Even with the current (mostly) “dirty” electricity generation, converting to electric vehicles STILL reduces greenhouse gas emissions, typically on the order of 20-30%.

Take this example illustrated in the following Slate magazine article:
http://www.slate.com/id/2179609/

“Let’s compare the Toyota compact to the forthcoming all-electric Tesla Roadster, which promises 245 miles’ worth of travel per charge. The relatively fuel-efficient 2006 Corolla gets an average of 31 miles per gallon of gas, assuming it has a manual transmission. Over 100 miles, then, the Corolla will consume 3.23 gallons of gas, which in turn produces 63.11 pounds of carbon dioxide. (According to the Energy Information Administration, a gallon of gas produces 19.564 pounds of carbon dioxide—yes, seriously.) That figure, of course, doesn’t include the energy expended to pump the oil out of the ground, ship it across the oceans, refine it, and get it to your local filling station.

Now let’s look at the Roadster over that same distance. A recent analysis by Automotive Testing and Development Services found that for every 100 miles of travel, a Roadster needs to be recharged with 31 kilowatt hours of electricity. (Only about 70 percent of that charge goes toward creating motion; the rest is lost due to inefficiencies in the charging process.) Generating a kilowatt hour of electricity produces an average of 1.55 pounds of carbon dioxide, which means the Tesla vehicle emits 48.05 pounds of CO2 per 100 miles.“

Neighborhoods with more density can support more nearby jobs/shops and better transit (e.g. Manhattan). When the stuff you do is closer you don’t have to drive or if you do drive you don’t have to drive as far.

That’s how density reduces GHG emissions on a per capita basis: by enabling people to get around without driving.

In the suburbs most of what you do is too far away and you end up driving. Higher density housing is a critical and indispensable part of any effort to combat climate change.

This is nothing more to this than opening up already built out housing markets to additional development. That environmental issues are being used as cynically as they are will do no one any good in the long run.

Something else I was wondering: does there come a point at which adding density to a neighborhood, which promotes walkability and better transit service, cancel out those benefits (environmentally speaking) through added elevator use? I was staring at a huge apartment building in South Park the other day and wondering if a thirty-story elevator ride to get a stick of gum really counts as “pedestrian oriented”?

Anyway, just food for thought . . .