Future Climate Under CMIP6 Solar Activity Scenarios

Predictions of solar activity in the future are difficult to make due to the chaotic state of solar dynamo and the high nonlinearity of physical processes on the Sun. Therefore, the Climate Intercomparison Project Phase 6 (CMIP6) used a statistical approach and recommended two different solar forcing scenarios for the simulations. The reference scenario was developed as the standard forcing, whereas the alternative forcing has lower solar activity (EXT CMIP6). In this study, we use both forcings in a set of experiments to explore the importance of the alternative CMIP6 solar forcing for future climate and ozone layer variability. In general, the difference in solar forcing scenarios is small, and thus most changes at the surface and at high altitudes are not significant. In addition, only the active phases of the Sun, which have the largest difference in amplitude of the forcing, are investigated. In this case, some statistically significant patterns emerge, mostly in the stratosphere, but still, the magnitude of the changes is not very large and a noticeable surface climate response to these changes is not expected and also not found. Our results indicate that low amplitude solar forcings such as the EXT CMIP6 or similar are not worthwhile considering during the next CMIP type of activities. The proposed solar irradiance decline does not represent any danger to the ozone layer. Plain Language Summary Predictions of future solar activity are very difficult a make. Therefore, the Climate Model Intercomparison Project Phase 6 (CMIP6) used statistical methods to develop solar forcing scenarios and recommended two different forcings. One is the reference forcing and one is a low solar activity forcing scenario. In general, the difference between the two solar forcing scenarios is small and thus most changes at the surface and at high altitudes are not significant. In addition, only the active phases of the sun are investigated. In this case, some statistically significant patterns emerge, but still, the response signal is weak. Our results suggest that low amplitude solar forcings as proposed for CMIP6 are not worthwhile considering in the next CMIP type of activity. Key Points The proposed Climate Intercomparison Project Phase 6 (CMIP6) lower solar activity scenario is investigated with an Earth System Model The analysis shows no pronounced impact of the CMIP6 lower solar activity on future climate change, as the change in forcing is very small The impact on