@article{Malik:2019:10.5194/acp-2018-1312,
author = {Malik, A and Nowack, PJ and Haigh, JD and Cao, L and Atique, L and Plancherel, Y},
doi = {10.5194/acp-2018-1312},
title = {Tropical Pacific Climate Variability under Solar Geoengineering: Impacts on ENSO Extremes},
url = {http://dx.doi.org/10.5194/acp-2018-1312},
year = {2019}
}

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TY  - JOUR
AB  - <jats:p>Abstract. Many modelling studies suggest that the El Niño Southern Oscillation (ENSO), in interaction with the tropical Pacific background climate, will change under rising atmospheric greenhouse gas concentrations. Solar geoengineering (reducing the solar flux from outer space) has been proposed as a means to counteract anthropogenic greenhouse-induced changes in climate. Effectiveness of solar geoengineering is uncertain. Robust results are particularly difficult to obtain for ENSO because existing geoengineering simulations are too short (typically ~ 50 years) to detect statistically significant changes in the highly variable tropical Pacific background climate. We here present results from a 1000-year sunshade geoengineering simulation, G1, carried out with the coupled atmosphere-ocean general circulation model HadCM3L. In agreement with previous studies, reducing the shortwave solar flux more than compensates the warming in the tropical Pacific that develops in the 4×CO2 scenario: we observe an overcooling of 0.3 °C (5 %) and 0.23-mm day−1 (5 %) reduction in mean rainfall relative to preindustrial conditions in the G1 simulation. This is due to the different latitudinal distributions of the shortwave (solar) and longwave (CO2) forcings.The location of the Intertropical Convergence Zone (ITCZ) located north of equator in the tropical Pacific, which moved 7.5° southwards under 4×CO2, is also restored to its preindustrial location. However, other aspects of the tropical Pacific mean climate are not reset as effectively. Relative to preindustrial conditions, in G1 the zonal wind stress, zonal sea surface temperature (SST) gradient, and meridional SST gradient are reduced by 10 %, 11 %, and 9 %, respectively, and the Pacific Walker Circulation (PWC) is consistently weakened. The overall amplitude of ENSO strengthens by 5–8 %, but there is a 65 % reduct
AU  - Malik,A
AU  - Nowack,PJ
AU  - Haigh,JD
AU  - Cao,L
AU  - Atique,L
AU  - Plancherel,Y
DO  - 10.5194/acp-2018-1312
PY  - 2019///
TI  - Tropical Pacific Climate Variability under Solar Geoengineering: Impacts on ENSO Extremes
UR  - http://dx.doi.org/10.5194/acp-2018-1312
ER  - 

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