Influence of ENSO on stratospheric sulfur dioxide injection in the CESM2
Climate and Earth system models are important tools to assess the
benefits and risks of stratospheric aerosol injection (SAI) relative to
those associated with anthropogenic climate change. A “controller”
algorithm has been used to specify injection amounts of sulfur dioxide
in SAI experiments performed with the Community Earth System Model
(CESM). The experiments are designed to maintain specific temperature
targets, such as limiting global mean temperature to 1.5ºC above the
pre-industrial level. However, the influence of natural climate
variability on the injection amount has not been extensively documented.
Our study reveals that more than 70% of the year-to-year variation in
the total injection amount (excluding the long-term trend) in CESM SAI
experiments is attributed to the El Niño-Southern Oscillation (ENSO). A
simplified statistical model further suggests that the intrinsic, lagged
response of the controller to the climate can increase the variance of
global mean temperature in the model simulations.