Urban heat islands compound economic impact of climate change


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A 2011 heatwave in New York City produces an orange sunset. (Chris Goldberg/flickr)
Jenna Ladd | May 30, 2017

A recent study published in Nature Climate Change revealed that the climate change is likely to be twice as costly in cities than in rural areas.

An international group of economists found that the world’s largest cities could see temperature spikes of 46 degrees Fahrenheit by 2100 if greenhouse gases continue to rise at the current rate. The top 25% largest cities could are likely to see temperatures rise by about 45 degrees Fahrenheit in the same period of time.

The report explains that about 41 degrees Fahrenheit of warming can be explained by global climate change, but the additional four to five degrees of warming will be the result of the urban heat island effect. Urban heat islands are formed when naturally cooling surfaces like vegetation and bodies of water are replaced by surfaces that trap heat like concrete and asphalt.

Based on their analysis of 1,692 cities, the economists expect the combined heating affect to have negative economic consequences for urban areas. Higher temperatures cause workers to be less productive, raise cooling costs for buildings, and deteriorate water and air quality.

On average, the global gross domestic product (GDP) is expected to drop by 5.6 percent by 2100 due to climate change. In contrast, the most-impacted cities are expected to lose 10.9 percent of their GDP. The researchers provided cost-benefit analyses of several cooling measures in the report, including cooling pavements, green roofs and the reintroduction of vegetation in urban areas. For example, transforming 20 percent of a city’s pavement and rooftops to cooling surfaces could save a city up to 12 times what the structures cost to maintain and install, providing a bump to the local GDP.

The researchers conclude that local efforts to mitigate the effects of climate change can play an important role in global efforts. One of the study’s authors, Professor Richard S.J. Tol, Professor of Economics at the University of Sussex, said, “Any hard-won victories over climate change on a global scale could be wiped out by the effects of uncontrolled urban heat islands.” Tol added, “It is clear that we have until now underestimated the dramatic impact that local policies could make in reducing urban warming.”

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