Hamburg Climate Futures Outlook 2024 E-Book

• Herausgeber: transcript Verlag
• Kategorie: Wissenschaft und neue Technologien
• Serie: Neue Ökologie
• Sprache: Englisch

Seitenzahl: 620

Veröffentlichungsjahr: 2024

Beschreibung

Many countries, communities, and social actors around the world are struggling to cope with the impacts of climate change. Adapting to climate change in a sustainable manner involves a huge collective effort and is barely happening. How can sustainable climate change adaptation become plausible? The Hamburg Climate Futures Outlook 2024 provides a unique systematic and global assessment of the context conditions for sustainable climate change adaptation, evaluating the social dynamics of deep decarbonization and the physical dynamics in regional climate variability and extremes. Through nine case studies across the globe, the assessment provides insights into key barriers and opportunities for sustainable climate change adaptation.

Leseprobe

About CLICCS

Researchers from a wide range of disciplines have joined forces at the Cluster of Excellence CLICCS (Climate, Climatic Change, and Society) to investigate how climate and society co-evolve. The CLICCS program is coordinated through Universität Hamburg’s Center for Earth System Research and Sustainability (CEN) in close collaboration with multiple partner institutions and is funded by the Deutsche Forschungsgemeinschaft (DFG), EXC 2037 „CLICCS – Klima, Klimawandel und Gesellschaft“ – Projektnummer: 390683824.>

About the Outlook

In the annual Hamburg Climate Futures Outlook, CLICCS researchers make the first systematic attempt to assess which climate futures are plausible, by combining multidisciplinary assessments of plausibility. The 2024 Hamburg Climate Futures Outlook addresses the question: Under which conditions is sustainable climate change adaptation plausible?

DOI: https://doi.org/10.14361/9783839470817

URL: www.cliccs.uni-hamburg.de/results/hamburg-climate-futures-outlook.html

Citation

Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence Climate, Climatic Change, and Society (CLICCS). transcript Verlag, Bielefeld.

Key Findings

In a world with global greenhouse gas emissions still on the rise, higher temperatures, more extreme weather and climate events, and multiple impacts of climate change, communities face big challenges. Adaptation to climate change is needed, but not all adaptation measures are sustainable; some even worsen conditions, especially in the long run. Sustainable climate change adaptation cannot be taken for granted since whether and how local communities succeed in enhancing resilience depends on a variety of social conditions. Based on nine case studies, the Hamburg Climate Futures Outlook 2024 identifies key conditions that influence the plausibility of achieving sustainable climate change adaptation and their connections to mitigation goals. The current Outlook provides a realistic assessment that sets expectations straight and helps to identify social conditions for effective climate action.

▶The Social Plausibility Assessment confirms our previous finding that achieving deep decarbonization, that is, net-zero CO2 emissions by 2050, is not plausible. No overall shift can be observed since the previous assessment in 2023. Therefore, meeting the Paris Agreement goal of limiting the temperature increase to 1.5°C remains not plausible. Currently, none of the 10 social drivers supports deep decarbonization by 2050, with only six social drivers supporting decarbonization. These are: UN climate governance, transnational cooperation, climate-related regulation, climate activism and social mobilization, climate litigation, and knowledge production. The media driver remains ambivalent as it sometimes supports and sometimes inhibits deep decarbonization. Since 2023, fossil-fuel divestment showed a significant change, from a social driver that supported decarbonization to one inhibiting deep decarbonization. This, along with corporate responses and consumption trends, makes three drivers that currently inhibit deep decarbonization by 2050.

▶Social drivers relate to and affect each other in different ways. All social drivers offer empirical evidence for an increase in their dynamics contributing to climate action. This happens also by creating new resources for other drivers, for instance new court rulings, new forms of knowledge, and increased political pressure. Nevertheless, despite the plethora of new resources, there is less change affecting key structural and institutional context conditions of drivers, and therefore no qualitative transformative shift toward deep decarbonization can be observed. Some driver dynamics highlight that available resources may also be used to undermine or counteract climate action.

