Stratospheric geoengineering impacts on El Ni?o/Southern Oscillation

摘要

To examine the impact of proposed stratospheric geoengineering schemes on theamplitude and frequency of El Ni?o/Southern Oscillation (ENSO) variationswe examine climate model simulations from the Geoengineering ModelIntercomparison Project (GeoMIP) G1–G4 experiments. Here we compare tropicalPacific behavior under anthropogenic global warming (AGW) using severalscenarios: an instantaneous quadrupling of the atmosphere's CO₂concentration, a 1 % annual increase in CO₂ concentration, and therepresentative concentration pathway resulting in 4.5 W m?2 radiativeforcing at the end of the 21st century, the Representative ConcentrationPathway 4.5 scenario, with that under G1–G4 and under historical modelsimulations. Climate models under AGW project relatively uniform warmingacross the tropical Pacific over the next several decades. We find nostatistically significant change in ENSO frequency or amplitude understratospheric geoengineering as compared with those that would occur underongoing AGW, although the relative brevity of the G1–G4 simulations may havelimited detectability of such changes. We also find that the amplitude andfrequency of ENSO events do not vary significantly under either AGW scenariosor G1–G4 from the variability found within historical simulations orobservations going back to the mid-19th century. Finally, while warming ofthe Ni?o3.4 region in the tropical Pacific is fully offset in G1 and G2during the 40-year simulations, the region continues to warm significantly inG3 and G4, which both start from a present-day climate.