Active Amplification of the Terrestrial Albedo to Mitigate Climate Change: An Exploratory Study

To date, international efforts to mitigate climate change have focussed on reducing emissions of greenhouse gases in the energy, transportation and agriculture sectors, and on sequestering atmospheric carbon dioxide in forests. Here, the potential to complement these efforts by actions to enhance the reflectance of solar insolation by the human settlement and grassland components of the Earth's terrestrial surface is explored. Preliminary estimates derived using a static two dimensional radiative transfer model indicate that such efforts could amplify the overall planetary albedo enough to offset the current global annual average level of radiative forcing caused by anthropogenic greenhouse gases by as much as 30% or 0.76 Wm^{− 2}. Terrestrial albedo amplification may thus extend, by about 25 years, the time available to advance the development and use of low-emission energy conversion technologies which ultimately remain essential to mitigate long-term climate change. While a scoping analysis indicates the technical feasibility of sufficiently enhancing human settlement and grassland albedos to levels needed to achieve reductions in radiative forcing projected here, additional study is required on two fronts. Firstly, the modelled radiative forcing reductions are static estimates. As they would generate climate feedbacks, more detailed dynamic climate modelling would be needed to confirm the stationary value of the radiative forcing reduction that would result from land surface albedo amplification. Secondly, land surface albedo amplification schemes may have important economic and environmental impacts. Accurate ex ante impact assessments would be required to validate global implementation of related measures as a viable mitigation strategy.