= Solution
Increasing <greenhouse gases> generally strengthen the wave-driven <Brewer-Dobson circulation>: tropical stratospheric upwelling, poleward transport and extratropical descent intensify in model projections. This can shorten transit times, reduce tropical lower-stratospheric <ozone> by importing ozone-poor air, and increase <ozone> supply to extratropical regions or the <troposphere>. Changes in wave propagation and momentum deposition drive the residual circulation; it is not simply a direct thermal overturning inferred from local <temperature> alone. Regional branches and variability need not all accelerate equally.<Scientific Assessment of Ozone Depletion 2022 executive summary>[Ozone, climate, and circulation: greenhouse-gas-driven acceleration of global stratospheric transport]{ref}
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