Detroit gets a lot of negative press these days, mainly because it has become a poster child for badly managed cities and decline, but it does seem to have UHI going for it and is no stranger to downtown heat waves.
Bruce Hall writes in with this interesting comparison graph he put together, which suggests that Detroit has a higher average annual temperature due to the Urban Heat Island (UHI) effect. It seems you can experience the temperature increase claimed to be from CO2 globally (about 1.4°F) by moving from Ann Arbor to Detroit, though I doubt many people would choose to do so.
If you did the opposite, and moved from Detroit to Ann Arbor (something I’ll bet a lot of people have already done), would that qualify you to be a climate refugee?
Click image to enlarge
(which appears to be using the GHCN dataset.)
You’d expect Detroit to be warmer than Flint, simply by latitude effect, and about the same as Ann Arbor, but cooler than Toledo. Detroit is warmer than all of them.
Despite this, Detroit still has not surpassed the “Grandaddy of heat waves” in July 1936
I decided to test Hall’s method, just to make sure it isn’t a fluke, so I chose a city that isn’t in decline, Atlanta, GA and some nearby smaller cities and plotted a similar map:
The result is essentially the same as for Detroit.
And, it works just as well for Phoenix:
What I found most interesting was that Phoenix has an average annual temperature (72.8°F) higher than that of Casa Grande (69.5°F), by 3.3°F. Yet, the average max temperature for Phoenix (84.5°F) is lower than that of Casa Grande (87.4°F) by almost the same amount, 2.9°F. That’s quite an achievement since the thermometer at Casa Grande National Monument is mostly rural, but sited near to a building and parking lot.
Casa Grande is often listed as the hottest places in the nation on the daily weather summary by NOAA. According to the web page
The area has a low elevation and hence is very hot – often over 110°F for several months in the summer. During spring, this part of Arizona is sometimes the hottest place in the whole USA, and even in winter, daytime temperatures can reach 80°F.
The UHI to population relationship has been defined by Dr. Roy Spencer: