Cities play a unique role in addressing climate change. Over 80 percent of Americans live in urban areas, as does over half of the world’s population. The design of cities, from their built environment to their transportation systems, has a profound influence on global greenhouse gas (GHG) emissions. City planners, as well as the market forces they can influence, will determine whether urban areas will be car-intensive or transit-oriented, how buildings will be built and maintained, and even where electricity and heat will be sourced.
With one and a half billion new urban dwellers expected in the next two decades, it is critical that cities demonstrate how they can dramatically reduce their GHG emissions, while creating more vibrant and prosperous places to live and do business.
In the U.S., cities have long been vocal proponents of climate action. For example, in 2005, the City of Seattle led an effort to convince over one thousand U.S. mayors to commit to reducing GHGs. Last year, the Seattle City Council adopted a more profound and ambitious vision for Seattle: to become a carbon-neutral city.
To illustrate the possibility (and the challenge) of this ambitious goal, we recently conducted a scenario analysis for Seattle until 2050. We found that with about 20 measures, Seattle could cut GHG emissions dramatically: by 30 percent (per capita) by 2020, 60 percent by 2030, and 90 percent by 2050. Three broad outcomes were essential:
· Shifts to less GHG-intensive travel modes such as ride-sharing, transit, walking and biking. These measures could lead to 30 percent less per-capita travel by light-duty vehicles in 2030 and 50 percent less by 2050, relative to 2008 levels.
· Second, dramatic increases in energy efficiency in buildings and vehicles, measures that result in over 30 percent energy savings by 2030 and over 50 percent by 2050.
Finally, homes, businesses, and vehicles transition to lower carbon energy sources: electricity (or possibly hydrogen) in the long run, biofuels for vehicles until electric vehicles predominate, and to a much lesser extent, sustainable biomass sources (for district energy systems).
Several of the measures we studied are already part of the charge of city government. For example, Seattle has substantial influence over alternative transportation modes, building energy use and emissions, and development of electric vehicle infrastructure. That said, federal and international action will be essential. Over half of the reductions in our scenario result from efficient vehicles and appliances and alternative fuels. These technologies will require global demand, development, and deployment that only national and international actions can provide.
And, even with concerted action at all levels of society, eliminating every ton of GHG emissions may prove too difficult or costly to achieve, especially in the next few decades. To get to net zero emissions, Seattle would have to offset some emissions, for example, through increased sequestration activities, or by supporting and taking for credit emissions reductions in poorer regions. And if we are serious about limiting warming to 2 degrees, wealthier regions may ultimately need to take even greater responsibility for reducing emissions. As our SEI colleagues have noted, from a pragmatic as well as a moral perspective, Seattle, like other rich cities and nations, may need to go carbon “negative,” offsetting more than just their own remaining emissions.
Our scenario offers proof of concept that a very low emission future is achievable for Seattle, even if the implementation challenges are daunting. The City’s Office of Sustainability and Environment is now developing a new Climate Action Plan, to be finalized in 2012, to chart Seattle’s path forward and translate the carbon neutral vision into discrete policies and actions for implementation.