▶Internal climate variability arises spontaneously and randomly within the climate system. The assessment emphasizes that it is essential to explicitly consider internal variability to better predict changes in extreme events. The quality of these predictions is affected by the uncertainties and limitations of climate models. Knowledge and understanding of these uncertainties and limitations are crucial for communities facing adaptation challenges to climate change. They need to adapt to extreme events, which are strongly influenced by internal climate variability. Such knowledge can make a difference in effective and sustainable climate change adaptation strategies to high-impact events with respect to time-horizons, plans, or expenses.

▶The interplay of climate change and internal variability can lead to ecosystem and socio-economic disruptions with potentially devastating consequences. Adaptation strategies are needed, for example in compound extreme events in crop-growing regions that may threaten local and global food security, in costly precipitation extremes and severe floodings that damage infrastructure and cause fatalities, and in marine heatwaves that are powerful catalysts of ecosystem disruption, with severe consequences for local communities.

▶The analysis of nine case studies emphasizes key conditions that affect the plausibility of achieving sustainable climate change adaptation. Long-standing political conflicts, social inequalities, and other structural problems ought to be addressed for sustainable adaption to become plausible. The same is true of increasing socio-cultural embedded capacities so as to bridge the gap between adaptive capacities and local climate vulnerabilities. Establishing climate-friendly laws, regulations, and adaptation plans are not sufficient unless the people who have to implement adaptation are involved, unless the measures are actively put into practice, and unless the plans are connected to clear indicators and measurable goals based on both scientific assessments and climate justice principles. It is essential to strengthen enabling conditions for sustainable climate change adaptation.

▶Engaging social actors and communities through participatory, trustworthy, and mobilizing strategies is key to foster social involvement and to hold policymakers accountable for their commitments. There is significant potential for collective social action to co-produce knowledge and tackle challenges related to sustainable climate change adaptation. Leveraging past experiences and local knowledge in handling extreme events and climate risks can inform public policies that align climate change adaptation with socio-economic development, as well as the promotion of health and well-being.

▶Sustainable climate change adaptation requires substantial changes on different levels. Key aspects include improving knowledge about interdependencies between mitigation and adaptation scenarios, and increasing considerations of localities and socio-cultural dimensions in the processes of designing and implementing climate adaptation strategies. Sustainable climate change adaptation further requires considering trade-offs and potential synergies as well as reconsidering current path dependencies in coping strategies that reproduce unsustainable adaptation practices, and an increase in the societal support for and political action toward structural transformations.

▶The assessment underlines how ambition and implementation gaps are reproduced. For example, the integration of empirical findings shows how these gaps are the outcome of (1) existing power dynamics and inequalities, (2) different ways of understanding, interpreting, and translating climate change-related norms and practices, (3) a lack of political coherence on different scales of climate governance, and (4) climate change mitigation and adaptation as multifaceted and wicked problems. In addition, uncertainty in social and physical dynamics as well as the interrelation of global and local dynamics affect the plausibility of sustainable climate change adaptation in different ways.

There is never just one agreed climate goal or one way to achieve that goal. To increase the future plausibility of climate change mitigation and adaptation, it is just as important to fight back constraining conditions as it is to strengthen enabling conditions in order to achieve qualitative shifts. The integration of diverse ways of knowing, for instance from local communities or Indigenous Peoples, is crucial for mitigation and adaptation practices, as it is to reduce social inequalities, foster just negotiation processes, and create synergies toward effective climate action.

Author List

1 The Hamburg Climate Futures Outlook 2024: Goals and Structure

Eduardo Gonçalves Gresse, Andrés López-Rivera, Anna Pagnone, Jan Wilkens, Anita Engels, Jochem Marotzke, Beate Ratter

2 The Plausibility of Climate Futures: Explaining the Methodology

Anita Engels, Jan Wilkens, Andrés López-Rivera, Eduardo Gonçalves Gresse, Anna Pagnone, Beate Ratter, Martin Döring, Jochem Marotzke, Stefan C. Aykut, Antje Wiener

Box 1: The Implications of Degrowth Scenarios for the Plausibility of Climate Futures

