Here is what Ken Caldeira says:
Carbon dioxide emissions will have to be all but eliminated by the end of this century if the world is to avoid a temperature rise of more than 2 ºC, scientists warned yesterday. And it might even be necessary to start sucking greenhouse gases out of the atmosphere.
The findings are the culmination of five years work by Ensembles, a major European research consortium led by the UK Met Office Hadley Centre and involving 65 other research institutes worldwide. In the first study of its kind, scientists in the project used a variety of the latest global climate models to determine the reductions needed to stabilize levels of greenhouse gases, termed CO2 equivalents, at 450 parts per million. That level, which offers a reasonable chance of keeping the temperature rise under 2ºC, is the goal of European climate policy.
The results suggest that to achieve that target, emissions would have to drop to near zero by 2100. One of Ensemble's models predicted that by 2050, it might also be necessary to introduce new techniques that can actually pull CO2 out of the atmosphere.
Any bets on whether or not people will "stop building new CO2-emitting devices within the next decade"? As I have often said, no one really knows the possibilities of air capture (chemical, biological, geological) and sequestration at scale, and we won't until a greater effort is devoted to it. But whether you like it or not, the slow pace of mitigation policies to meaningfully deflect trajectories from business-as-usual means that air capture is gaining traction as a policy option, and will continue to do so. It is not at the center of debates over climate -- yet -- but it is moving closer.
The results suggest that simply switching to renewable sources of energy may not be enough to stabilize emissions. "It's clear that if we continue our current emissions trajectory and we want to stay at 450 parts per million, we'll need to pull CO2 out of the atmosphere," says atmospheric scientist Ken Caldeira, who works at the Carnegie Institution for Science's Department of Global Ecology in Stanford, California. That could mean deploying new techniques for capturing carbon, such as biochar, reforestation or air filtering, on a massive scale.
Caldeira adds that action now could be a better option. If people stop building new CO2-emitting devices within the next decade, they could achieve the same result at a lower cost.