Atmospheric CO2 Removal

To some, the technical solution of capturing CO2 from the atmosphere using, for example, artificial “trees” is very enticing.

The first peer-reviewed study of the climate’s response to atmospheric CO2 removal, however, shows such action is far from a solution.  Long Cao and Ken Caldeira from the Department of Global Ecology at the Carnegie Institution are the researchers responsible for the study and they investigated the response of the coupled climate–carbon system to an instantaneous removal of all anthropogenic CO2 from the atmosphere.

In their extreme and idealized simulations, anthropogenic CO2 emissions are halted (very unlikely) and all anthropogenic CO2 removed from the atmosphere at year 2050.  In the simulations, a one-off removal of all anthropogenic CO2 in the atmosphere reduces surface air temperature by 0.8 °C within a few years but 1 °C surface warming above pre-industrial levels lasts for several centuries.

In other words, a one-off removal of 100% excess CO2 from the atmosphere offsets less than 50% of the warming experienced at the time of removal.

Evolution of atmospheric CO2 and change in surface air temperature (relative to pre-industrial)

Evolution of atmospheric CO2 and change in surface air temperature (relative to pre-industrial)

To maintain atmospheric CO2 and temperatures at low levels, not only does anthropogenic CO2 in the atmosphere need to be removed but anthropogenic CO2 stored in the ocean and land needs to be removed as well when it outgasses to the atmosphere.

To maintain atmospheric CO2 concentrations at pre-industrial levels for centuries, the simulation showed that an additional amount of CO2 equal to the original CO2 captured would need to be removed over the subsequent 80 years.

David M. Davison

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