St Petersburg, London and Amsterdam are not "modern cities". Obviously there are tons of large cities that have been around before AC, but the article cites the rise of cities (and population) in places that were previously undesirable because of the warm climate. AC has caused a migration of sorts towards warmer places.

> Cities have boomed in places where, previously, the climate would have held them back. In 1950, 28% of the population of the US lived in its sunbelt, 40% in 2000. The combined population of the Gulf cities went from less than 500,000 before 1950 to 20 million now. Neither the rise of Singapore, nor the exploding cities of China and India, would have happened in the same way if they had still relied on punkah fans, shady verandas and afternoon naps.

The article also mentions developments which affect even those old cities that A/C made possible -- such as the glass skyscraper

Don't know what you mean, chief. St Petersburg, Florida is quite hot.