North Atlantic Oscillation response in GeoMIP experiments G6solar and G6sulfur: why detailed modelling is needed for understanding regional implications of solar radiation management
The realisation of the difficulty of limiting global mean temperatures to within 1.5 °C or 2.0 °C above pre-industrial levels stipulated by the 21 st Conference of Parties in Paris has led to increased interest in solar radiation management (SRM) techniques. Proposed SRM schemes aim to increase plan...
| Main Authors: | , , , , , |
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| Format: | Text |
| Language: | English |
| Published: |
2020
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/acp-2020-802 https://acp.copernicus.org/preprints/acp-2020-802/ |
| Summary: | The realisation of the difficulty of limiting global mean temperatures to within 1.5 °C or 2.0 °C above pre-industrial levels stipulated by the 21 st Conference of Parties in Paris has led to increased interest in solar radiation management (SRM) techniques. Proposed SRM schemes aim to increase planetary albedo to reflect more sunlight back to space and induce a cooling that acts to partially offset global warming. Under the auspices of the Geoengineering Model Intercomparion Project, we have performed model experiments whereby global temperature under the high forcing SSP5–8.5 scenario is reduced to follow that of the medium forcing SSP2–4.5 scenario. Two different mechanisms to achieve this are employed, the first via a reduction in the solar constant (experiment G6solar) and the second via modelling injections of sulfur dioxide (experiment G6sulfur) which forms sulfate aerosol in the stratosphere. Results from two state-of-the-art coupled Earth system models both show an impact on the North Atlantic Oscillation (NAO) in G6sulfur but not in G6solar. Both models show a persistent positive anomaly in the NAO during the Northern Hemisphere winter season in G6sulfur, suggesting an increase in zonal flow and an increase in North Atlantic storm track activity impacting the Eurasian continent leading to regional warming. These findings are broadly consistent with previous findings on the impact of stratospheric volcanic aerosol on the NAO and emphasise that detailed modelling of geoengineering processes is required if accurate impacts of SRM impacts are to be simulated. Differences remain between the two models in predicting regional changes over the continental USA and Africa, suggesting that more models need to perform such simulations before attempting to draw any conclusions regarding potential continental-scale climate change under SRM. |
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