On October 26 2009 Len Ornstein posted a guest weblog titled “How To Quickly Lower Climate Risks, At ‘Tolerable’ Costs?”. He has requested that I comment on his proposal to reduce carbon dioxide concentrations in the atmosphere.
As I have written previously, I am very concerned about geoengineering as a way to mitigate climate change from the addition of CO2 and other greenhouse gases; e.g. see
I wrote in that post
The claim in the Levi Physics Today article that geoengineering “intervention” [can] prevent or slow changes in the climate system is completely wrong. Geoengineering would cause changes in the climate system! The Levi focus almost exclusively on the role of the addition of carbon dioxide into the atmosphere is blind to the importance of altering the spatial pattern of climate forcing as a result of geoengineering.
I do find that Len’s study further confirms the role of landscape change (in this case deliberate change) as a first order climate forcing. However, this means that weather patterns will be altered since the spatial distribution of diabatic heating in the atmosphere will be different (e.g. see also our study of this diabatic heating effect due to aerosols in Matsui and Pielke 2006). The teleconnection effect seen in their model runs seem muted at very long distance (e.g. see Figure 5) but they are present. For example, there is a possible effect on Atlantic hurricanes, as noted in Section 6 of Ornstein et al. This raises the issue of unintended consequences. With respect to Atlantic tropical cyclones, these bring much needed rain to the western tropical and subtropical Atlantic Ocean land areas as well as the southeast USA. If this is altered, as suggested in the model results, this would be an unintended negative effect to those countries.
I do agree with Len on the concern on the biogeochemical effect of added atmospheric concentrations of CO2. We do not know all of the potential effects, but there will be some. Thus the elevation of CO2 to too high a concentration should be prevented, and the engineering of Len’s proposal seems feasible. However, as written above, unintended consequences on the climate elsewhere would need to be very thoroughly studied.
I remain convinced that the mitigation approach with the least negative effects is the air capture of CO2 as discussed in
Pielke, Jr., R. A., 2009. An Idealized Assessment of the Economics of Air Capture of Carbon Dioxide in Mitigation Policy, Environmental Science & Policy, Vol. 12, Issue 3, pp. 216-225.