The news on reduction of global greenhouse gas emissions is not good. A famous study (“wedges”) on approaching the enormous problem released a pessimistic update recently, arguing we need many more of them.

There is also so much we do not know. Key questions are what will climate change cost, per capita? Where is the point where natural seeps and emissions of greenhouse gases accelerated by warming and forcings start being significant compared to human emissions? And how do we motivate people to act when the climate payoff from action won’t be experienced for nearly a century, due to inertia of the climate system? How close are polar regions to devastating collapse?

With that pessimistic report, it seems essential to turn to ways to buy ourselves time to get this fixed. One approach, studied by Professor Klaus Lackner and others, involves capturing carbon dioxide directly from the atmosphere.

Another approach, which I just learned about today, involves capturing carbon dioxide directly from seawater. CO₂ is 142 times more soluble in oceans than in air, which is in part why a third of each unit of human emission of greenhouse gas tends to end up in the oceans rather than atmosphere. Something like 40% of what ends up in atmosphere will be there for a millennium or more, so this is good. Alas, it is possible that, eventually, the mixing portion of the oceans will saturate with CO₂, and this pleasant circumstance will change, driving CO₂ into the atmosphere ever faster. And CO₂ in seawater has its own effects, such as killing phytoplankton, which, through photosynthesis, capture and sequester CO₂ themselves.

So, John Morgan and others have been looking at chemical technology for extracting CO₂ directly from seawater and doing good things with it, paying attention to both the unit cost and the energy cost, in terms of CO₂ equivalents. Barry Brook had Dr Morgan do a very detailed and wonderful guest post at Brave New Climate, which I very much recommend.

Presumably, if enough CO₂ can be taken out of oceans, that, indirectly, may serve as a better sink for atmospheric CO₂, as well as, in this case, provide an alternative synthetic fuel. But Morgan’s article addresses this as well as the primary proposal. It could be used in combination with other measures.

This could buy us some time. We really, really need it. And what this will cost keeps escalating.