The present atmosphere contains approximately 700 Gton(C) in the form of CO2. Earth’s total recoverable fossil fuel reserves contain at least 4200 Gton(C), mostly in the form of coal. (We shall use the value 4200 Gton(C) to be specific.) At present, about half the CO2 produced by the burning of fossil fuels stays in the atmosphere. The other half dissolves in the oceans or is taken up by the terrestrial biosphere. If this ratio remained constant and we burned up all of our fossil fuels instantaneously, by how much would atmospheric CO2 concentrations rise? (Express your answer in terms of the new CO2 level divided by the old one.)