Stratospheric geoengineering with black carbon aerosols

• Main Author: Kravitz, Benjamin S.
• Format: Text
• Language: unknown
• Published: No Publisher Supplied 2011
• Subjects: Arctic; albedo; black carbon; Sea ice
• Online Access: https://dx.doi.org/10.7282/t3m61jkc; https://rucore.libraries.rutgers.edu/rutgers-lib/33892/

I use a general circulation model of Earth's climate to simulate stratospheric geoengineering with black carbon aerosols, varying the altitude of injection, initial particle size, and whether the deposited black carbon modifies ground albedo. 1 Tg of black carbon aerosols injected into the stratosphere each year will cause significant enough surface cooling to negate anthropogenic warming if the aerosols are small (r=0.03 μm) or if the aerosols are injected into the middle stratosphere, although using small aerosols causes large regional cooling effects that would be catastrophic to agriculture. The aerosols cause significant stratospheric heating, resulting in stratospheric ozone destruction and circulation changes, most notably an increase in the Northern Hemisphere polar jet, which forms an Arctic ozone hole and forces a positive mode of the Arctic Oscillation. The hydrologic cycle is perturbed, specifically the summer monsoon system of India, Africa, and East Asia, resulting in monsoon precipitation collapse. Global primary productivity is decreased by 35.5% for the small particle case. Surface cooling causes some sea ice regrowth, but not at statistically significant levels. All of these climate impacts are exacerbated for small particle geoengineering, with high altitude geoengineering with the default particle size (r=0.08 μm) causing a reasonable amount of cooling, and large particle (r=0.15 μm) geoengineering or particle injection into the lower stratosphere causing few of these effects. The modification of ground albedo by the soot particles slightly perturbs the radiative budget but does not cause any distinguishable climate effects. The cheapest means we investigated for placing 1 Tg of black carbon aerosols into the stratosphere by diesel fuel combustion would cost $1.4 trillion initially and $541 billion annual, or 2.0% and 0.8% of GDP, respectively. The additional carbon dioxide released from combusting diesel to produce these aerosols is about 1% of current emissions, but the additional NOx would be 17% of current sources and could further reduce the total ozone column by up to 10%. Geoengineering with carbon black, if technically feasible, would be much cheaper, costing approximately $1 billion initially and $1.3 billion annually, with few troublesome emissions factors.