講演情報
[ACG64-P02]Comparison of Forcing Data used in Climate Model Experiments Between CMIP7 and CMIP6
*阿部 学1 (1.海洋研究開発機構)
キーワード：
CMIP、地球温暖化、地球システムモデル
The forcing dataset constitutes the basis for conducting experiments in CMIP7. This is because climate change projections from multiple climate models within CMIP are performed using common forcing data. Moreover, these data contribute to the reliability of experiments aimed at understanding past climate change and provide crucial conditions for assessing the reliability of future climate change projections. For the CMIP7 experiments currently underway, the forcing data have been made available, with some of these datasets incorporating revisions or modifications to earlier versions.
To understand the CMIP7 experiment results with our Earth System Model (ESM), the new forcing data were compared with those from CMIP6. This presentation provides a comprehensive overview of the forcing data to be used in the CMIP7 AFT experiments with our ESM and emphasizes the differences between CMIP7 and CMIP6.
Regarding the forcing datasets, substantial improvements have been made to address known biases in CMIP6. The most notable update concerns volcanic aerosol forcing. In CMIP6, historical volcanic forcing, particularly before the satellite era (pre-1979), led to an underestimation of the cooling effect from small-to-moderate eruptions. CMIP7 adopts a new multi-proxy approach, integrating ice-core and geological data with the EVA_H v2 model (Aubry et al. 2025) to derive optical properties directly from emissions. This has resulted in a roughly 29% increase in the estimated historical stratospheric aerosol optical depth (SAOD), which is expected to correct the cold bias previously observed in models during the late 20th century.
Solar forcing data has also been updated with a new reference scale (SOLARIS-HEPPA v4.6), resulting in a slightly higher Total Solar Irradiance (TSI) and significantly revised future scenarios for solar activity amplitude and phase beyond the 21st century. Similarly, emissions datasets for short-lived climate forcers (SLCFs) and greenhouse gases (GHGs) have been refined. CMIP7 integrates diverse sources for biomass burning and anthropogenic emissions, aiming for greater consistency, though this has revealed divergent trends in recent years for species such as SO2 and organic carbon relative to CMIP6.
Finally, the ScenarioMIP framework has been redesigned to prioritize emission-driven runs over concentration-driven ones. The new scenario matrix includes a wider range of pathways, such as high-overshoot scenarios, to explore the reversibility of climate change and the impact of carbon dioxide removal technologies. We intend to report on the comparisons in the data to be used in the scenario MIP, as far as the data is available.
To understand the CMIP7 experiment results with our Earth System Model (ESM), the new forcing data were compared with those from CMIP6. This presentation provides a comprehensive overview of the forcing data to be used in the CMIP7 AFT experiments with our ESM and emphasizes the differences between CMIP7 and CMIP6.
Regarding the forcing datasets, substantial improvements have been made to address known biases in CMIP6. The most notable update concerns volcanic aerosol forcing. In CMIP6, historical volcanic forcing, particularly before the satellite era (pre-1979), led to an underestimation of the cooling effect from small-to-moderate eruptions. CMIP7 adopts a new multi-proxy approach, integrating ice-core and geological data with the EVA_H v2 model (Aubry et al. 2025) to derive optical properties directly from emissions. This has resulted in a roughly 29% increase in the estimated historical stratospheric aerosol optical depth (SAOD), which is expected to correct the cold bias previously observed in models during the late 20th century.
Solar forcing data has also been updated with a new reference scale (SOLARIS-HEPPA v4.6), resulting in a slightly higher Total Solar Irradiance (TSI) and significantly revised future scenarios for solar activity amplitude and phase beyond the 21st century. Similarly, emissions datasets for short-lived climate forcers (SLCFs) and greenhouse gases (GHGs) have been refined. CMIP7 integrates diverse sources for biomass burning and anthropogenic emissions, aiming for greater consistency, though this has revealed divergent trends in recent years for species such as SO2 and organic carbon relative to CMIP6.
Finally, the ScenarioMIP framework has been redesigned to prioritize emission-driven runs over concentration-driven ones. The new scenario matrix includes a wider range of pathways, such as high-overshoot scenarios, to explore the reversibility of climate change and the impact of carbon dioxide removal technologies. We intend to report on the comparisons in the data to be used in the scenario MIP, as far as the data is available.