Eric Drexler is apparently at the Renaissance Weekend with the intent to speak to the assembled interesting people about how “advanced nanotechnology can address the climate change problem providing low-cost solar energy and by removing accumluated CO2 from the atmosphere.”  In the same spirit, for the rest of us, here’s how I think we should go about using advanced nanotechnology to address the problem of climate change:

  • Develop advanced nanotechnology already!  In particular, develop a self-replicating machine technology at the molecular scale. This could be done by using any or many of the approaches outlined in the Roadmap or by a direct approach I call the Feynman Path which I will be writing more about in detail in the coming weeks. But the bottom line is simple, and can be stated: “Just do it.” There isn’t any major, well-funded effort to do this, by whatever pathway.  There should be, and at best, all the possibilities should be explored in parallel.
  • Decide what the Earth’s climate ought to be.  It strains the bounds of credibility to imagine that the optimal climate is just what we happened to have in 1950 (or any other particular year). This includes how much natural variability we want to allow: In the absence of any human influence, climate ranges to the steaming jungles of the dinosaur age 100 million years ago to the ice ages of 100 thousand. Do we want to freeze any possible dinosaurs out of our future?  Do we want to preclude any ice ages?

    (note that the apparent levelling off of temperature is due to the logarithmic scaling of the time axis — the 10,000 year holocene is the same width as the peaks in the Pleistocene or the squiggles in the Pliocene, and wouldn’t show up at all on the left side of the chart.)

  • Decide how much CO2 we want in the atmosphere. This is essentially independent of the question of temperature: CO2 is a relatively minor greenhouse gas, the major one being of course H2O. Greenhouses are typically kept at 1000 ppm for good plant
    growth (think agricultural productivity) and OSHA limits for humans allow up to 5000 ppm. Set the CO2 level to whatever we want by choking or amplifying the natural flows to and from sources and sinks:
    co2 flows
    (Probably the easiest flow to interdict is rotting vegetation; nanoengineer a way to make plastic from cornstalks, hay, etc.)
  • If the temperature we want is higher than the equilibrium one for the level of CO2 we want, add additional greenhouse gases to the air. We are actually doing that in a fairly major way by irrigation, raising the humidity of the air in large areas (e.g. California) where it would naturally be dry. However, there are other gasses such as methane which are quite potent and could be used.
  • If we want it colder, we either remove some water from the air, or construct a negative GHG using nanotech — that is, a molecule or nanoballoon which reflects near-IR and is transparent to thermal IR — and administer whatever amount is necessary.
  • If all else fails, build a Weather Machine. Be careful, though: while natural climate variability is not an existential risk — we do fine in steaming jungles and have lived through ice ages — a Weather Machine run by the same people who ran our financial system recently could be a very dangerous toy.