Our world is like a lakebed being filled with excess carbon dioxide. At first the lake filled very slowly, but as we industrialized it filled more quickly. Between England, Germany, and the United States the lake became one-quarter full by 1950. Since then the lake has again doubled in depth, much of it a result of the United States, but more recently from new countries like China and India. Within a few decades, our world will be drowning in one trillion tons of excess carbon dioxide.