The Tipping Points Modelling Intercomparison Project (TIPMIP): Assessing tipping point risks in the Earth system

Winkelmann, Ricarda; Dennis, Donovan P.; Donges, Jonathan F.; Loriani, Sina; Klose, Ann Kristin; Abrams, Jesse F.; Alvarez-Solas, Jorge; Albrecht, Torsten; Armstrong McKay, David; Bathiany, Sebastian; Blasco Navarro, Javier; Brovkin, Victor; Burke, Eleanor; Danabasoglu, Gokhan; Donner, Reik V.; Drüke, Markus; Georgievski, Goran; Goelzer, Heiko; Harper, Anna B.; Hegerl, Gabriele; Hirota, Marina; Hu, Aixue; Jackson, Laura C.; Jones, Colin; Kim, Hyungjun; Koenigk, Torben; Lawrence, Peter; Lenton, Timothy M.; Liddy, Hannah; Licón-Saláiz, José; Menthon, Maxence; Montoya, Marisa; Nitzbon, Jan; Nowicki, Sophie; Otto-Bliesner, Bette; Pausata, Francesco; Rahmstorf, Stefan; Ramin, Karoline; Robinson, Alexander; Rockström, Johan; Romanou, Anastasia; Sakschewski, Boris; Schädel, Christina; Sherwood, Steven; Smith, Robin S.; Steinert, Norman J.; Swingedouw, Didier; Willeit, Matteo; Weijer, Wilbert; Wood, Richard; Wyser, Klaus; Yang, Shuting

doi:https://doi.org/10.5194/egusphere-2025-1899

Preprints

https://doi.org/10.5194/egusphere-2025-1899

Preprints

18 Jun 2025

| 18 Jun 2025

The Tipping Points Modelling Intercomparison Project (TIPMIP): Assessing tipping point risks in the Earth system

Ricarda Winkelmann, Donovan P. Dennis, Jonathan F. Donges, Sina Loriani, Ann Kristin Klose, Jesse F. Abrams, Jorge Alvarez-Solas, Torsten Albrecht, David Armstrong McKay, Sebastian Bathiany, Javier Blasco Navarro, Victor Brovkin, Eleanor Burke, Gokhan Danabasoglu, Reik V. Donner, Markus Drüke, Goran Georgievski, Heiko Goelzer, Anna B. Harper, Gabriele Hegerl, Marina Hirota, Aixue Hu, Laura C. Jackson, Colin Jones, Hyungjun Kim, Torben Koenigk, Peter Lawrence, Timothy M. Lenton, Hannah Liddy, José Licón-Saláiz, Maxence Menthon, Marisa Montoya, Jan Nitzbon, Sophie Nowicki, Bette Otto-Bliesner, Francesco Pausata, Stefan Rahmstorf, Karoline Ramin, Alexander Robinson, Johan Rockström, Anastasia Romanou, Boris Sakschewski, Christina Schädel, Steven Sherwood, Robin S. Smith, Norman J. Steinert, Didier Swingedouw, Matteo Willeit, Wilbert Weijer, Richard Wood, Klaus Wyser, and Shuting Yang

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.

Received: 22 Apr 2025 – Discussion started: 18 Jun 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.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.

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RC1:
'Comment on egusphere-2025-1899', Anonymous Referee #1, 27 Jun 2025
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
RC2: 'Comment on egusphere-2025-1899', Anonymous Referee #2, 23 Sep 2025

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1899/egusphere-2025-1899-RC2-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2025-1899-RC2

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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.


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