Eduardo Gonçalves Gresse, Anita Engels, Jan Wilkens

Box 2: The Costs of Military Spending, Wars and the Plausibility of Climate Futures

Michael Brzoska

3 The Plausibility of Achieving Deep Decarbonization by 2050

Jan Wilkens, Andrés López-Rivera, Anita Engels, Eduardo Gonçalves Gresse

3.1 The Social Plausibility Assessment Framework

Stefan C. Aykut, Antje Wiener, Anita Engels, Jan Wilkens, Andrés López-Rivera

3.2 UN Climate Governance

Stefan C. Aykut, Emilie D’Amico, Anna Fünfgeld, Jan Wilkens

3.3 Transnational Cooperation

Thomas Frisch, Emilie D’Amico, Cathrin Zengerling

3.4 Climate-Related Regulation

Grischa Perino, Anne Gerstenberg, Steffen Haag, Franziska Müller, Martin Wickel, Cathrin Zengerling

3.5 Climate Activism and Social Mobilization

Charlotte Huch, Christopher Pavenstädt, Jan Wilkens

3.6 Climate Litigation

Cathrin Zengerling, Stefan C. Aykut, Antje Wiener, Jill Bähring, Lea Frerichs

3.7 Corporate Responses

Matthew Philip Johnson, Theresa Rötzel, Thomas Frisch, Solange Commelin, Timo Busch, Anita Engels

3.8 Fossil-Fuel Divestment

Anita Engels, Steffen Haag, Franziska Müller, Timo Busch, Theresa Rötzel

3.9 Consumption Trends

Eduardo Gonçalves Gresse, Anita Engels, Svenja Struve, Erika Soans

3.10 Media Debates

Katharina Kleinen-von Königslöw, Michael Brüggemann, Lars Guenther

3.11 Knowledge Production

Delf Rothe, Andrés López-Rivera, Jan Wilkens

3.12 Summary of Social Driver Assessments

Jan Wilkens, Andrés López-Rivera, Eduardo Gonçalves Gresse

4 Regional Climate Variability and Extremes: Challenges for Adaptation

Anna Pagnone, Jochem Marotzke

4.1 Introduction

Jochem Marotzke, Anna Pagnone

4.2 Single-Model Initial-Condition Large Ensembles Quantify Internal Climate Variability and its Changes

Dirk Olonscheck, Leonard Borchert, Adrien Deroubaix

4.3 Are Recently Observed Heavy Precipitation Extremes Realistically Represented by State-of-the-art Spatial Resolutions of Global Climate Models?

Dirk Olonscheck and Franziska S. Hanf

4.4 High-Impact Marine Heatwaves

Armineh Barkhordarian

4.5 How Will Extreme Heat in the World’s Breadbasket Regions Change in the Future?

Leonard Borchert, Victoria Dietz, Joscha N. Becker, Kerstin Jantke

4.6 Summary

Anna Pagnone

5 Sustainable Climate Change Adaptation: Insights and Reflections from the Field

Beate Ratter, Martin Döring, Eduardo Gonçalves Gresse

5.1 Introduction

Martin Döring, Beate Ratter, Eduardo Gonçalves Gresse

5.2 Towards Plausible Sustainable Climate Change Adaptation in Urban, Rural, and Coastal Areas

Martin Döring, Beate Ratter, Eduardo Gonçalves Gresse

5.3 Hamburg, Germany

Franziska S. Hanf, Jörg Knieling, Malte von Szombathely, Martin Wickel, Jürgen Oßenbrügge, Sonja Schlipf, Jana Sillmann

5.4 São Paulo, Brazil

Eduardo Gonçalves Gresse, Marcelo Soeira, Gabriela Di Giulio, Denise Duarte, Anita Engels

5.5 Ho Chi Minh City, Vietnam

Michael Waibel, Thuy Thi Thu Nguyen, Pham Tran Hai, Steven Petit, Le Hong Nhat

5.6 Rural Areas of Northeast Lower Saxony, Germany

Uwe Schneider, Kerstin Jantke, Michael Köhl, Annette Eschenbach, Martina Neuburger

