Carbon Dioxide Removal (CDR)
The first group of geoengineering options that I'm going to discuss are based upon the engineered removal of CO₂ from the atmosphere by enhancing land or ocean carbon sink or creating new carbon sinks (Keith, 2000).
However for any CDR option, the effects will decay over time due to natural responses of carbon reservoirs to atmospheric perturbations; it will also decay if carbon storage is not permanent (Lenton and Vaughan, 2009).
Lenton and Vaughan go on to propose that in the long-term, the only way to return atmospheric CO₂ to pre-industrial levels is to permanently store (in some combination of the crust, sediments, soils, ocean, and terrestrial biosphere) an equivalent amount of CO₂ to the total emitted to the atmosphere.
Solar Radiation Management (SRM)
The first group of geoengineering options that I'm going to discuss are based upon the engineered removal of CO₂ from the atmosphere by enhancing land or ocean carbon sink or creating new carbon sinks (Keith, 2000).
However for any CDR option, the effects will decay over time due to natural responses of carbon reservoirs to atmospheric perturbations; it will also decay if carbon storage is not permanent (Lenton and Vaughan, 2009).
Lenton and Vaughan go on to propose that in the long-term, the only way to return atmospheric CO₂ to pre-industrial levels is to permanently store (in some combination of the crust, sediments, soils, ocean, and terrestrial biosphere) an equivalent amount of CO₂ to the total emitted to the atmosphere.
Solar Radiation Management (SRM)
The other side of geoengineering ideas seek to rectify the increasing radiative forcing caused
by anthropogenic greenhouse gas emissions by reducing the amount of solar radiation absorbed. Some proposals range from the wildly ridiculous and James Bond Villain-esque mirrors in space and other ideas which reduce the amount of solar radiation reaching the top of the atmosphere. The other proposals centre around increasing the reflection of shortwave radiation
(albedo) within the atmosphere or at the surface (Keith 2000).
Generally a doubling of atmospheric CO₂ and the radiative forcing increase which comes with it (3.7 Wm−2) is taken as the target to counteract, although actual anthropogenic radiative forcing will continue to vary over time. Each individual idea has specific merits and drawbacks (NAS 1992; Keith 2000; Schneider 2008; Boyd 2008), which will be outlined in later blog posts.
However.....
The SRM range of ideas do pose some problems; in particular, reducing incoming solar radiation does not ameliorate ocean acidification caused by rising atmospheric CO₂. Indeed successful planetary cooling would be expected to increase ocean CO₂ uptake, thus amplifying ocean acidification (Matthews and Caldeira 2007).
That's it for now, take care...
Generally a doubling of atmospheric CO₂ and the radiative forcing increase which comes with it (3.7 Wm−2) is taken as the target to counteract, although actual anthropogenic radiative forcing will continue to vary over time. Each individual idea has specific merits and drawbacks (NAS 1992; Keith 2000; Schneider 2008; Boyd 2008), which will be outlined in later blog posts.
However.....
The SRM range of ideas do pose some problems; in particular, reducing incoming solar radiation does not ameliorate ocean acidification caused by rising atmospheric CO₂. Indeed successful planetary cooling would be expected to increase ocean CO₂ uptake, thus amplifying ocean acidification (Matthews and Caldeira 2007).
That's it for now, take care...
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