Global And Arctic Climate Engineering: Numerical Model Studies

Climate engineering is an intentional large-scale intervention in the Earth’s climate system to counteract the anthropogenic warming. It has been proposed and recently gained attention as a potential option for tackling global warming. To evaluate the feasibility and impacts of geoengineering, we performed idealized climate simulations using solar geoengineering scheme by artificially reducing the incoming solar radiation at the top of the atmosphere (TOA) either globally or over the polar regions. Four simulations were conducted, i.e. pre-industrial control simulation, global warming simulation with 4xCO2, global uniform solar reduction and reduction of solar radiation regionally over both poles. Our results indicate that the 4xCO2 induced a 6.7 K global mean surface temperature raise, amplified over both poles primarily during the hemisphere winter. Besides, the warming also cause intensification and poleward shift of the global precipitation pattern. A 4.2% globally uniform solar reduction can largely compensate the global mean warming caused by 4xCO2. We find that solar reduction is efficient to reduce the warming at the region where the background sunshine is strong, such as the low-latitude summer warming. However, the CO2 induced warming over high latitudes during winter are less sensitive to solar reduction. The solar reduction leads to more residual warming over land than over the ocean. Therefore, it could result in hemisphere asymmetric residual warming due to the hemisphere asymmetric land-sea distribution. This will eventually cause northward shift of the Intertropical Convergence Zone and the associated low-latitude precipitation pattern. Moreover, we notice that solar reduction could lead to an overall weakening of the global hydrological cycle, suggesting that over reduction of solar radiation may result in large-scale drought. The CO2 forcing introduces more warming over the poles than low-latitudes. The ice sheets around both poles are critical for further sea level rise. Our experiments indicate that 16% solar reduction over both poles (higher than 60 ◦N/S) is able to restore the summer temperature and sea ice extent. However, such polar regional geoengineering leads to stronger and more frequent high-latitude storms. Our simulation results show that Solar Radiation Management is an effective way to offset global mean temperature raise. Nevertheless, climate engineering by reducing insolation at the TOA, either globally or regionally, have strong impact on the hydrological cycle and the regional climate. In spite of the fact that our climate simulations are being highly idealised, these simulations can provide useful information about the climate respond to scenarios with more realistic GHG forcing