at the present rate, carbon dioxide emissions to the air will probably increase from 6 billion tons, which is what they are at present, to 15 billion tons as the less-developed countries develop their economies. We cannot expect, and we probably should not even ask, that these nations not use their fossil fuels. The fossil fuel that both China and India have in abundance is coal, not oil or gas, and coal is a messy, dirty, poisonous substance. I hope we can at least reduce its use to a considerable extent in the United States. But until the economies of India and China develop much more than they are now, we cannot expect much reduction in their use of coal.
Many ways have been suggested for reducing carbon dioxide emissions. The principal ones, from my viewpoint, are the use of nuclear power as a substitute for fossil fuels and the use of hydrogen (produced by the electrolysis of water, with the primary energy coming from nuclear reactors) as a fuel for transportation.
In any case, the concentration of carbon dioxide in the atmosphere will not increase indefinitely, because we will ultimately exhaust the world's reserves of fossil fuels. A quadrupling of atmospheric carbon dioxide compared to mid-nineteenth century levels would be about the highest atmospheric concentration that could be expected in the future and could possibly occur in the twenty-second century.