Michael Oppenheimer, a professor of geosciences and international affairs at Princeton University, noted that solving climate change means undertaking a large number of seemingly small measures, like curbing emissions from automobiles, oil and gas wells, air travel, landfills, buildings and more. ‘Just because there are multiple contributors to a problem doesn’t mean we should excuse all but the top one,’ Dr. Oppenheimer said. ‘Just because a polluter’s emissions are decreasing doesn’t mean that they aren’t still far too high.’ “