5.7 Rural Communities in Nepalese highlands, Nepal

Prem Raj Neupane, Kumar Bahadur Darjee, Jürgen Böhner, Michael Köhl

5.8 Pastoralists in Kunene, Namibia

Michael Schnegg, Kerstin Jantke, Annette Eschenbach, Uwe Schneider

5.9 Coastal Adaptation in North Frisia, Germany

Martin Döring, Philipp Jordan, Kirstin Dähnke, Johannes Pein, Beate Ratter, Peter Fröhle

5.10 Small Islands Adaptation in the Maldives

Beate Ratter, Arne Hennig, Zahid

5.11 Coastal Adaptation in Taiwan

Hsiao-Wen Wang, Peter Fröhle, Natasa Manojlovic, Dong-Jiing Doong

5.12 Conclusion and Assessment

Martin Döring, Beate Ratter, Eduardo Gonçalves Gresse

6 Integration and Synthesis of Assessments

Andrés López-Rivera, Jan Wilkens, Eduardo Gonçalves Gresse, Anna Pagnone, Anita Engels, Jochem Marotzke, Beate Ratter, Antje Wiener, Achim Oberg, Martin Döring

Box 3: Toward a More Inclusive and Connected Repertoire of Climate Action

Anita Engels, Jochem Marotzke, Beate Ratter, Eduardo Gonçalves Gresse, Andrés López-Rivera, Anna Pagnone, Jan Wilkens

7 Implications for Shaping Climate Futures

Anita Engels, Jochem Marotzke, Beate Ratter, Eduardo Gonçalves Gresse, Andrés López-Rivera, Anna Pagnone, Jan Wilkens

External Authors and Contributions

Gabriela Di Giulio, University of São Paulo (USP), São Paulo, Brazil

Denise Duarte, University of São Paulo (USP), São Paulo, Brazil

Dong-Jiing Doong, National Cheng Kung University, Tainan City, Taiwan

Le Hong Nhat, Trends & Technologies Inc. Vietnam, Ho Chi Minh City, Vietnam

Arne Hennig, Arepo Consult, Berlin, Germany

Natasa Manojlovic, Hamburg University of Technology, Hamburg, Germany

Steven Petit, Institute of Smart City and Management, Ho Chi Minh City, Vietnam

Sonja Schlipf, Hamburg Wasser, Hamburg, Germany

Marcelo Soeira, State University of Campinas, Brazil

Thuy Thi Thu Nguyen, Hong Bang International University, Ho Chi Minh City, Vietnam

Pham Tran Hai, Ho Chi Minh City Institute for Development Studies, Ho Chi Minh City, Vietnam

Hsiao-Wen Wang, National Cheng Kung University, Tainan City, Taiwan

Zahid, Male’ Envergy Consultancy Pvt Ltd., Maldives

Reviewers

Julia Arieira, Johanna Baehr, Stefan C. Aykut, Peter Driessen, Simin Davoudi, Greg Flato, Pierre Friedlingstein, Oliver Geden, Franziska S. Hanf, Gabriele Hegerl, Jim Hall, Peter Haugan, Lars Kutzbach, Michael Köhl, David Marcolino Nielsen, Nicola Maher, Vladimir Metelitsa, Carlos Nobre, Achim Oberg, Grischa Perino, Simone Pulver, Karl Steininger, Rodolfo Salm, Uwe Schimank, Detlef van Vuuren, Ingrid van Putten, Karin von Schmalz, Anke Weidlich

CLICCS Scientific Steering Committee

Johanna Baehr, Anita Engels, Annette Eschenbach, Eduardo Gonçalves Gresse, Lars Kutzbach, Andreas Lange, Jochem Marotzke, Achim Oberg, Grischa Perino, Corinna Schrum, Jana Sillmann

