A new study in Nature Climate Change has found that North American cities, with their massive consumption of energy, are causing winter warming thousands of miles and even a continent away. Indeed, so-called waste heat — the extra warmth generated by cities from the coal and oil burned to fuel buildings, cars and more — is heating up areas far away, including prairies in Canada.
Scientists also found the same warming trend in Russia, northern Asia and eastern China. However, Europe has seen autumn temperatures fall by about 1 degree Celsius.
This phenomenon of waste heat is different from what has been known as the urban-heat island effect, in which “city buildings, roads and sidewalks hold on to the day’s warmth and make the urban area hotter than the surrounding countryside,” says Reuters.
The temperature increases of waste heat can actually “disrupt the normal atmospheric circulation pattern” of both air and ocean currents including the jet stream. The result is “a far-reaching effect on surface air temperature,” says the study, borne out in the finding that, even in remote areas, temperatures have risen by as much as 1 degree Celsius or 1 degree Fahrenheit.
The actual impact of waste heat on average global temperatures is “negligible,” says Reuters. The total amount of waste heat generated by human activities only comprises “one-third of one percent of the total amount of heat carried across high latitudes by air currents and oceans.”
But anthropogenic heating very likely helps to explain additional warming in some places that existing climate computer models have not yet been able to account for. As the study’s lead author, Guang Zhang of the Scripps Institution of Oceanography, says in the Guardian, “what really surprised us was that this energy use was a tiny amount, and yet it can create such a wide impact far away from the heat source.”
The sky to the west of my New Jersey town never gets fully dark at night. It glows orange from all the lights of New York City’s skyscrapers. As the new study shows, all the energy that the U.S.’s and the world’s major cities consume is not only causing light pollution so we can’t see the stars. Even though the increase to global temperatures is barely 0.01 degrees Celsius on average, the bright lights of big cities are having a real, measurable impact on temperatures on a continental scale.
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