Geoengineering climate by stratospheric sulfur injections: Earth system vulnerability to technological failure

Abstract

We use a coupled climate-carbon cycle model of intermediate complexity to investigate scenarios of stratospheric sulfur injections as a measure to compensate for CO 2 -induced global warming. The baseline scenario includes the burning of 5,000 GtC of fossil fuels. A full compensation of CO 2 -induced warming requires a load of about 13 MtS in the stratosphere at the peak of atmospheric CO 2 concentration. Keeping global warming below 2 • C reduces this load to 9 MtS. Compensation of CO 2 forcing by stratospheric aerosols leads to a global reduction in precipitation, warmer winters in the high northern latitudes and cooler summers over northern hemisphere landmasses. The average surface ocean pH decreases by 0.7, reducing the calcifying ability of marine organisms. Because of the millennial persistence of the fossil fuel CO 2 in the atmosphere, high levels of stratospheric aerosol loading would have to continue for thousands of years until CO 2 was removed from the atmosphere. A termination of stratospheric aerosol loading results in abrupt global warming of up to 5 • C within several decades, a vulnerability of the Earth system to technological failure.V. Brovkin (B) · M. Claussen

Unintended consequences of atmospheric injection of sulphate aerosols.

“…In absolute units, the largest decrease of annual precipitation is simulated in the tropics and in the Southern Hemisphere storm tracks. This agrees with other empirical and model-based studies (Groisman 1985;Matthews and Caldeira 2007;Trenberth and Dai 2007;Robock, Oman et al 2008;Brovkin, Petoukhov et al 2009;Eliseev, Chernokulsky et al 2009). …”

“…The predicted precipitation decrease in the south-east of Asia is in agreement with the suppression of summer monsoon there. A similar precipitation decrease was also simulated by Brovkin et al (2009) and Eliseev et al (2009).…”

“…Similar precipitation response has been calculated by Brovkin et al (2009) . Marked reduction in precipitation over the tropical west Pacific as a response to the combined anthropogenic and geoengineering forcing was also simulated by Robock et al (2008), and the reduction of precipitation over the near-equatorial continental areas under a similar scenario was predicted by Matthews and Caldeira (2007).…”

Is there room for geoengineering in the optimal climate policy mix?

“…Here, we additionally account for negative externalities from sulfur injection. According to Ramanathan et al (2001) and Brovkin et al (2009), dissipating large amounts of sulfur in the upper atmosphere may have potentially disruptive effects on weather patterns and the water cycle. Additional damages are expected in case sulfur particles enter the troposphere and add to the sulfur concentration in soil (Crutzen, 2006).…”

Anthropocene: another academic invention?

“…It is interesting to compare these data with the requirement envisaged for geoengineering the climate (Brovkin et al 2009). A possible scenario would be the injection of an average 7 Mt S/year staring from 2,070 to ending in 2,300.…”