Keeping Current

City latitude and current temperature, from northernmost to southernmost.

55º57' N Edinburgh, Scotland. Currently 59º Fahrenheit
55º45' N Moscow, Russia. Currently 28º Fahrenheit
55º43' N Copenhagen, Denmark Currently 48º Fahrenheit
55º10' N Grande Prairie, Alberta, Canada. Currently 30º Fahrenheit

Edinburgh, the northernmost city, is by far the warmest. What gives?

Two factors are at work here. The two warmest cities on the list are Edinburgh and Copenhagen. Both of these cities benefit from their proximity to the ocean. Water, as I repeatedly attempted to convince my students over the last two years, has a moderating effect on temperature. Water tends to retain its temperature much longer than land. A coastal city will have a cooler spring even as days become longer and more light warms the land, because air off the ocean will always blow in cool. In the fall, however, that same ocean soaked up sun heat all summer and takes much longer to cool down. Consequently, ocean air will warm the city well after the days shorten. Moscow and Grande Prairie, being very far inland, do not have any water temperatures to mitigate their response to the shorter fall days.

The other factor is the North Atlantic Current (what, you thought the title came from the current temperature? It does! Badum-CHING!) If you don't like the Wikipedia link, you can check out an old New York Times article here - assuming, of course, that you believe that the New York Times is more reliable than Wikipedia.

The current is an extension of the Gulf Stream, warmed in the Caribbean, which then travels up the east coast of the USA. It carries that tropical heat across the Atlantic, although I assume it loses heat as it travels, and cities further West/closer to the US would get more benefit. This would explain why Reykjavik, the capital of Iceland, is a balmy 52º Fahrenheit right now in spite of being located at 64°08′N, ten full degrees north of Edinburgh (Fairbanks, Alaska, at a similar latitude, is 21). Some scientists worry through complicated methods involving global warming, the polar ice caps, convection, and ocean salinity, the North Atlantic Current is in danger of shutting down. Others think this is hogwash ("hogwash" is a technical scientific term). We all must hope it is, as the end of the current would spell catastrophic consequences for climate and population the British Isles*, and then where would we get our costume dramas?

And that's today's science lesson. Hope you all enjoyed it!

*also the rest of Europe, but that spoiled the pacing of the joke.