The National Academy of Sciences this week released a much-heralded report on “geoengineering” of climate: large-scale interventions that alter climate in ways that compensate for human greenhouse gas emissions. (Sometimes the term also encompasses methods to pull CO2 out of the atmosphere.) The most widely discussed method is to place tiny reflecting particles in the stratosphere, which would cool the climate in the same way that a large volcanic eruption does.
No reputable scientist I know thinks this is a good idea, although some support studying it (and I plead guilty to having written a few papers about it). The problems include
- unintended consequences: we don’t know what they might be;
- limited effectiveness: even at best, regional climatic changes would still be significant, and ocean acidification is not improved at all;
- governance: who makes the decision to go ahead with this? Who is responsible for continually maintaining it? and
- an “easy out:” if we mask climate change with geoengineering, then politicians might lose what little motivation they have to actually address the problem;
- commitment: if we put a geoengineering system in place and continue to emit greenhouse gases, then stopping the geoengineering would result in very rapid climate change. In that case, we would have to keep a geoengineering system in place for thousands of years.
I could go on, but that’s enough, isn’t it?
Most folks who say we should “consider” geoengineering suggest only a limited-time deployment, while we transition from fossil fuels to renewable energy. If we’re going to consider that, wouldn’t it be better to achieve the same goal by managing the biosphere? A recent paper by the WHRC Senior Scientist Richard “Skee” Houghton shows that aggressive management of the biosphere (halting deforestation, regrowing degraded areas, etc.) could pull substantial amounts of CO2 out of the atmosphere for several decades. In fact, in the best case the biosphere could absorb an amount equal to about half of global CO2 emissions today. That’s a lot! And rather than incur the unknown risks of geoengineering, restoring the biosphere has good side-effects: healthier species and ecosystems, greater biodiversity, cleaner water, and so on. Of course, it’s not so simple. A concerted, global scale effort would be needed, and large-scale reforestation can itself affect regional climate. But isn’t this a better direction for research and advocacy than science-fiction type climate manipulation?