Reduced mass loss from the Greenland ice sheet under stratospheric aerosol injection, and some general considerations about pros and cons of geoengineering techniques

Reduced mass loss from the Greenland ice sheet under stratospheric aerosol injection*, and some general considerations about pros and cons of geoengineering techniques IGS Global Seminar, 2024.03.07, 02:00 UTC Ralf Greve Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan * Based on Moore, J. C., R. Greve, C. Yue, T. Zwinger, F. Gillet-Chaulet and L. Zhao. 2023. Reduced ice loss from Greenland under stratospheric aerosol injection. JGR Earth Surface 128 (11), e2023JF007112, doi: 10.1029/2023JF007112. Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 2/24 Geoengineering techniques have been proposed to mitigate the impact of global warming Solar geoengineering Carbon dioxide removal Targeted geoengineering Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 3/24 Geoengineering techniques have been proposed to mitigate the impact of global warming Solar geoengineering Carbon dioxide removal Targeted geoengineering (e.g., Jones+ 2018, MacMartin & Kravitz 2019) One possibility: Stratospheric aerosol injection (SAI) https://www.deeplearning.ai/the-batch/issue-169/ Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 4/24 Study by Moore, Greve et al. (2023, JGR) (Kravitz+ 2011) Modelling the impact of an SAI scenario (“GeoMIP G4”) on the mass loss of the Greenland ice sheet. Background: Hokkaido University Foreign Visiting Professorship of John Moore (Univ. Lapland, Rovaniemi, Finland), December 2019 – February 2020. (see title slide) Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 5/24 ISMIP6: Ice Sheet Model Intercomparison Project for CMIP6 (Nowicki+ 2016, 2020) (https://theghub.org/groups/ismip6/wiki) (CMIP6: Coupled Model Intercomparison Project Phase 6) Primary goals of ISMIP6: State-of-the-art projections of ice-sheet contribution to future sea-level rise. Quantify associated uncertainties. → Input for IPCC AR6 WG I (2021). Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 6/24 ISMIP6: Ice Sheet Model Intercomparison Project for CMIP6 (Nowicki+ 2016, 2020) (https://theghub.org/groups/ismip6/wiki) (CMIP6: Coupled Model Intercomparison Project Phase 6) Primary goals of ISMIP6: State-of-the-art projections of ice-sheet contribution to future sea-level rise. Quantify associated uncertainties. → Input for IPCC AR6 WG I (2021). The ISMIP6 team (> 80 members): IGS Richardson Medal 2022 “for its academic and leadership activities in the design and production of future sea-level projections” Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 7/24 Our study: ISMIP6-like experiment design 1990 2090 Historical Initialization 2015 Projections Approach: Initialization: Modeller’s choice. (Not covered here; see Greve+ 2020.) Historical: Modeller’s choice. (Not covered here; see Greve+ 2020.) Projections: ISMIP6 protocol, climate forcings from selected GCMs. (but not ISMIP6-endorsed) Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 8/24 Climate forcing for projections Model time 2015–2090. Three scenarios: RCP8.5 (worst-case scenario), RCP4.5 (intermediate scenario), GeoMIP G4 (RCP4.5 + 5 Mt a–1 SO2 injection [~1/4 of 1991 Mt. Pinatubo eruption] to the equatorial lower stratosphere, 2020–2070). Climate model Ice-sheet model Four Earth system models (ESMs): BNU-ESM, HadGEM2-ES, MIROC-ESM, MIROC-ESM-CHEM. (Goelzer+ 2020, Nowicki+ 2020) Atmospheric forcing (SMB, ST) and oceanic forcing (retreat masks). Intermediary model SEMIC (Krapp+ 2017) Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 9/24 Climate forcing As expected, RCP8.5 > RCP4.5 > G4. Surface mass balance (SMB) anomaly Surface temperature (ST) anomaly Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 16/24 Geoengineering techniques have been proposed to mitigate the impact of global warming Solar geoengineering Carbon dioxide removal Targeted geoengineering (e.g., Jones+ 2018, MacMartin & Kravitz 2019) One possibility: Stratospheric aerosol injection (SAI) https://www.deeplearning.ai/the-batch/issue-169/ Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 17/24 Geoengineering techniques have been proposed to mitigate the impact of global warming Solar geoengineering Carbon dioxide removal Targeted geoengineering https://docs.climateinteractive.org/projects/enroads/en/latest/guide/tech_removal.html Consider global emissions: ~ 40 Gt a–1 CO2 ~ 35 km3 a–1 liquid CO2 ~ 1 Mount Fuji (400 km3) every 11.5 years! Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 18/24 Geoengineering techniques have been proposed to mitigate the impact of global warming Solar geoengineering Carbon dioxide removal Targeted geoengineering Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 19/24 Targeted glacial geoengineering (focusing on the PIG/Thwaites system of the Antarctic ice sheet) (Moore+ 2018) Extracting or freezing water at the glacier base, reducing sliding. Artificial island to resist ice-shelf flow, buttressing the upstream glacier. Artificial sea-bed sill or curtain, blocking warm water from melting the ice-shelf base. Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 20/24 Targeted glacial geoengineering (focusing on the PIG/Thwaites system of the Antarctic ice sheet) Extracting or freezing water at the glacier base, reducing sliding. Artificial island to resist ice-shelf flow, buttressing the upstream glacier. Artificial sea-bed sill or curtain, blocking warm water from melting the ice-shelf base. (Moore+ 2018, Wolovick and Moore 2018, You 2024) Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 21/24 Geoengineering is a highly contentious topic May be a tool to mitigate some of the worst aspects of global warming. “We won’t make it without it” (buys some time, unavoidable GHG emissions, already ongoing or committed West Antarctic MISI?). Pros Cons May serve as an excuse to delay tackling the root course of the problem (reducing GHG emissions) even further. Adverse side effects will likely hit people who have not demanded it. Resource-consuming: work time, money, energy, logistics. (e.g., AGU 2023; Moon 2018, 2023) Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 22/24 My personal stance… Technology brought us to the brink of climate catastrophe. Now even more technology is supposed to fix it? I’m sceptical… However, I’m not against doing further research into the matter. The ideas are out anyway, so let’s rather try to understand the potential implications (and not leave that to the corporate world). Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 23/24 Thank you! Funding acknowledgements: JSPS KAKENHI Grant Nos. JP16H02224 and JP17H06104; Arctic Challenge for Sustainability project (ArCS II) of MEXT (program grant no. JPMXD1420318865); Hokkaido University Foreign Visiting Professorship at the Institute of Low Temperature Science; National Key Research and Development Program of China (2021YFB3900105); State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University (2022-ZD-05); Finnish Academy COLD consortium grants 322430 and 322978. Ralf Greve: Greenland ice sheet under stratospheric aerosol injection, geoengineering in general 24/24 References AGU. 2023. Position statement on climate intervention. https://www.agu.org/share-and-advocate/share/policymakers/position-statements/climate-intervention-requirements Goelzer, H. and 41 others. 2020. The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6. Cryosphere, 14 (9), 3071-3096, doi: 10.5194/tc-14-3071-2020. Greve, R., C. Chambers and R. Calov. 2020. ISMIP6 future projections for the Greenland ice sheet with the model SICOPOLIS. Technical report, Zenodo, doi: 10.5281/zenodo.3971251. Jones, A. C., M. K. Hawcroft, J. M. Haywood, A. Jones, X. Guo and J. C. Moore. 2018. Regional climate impacts of stabilizing global warming at 1.5 K using solar geoengineering. Earth's Future, 6 (2), 230-251, doi: 10.1002/2017EF000720. Krapp, M., A. Robinson and A. Ganopolski. 2017. An efficient surface energy and mass balance model applied to the Greenland ice sheet. Cryosphere, 11 (4), 15191535, doi: 10.5194/tc-11-1519-2017. Kravitz, B., A. Robock, O. Boucher, H. Schmidt, K. E. Taylor, G. Stenchikov and M. Schulz. 2011. The geoengineering model intercomparison project (GeoMIP). Atmos. Sci. Lett., 12(2), 162-167, doi: 10.1002/asl.316. MacMartin, D. G. and B. Kravitz. 2019. Mission-driven research for stratospheric aerosol geoengineering. Proc. Natl. Acad. Sci. U.S.A., 116 (4), 1089-1094, doi: 10.1073/pnas.1811022116. Moon, T. 2018. Geoengineering might speed glacier melt. Nature, 556, 436, doi: 10.1038/d41586-018-04897-5. Moon, T. 2023. Glacial geoengineering statement, Dec 2023. YouTube. https://www.youtube.com/watch?v=rLnQe3ostoQ Moore, J. C., R. Gladstone, T. Zwinger and M. Wolovick. 2018. Geoengineer polar glaciers to slow sea-level rise. Nature, 555, 303-305, doi: 10.1038/d41586-01803036-4. Nowicki, S. and 8 others. 2016. Ice Sheet Model Intercomparison Project (ISMIP6) contribution to CMIP6. Geosci. Model Dev., 9 (12), 4521-4545, doi: 10.5194/gmd-94521-2016. Nowicki, S. and 29 others. 2020. Experimental protocol for sea level projections from ISMIP6 stand-alone ice sheet models. Cryosphere, 14 (7), 2331-2368, doi: 10.5194/tc-14-2331-2020. Wolovick, M. J. and J. C. Moore. 2018. Stopping the flood: could we use targeted geoengineering to mitigate sea level rise? Cryosphere, 12 (9), 2955-2967, doi: 10.5194/tc-12-2955-2018. You, X. 2024. Could giant underwater curtains slow ice-sheet melting? Nature (News article), doi: 10.1038/d41586-024-00119-3.