Computational Earth system models are used for simulations of the climatic impact of solar radiation management. Robust features can be detected by applying different models. Several state-of-the-art Earth system models simulate the impact of climate engineering. This GeoMIP experiment G1 mimics mirrors in space and reduces the incoming solar radiation at the surface. The radiative forcing from an instantaneous quadrupling of the CO₂ concentration (4xCO2), starting from the preindustrial level, is balanced by a reduction of the solar constant.  Model responses to the two counteracting forcings in G1 are compared to the control state, the preindustrial climate. While the global mean surface air temperature in G1 remains almost unchanged compared to the control simulation, regionally the temperature is decreased in the tropics and rises in polar regions. Therefore, the equator to pole temperature gradient is reduced in all models. Another robust response is the global reduction of precipitation with strong effects in particular over North and South America and northern Eurasia. These robust results of the model ensemble show that an engineered climate would not be the same as natural conditions, mainly because of the reduced solar radiation at surface. (See Schmidt et al (2012); Kravitz et al (2013))

Niemeier et al (2013) compare the impact of different geoenineering techniques, among them the injection of sulfur into the stratosphere, mirrors in space, and marine cloud brightening  through artificial emissions of sea salt. This study focuses on the question to what extent climate impacts of these three methods would be different. While global mean temperature increases slightly due to the inertia of the climate system and evolves very similar with time, responses of global mean precipitation differ considerably among the methods. The hydrological sensitivity is decrease d by SRM, most prominently for sea salt emissions, followed by the injection of sulfate into the stratosphere. A summary of the article was published as an EOS spotlight: Comparing climate impact of different geoengineering methods.

Jones et al (2013) shows the consequences of a sudden termination of geoengineering. The temperature increases in all models imediately after termination and reaches 60 to 100 % of the temperature in a non-geoengineered simulation within five years. Tilmes et al (2013) show changes in the monsoon as a consequence of SRM, Xia et al (2014) applies a Decision Support System for Agrotechnology Transfer (DSSAT) crop model to learn more about the impact on the growth rate of rice and corn in China.

Niemeier, U., H. Schmidt, K. Alterskjær, and J. E. Kristjánsson, Solar irradiance reduction via climate engineering--climatic impact of different techniques, Journal of Geophysical Research, submitted.

Schmidt, H. et al.: Solar irradiance reduction to counteract radiative forcing from a quadrupling of CO2: climate responses simulated by four earth system models, Earth Syst. Dynam., 3, 63-78, doi:10.5194/esd-3-63-2012, 2012.

Robock, Alan, 2008:  20 reasons why geoengineering may be a bad idea.  Bull. Atomic Scientists, 64, No. 2, 14-18, 59, doi:10.2968/064002006

Royal Society: Geoengineering the climate: science, governance and uncertainty