Parallel Session 1.2: The Geoengineering Model Intercomparison Project: Where have we been and where should we go?

Tuesday, 11:00 - 12:30
01 I Großer Saal

GeoMIP is one of the largest CE research projects in the world.  What has it done, what is it planning to do, and is it meeting the needs of the broader CE research community?  We’re here to find out!



  • Helene Muri
    • Scenario studies have shown that in order to limit global warming to 1.5°C above pre-industrial levels, as set out as the Paris Agreement’s most ambitious goal, negative emissions are required. Currently, no safe and well-established technologies exist for achieving such negative emissions. Hence, although carbon dioxide removal may appear less risky and controversial than radiation management climate engineering techniques, the latter type of climate engineering techniques cannot be ruled out as a future policy option.
      Here, the potential and risks of radiation management are explored through Earth system model simulations. The results from three different radiation management techniques are compared: Stratospheric Aerosol Injections, Marine Sky Brightening, and Cirrus Cloud Thinning. The experiments follow the GeoMIP G6sulfur scenario, where the radiative forcing in the RCP8.5 scenario is offset down to the RCP4.5 scenario through these three techniques individually. Although they obtain approximately the same global temperature evolution, various aspects of the Earth system exhibits sensitivity to the choice of radiation management technique. Important differences the climate response will be discussed.
  • Maxime Plazzotta
    • Solar radiation management by stratospheric aerosol injection (SRM-SAI) is thought to be one of the most effective geoengineering methods to counteract anthropogenic global warming. Coordinated simulations performed with the Geoengineering Model Intercomparison Project (GeoMIP) have shown that the extent of global cooling resulting from a continuous injection of 5 Tg of SO2 per year under RCP4.5 future projection (the so-called G4 experiment) still remains poorly constrained, implying much higher uncertainties about potential impacts and risks of SRM-SAI for natural and human ecosystems. Here we identify an emergent relationship linking the long-term global land surface cooling due to SRM-SAI and the short-term cooling following the 20th century major volcanic eruptions across an ensemble of nine Earth System Models. This emergent relationship, which explain at least 85% of the multi-model spread, is combined with observations and reanalysis, and then used to constrain the global land surface temperature (GLST) response to declining downward solar radiation. Compared with the prior response (0.55±0.34 K per W.m-2), we show that GLST will only decline by 0.45 K per W.m-2 ([0.19,0.69]). With a 15% smaller effectiveness than previous estimates, trade-off between cost, risk and effectiveness to counteract global warming of SRM-SAI might need to be reconsidered.
  • Alan Robock - The Geoengineering Model Intercomparison Project: History, accomplishments, limitations, and future directions
    • I am a co-founder of the Geoengineering Model Intercomparison Project (GeoMIP), along with Ben Kravitz. I will review the history of GeoMIP, including the original protocols and the reasons for them, and the new climate modeling intercomparisons that are now being undertaken. I will summarize the results of the more than 50 GeoMIP papers that have so far been published, and discuss their strengths, including robust conclusions now generally accepted by the community, and their limitations, including over-interpretation of highly idealized experiments, which were never designed as potential recommended implementation schemes. I will then encourage questions and discussion from the audience on the future of GeoMIP, including new ideas about answering scientific questions by analyzing the output of the many completed experiments, new experimental designs, and communication of GeoMIP results.
  • Simone Tilmes
    • GeoMIP has proposed several Tier 1 experiments that are all targeted to advance our process understanding of geoengineering. None of the proposed Tier 1 experiments include a scenario that considers solar radiation management in addition to different ways of enhanced carbon dioxide removal and mitigation, as a way to reach the COP21 Paris climate goals. For instance, the experiment to simulate a temperature overshoot scenario has been proposed as one of the Tier 2 GeoMIP experiments, but may need to be moved up in priority. A justification to discuss priorities of experiments is motivated by the achieved Paris agreement that was reached after the GeoMIP proposal was written. Additional discussions on how strategic geoengineering could be included in GeoMIP will be also motivated.
  • Masahiro Sugiyama - Augmenting GeoMIP with interdisciplinary collaboration and participatory scenario approach
    • Authors: Masahiro Sugiyama, Shinichiro Asayama, Takanobu Kosugi, Atsushi Ishii
    • GeoMIP has been instrumental in enhancing our understanding of the natural science aspects of solar geoengineering. The previous GeoMIP scenarios have not encompassed all the social choices at hand, and this has led to confusion about the risks of geoengineering and detachment of GeoMIP research from the wider governance discourse. Here we argue that in addition to the disciplinary approach, the GeoMIP should augment its research with explicit interdisciplinary collaboration and an additional, new approach to scenario building, learning from the literature on shared socioeconomic pathways (SSPs) and participatory scenario research. The new tracks should focus on social science collaboration to inform governance and critical discourse, and engaging stakeholders and citizens in the scenario development. Additional components can be aided by the use of a GeoMIP emulator and simplified models. When presenting its results to society at large, the GeoMIP should fully reflect different tracks of the GeoMIP research in order to open up social choices we are facing.
Convened by: 

Ben Kravitz

Indiana University, & Pacific Northwest National Laboratory
United States
CEC21 steering committee
CEC17 steering committee
CEC14 steering committee

