Helping climate science make sense.

Wacky Winter Weather May Be Global Weirding

Its been a weird wacky winter across most of the country, with crazy hot temperatures smashing hundreds of records, and snow droughts in large swaths of the northeast, mid-Atlantic, the California Sierra, Colorado and Utah.

Is this climate change? Global warming? Perhaps global weirding?

“Too soon to tell” is what my staff scientists and PhDs tell me. “You can’t cry global warming every time you have a warm year”

Really? What do you call it then? Or maybe I should ask, when? When will we have enough goofy weather in a row so that we can start calling it climate change?

I guess they’ll get back to me on that one. “Limitations with the climate models, blah, blah, blah . . . “

Luckily, we have more information than just the models (don’t get me wrong, we love climate models here at Climate Central; they just have their limits, like anything else with a million zillion moving parts).

We have the observational record!  Which is weather-geek speak for a whole bunch of thermometers telling us how hot and cold it was, every day, at thousands of locations across the country for the past 120 years or so. 

Thermometers are good because they tend to be non-partisan, which is extra important when it comes to climate change. There are no ruthless, ice-cold Santorum thermometers, no warm and fuzzy Obama thermometers and no wishy-washy Romney thermometers that change temperature depending on who is collecting the data.

Nope. Just thermometers. Thousands of ‘em doing the same job, day in and day out, 365 days a year, for more than a 100 years.

So to see what’s going on this winter and whether it lines up with a more general trend, we  have collected the thermometer data and analyzed it.  The results confirm what most people sense: winters are getting warmer, and for the lower 48, the large-scale behavior is very much in step with the  overall warming trend (global and on the continental scale) caused primarily by air pollution with carbon dioxide, methane, fluorocarbon refrigerants and other greenhouse gasses. (OK. I’m not sure most people “sense” that last half of that sentence, but they should).

We analyzed the thermometer data a couple of ways. First, for the whole country, where the winter-warming trend is clear:

Click here for a larger view

Then, for our 11 places we looked at it two ways. First, we looked at the numbers of day below freezing per year, over time. Nine of our 11 cities show a clear winter-warming trend.

Second, we calculated the average temperature of the coldest month in our 11 states (you can’t just do the city — not enough thermometers to generate good statistics).

In this case, 8 of the 11 states show clear warming trends over time:

 

But what about the exceptions? Well, it turns out that warming exhibits different regional and seasonal trends, meaning that even as the entire U.S. has clearly warmed, not every place — like Raleigh, N.C. — has warmed for every season or even overall. It is notable, though, that of the 11 cities, only Raleigh bucked the warming winter trend by both measures.

Some places, like Miami and Columbia, S.C., show warming winters in the form of fewer cold days, even though the average temperature of the coldest month has actually gotten slightly colder. And Denver showed a clear warming trend for the average temp of the coldest month, but the number of days below freezing has remained about the same.

There are a number of other ways to measure warming winters. We could have looked at the average temperature of the entire winter, or the number of days below 0. We’ll put these analyses on the list. In the meantime, maybe the lesson of Raleigh is the lesson of this weird weather winter.

One southern state that is off the reservation doesn’t disprove a larger theory.

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