Mitigation of Anthropogenic Climate Change Via a Macro-Engineering Scheme: Climate Modeling Results

Abstract

It has been suggested that climate change induced by anthropogenic CO2 could be cost-effectively counteracted with macro-engineering schemes designed to diminish the solar radiation incident on Earth’s surface. It is clear that such schemes could counteract global and annual mean global warming. However, the spatial and temporal pattern of radiative forcing from greenhouse gases such as CO2 differs from that of sunlight, therefore it is uncertain to what extent these macro-engineering schemes would mitigate regional or seasonal climate change. The NCAR atmospheric general circulation model, CCM3, has been used to study this issue; in these simulations, the solar radiation incident on the Earth was diminished to balance the increased radiative forcing from a doubling and quadrupling of atmospheric CO2 content. The results indicate that, despite differences in radiative forcing patterns, large-scale macro-engineering schemes could markedly diminish regional and seasonal climate change from anthropogenic CO2 emissions. However, there are some residual climate changes in the Macro-engineered 4xCO2 climate: a significant decrease in surface temperature and net water flux occurs in the tropics; warming in the high latitudes is not completely compensated; the cooling effect of greenhouse gases in the stratosphere increases and sea ice is not fully restored. The stratospheric cooling becomes larger also in the Macro-engineered 2xCO2 climate, and the additional cooling due to macro-engineering could enhance stratospheric ozone depletion. The impact of these climate stabilization schemes on terrestrial biosphere is also investigated using the same climate model∈dex climate model. Results indicate that climate stabilization would tend to limit changes in vegetation distribution brought on by climate change∈dex climate change, but would not prevent CO2-induced changes in Net Primary Productivity∈dex Net Primary Productivity (NPP) or biomass; indeed, if CO2 fertilization∈dex fertilization is an important factor, then a CO2-rich world with compensating reductions in solar radiation could have higher net primary productivity than our current world. However, CO2 effects on ocean chemistry could have deleterious consequences for marine biota. Caution should be exercised in interpretation because these results are from a single model with many simplifying assumptions. The most prudent and least risky option to mitigate global warming may be to curtail emissions of greenhouse gases∈dex greenhouse gases. Nevertheless, studying macro-engineering will provide us the scientific basis to understand the possibility of rapidly counteracting catastrophic global warming without inadvertently creating a bigger problem