Climate change mitigation via sulfate injection to the stratosphere: impact on the global carbon cycle and terrestrial biosphere

Abstract

The climate model (CM) of the A.M. Obukhov Institute of Atmospheric Physics (IAP), Russian Academy of Sciences (RAS), was used to estimate the geoengineering effect on the characteristics of the climate and carbon cycles. The geoengineering impact is implemented in the model during the period of 2020–2070 to mitigate the warming in the case of the aggressive anthropogenic scenario RCP 8.5. Assuming that stratospheric sulfates are distributed horizontally uniform, complete compensation of the globally averaged anthropogenic warming, which, in this scenario, is developing in the 21st century, reduces the amount of precipitation and is accompanied by regional temperature anomalies. The geoengineering effect on the solar radiative influx to the Earth’s surface and on the fraction of diffuse radiation in this influx depends substantially on the season. Geoengineering suppresses the gross primary production of plants and decreases the carbon stock in terrestrial vegetation, especially in Siberian taiga regions. In this case, when compared to nogeoengineering calculations, the global gross primary production during 2060–2070 decreases by 17 PgC·yr−1, and the global carbon stock in terrestrial vegetation decreases by 33 PgC. On the other hand, the geoengineering mitigation of the warming leads to the effect that the soil accumulates carbon, rather than losing it, in the 21st century. The maximal difference in soil carbon stock between geoengineering and no-geoengineering calculations is 97 PgC. Thus, the geoengineering slows down the CO2 buildup in the atmosphere by 52 ppm in the case of anthropogenic emissions in the last years of the 21st century, but this does not influence appreciably the climatic efficiency of geoengineering.