The world cannot afford to dump more carbon dioxide into the atmosphere. Yet it is not cutting back. All indications are that the concentration of CO2 will continue to rise for decades. Despite great support for renewable energy, developed and developing countries will probably burn more oil, coal and natural gas in the future.
For transportation, the alternatives to petroleum appear especially far off. Onboard energy storage for electric vehicles is difficult; for a given mass, batteries hold less than 1 percent of the energy stored in gasoline. Carrying hydrogen on vehicles requires 10 times the storage volume of gasoline, and the high-pressure tank needed to hold it is very heavy. Although a few maiden flights of airplanes powered by jet fuel derived from biomass have taken place, it is unclear that biofuels can be produced at the quantities and low prices required by airliners ... or by ships for that matter.