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https://doi.org/10.5194/egusphere-2025-1899
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/egusphere-2025-1899
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
18 Jun 2025
| 18 Jun 2025
Status: this preprint is open for discussion and under review for Earth System Dynamics (ESD).
The Tipping Points Modelling Intercomparison Project (TIPMIP): Assessing tipping point risks in the Earth system
Abstract. The risk of transgressing critical thresholds triggering nonlinear change in the Earth system increases with rising human pressures from greenhouse gas emissions, land-use change and other drivers. Several key components of the Earth System such as the Greenland and Antarctic ice sheets, permafrost, the Atlantic Meridional Overturning Circulation (AMOC), and boreal and tropical forests as well as mountain glaciers, terrestrial hydrological systems and the Sahel region have been suggested to exhibit self-amplifying feedback processes that could lead to non-linear and often abrupt and/or irreversible transitions with far-reaching biophysical and socio-economic consequences. While concerns within the scientific community, general public and among policy- and decision-makers are growing, significant uncertainties remain regarding the critical thresholds, timescales, interactions and impacts of such tipping dynamics. To address these critical knowledge gaps, we here present the Tipping Points Modelling Intercomparison Project (TIPMIP), an international collaborative effort to systematically assess tipping point risks using state-of-the-art coupled Earth System Models and stand-alone domain models, e.g., ice sheet and land system models. Building on the success of established Model Intercomparison Projects (MIPs), TIPMIP aims to standardize model experiments, quantify uncertainty ranges for critical forcing thresholds, and provide a multi-model assessment of tipping dynamics across key Earth system components. TIPMIP will enhance our ability to anticipate and mitigate the risks associated with Earth system tipping points, and support science-based decision-making in the face of high-end impacts and deep uncertainties.
How to cite. Winkelmann, R., Dennis, D. P., Donges, J. F., Loriani, S., Klose, A. K., Abrams, J. F., Alvarez-Solas, J., Albrecht, T., Armstrong McKay, D., Bathiany, S., Blasco Navarro, J., Brovkin, V., Burke, E., Danabasoglu, G., Donner, R. V., Drüke, M., Georgievski, G., Goelzer, H., Harper, A. B., Hegerl, G., Hirota, M., Hu, A., Jackson, L. C., Jones, C., Kim, H., Koenigk, T., Lawrence, P., Lenton, T. M., Liddy, H., Licón-Saláiz, J., Menthon, M., Montoya, M., Nitzbon, J., Nowicki, S., Otto-Bliesner, B., Pausata, F., Rahmstorf, S., Ramin, K., Robinson, A., Rockström, J., Romanou, A., Sakschewski, B., Schädel, C., Sherwood, S., Smith, R. S., Steinert, N. J., Swingedouw, D., Willeit, M., Weijer, W., Wood, R., Wyser, K., and Yang, S.: The Tipping Points Modelling Intercomparison Project (TIPMIP): Assessing tipping point risks in the Earth system, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-1899, 2025.
Competing interests: Some authors are members of the editorial board of the journal Earth System Dynamics. Otherwise, the authors have no competing interests to declare.
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Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
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RC1: 'Comment on egusphere-2025-1899', Anonymous Referee #1, 27 Jun 2025
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The authors of “The Tipping Point Modelling Intercomparisons Project (TIPMIP) Assessing tipping point risks in the Earth system” have laid out a plan for a highly comprehensive MIP. Their plans appear well informed by present uncertainties and gaps in our understanding of the Earth system. This project has broad implications, including, for example, the potential to provide important insight into tipping points in the Earth system relevant to international climate change policy. This manuscript will no doubt be read and cited by a broad audience, including earth system modelers, domain-specific modelers, as well as observationalists working within these systems.
That said, the manuscript nonetheless requires some revision. I have several comments aimed at improving the clarity of the manuscript and its accessibility for a broad audience. Significant revisions are needed for clarity, improved readability, clear comprehension of the figure, and to ensure important terms are defined in the text and used consistently. Finally, as a broader comment, I suggest that explanations of the model’s process or structural limitations and their implications should have their nuances explored in greater detail and be accompanied by citations. I suggest framing calls to action around model development aimed at reducing structural limitations and improving process representation by identifying specific processes or model representations that can be targeted for improvement.
Major comments:
- Lines 20, 22, and throughout the manuscript: Much of this text uses very long sentences with complex punctuation structures. Suggest splitting sentences as a strategy to improve readability, especially when introducing complex concepts.
- Figure 1:
- Consider removing the arrow on the y-axis, given that it’s categorical.
- Improve the clarity of the lower axis (e.g., “past” may not be relevant given that no data is shown and the axis is relative to pre-industrial).
- Label the color scale for clarity; replace “undetectable” with “low,” and make “not assessed” a separate indicator. Since “not assessed” is always at the high end of the range, it is reasonable to assume the risk is likely greater than what precedes it.
