Most readers will be familiar with Dr Brian Brettschneider of UAF, who has become a sought-after authority on Alaska climate. Brian recently wrote an article on his own blog that I thought would be worth linking here:
Are Summer/Winter Longer/Shorter Than They Used To Be?
Using a simple method, Brian demonstrates that the "summer" and "winter" temperatures of a prior climate period (1960-1989) in Alaska have become considerably longer and shorter respectively in the most recent 30-year period (1990-2019). The changes have been particularly dramatic in winter across Alaska, and most notably of course on the North Slope.
Brian's work provides a nice visualization and easy-to-understand interpretation of temperature changes over the past several decades. In my opinion, it would also be interesting to extend the work to build in the different perceived length of summer/winter at different latitudes. For example, the introduction acknowledges that Houston has a longer summer than Omaha, and Chicago has a longer winter than Oklahoma. Most people would say Alaska has a very long winter and a short summer; and despite the dramatic warming on the North Slope, winter certainly hasn't disappeared there, as Brian's simple method would imply.
Obviously it would be difficult to come up with a good metric to capture subjective opinions of summer and winter, but perhaps a threshold temperature could be added that would demand a "summer" or "winter" classification, regardless of how long that season might be. For example, perhaps:
- Normal daily mean temperature above 27°C -> summer
- Normal daily mean temperature below -10°C -> winter
The winter threshold would then produce a (1981-2010 climate) winter season from October 28 to March 21 in Fairbanks, and October 22 through May 3 in Utqiaġvik. Perhaps readers would like to comment on this or other ideas to refine the analysis without losing too much of the attractive simplicity.