Cross-posted from ThinkProgress Green.

Over 80 percent of Americans and over half of the world’s population live in cities. By 2050, over 70 percent of the global population is expected to be urban. By then — less than four decades away — human civilization needs to be carbon neutral if we are to have any hope of averting catastrophic climate change. Figuring out how to eliminate greenhouse pollution from cities is a necessary component of that challenge.

The city of Seattle, a global leader in the fight against climate change, commissioned the Stockholm Environment Institute, Cascadia Consulting Group, and ICF International “to develop a scenario [PDF] of how the city might be able to achieve carbon neutrality” by 2050:

• Shifting to less GHG-intensive travel modes such as ride sharing, transit, walking, and biking, to produce a 30 percent reduction in per capita travel in light-duty vehicles by 2030 and a 50 percent reduction by 2050, relative to 2008 levels.


• Dramatically increasing energy efficiency in building design and operations, as well as in vehicle efficiency, to produce over 30 percent in energy savings by 2030 (per capita in residential, per square foot in commercial, and per mile in vehicles) and over 50 percent by 2050, relative to 2008 levels.


• Transitioning homes, businesses, and vehicles to lower-carbon energy sources: electricity (or possibly hydrogen) in the long run, biofuels as a bridging strategy for transportation until electric vehicles predominate, and to a much lesser extent, sustainable biomass sources (for district energy systems).