Whenever global warming drops off Congress’s radar, some environmentalists point out the real action is occurring locally, anyway. Some 500 U.S. mayors have signed pledges to reduce carbon emissions. Berkeley, for one, promises an 80 percent cut by 2050. But do these plans actually do anything?

(Mike Blake/Reuters)

For example, cities that have enacted official climate action plans do contain more energy-efficient, LEED-certified buildings than cities without plans. But Millard-Ball’s analysis reveals there’s so much variation among cities with plans that the plans themselves seem to matter very little. Instead, factors like higher employment and non-residential growth appear to be the main drivers of green building development. What’s more, if a city is already erecting lots of green structures, then it’s more likely to adopt a climate plan — at that point, the plan is an easy, painless step. But the act of adopting a climate action plan doesn’t seem to change anything.

That doesn’t mean it’s impossible to take local action to reduce emissions on a modest scale. Millard-Ball found that California cities with environmentally-minded residents do seem to take a number of significant steps to curtail fossil-fuel use: car pooling, biking more, implementing waste-reduction measures, using efficient LEDs in their street lights, and so forth. (There was one curious exception: Green-minded residents are no more likely to adopt solar panels than anyone else.)

But this suggests cities should focus on those smaller, concrete steps rather than sweeping, meaningless plans and emissions targets. “Rather than a focus on the creation of city-level climate plans,” Millard-Ball concludes, “policymakers might be better served by redirecting those efforts towards the implementation of specific programs; on funding emission-reduction projects in the progressive cities that already want to implement them; and on taking action (perhaps in the form of marketing campaigns) to shape environmental preferences in a direction supportive of climate change mitigation.”

That last point is a particularly crucial one — having an elaborate plan drafted by local elected officials is no substitute for convincing voters that climate change is worth caring about. And, taking this one step further, modest local efforts, while helpful at the margins, are still no substitute for a national policy on carbon emissions.