PNNL

Abstract

Understanding the climate impacts of solar geoengineering is essential for evaluating its benefits and risks. Most previous simulations have prescribed a particular strategy and evaluated its modeled effects. Here we turn this approach around by first choosing climate objectives and then designing a strategy to meet those objectives in climate models. There are four essential criteria for designing a strategy: (i) An explicit specification of the objectives, (ii) Defining what climate forcing agents to modify so the objectives are met, (iii) A method for managing uncertainties, and (iv) Independent verification of the strategy in an evaluation model. We demonstrate this design perspective through two multi-objective examples. First, changes in Arctic temperature and the position of tropical precipitation due to CO2 increases are offset by adjusting high latitude insolation in each hemisphere independently. Second, three different latitude-dependent patterns of insolation are modified to offset CO2-induced changes in global mean temperature, interhemispheric temperature asymmetry, and the equator-to-pole temperature gradient. In both examples, the ``design'' and ``evaluation'' models are state-of-the-art fully coupled atmosphere-ocean general circulation models.