The Southern Annular Mode is a major mode of climate variability that influences climate extremes across the Southern Hemisphere, including drought in southern Australia. Proxy-based Southern Annular Mode reconstructions show large changes during the last millennium that current climate simulations don’t reproduce. Research led by Dr Nicky Wright tested the Southern Annular Mode’s sensitivity to solar forcing by using simulations with a range of constant solar values and transient last-millennium simulations with large-amplitude solar variations. The work found that solar forcing can alter the Southern Annular Mode and that transient simulations forced with a large-amplitude option for solar forcing during the last millennium better match proxy-based reconstructions. The findings suggest that the effects of solar forcing on high-latitude climate may not be adequately incorporated in most last-millennium simulations, due to solar irradiance changes that are too small and/or the absence of interactive atmospheric chemistry in global climate models.
Wright, N.M., Krause, C.E., Phipps, S.J., Boschat, G., Abram, N.J., 2022. Influence of long-term changes in solar irradiance forcing on the Southern Annular Mode. Climate of the Past 18, 1509–1528. https://doi.org/10.5194/cp-18-1509-2022