- Line 88: More detail is needed for clarity when discussing “ensembles of scenarios, modeling choices and parameters,” as this is a complex concept, so tough to convey in this brief text.
- Box 2: In statements like “none of the Earth system components/potential tipping systems considered is in equilibrium,” I suggest building a bit more distinction between the real world and the model world. In ESMs, the system is often represented as being in equilibrium before responding to forcing over time, which is a necessary simplification of reality. The same logic applies in discussions of different types of tipping — my impression is this is primarily referring to real-world processes, not necessarily what is represented in model equations.
- Figure 3: Only a subset of readers will be familiar with the plots and notation used here. I suggest adding explanatory captions to panels a-c to clarify the role of the arrows. Also, the left side of the figure does not appear to be fully described in the figure text; please explain this portion in detail.
- Figures 3 and 4: The inclusion of examples in the Figure 4 caption is helpful, but I suggest moving these examples into the main text and adding similar examples for the processes mentioned in Figure 3 (potentially expanding the figure). This would enhance the value of the figures for a broad audience.
- Figure 5: This figure is very informative, but I suggest revising it for readability:
- Ensure consistent color coding for "landing climate," "peak warming," etc., between the a panel and other panels.
- Use more distinct color coding for panels b-e, and apply it consistently within each panel.
- Many terms are introduced in the figure but are not defined or referenced in the caption or main text. Please define all terminology in the text and guide the reader through it purposefully.
- Clarify that the forcing axis on plots b-e maps to plot a, with the time axis removed.
- The y-axis on plot a needs a label.
- Consider using plot a to better illustrate the y-axis in plots b-e. The colored circles, lines, and their closed variants are not defined — these should be explained.
- Line 374: The phrase “as the current vegetation components in ESMs are expected to be too stable” is unclear and not accompanied by citations. Some ESMs prescribe vegetation cover, which can be advantageous because the simulation is not influenced by biases in present-day vegetation cover, allowing analysis to focus elsewhere. ESMs with dynamic vegetation (e.g., employing a representation based on the Lotka-Volterra models for interacting populations) are based on our present understanding of fundamental ecological concepts. Certain processes, like deforestation driven by economic factors, are challenging to simulate dynamically and may require interdisciplinary modeling approaches. I suggest specifying which processes underlie this statement to better inform the questions asked by the MIP and broader model development efforts.
- Box 2: Regarding “structural and process limitations,” couple models are referenced explicitly. However, structural and process limitations exist in all modeling frameworks, arising from trade-offs between realism and parsimony. Identifying key tipping points can inform necessary processes for inclusion in ESMs or other model classes. However, any model can have structural and process limitations, depending on its purpose (e.g., a DGVM driven by reanalysis cannot simulate the impact of vegetation carbon cycle feedbacks on climate change). TIP MIP seems to strive to formulate hypotheses and simulations tailored to each modeling framework’s limitations.
- Line 575: These numbered points could be better integrated with the relevant questions posed in Box 2 earlier in the text.
Minor comments
- Line 1: I suggest using “crossing” rather than “transgressing” here and elsewhere in the text, due to the connotations of the latter.
- Line 33: Given the potentially broad audience, I suggest explicitly defining "abruptness" and "irreversibility."
- Line 55: I recommend rewording “while the need…high (Fig 1)” for improved clarity.
- Line 116: Clarify whether these definitions are introduced here for the first time by the authors or are sourced from existing literature. Box 1 suggests multiple sources; if so, please provide citations within the text.
- Line 116: “positive feedback” is used elsewhere in text and I think would be more commonly known than “amplifying feedback”.
- Line 144: The phrase “instructive, but rather conceptual” is unclear; please clarify its intended meaning.
- Line 301: The sentence reads as a call for mitigation and adaptation, but instead, I suggest highlighting how TIPMIP outputs can inform our understanding of these systems, even though some processes are not yet fully represented.
- Line 35: The statement regarding “perceived stability” requires additional explanation.
