According to Gert Jan Kramer and Martin Haigh at Shell, not very fast (Kramer and Haigh, 2009). In a concise opinion piece in Nature they coin two laws of energy-technology development—that in the often 30-year start-up phase, all new energy initiatives such as oil, nuclear, liquid natural gas (LNG), biofuels, wind, and solar photovoltaics have grown exponentially at about 26% a year until they finally are producing a world-wide equivalent of about 500 barrels of oil a day, then the grow linearly until they reach their natural market share and level off. Even by shaving off some years in a concerted push to fully develop photovoltaics and carbon capture more quickly, by 2050 two-thirds of the world’s energy will still come from fossil fuels and CO2 concentrations would stabilize at around 550 ppm. If we were to try to stabilize CO2 at 450 ppm which is often thought of as the appropriate goal, we would have to be fully decarbonized—no more fossil fuel burning by the energy sector, or at least capturing all of the CO2 that results—by 2050. The only real solution to meet such an ambitious goal, they suggest, is to accept a decrease in energy consumption.—Emil Morhardt
Kramer, G., Haigh, M., 2009. No quick switch to low-carbon energy. Nature 462, 568-569.