Potential climate engineering effectiveness and side effects during a high carbon dioxide-emission scenario

Abstract

The realization that mitigation efforts to reduce carbon dioxide emissions have, until now, been relatively ineffective has led to an increasing interest in climate engineering as a possible means of preventing the potentially catastrophic consequences of climate change. While many studies have addressed the potential effectiveness of individual methods there have been few attempts to compare them. Here we use an Earth system model to compare the effectiveness and side effects of afforestation, artificial ocean upwelling, ocean iron fertilization, ocean alkalinization and solar radiation management during a high carbon dioxide-emission scenario. We find that even when applied continuously and at scales as large as currently deemed possible, all methods are, individually, either relatively ineffective with limited (<8%) warming reductions, or they have potentially severe side effects and cannot be stopped without causing rapid climate change. Our simulations suggest that the potential for these types of climate engineering to make up for failed mitigation may be very limited.

Figure 1. Experimental design.

The simulations performed for each climate engineering method. The control run is also depicted.

Figure 2. Comparison of climate engineering method effects on key global properties.

Simulated changes in globally averaged annual atmospheric CO₂ and surface air temperature (relative to a pre-industrial temperature of 13.05 °C) and the total amount of annual global precipitation and ocean oxygen for model runs where climate engineering was continuously deployed (a,c,e and g) and runs where it was discontinued after 50 years (b,d,f and h). The control run, with no climate engineering, is also shown.

Figure 3. Climate engineering method effects on temperature and carbon storage.

The simulated year 2100 mean annual differences between the climate engineering runs and the control run (climate engineering run minus the control run) for surface air temperature (a,c,e,g and i) and terrestrial and oceanic carbon inventories (b,d,f,h and j). Note the difference in the surface air temperature scale for solar radiation management.

Figure 4. Comparison of climate engineering method effectiveness.

(a) Insolation at the top of the atmosphere for the SRM (yellow line) model run and all other simulations (dotted red line). The climate engineering model run differences (relative to the no climate engineering model run) in the annually averaged fluxes of carbon from the atmosphere to the (b) land and (c) ocean. Comparison (d) of surface air temperature versus atmospheric CO₂ differences (relative to the no climate engineering model run) for the climate engineering simulations.