Monday, June 21, 2021

Arctic Temperature Trends

Following up on the topic of Arctic-wide temperatures (see this post from a couple of weeks ago), I've started working on some new graphics to visualize the ongoing ebb and flow of temperature anomalies across the 32 longstanding climate observing sites that I mentioned before.  But first, here's another view of monthly anomalies since 2010, but this time presented in terms of standard deviations; so this puts all seasons on a level playing field and eliminates the spike in temperature variance during winter.

The message is the same: Arctic-wide temperatures saw a jump up in winter 2015-16 and have remained generally elevated.  Since 2016, there have only been a handful of months in which any of the sites was 2 standard deviations below the 1991-2020 normal (last February at Bettles was one of them), but more often than not at least one site has been 2-3 standard deviations warmer than normal.  The community of Resolute in northern Canada saw a +3.5 SD anomaly in January last winter (it was the warmest January on record).

Here's a look at the 1980-2020 linear trend by calendar month, for the 32-site average temperature.  The absolute value of the trend is smallest in summer (a "mere" 0.4 °C/decade), but the statistical significance of the summer warming is on par with the rest of the year, and considerably exceeds the late winter minimum in significance.  All in all, the trend is most pronounced in late autumn, as we well know from discussing Utqiaġvik over the years (e.g. here).

Now on to a map view of monthly anomalies so far this year: below are pairs of maps for each month, showing departures from normal in both absolute and standardized terms.






As noted in the previous post, February and March were slightly colder than (the 1991-2020) normal overall, but this was a mere blip in the context of the sustained warmth of recent years, as the top chart above shows.  Two Canadian sites - Resolute and Pond Inlet - had their warmest January on record, and the widespread warmth in Siberia in May echoed the persistent, excessive warmth of last year (see here for comments on 2020 in Siberia).

This month will also end up much warmer than normal in most of northern Siberia, because there's a major heat wave under way at present.  Here's a chart for Suhana at 118°E longitude, showing daily mean temperatures in the last 60 days as well as a forecast from today's ECMWF ensemble.  Temperatures are peaking at well over 10°C above normal for the time of year; today's high temperature was 32.7°C or 91°F.

For the 32 sites collectively, we see that temperatures have been running about 1-2°C above normal since late May.  The forecast suggests a respite towards the end of the month, with temperatures dropping back to near or just below normal Arctic-wide; we'll see if this pans out.


  1. Richard, could you do similar diagrams like in the post but for northward wind flux? (Like taking the dot product of the northward component of the wind direction and multiplying by the wind speed - if that is such a thing.) The idea is that if the monthly wind direction is overall advecting into the arctic basin, then the arctic is more likely to warm up. Some of the warming in the arctic could be explained this way.

    1. Hi Eric. Yes, an analysis of temperature advection would be possible with reanalysis data. It would make more sense to do this aloft than at the surface, where winds are usually light.

      We would be able to explain some of the regional and monthly/interannual variations in this way (e.g. temperature correlation with the Arctic Oscillation), but it wouldn't explain long-term trends for the simple reason that the circulation patterns haven't changed significantly over time. But on shorter time scales - yes, it would be an interesting analysis.

      Along similar lines, you might find this study interesting: