One of the best articles I've seen to actually implement CO2 reduction and energy/water conservation is here. It lays out strategic approaches to all aspects of conservation in a brief summary. It's written by Steve Burrows, the leader of the Arup Property Business in the Americas. Arup is one of the top global engineering companies in the world with a hugely innovative practice. He discusses an important principle in carbon reduction: recycling existing commercial buildings.
70 percent of the average city’s greenhouse gas emissions come from buildings (includes traffic emissions to deliver its components, equipment and products) LEED standards quantify this interconnection.
Since cities consume 75 percent of the world’s energy and are home to 75 percent of the world’s population, the upside becomes that with this increased population density comes a reduction in gasoline usage and energy costs per capita. (This applies to dense city cores) Its "converse" is that suburban sprawl is unsustainable, but the older "grid" communities relatively close to city centers are not a problem, especially if they have not mansionized .
This is the concept that SCAG is completely missing the ball with. Their solution is adding traffic to areas that don't have the ability to densify due to their old infrastructure and scale. Then this adds a load of traffic to arterials and freeways that did not exist before, since older communities are not linked directly to downtown. It's different on the east coast, for example, where the old grid communities were built up around the commuter rail into NYC. That is a form-based configuration that can't be imposed on vast tracts of suburbia.
Thus Southern California will need to try to adapt some "hub" concentrations in the medium cities like Pasadena, Glendale, Burbank, etc. but they're pretty much at their limits now. There's a huge backlash building in Pasadena and adjacent communities over the amount and density of growth that has already occurred, mostly due to the major increase in traffic. Which this configuration was supposed to solve, but frankly is simply a justification for more square footage, and that always adds CO2 no matter what you do.
Remember Elizabeth Kubler-Ross and the five emotional stages of dealing with approaching death? Collectively we're still in denial about what the impact of human societies are on the planet, moving into bargaining. Hope it's not inevitable that humanity moves into acceptance and death, which is a fatalistic response to a solvable problem. You can't have it all without a cost, so you shrink Bigfoot.