To the Editor:

“The Cost of Cool” (Sunday Review, Aug. 19), about the exorbitant — and rapidly rising — costs of air-conditioning in the increasingly crowded cities in the tropics, where cool living and working conditions appear to be a prerequisite to economic development, points to an urgent need for family planning.

Three inexorable global trends — climate change, resource depletion and population growth — are on a catastrophic collision course. Although substituting clean energy sources — solar, wind, tidal — for reliance on fossil fuels may have promise in some undefined future, the only practical immediate course is to limit population growth.

It’s worth noting that of the 23 hottest metro areas — those with more than 1,000 annual cooling degree days — only three are in the Western Hemisphere, which has about one-seventh of the total global population.

So family planning primarily needs to target the planet’s most densely populated regions in the Eastern Hemisphere — in Asia and Africa. This will be characterized by some as racist or chauvinist, but the reality is that those regions will suffer the most.