Ben Kravitz is an expert in climate modeling studies of solar geoengineering.  He is the co-founder and coordinator of the Geoengineering Model Intercomparison Project (GeoMIP), a collaboration between climate modeling centers throughout the world to better understand the expected climate effects of various geoengineering scenarios.  Results from GeoMIP are featured in the Fifth and Sixth IPCC assessment reports, for which Ben serves as a contributing author, the 2015 National Research Council reports on climate intervention, and recent testimony to Congress.  Ben is an assistant professor at Indiana University in the Department of Earth and Atmospheric Sciences, and he maintains a joint appointment in the Atmospheric Sciences and Global Change Division at Pacific Northwest National Laboratory.  In addition to coordinating and participating in GeoMIP, his current activities include using engineering and mathematical techniques in climate models to better understand climate feedbacks, studying teleconnections in high latitude climate, and developing climate model emulators for use in Integrated Assessment Models.

Alan Robock

Rutgers University
United States of America
CEC21 advisory group
CEC17 advisory group
CEC14 advisory group

Dr. Alan Robock is a Distinguished Professor of climate science in the Department of Environmental Sciences at Rutgers University.  He graduated from the University of Wisconsin, Madison, in 1970 with a B.A. in Meteorology, and from the Massachusetts Institute of Technology with an S.M. in 1974 and Ph.D. in 1977, both in Meteorology.  Before graduate school, he served as a Peace Corps Volunteer in the Philippines.  He was a professor at the University of Maryland, 1977-1997, and the State Climatologist of Maryland, 1991-1997, before coming to Rutgers.  Prof. Robock has published more than 400 articles on his research in the area of climate change, including 250 peer-reviewed papers.  His areas of expertise include geoengineering, climatic effects of nuclear war, effects of volcanic eruptions on climate, and soil moisture.  He serves as Associate Editor of Reviews of Geophysics, the most highly-cited journal in the Earth Sciences.  His honors include being a Fellow of the American Geophysical Union, the American Meteorological Society (AMS), and the American Association for the Advancement of Science, and a recipient of the AMS Jule Charney Award.  He recently served as a member of the Board of Trustees of the University Corporation for Atmospheric Research, which operates the National Center for Atmospheric Research.  Prof. Robock was a Lead Author of the 2013 Working Group 1 Fifth Assessment Report of the Intergovernmental Panel on Climate Change (awarded the Nobel Peace Prize in 2007).  In 2017 the International Campaign to Abolish Nuclear Weapons was awarded the Nobel Peace Prize for “for its work to draw attention to the catastrophic humanitarian consequences of any use of nuclear weapons and for its groundbreaking efforts to achieve a treaty-based prohibition of such weapons” based on the work of Prof. Robock.


Helene Muri

University of Oslo
CEC17 contributor

Helene Muri is a researcher at the University of Oslo’s Meteorology and Oceanography Section. Current work is focused on Earth system modelling of various climate geoengineering techniques including BECCS, SRM and cirrus cloud thinning, and actively participates in GeoMIP (Geoengineering Model Intercomparison Project) and CDR-MIP. Furthermore, she contributed towards the EuTRACE climate geoengineering assessment report. Previously, she held an ERC Advanced grant post-doc at Université catholique de Louvain working on climate model - data comparisons for paleo-climate studies. She gained her D.Phil degree from the University of Oxford’s Atmospheric Oceanic and Planetary Physics department in 2009 on the topic of forcing evaluation in climate model ensembles, as part of the project.

Maxime Plazzotta

Météo France
CEC17 contributor

Maxime Plazzotta is a doctoral candidate in climate science at Météo-France/CNRM (National Center for Meteorological Research, Météo-France/CNRS). His research focuses on the impact of geoengineering on the Earth’s climate system, especially the hydrological cycle and the climate-carbon cycle feedbacks. He also works on the representation of solar radiation management (SRM) simulations in climate models. At Météo-France, he is responsible for implementing SRM simulations in the Earth system model in order to contribute to the next phase of the Geoengineering Model Intercomparison Project (GeoMIP6).

Simone Tilmes

National Center for Atmospheric Research
CEC17 contributor

Dr. Simone Tilmes is a Project Scientist II at National Center for Atmospheric Research (NCAR) and the liaison for the Community Earth System Model (CESM) chemistry-climate working group. Her scientific interests cover the understanding and evaluation of chemical, aerosol and dynamical processes in chemistry-climate models. She has investigated past, present and future evolution of the ozone hole in both hemispheres based on models and observations. Further research includes interactions in tropospheric chemistry, aerosols, air quality, long-range transport of pollutants, and tropospheric ozone. She also studies the impact of geoengineering on the Earth’s climate system, the hydrological cycle, and the impact of solar radiation management on dynamics and chemistry in both troposphere and stratosphere.

Masahiro Sugiyama

University of Tokyo
CEC17 contributor

Masa Sugiyama is an associate professor at the Policy Alternatives Research Institute, The University of Tokyo. His recent research focuses on public engagement (particularly from an Asian perspective) and governance of solar geoengineering as well as integrated assessment of mitigation.