Saturday, February 19, 2011

Estimating cities’ share of GHG reductions in California

In preparation for implementing Senate Bill 375, California’s metropolitan areas recently proposed regional greenhouse gas (GHG) emission reduction targets that reflected how much they could feasibly reduce transportation emissions over the next few decades.  This was an important step in reconciling urban planning with climate action.  However, given that we face irreversible, catastrophic climate change if the world doesn’t reduce its emissions to 80 percent below 1990 levels by 2050, a target that Governor Schwarzenegger committed California to with Executive Order S-3-05, the question to ask may not be how much can cities reduce emissions, but instead how much do they need to reduce emissions?

In the past, America has used technology to fight its environmental battles, and many expect that technology will also solve the climate challenge.  California has led the way in mandating cleaner technologies in order to meet its interim goal of reducing emissions to 1990 levels by 2020 with policies that reduce the carbon content of gasoline by 10 percent, require utilities to generate at least 33 percent of their power from renewable sources by 2020, and institute new efficiency standards for passenger vehicles.  But even if technology continues to evolve at the pace set by these measures through 2050, cities will still need to reduce their emissions by almost 60 percent in order to meet California’s 2050 GHG reduction target.   

Even in the sector that has been the focus of policy makers and have seen the most progress in reducing emissions—passenger cars—cities will be responsible for reducing GHG emissions by an additional 20 percent.  

These reductions will likely come from planning and building communities that allow people to live more efficiently. 

Over 250 local governments have created or are in the process of creating climate action plans.  Unlike state and federal policies that focus on technological improvements, local climate plans generally focus on creating communities that allow residents to live more efficiently.   The Bay Area Air Quality Management District (BAAQMD) recently created GHG emissions thresholds for land use projects by figuring out how much existing policies could reduce emissions, and then assuming that urban planning would be responsible for covering the gap between what existing policies could account for and the state's 2020 targets.  We simply assumed that the policy reductions calculated by BAAQMD would continue out to the year 2050, and compared them to the State's 2050 GHG reduction goals.  This is a simplistic method of creating projections, but it leads us to some pretty ambitious assumptions, including:
  • Transportation fuel will contain 72 percent of the carbon that it does today.  This is roughly the equivalent of shifting from gasoline to ethanol derived from sugarcane, which is one of the most efficient ethanol fuel stocks.
  • Passenger vehicles will consume 18 percent of the fuel that they do today, and the average car on the road will get 105 MPG.
  • Electricity would have one-sixth the carbon content that it does today.  For Pacific Gas and Electric, which provides electricity for most of the Bay Area, this would mean supplying electricity generated from 91 percent renewable energy, with the remaining nine percent coming from natural gas.
  • The average home would consume 46 percent less energy than it currently does; which would mean that all new homes get built to maximize energy efficiency, and all existing homes receive the maximum possible efficiency retrofit. 
  • Over four million homes—roughly 30 percent of the state's projected number of single-family homes in 2050—will have rooftop solar arrays.

Even with a pretty astounding rate of technological improvement over the next 40 years, good community design will still need to reduce GHG emissions by over half.  Compare that to the 2035 targets that ARB recently set for California's largest and fastest-growing metro areas, which range from 10 to 16 percent.  Planners and policy makers at both the local and state levels will need to focus on achieving more aggressive land use changes if California is serious about fighting climate change.

We'll be posting the full report on our website soon--stay tuned. 

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