, we’ve calculated the number of nights below a specific temperature threshold for each market based on your local climatology and current weather (for areas not affected by this Arctic push, we chose a threshold that would represent cold winter nights). The calculations run from July through June of the following year, so that we wouldn't break up the winter season. The numbers show that overall there is a downward trend in the number of extreme cold nights like we’re currently experiencing – although there are variations in a few markets. This trend is consistent with what climate scientists have been saying: Overall, winters across the contiguous U.S. have warmed by .61°F per decade since 1970, and every region has warmed at least somewhat over that time. In February 2013, we released an in-depth report titled “Warming Winters: U.S. Temperature Trends” (complete with an interactive that can be shared online) which breaks down the numbers on a state by state basis. It shows that the states with the coldest winters are the ones warming the fastest.

This is a brutally cold round of air, but let’s step back and take a look at the big picture which shows that global temperatures are on the rise, as overwhelming evidence proves. The rate of warming may have slowed over the last 15 years, but even so, each of those years was warmer than the 20th-century average. In fact, it’s now been 345 consecutive months and counting where global average temperatures have been above the average for the last century (as of November, that is - we are still waiting on December numbers to be finalized). And there is ongoing research that rapid Arctic warming, which has been linked to human-caused global warming, may be creating more amplified weather patterns like the one that we are currently seeing. If that hypothesis is true, we could experience more extreme but less frequent cold snaps, even as the planet continues to warm.