One of the many arguments that deniers rely on to pooh-pooh climate change is the prevalence of the "urban heat island" effect, i.e. the tendency for cities to absorb and retain heat. The problem’s not gas-belching cars and factories, it’s all those city-dwelling lefties! But according to a new study from Stanford University, there's just no possible way that cities are causing global warming, at least not on the same scale that greenhouse-gas emissions are.

At most 4 percent of "gross global warming since the Industrial Revolution" can be traced back to urban heat island, the study found. Greenhouse gases are responsible for 79 percent. So, if you live in a city, don't sweat it! If you've commuted for 1.5 hours in a car for the past two decades, maybe sweat it.

The study also contained some bad news about white roofs, a favored cheap and simple solution for mitigating the urban heat island effect. White roofs were supposed to reduce global warming by reflecting more light back into the atmosphere and reducing the need for air conditioning. But the Stanford study found that if all roofs were painted white, they'd cause other changes that would cancel out their benefits. Sticking solar panels on the roof, however, would reduce the urban heat island effect and help scale back climate change.

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