Table of Contents

Key Findings

Author List

Recommended Citations

1The Hamburg Climate Futures Outlook 2024: Goals and Structure

2The Plausibility of Climate Futures: Explaining the Methodology

3The Plausibility of Achieving Deep Decarbonization by 2050

3.1The Social Plausibility Assessment Framework

3.2UN Climate Governance

3.3Transnational Cooperation

3.4Climate-Related Regulation

3.5Climate Activism and Social Mobilization

3.6Climate Litigation

3.7Corporate Responses

3.8Fossil-Fuel Divestment

3.9Consumption Trends

3.10Media Debates

3.11Knowledge Production

3.12Summary of Social Driver Assessments

Box I  The Implications of Degrowth Scenarios for the Plausibility of Climate Futures

Box II  The Costs of Military Spending, Wars, and the Plausibility of Climate Futures

4Regional Climate Variability and Extremes: Challenges for Adaptation

4.1Introduction

4.2Single-Model Initial-Condition Large Ensembles Quantify Internal Climate Variability and its Changes

4.3Are Recently Observed Heavy Precipitation Extremes Realistically Represented by State-of-the-Art Spatial Resolutions of Global Climate Models?

4.4High-Impact Marine Heatwaves

4.5How Will Extreme Heat in the World’s Breadbasket Regions Change in the Future?

4.6Summary

5Sustainable Climate Change Adaptation: Insights and Reflections from the Field

5.1Introduction

5.2Toward Plausible Sustainable Climate Change Adaptation in Urban, Rural, and Coastal Areas

5.3Hamburg, Germany

5.4São Paulo, Brazil

5.5Ho Chi Minh City, Vietnam

5.6Rural Areas of Northeast Lower Saxony, Germany

5.7Rural Communities in Nepalese Highlands, Nepal

5.8Pastoralists in Kunene, Namibia

5.9Coastal Adaptation in North Frisia, Germany

5.10Small Islands Adaptation in the Maldives

5.11Coastal Adaptation in Taiwan

5.12Conclusion and Assessment

6Integration and Synthesis of Assessments

Box III  Toward an Inclusive and Connected Repertoire of Climate Action

7Implications for Shaping Climate Futures

References

Imprint

Table of Contents for Figures and Tables

Table 2.1: Learning Assessment: Conceptual developments between Outlook versions

Figure 3.1: Social Plausibility Assessment Framework

Figure 3.2: Global carbon inequality

Figure 3.3: Global inequality of individual emissions

Figure 3.4: Climate actions mentioned or demanded in media reporting on climate futures

Figure 4.1: Schematic of the MPI-GE

Figure 4.2: Representation of observed heavy precipitation extremes

Figure 4.3: Representation of the heavy precipitation extreme observed in Mirante de Santana, São Paulo City

Figure 4.4: Time series of annual marine heatwave days

Figure 4.5: Ensemble probability for a heatwave to occur in Northern Namibia

Figure 4.6: Ensemble probability for a heatwave to occur during the same maize growing season

Figure 5.1: Case study locations and climate change effects

Table 5.1: Case studies – Basic information

Figure 5.2: Hamburg, Germany

Figure 5.3: São Paulo, Brazil

Figure 5.4: Ho Chi Minh City, Vietnam

Figure 5.5 Lower Saxony, Germany

Figure 5.6: Lake Tsho Rolpa, Nepal

Figure 5.7: Kunene, Namibia

Figure 5.8: Amrum, Germany

Figure 5.9: Beach of Fuvahmulah, Maldives

Figure 5.10: Tainan, Taiwan

Figure 5.11: Climate change adaptation assessment

Recommended Citations

Chapter 1

Gresse, Eduardo Gonçalves; Andrés López-Rivera; Anna Pagnone; Jan Wilkens; Anita Engels; Jochem Marotzke; Beate Ratter (2024). The Hamburg Climate Futures Outlook 2024: Goals and Structure. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 14-17. transcript Verlag, Bielefeld. DOI: 10.14361/9783839470817-002

Chapter 2

Engels, Anita; Jan Wilkens; Andrés López-Rivera; Eduardo Gonçalves Gresse; Anna Pagnone; Beate Ratter; Martin Döring; Jochem Marotzke; Stefan Aykut; Antje Wiener (2024). The Plausibility of Climate Futures: Explaining the Methodology. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 18-25. transcript Verlag, Bielefeld. DOI: 10.14361/9783839470817-003

