The biggest problem

"The biggest problem confronting the world, Lackner was deciding at that time, is not whether quarks could exist in a free, unconfined state outside the atomic nucleus - the question that had exercised his brain as a theoretical physicist, and that he pursues these days as a hobby, the way other men might go bowling. The biggest problem was environmental. Malthus and his followers were right: we are headed for a brick wall. But the wall our growing population would soon crash into was not, as the Malthusians thought, the limited resources of the planet. It was the limited ability of the planet's thin biosphere to sustain the environmental impact our growing population and spreading industry are inflicting on it.
Ultimately that problem came down to energy. "If we had cheap, clean, and copious energy, we could solve our problems about being sustainable," Lackner says. Unlike other energy sources, fossil fuels are cheap and copious right now. If we could just make them clean, they would be perfect."

Wallace Broecker and Robert Kunzig, "CO2 - Fixing Climate", chapter "Scrubbing the air".

As the title of this chapter suggests, Klaus Lackner thinks there is a solution: capturing CO2 out of the ambient air, and storing it as carbonates, the way nature does it with the weathering process, albeit at much too slow a rate to keep up with our emissions. As crazy as it may sound, some people have thought about it seriously, and are beginning to show it could be feasible. I'll make another post about it later, but I just would like to add here an excerpt from Lackner's 2003 Science paper ("A guide to CO2 sequestration"):
"CO2 is three times as heavy as fuel and therefore cannot be stored in cars or airplanes. CO2 from these sources will have to be released into the atmosphere and recaptured later. Currently, photosynthesis is the only practical form of air capture. Capture from air flowing over chemical sorbents - such as strong alkali solutions or activated carbon substrates - appears feasible but needs to be demonstrated. [...]
Because the atmosphere mixes rapidly, extraction at any site, however remote, could compensate for emissions from anywhere else. By decoupling power generation from sequestration, air capture would allow the existing fossil fuel-based energy infrastructure to live out its useful life; it would open remote disposal sites and even allow for the eventual reduction of atmospheric CO2 concentration."