In response to the timely news article on global warming in New Times last week ("One gaseous goal," April 5), we would like to state that in spite of some opinions in Sacramento to the contrary, there are models for building green communities and buildings as a response to global warming. Furthermore, these models contain numerical analysis that shows how effective doing this can be in climate recovery efforts.

Looking at carbon dioxide emissions in the atmosphere, we see a sharp rise over the last 50 years. This trend must level off over the next 50 years and then be reduced over the following 50 years to stop runaway global warming. The difference between present emissions and no more increase in emissions can be visualized as a stabilization wedge representing a reduction of 7 billion tons of carbon emissions per year (see chart).

By breaking this into seven smaller wedges each representing a reduction of 1 billion tons of carbon emissions per year we can compare the effects of a variety of carbon-reduction strategies. For example, if we reduce the birth rate worldwide a certain amount, we would achieve one of these smaller reduction wedges. Stopping all deforestation worldwide would also give us one reduction wedge. Having 2 billion cars get 60 mpg rather than 30 mpg would give us another wedge. All this sounds pretty difficult to implement, so let's look at some easier strategies.

If we reduce electricity demand in buildings by half, we can achieve two carbon reduction wedges. This is relatively easy to do, since most of the electrical use in buildings in the United States is for lighting. Designing buildings for natural day lighting, turning off unnecessary artificial light during the day, and using more efficient fixtures for the reduced artificial lighting would allow us to achieve this goal. The added bonus of natural daylighting, a simple solution, is an improvement in the health and productivity of occupants. This demonstrates the power of green building!

Let's go one step further and design zero-energy buildings. This may sound difficult, but several such buildings exist in California today. (One in Los Altos Hills was designed by San Luis Sustainability Group.) If we could convert to building zero-energy buildings, we could obtain four carbon reduction wedges out of the seven we need. One further step is making buildings net energy producers by integrating photovoltaic cells as an integral part of every building. This has already started in California, Europe, and Japan. Doing this would give us another reduction wedge, bringing us up to five reduction wedges achieved through existing green-building practices.

The next step is to develop green concepts as a major part of community planning, especially in regard to implementing smart growth principles, the Ahwahnee water principles (adopted by San Luis Obispo), and related appropriate technology. This would give us one more wedge by reducing the present massive infrastructure and transportation costs of development. This approach was pioneered in California with the very successful Village Homes development in Davis. Another successful green community plan was recently built in Beddington, England. By applying these concepts, we could get another wedge. Now we're up to six wedges.

Finally, we get serious about new building materials that take less energy to produce and work as passive solar components. Straw bale buildings are one example of this approach. They create a superior building while utilizing what was considered a waste product to be burned. They also work better as passive solar components. Presently there are at least 60 straw bale homes in San Luis Obispo County. This strategy of reducing the embodied energy of materials while simultaneously sequestering carbon in the building process potentially allows one more carbon reduction wedge, so we have now reached our goal of seven wedges. Eureka!

To conclude, global warming is a huge challenge, but models do exist for dealing with it. Some are reactive and require big changes in behavior. Some are proactive and easier to accomplish. If we use the existing sustainable planning, green building, and appropriate technology model and develop the cultural will we can build our way out of this big problem.

Ken Haggard and Rachel Aljilani serve SLO Green Build on the board and technical committee, respectively. They're also part of San Luis Sustainability Group architects. They can be reached at [email protected].