Can stratospheric geoengineering alleviate global warming-induced changes in deciduous fruit cultivation? The case of Himachal Pradesh (India)

Using Hadley Global Environment Model 2 - Earth System and Max Planck Institute Earth System Model simulations, we assess the impact of global warming and stratospheric geoengineering on deciduous fruit production in Himachal Pradesh (the second-largest apple-producing state in India). The impacts have been assessed for the Representative Concentration Pathways 4.5 (RCP4.5) global warming scenario, and a corresponding geoengineered scenario (G3) from the Geoengineering Model Intercomparison Project, in which stratospheric aerosols are increased for 50 years from 2020 through 2069 to balance the global warming radiative forcing, and then aerosol precursor emissions are terminated. We used the period 2055–2069 (with the largest geoengineering forcing) and the period 2075–2089 (beginning 5 years into the termination phase) and evaluated winter chill and growing season heat accumulation. We found that although stratospheric geoengineering would be able to suppress the increase in temperature under an RCP4.5 scenario to some extent during both switch-on and switch-off periods, if the geoengineering was terminated, the rate of temperature increase would be higher than RCP4.5. The agroclimatically suitable area is projected to shift northeastwards (to higher elevations) under RCP4.5 as well as G3 during both periods. However, during the switched on period, geoengineering would restrict the shift, and areas of Shimla and Mandi districts (most suitable under the current climate) would not be lost due to global warming. Even during the switched off period, before the climate returned to RCP4.5 levels, the above areas would, although to a lesser extent, have reduced harmful climate effects from global warming. However, the area of suitable land (the intersection of soil and agroclimatic suitability) would decrease in both periods for RCP4.5 as well as G3, because as more high-elevation regions become agroclimatically suitable, they do not have suitable soils to support cultivation. Geoengineering could benefit deciduous fruit production by reducing the intensity of global warming; however, if geoengineering was terminated abruptly, the rate of change in temperature would be quite high. This could lead to a rapid change in land suitability and might result in total crop failure in a shorter period compared to RCP4.5.