Tuesday, September 12, 2006

Well, CAN we do anything about it?

One of the ongoing debates in the global warming biz is whether we can solve the problem with known technology or whether we have to rush to develop something revolutionary (can you say “hydrogen fuel cell”?). We need both, argue scientists Robert Socolow and Stephen Pacala in a 2004 paper in Science magazine (re-presented as a well-written piece in the September issue of Scientific American): we can level off our CO2 emissions for the next fifty years using existing technology, then plan on new technologies to help us reduce our emissions substantially over the following fifty years.

One major benefit of a plan like theirs is that we actually do something while we’re waiting the 30-50 years for new technologies to be developed to the point where they can make a measurable difference.

A second is that they provide a practical reference frame for actions we can do.

Here’s the background:
  1. To avoid disaster, we have to avoid doubling the concentration of CO2 in the atmosphere. They set a target maximum of 500 parts-per-million (ppm) (vs. the 280 ppm pre-industrial level).
  2. To stay below 500 ppm, we have to basically hold the current CO2 emission rate constant for the next 50 years, and then substantially reduce it in the 50 years after that.
  3. The current emissions rate is 7 billions tons of carbon per year (7 GtC/yr). If we do nothing, this rate will double in the next 50 years (to 14 GtC/yr). Therefore, we have to look for solutions that will, in aggregate, reduce emissions by 7 GtC/yr by 2056.

The authors acknowledge that no single solution can accomplish this goal, so they break it up into seven more manageable chunks (which they call “wedges” from their graphical illustration) of 1 GtC/yr each. So at least seven existing, proven technologies can accomplish an emission savings that will amount to 1 GtC/yr by 2056.

Once such “wedge” can be obtained by doubling our automobile gas mileage from 30 mpg to 60 mpg. The math: assume each auto travels 10,000 miles a year and gets 30 miles to the gallon. With current fuels, each car therefore puts about ton of carbon in the atmosphere each year. Assuming 2 billion cars on the road in 2056 (a four-fold increase), they would put out 2 GtC/yr in greenhouse emissions. A doubling of the vehicles’ fuel efficiency would halve that amount – a savings of 1GtC/yr or one “wedge.”

The authors present a list of 15 such solution, including substituting natural gas for coal in power plants, capturing and storing CO2 generated by existing and future plants, using electricity more efficiently in buildings, etc. Admittedly, some of these interact, so you can’t simply do all 15 and expect a 15GtC/yr savings. For example, producing cleaner electricity means that you can’t save as much by using that electricity more efficiently.

Still, with 15 (at least) technically feasible methods at our immediate disposal to combat global warming, what are we waiting for?

No comments:

Post a Comment