How warm is it really?

It’s 67°F at National Airport as I write this. We had temperatures in the 70s this past weekend; Saturday topped out at 68° and Sunday hit 71°. So yes, it’s warm. But in the broader context, this warmth is actually more common than you might expect. The data presented below are from the National Centers for Environmental Information, which are part of NOAA. These are maximum daily temperatures from February 15-25 at National Airport (located in Arlington, VA) from 1981 through 2015.

Histogram of Maximum Temperatures at DCA

The average high temperature for that timeframe is 49.2° with a standard deviation of 10.7°. Thirty-three days between Feb. 15-25, 1981-2015 have had high temps above 65° (roughly 8.6%). About half of those days were during active La Niña events.

So how common are these warm temperatures? Well, they’ve happened about 8.6% of the time, which seems rare. However, they occurred in 19 of the 35 years I looked at, which is just over half the time. That’s quite common.

When drought hits Wine Country

Most of California has been in a drought for about five years now. Over the past couple of months we’ve seen this drought erode as precipitation and snow pack has taken over the area. Below is a map showing the changes in the drought conditions over the past three months (from US Drought Monitor).

Drought Conditions (redder colors indicate stronger drought conditions) from the United States Drought Monitor

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The Arctic is really warm

This hasn’t just been a warm winter in the United States. The Arctic has been very warm; take a look at the latest temperature anomalies below.

Temperature Anomalies

The very red area over the Arctic Circle (roughly north of 66°N) represents temperature anomalies that are over 10°F above normal. This warmth has had a significant impact on Arctic ice extent this year. Below are two images from the National Snow and Ice Data Center showing the ice extent this year.


Arctic ice images from the National Snow and Ice Data Center

The current year’s sea ice extent is shown in blue in the graph on the left. This year clocks in at roughly 1 million square kilometers under the long-term median. The map on the right shows that the current sea ice extent is particularly low between eastern North America and Europe. Perhaps more disturbingly, the total sea ice volume is roughly 7,500 cubic kilometers lower than its long-term average and is at its lowest level since at least 2010. This is shown below in the image from the Polar Science Center.

Total sea ice volume

So what does declining sea ice mean for those of us in the United States? Well, to first order one could argue that a warmer arctic would result in a decreased meridional (north/south) temperature gradient, which would lead to a weak polar jet. This would lead to more cold outbreaks and storms over the CONUS in winter. The lack of sea ice would also result in a lower albedo, which means more of the sun’s energy would be absorbed at the poles. This would lead to an enhanced warming effect.

Of course the real world is often too complicated to be described by first principles alone. Does anyone know of any modeling studies that have taken a stab at this question? I’d be interested to know what they’ve found.