Actually, no it isn’t, at least not where I am. I’ve just been outside and the air is definitely brisk, I’d want a coat if I stayed out long, but it’s not unpleasant and the day looks beautiful and bright. But it is noticeably colder than it was yesterday, and I understand almost all of the United States is in a cold snap right now.
Predictably, the Internet is chattering about a “polar vortex” again, as if the term simply meant an unusually severe cold snap. It doesn’t–the polar vortex is not a weather event but a current within the atmosphere. There is always a polar vortex; it is the southern boundary of the polar air mass. It’s basically another name for the familiar jet stream. Sometimes the jet stream is almost straight, a circle drawn around the northern part of the globe. Sometimes it is wavy, bringing cold air farther south in some places and warmer air further north in other places. Right now, the boundary between polar and non-polar air is extremely wavy, and it is colder in Texas than in Alaska. What this is, really, is a good old fashioned cold-snap, albeit one that extends unusually far south.
There are signs that this year the media may shift to “arctic outbreak” as their buzzword of choice.
The current cold-snap is a little different than last year’s, where the cause of the extremely wavy boundary was debatable but might have been related to melting sea-ice in the arctic. Right now, we’re looking at the effects of the former Super Typhoon Nuri, which formed in the Western Pacific, became one of the most powerful storms of the year, and then weakened and recurved, heading northeast. By the time it reached Alaska it had lost its tropical characteristics (meaning its structure and the way energy moves through the system were no longer hurricane-like) but retained much of its power. Last week, the air mass formerly known as Nuri was among the most powerful storms in the Bering Sea ever recorded. Pacific storms can and do interact with the jet stream, causing weather changes hundreds of miles away. In this case, Nuri caused the boundary to become extremely wavy, freezing Texas.
Probably, some climate skeptics are wondering about global warming about now, and while I haven’t seen it yet, I expect some deniers are going to advance this cold-snap as proof against climate change. In writing this post, I’m being preemptive.
Yes, cold weather can be a symptom of global warming. A warmer atmosphere is generally more active, more prone to extremes of all kinds. A destabilized, extremely wavy polar vortex specifically could well be more common now that the arctic ice is melting, and Nuri, like all tropical cyclones, has a link to to global warming through the rising temperature of ocean water. This year’s Western Pacific typhoon season has not been startlingly intense (except for the monstrous Super Typhoon Vonfong, which fortunately weakened before it hit anyone), but it has been stronger than average. The sea has also been exceptionally warm.
But there are a couple of other points worth bearing in mind:
- It isn’t cold everywhere. Yes, the weather is unusually cold today in the eastern half of the United States, but there are other parts of the world and some of those parts are unusually warm. An unstable polar vortex doesn’t actually make the average temperature of the world drop, it just redistributes cold air. Last year, while the Eastern U.S. was freezing and questioning the existence of climate change, the same weather patterns were causing record-breaking heat in California, Alaska, and parts of Europe. The hot weather exacerbated the California drought and caused a dangerous avalanche in Alaska that completely cut off one town’s road access. For the people there, global warming was not in doubt.
- Coldness is relative and we have been spoiled by warm weather in recent years. Although the current “arctic blast” may break some local temperature records, it feels a lot colder than it really is because we’ve gotten used to the new normal of warm temperatures. Much of what we saw last winter would have been quite normal twenty or forty years ago (yes, I did just cite the cartoon, XKCD, but the cartoon in question does cite its sources and its author is an actual scientist).
- Global warming means cold weather is rare, not that it never gets cold anymore. Yes, there are going to be genuinely cold years going forward, probably including some record-breakers where the entire planet is colder than it has been since record-keeping began. The weather on Planet Earth is extremely variable, and that isn’t going to change. What we are seeing, and will continue to see, is that the cold snaps are fewer and less severe than the warm spells. On average, we’re going up.
This year, we have been especially far up. May, June, August, and September each broke global heat records. I am not certain, from the wording of my sources, whether May, June, and August were each in turn the hottest month ever, or simply the hottest May, June, and August ever. In either case, the records were based on a global average, meaning that they included measurements from places experiencing Fall or Winter at the time. September was definitely the hottest of any month ever recorded. 2014 is likely to be the planet’s hottest year on record, cold snaps in the U.S. notwithstanding. This is a big deal.
Weather.com put the situation in startling perspective:
Earth hasn’t set a monthly record for cold since December 1916, but all monthly heat records have been set after 1997.