The heat is on the world’s cities—literally. A new study published in Nature Climate Change predicts that cities will grow hotter by 8oC by the turn of the century. Global warming and what is called the urban heat island effect—cities trap more heat as they lose green spaces and water bodies and add concrete and asphalt structures—will cause the top 5% of the world’s most populous cities to heat by 8oC or more while the top quarter will see mercury rise by 7oC or more.
The researchers at the Institute for Environmental Studies in the Netherlands say that for most cities, about 5oC of the overall rise in temperature will be because of global warming. As cities bake, the consequences will be devastating—the median city will be losing some 2.3% to 5.6% of its GDP annually by 2100 even as the worst-off see growth erode by almost 11% every year. The problem is a double-edged one—checking urbanisation is certainly not in any one’s interest, but the trade-off is vegetation and green spaces that act as heat sinks.
Managing urbanisation would thus require greater use of construction material that keep cities cooler—a focus of current material science research. Creating or co-opting green spaces, too, could help. But the larger focus has to be on action on curbing climate change.
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The Trump presidency hangs like a sword over coordinated global action. If the US, the largest per capita contributor of greenhouse gases and the largest overall emitter, opts out of the accord reached in Paris in 2015—Trump has been very vocal about doing this—the brakes on climate change are off. Cities are already running dry—the water table in Bengaluru has dropped at a dangerous pace in the last decade and a half. Left parched and scorched, the urbanscape of tomorrow could well be dystopia if urgent action is not taken.