The combination of high inertia and high uncertainty makes the system formed by coupling the climate to human industrial metabolism dangerously hard to control. If the climate's sensitivity is at the high end of current estimates, it may be too late to avert dramatic consequences for human societies or natural ecosystems even with immediate and aggressive mitigation efforts. The engineered alteration of planetary radiation budgets--geoengineering--offers a means of managing climate risk, but it entails a host of new risks.

Results/Conclusions

I will describe new methods of engineering albedo using tailored stratospheric scatterers. Using a decision-analytic approach to geoengineering I will assess the value of research that might increase our confidence about its effectiveness and risks. How will ecosystems respond to reduced isolation and high CO2 levels, or to changes in the ratio of direct to diffuse radiation? How might we balance these risks against the potential benefits to valuable ecosystems if we can reduce the rate of climate change?