. It is now widely accepted that increasing carbon dioxide levels in the atmosphere are causing warming of the planet by preventing the escape of infrared radiation into outer space. This is a kinetic problem rather than an equilibrium one. Carbon dioxide from the atmosphere dissolves into the sea and is then deposited as limestone, either by precipitation or via secretion into animal shells. The capacity of the sea to hold carbon dioxide is vastly larger than the amount of carbon held in reserves of fossil fuels, and the amount of carbon locked away in limestone is many thousand times larger again. Projects are under consideration for speeding the transfer of carbon dioxide from the atmosphere to the oceans and rocks. Suggest criteria that should be used to asses these projects and rank these criteria.