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Urban Heat Islands of Cities in Tropical Mexico
Reference
Juregui, E. 2005. Possible impact of urbanization on the thermal climate of some large cities in Mexico. Atmosfera 18: 249-252.

What was done
A mass population migration from rural Mexico into medium- and large-sized cities took place throughout the second half of the 20th century. The author examines the effect of this rapid urbanization on city air temperatures, analyzing the 1950-1990 minimum air temperature series of seven large cities with populations in excess of a million people and seven medium-sized cities with populations ranging from 125,000 to 700,000 people.

What was learned
Temperature trends were positive at all locations, ranging from 0.02C per decade to 0.74C per decade. Grouped by population, the average trend for the seven large cities was 0.57C per decade, while the average trend for the seven mid-sized cities was 0.37C per decade.

What it means
In the words of the author, the above results "suggest that the accelerated urbanization process in recent decades may have substantially contributed to the warming of the urban air observed in large cities in Mexico." Once again, therefore, we are reminded of the huge magnitude of the urban heat island effect, even compared to the global warming of the past century, which climate alarmists claim was unprecedented over the past twenty centuries, as well as the urban heat island's dependence upon the nature of the urban landscape. These observations suggest to us that it is essentially impossible to adequately adjust surface air temperature measurements made within an urban area to the degree of accuracy required to correctly quantify background or rural climate change, which may well be an order of magnitude smaller than the perturbing effect of the city.

Reviewed 29 March 2006