Knowing the unknowns

Abstract

The Earth's atmosphere is not the only source of radiative forcing and anthropogenic climate change. As surely as people and civilizations have carbon footprints, they have albedo footprints as well. By altering the reflectivity of roughly half the land surface of the Earth in the past, mankind has made inadvertent geoengineering a part of the landscape of history. This worldwide alteration of reflectivity raises questions about the future of climate change, for albedo is a first‐order determinant of the Earth's radiative equilibrium. As surfaces absorb roughly 100 times more solar energy than the CO 2 in the atmosphere, future anthropogenic changes in both land and water albedo may figure significantly in climate policy outcomes. There is more to climate change than the atmosphere The future of albedo counts almost as much as future atmospheric chemistry The future of the hydrosphere, climate, and albedo are intertwined