Over the past decade, cities have been taking the lead in creating policies to fight climate change; conducting inventories of local greenhouse gas emissions, setting goals to reduce emissions, and identifying a set of actions to meet these goals. I've posted greenhouse gas inventories conducted by, respectively, the City of Chicago, the City of Berkeley, and Portland Metro, the regional government for the Portland, OR metro area, below. Take a look at them. Here's Chicago:
And Portland Metro:
Why the differences? Are Chicago's buildings older, or its winters colder? Do people in Berkeley drive more? Do residents of the Portland area buy a lot of goods from halfway around the world? For that matter, do residents of Berkeley and Chicago buy any goods or food that contribute greenhouse gas emissions to the environment?
Figuring out how much a given activity contributes to climate change is a challenging task. But figuring out how much control a local government has over the activities that take place within its jurisdiction--and therefore which categories of greenhouse gas emissions a government should take into account, as well as how effective the different options that are available to planners and policy makers might be in reducing these emissions--is even trickier. When cities create climate policy, they're thinking not only about what's technically effective, but also what's politically feasible.
The differences in the above graphs speak to this fact. Some are technical in nature. For example, electricity in Berkeley and Portland, both of which are located in areas with abundant hydroelectric resources, is relatively clean compared to Chicago's electricity, and Chicago's hot, humid summers and chilly winters mean that residents burn a lot more energy keeping their homes comfortable than in the other two cities, both of which are relatively mild. Both factors may help to account for the large percentage of Chicago's greenhouse gas emissions attributable to "buildings and other energy uses." But politics may also be a factor; the City of Chicago's leverage over building codes and standards give it more direct control over these emissions, and the high-profile green roof atop city hall, constructed in 2001, may have also helped raise awareness of building energy use among citizens.
Meanwhile, according to Portland Metro's count, greenhouse gas emissions due to transportation are about on par with those due to electricity use. But this isn't because Portland area residents drive more: not only does electricity use contributes a smaller share of Portland's GHG emissions because electricity there is cleaner, but as a regional agency, Metro also accounts for longer commutes in suburban areas, while Chicago just examines the transportation emissions of urban residents who drive relatively little. As for the nearly 50 percent of Portland's emissions that come from goods and food consumption, counting such emissions is a rapidly-evolving science, and Portland Metro conducted its inventory much more recently than Berkeley or Chicago. Furthermore, since Metro oversees recycling programs for the entire Portland region, and because the region has a high number of "green consumers" concerned about the environmental impact of their choices, Metro may be more likely to perceive itself as having both the authority and the political advantage to address this category of emissions.
A lot of climate policy focuses more on technological shifts more than the types of changes that the cities above are trying to spur. Historically, our environmental protection policies have leaned heavily on technology, and greenhouse gas reductions are easier to quantify when you don't have to worry about unpredictable things like human behavior. This is part of the reason that SB 375's regional transportation-sector greenhouse gas reduction targets, which call for regional agencies to channel transportation funding toward projects that reduce driving, contribute under three percent of the progress toward California's 2020 reduction goals, according to the Air and Resources Board's AB 32 Scoping Plan. But just because the effect of community design on greenhouse gas emissions is difficult to quantify doesn't mean that it's not important. In fact, I'd argue that community-level climate action is even more important, because people have such a deep tie to the places that they live, so creating greener cities has an educational value that extends far beyond the actual greenhouse gas reductions. Witness Chicago, which since announcing its Green Building Agenda in 2004 has twice hosted the US Green Building Council's Greenbuild Expo, inspiring politicians and builders all over the country.
This is part of the reason that we're doing what we're doing here at CREC--to help cities better understand how to quantify the greenhouse gas reductions and environmental benefits of the decisions that they make, so that they can pursue the project and policies that count the most.