Citation: https://doi.org/10.5194/egusphere-2025-1899-RC1
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Integrative Earth System Science, Max Planck Institute of Geoanthropology, Jena, Germany
Earth Resilience Science Unit, Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany
Donovan P. Dennis
Integrative Earth System Science, Max Planck Institute of Geoanthropology, Jena, Germany
Earth Resilience Science Unit, Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Jonathan F. Donges
Integrative Earth System Science, Max Planck Institute of Geoanthropology, Jena, Germany
Earth Resilience Science Unit, Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Stockholm Resilience Centre, Stockholm University, Stockholm, Sweden
Sina Loriani
Integrative Earth System Science, Max Planck Institute of Geoanthropology, Jena, Germany
Earth Resilience Science Unit, Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Ann Kristin Klose
Earth Resilience Science Unit, Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany
Jesse F. Abrams
Global Systems Institute, University of Exeter, Exeter, UK
Jorge Alvarez-Solas
Institute of Geosciences, CSIC-UCM, Madrid, Spain
Department of Earth Physics and Astrophysics, Complutense University of Madrid, Madrid, Spain
Torsten Albrecht
Integrative Earth System Science, Max Planck Institute of Geoanthropology, Jena, Germany
Earth Resilience Science Unit, Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
David Armstrong McKay
Global Systems Institute, University of Exeter, Exeter, UK
School of Global Studies, University of Sussex, Brighton, UK
Sebastian Bathiany
Department of Earth System Modeling, School of Engineering and Design, Technical University of Munich, Munich, Germany
Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Javier Blasco Navarro
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
Victor Brovkin
Max Planck Institute for Meteorology, Hamburg, Germany
Met Office Hadley Centre, Exeter, UK
Eleanor Burke
Met Office Hadley Centre, Exeter, UK
Gokhan Danabasoglu
US National Science Foundation, National Center for Atmospheric Research, Boulder, USA
Reik V. Donner
Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Magdeburg-Stendal University of Applied Sciences, Magdeburg, Germany
Markus Drüke
Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Department of Hydrometeorology, Deutscher Wetterdienst, Germany
Goran Georgievski
Max Planck Institute for Meteorology, Hamburg, Germany
Heiko Goelzer
NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway
Anna B. Harper
University of Georgia, Department of Geography, Athens, USA
Gabriele Hegerl
School of GeoSciences, University of Edinburgh, Edinburgh, UK
Marina Hirota
Group IpES, Department of Physics, Federal University of Santa Catarina, Florianópolis, Brazil
US National Science Foundation, National Center for Atmospheric Research, Boulder, USA
Laura C. Jackson
Met Office Hadley Centre, Exeter, UK
Colin Jones
National Centre for Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK
Hyungjun Kim
Korea Advanced Institute of Science and Technology, Daejeon, Korea
Torben Koenigk
Swedish Meteorological and Hydrological Institute, Norrköping, Sweden
Peter Lawrence
US National Science Foundation, National Center for Atmospheric Research, Boulder, USA
Timothy M. Lenton
Global Systems Institute, University of Exeter, Exeter, UK
Hannah Liddy
Columbia Climate School, Columbia University, New York, NY, USA
NASA Goddard Institute for Space Studies, New York, NY, USA
José Licón-Saláiz
Earth Resilience Science Unit, Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Maxence Menthon
Vrije Universiteit Amsterdam, Earth Science Department, Amsterdam, The Netherlands
Marisa Montoya
Institute of Geosciences, CSIC-UCM, Madrid, Spain
Department of Earth Physics and Astrophysics, Complutense University of Madrid, Madrid, Spain
Jan Nitzbon
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
Sophie Nowicki
Department of Earth Science, University at Buffalo, Buffalo, New York, USA
Bette Otto-Bliesner
US National Science Foundation, National Center for Atmospheric Research, Boulder, USA
Francesco Pausata
ESCER (Centre pour l'étude et la simulation du climat à l'echelle régionale), Department of Earth and Atmospheric Sciences, University of Quebec in Montreal, Montreal, Canada
GEOTOP (Research Center on the Dynamics of the Earth System), Department of Earth and Atmospheric Sciences, University of Quebec in Montreal, Montreal, Canada
Stefan Rahmstorf
Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Karoline Ramin
Earth Resilience Science Unit, Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Alexander Robinson
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
Johan Rockström
Earth Resilience Science Unit, Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Institute of Environmental Science and Geography, University of Potsdam, Potsdam, Germany
Anastasia Romanou
NASA Goddard Institute for Space Studies, New York, NY, USA
Department of Applied Physics and Applied Mathematics, Columbia University, New York, USA
Boris Sakschewski
Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Christina Schädel
Woodwell Climate Research Center, Falmouth, MA, USA
Steven Sherwood
Climate Change Research Centre, University of New South Wales, Sydney, New South Wales, Australia
ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, New South Wales, Australia
Robin S. Smith
National Centre for Atmospheric Science, Department of Meteorology, University of Reading, Reading, UK
Norman J. Steinert
CICERO Center for International Climate Research, Oslo, Norway
Didier Swingedouw
Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC) Université de Bordeaux, CNRS, Bordeaux, France
Matteo Willeit
Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
Wilbert Weijer
Los Alamos National Laboratory, Los Alamos, NM, USA
International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, AK, USA
Richard Wood
Met Office Hadley Centre, Exeter, UK
Klaus Wyser
Swedish Meteorological and Hydrological Institute, Norrköping, Sweden
Shuting Yang
Danish Meteorological Institute, Copenhagen, Denmark
Short summary
The Tipping Points Modelling Intercomparison Project (TIPMIP) is an international collaborative effort to systematically assess tipping point risks in the Earth system using state-of-the-art coupled and stand-alone domain models. TIPMIP will provide a first global atlas of potential tipping dynamics, respective critical thresholds and key uncertainties, generating an important building block towards a comprehensive scientific basis for policy- and decision-making.
The Tipping Points Modelling Intercomparison Project (TIPMIP) is an international collaborative...