Chapter 3

Wilkens, Jan; Andrés López-Rivera; Anita Engels; Eduardo Gonçalves Gresse (2024). The Plausibility of Achieving Deep Decarbonization by 2050. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 26-71. transcript Verlag, Bielefeld. DOI: 10.14361/9783839470817-004

Section 3.1

Aykut, Stefan C.; Antje Wiener; Anita Engels; Jan Wilkens; Andrés López-Rivera (2024). The Social Plausibility Assessment Framework. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 28-32. transcript Verlag, Bielefeld.

Section 3.2

Aykut, Stefan C.; Emilie D’Amico; Anna Fünfgeld; Jan Wilkens (2024). UN Climate Governance. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 32-36. transcript Verlag, Bielefeld.

Section 3.3

Frisch, Thomas; Emilie D’Amico; Cathrin Zengerling (2024). Transnational Cooperation. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 36-39. transcript Verlag, Bielefeld.

Section 3.4

Perino, Grischa; Anne Gerstenberg; Steffen Haag; Franziska Müller; Martin Wickel; Cathrin Zengerling (2024). Climate-Related Regulation. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 39-41. transcript Verlag, Bielefeld.

Section 3.5

Huch, Charlotte; Christopher Pavenstädt; Jan Wilkens (2024). Climate Activism and Social Mobilization. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 42-46. transcript Verlag, Bielefeld.

Section 3.6

Zengerling, Cathrin; Stefan Aykut; Antje Wiener; Jill Bähring; Lea Frerichs (2024). Climate Litigation. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 46-48]. transcript Verlag, Bielefeld.

Section 3.7

Johnson, Matthew Philip; Theresa Rötzel; Thomas Frisch; Solange Commelin; Timo Busch; Anita Engels (2024). Corporate Responses. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 49-51. transcript Verlag, Bielefeld.

Section 3.8

Engels, Anita; Steffen Haag; Franziska Müller; Timo Busch; Theresa Rötzel (2024). Fossil-Fuel Divestment. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 52-54. transcript Verlag, Bielefeld.

Section 3.9

Gresse, Eduardo Gonçalves; Anita Engels; Svenja Struve; Erika Soans (2024). Consumption Trends. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 54-58. transcript Verlag, Bielefeld.

Section 3.10

Kleinen-von Königslöw, Katharina; Michael Brüggemann; Lars Guenther (2024). Media Debates. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 58-61. transcript Verlag, Bielefeld.

Section 3.11

Rothe, Delf; Andrés López-Rivera; Jan Wilkens (2024). Knowledge Production. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 61-64. transcript Verlag, Bielefeld.

Section 3.12

Wilkens, Jan; Andrés López-Rivera; Eduardo Gonçalves Gresse (2024). Summary of Social Driver Assessments. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 64-66. transcript Verlag, Bielefeld.

Box I

Gresse, Eduardo Gonçalves; Anita Engels; Jan Wilkens (2024). The Implications of Degrowth Scenarios for the Plausibility of Climate Futures. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 68-69. transcript Verlag, Bielefeld. DOI: 10.14361/9783839470817-005

Box II

Brzoska, Michael (2024). The Costs of Military Spending, Wars and the Plausibility of Climate Futures. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 70-71. transcript Verlag, Bielefeld. DOI: 10.14361/9783839470817-006

Chapter 4

Pagnone, Anna; Jochem Marotzke (2024). Regional Climate Variability and Extremes: Challenges for Adaptation. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 72-93. transcript Verlag, Bielefeld. DOI: 10.14361/9783839470817-007

Section 4.1

Marotzke, Jochem; Anna Pagnone (2024). Introduction. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 74-75. transcript Verlag, Bielefeld.

Section 4.2

Olonscheck, Dirk; Leonard Borchert; Adrien Deroubaix (2024). Single-Model Initial-Condition Large Ensembles Quantify Internal Climate Variability and its Changes. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 75-78. transcript Verlag, Bielefeld.

