Dangerous Consequences of Geoengineering Implementation and Termination for Natural Systems

With slow and uncertain progress towards reducing greenhouse gas emissions, geoengineering using solar radiation management has been increasingly promoted as a way to rapidly reduce the worst effects of climate change on humans. However, while geoengineering effects on temperature and precipitation have been investigated, essentially nothing is known about the potential ecological and social risks especially if geoengineering were terminated abruptly (e.g., due to undesirable side effects or political unrest). Here we show that temperature velocities—the speeds at which species are expected to have to move to track their thermal niches—are predicted to increase from a global median on land of 3.69 km yr-1 under a scenario with gradual anthropogenic warming (RCP 4.5) to 10.86 km yr-1 if geoengineering was terminated suddenly, and to more than triple in multiple biomes, marine and terrestrial biodiversity hotspots. Furthermore, implementing geoengineering may increase precipitation velocities significantly with strong drying over the Amazon, Australia, northern Europe and Asia. Finally, with abrupt geoengineering termination 32% of the global land surface is predicted to have temperature and precipitation velocities that are more than double RCP 4.5 and that diverge in direction by more than 90 degrees. This rapid climate fragmentation would pull moisture- and temperature-sensitive species in opposite directions such that the potential for rapid fragmentation of ecological communities may be extremely high. Geoengineering represents a serious threat to the persistence of many species with limited dispersal velocities in the most biodiverse places on Earth. Geoengineering is no easy substitute for large reductions in greenhouse gas emissions to reduce climate change risks to natural and human systems.