As the weather warms, so does the use of air conditioners. But running these devices requires power plants to ratchet up electricity production, causing air polluting emissions to rise. An analysis of 27 states found that, on average, summer emissions of sulfur dioxide (SO2), nitrogen oxides (NOx) and carbon dioxide (CO2) go up by hundreds to thousands of metric tons per degree Celsius increase. The report appears in the ACS journal Environmental Science & Technology.