Eduardo Porter calculates that keeping global warming below the 2°C limit recommended by most experts “probably requires that a good share of the world’s fossil fuel remains untapped”:
Fatih Birol, chief economist of the International Energy Agency, told me the atmosphere could absorb at most another one trillion tons of CO2. It got almost 32 billion tons in 2011 alone, 3.2 percent more than the year before. Even if emissions were to remain at the same level as last year — a highly unlikely prospect given the rapid growth of energy consumption in countries like China — the global economy, in about 30 years, would have to stop relying on fossil fuels entirely.
Most of the carbon in the ground is in the form of coal. But the world’s known reserves of oil and gas contain about one trillion tons of CO2. Applying Mr. Birol’s limit would require Saudi Arabia, Gazprom and Exxon to leave some of their reserves in the ground. They are unlikely to take kindly to this.
What’s more, Mr. Birol’s numbers may be too optimistic.
(Chart of the “Global annual fossil fuel carbon dioxide emissions through year 2007, in million metric tons of carbon, as reported by the Carbon Dioxide Information Analysis Center” from Wikimedia Commons)