Climate stabilisation schemes for example the SPICE project will have a profound affect on terrestrial biosphere. If this scheme works in the way that its proponents claim then we should all benefit from decreased solar radiation. However, CO2 will continue to increase nonetheless (causing CO2 fertilisation). However, what impacts will these changes have on Net Primary Production (NPP) and biomass?
Govindasamy et al. (2002) attempted to model these changes and yielded some staggering results. They judged that with a predicted decrease of 1.8% of solar fluxes then NPP would decrease by around 2.4%. However, with a model where CO2 reaches double that of the present level, NPP increases by around 76%. However, as noted by Schimel (1998), changes in nitrogen availability are crucial to the carbon cycle as they affect nutrient levels in the soil. Consequently, these nutrient levels (which are unaccounted for in the model) might in fact limit the NPP increases calculated.
The model used in this paper acts give an estimate and should be used more to give qualitative projections on future changes in the terrestrial biosphere. The authors admit that although they have produced quantitative data, it should be treated with caution. They have used a very simple ocean model and have prescribed the levels of CO2. With more in depth models and taking climate feedbacks into account, different results will likely be calculated.
Although this might appear to produce very positive affects on the terrestrial biosphere, we still must remind ourselves of the uncertainties that exist regarding geoengineering, many of which have been discussed in past posts
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