Section 4.3

Olonscheck, Dirk; Franziska S. Hanf (2024). Are Recently Observed Heavy Precipitation Extremes Realistically Represented by State-of-the-Art Spatial Resolutions of Global Climate Models? In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 79-83. transcript Verlag, Bielefeld.

Section 4.4

Barkhordarian, Armineh (2024). High-Impact Marine Heatwaves. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 83-87. transcript Verlag, Bielefeld.

Section 4.5

Borchert, Leonard; Victoria Dietz; Joscha N. Becker; Kerstin Jantke (2024). How Will Extreme Heat in the World’s Breadbasket Regions Change in the Future? In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 87-91. transcript Verlag, Bielefeld.

Section 4.6

Anna Pagnone (2024). Summary. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 91-92. transcript Verlag, Bielefeld.

Chapter 5

Ratter, Beate; Martin Döring; Eduardo Gonçalves Gresse (2024). Sustainable Climate Change Adaptation: Insights and Reflections from the Field. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 94-143. transcript Verlag, Bielefeld. DOI: 10.14361/9783839470817-008

Section 5.1

Döring, Martin; Beate Ratter; Eduardo Gonçalves Gresse (2024). Introduction. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 96-99. transcript Verlag, Bielefeld.

Section 5.2

Döring, Martin; Beate Ratter; Eduardo Gonçalves Gresse (2024). Toward Plausible Sustainable Climate Change Adaptation in Urban, Rural, and Coastal Areas. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 100-103. transcript Verlag, Bielefeld.

Section 5.3

Hanf, Franziska S.; Jörg Knieling; Malte von Szombathely; Martin Wickel; Jürgen Oßenbrügge; Sonja Schlipf; Jana Sillmann (2024). Hamburg, Germany. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 104-108. transcript Verlag, Bielefeld.

Section 5.4

Gresse, Eduardo Gonçalves; Marcelo Soeira; Gabriela Di Giulio; Denise Duarte; Anita Engels (2024). São Paulo, Brazil. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 109-113. transcript Verlag, Bielefeld.

Section 5.5

Waibel, Michael; Thuy Thi Thu Nguyen; Pham Tran Hai; Steven Petit; Le Hong Nhat (2024). Ho Chi Minh City, Vietnam. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 114-117. transcript Verlag, Bielefeld.

Section 5.6

Schneider, Uwe; Kerstin Jantke; Michael Köhl; Annette Eschenbach; Martina Neuburger (2024). Rural Areas of Northeast Lower Saxony, Germany. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 117-120. transcript Verlag, Bielefeld.

Section 5.7

Neupane, Prem Raj; Kumar Bahadur Darjee; Jürgen Böhner; Michael Köhl (2024). Rural Communities in Nepalese Highlands, Nepal. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 120-124. transcript Verlag, Bielefeld.

Section 5.8

Schnegg, Michael; Kerstin Jantke; Annette Eschenbach; Uwe Schneider (2024). Pastoralists in Kunene, Namibia. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 124-127. transcript Verlag, Bielefeld.

Section 5.9

Döring, Martin; Philipp Jordan; Kirstin Dähnke; Johannes Pein; Beate Ratter; Peter Fröhle (2024). Coastal Adaptation in North Frisia, Germany. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 127-130. transcript Verlag, Bielefeld.

Section 5.10

Ratter, Beate; Arne Hennig; Zahid (2024). Small Islands Adaptation in the Maldives. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 131-134. transcript Verlag, Bielefeld.

Section 5.11

Wang, Hsiao-Wen; Peter Fröhle; Natasa Manojlovic; Dong-Jiing Doong (2024). Coastal Adaptation in Taiwan. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 134-138. transcript Verlag, Bielefeld.

Section 5.12

Döring, Martin; Beate Ratter; Eduardo Gonçalves Gresse (2024). Conclusion and Assessment. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 138-142. transcript Verlag, Bielefeld.

Chapter 6

López-Rivera, Andrés; Jan Wilkens; Eduardo Gon-çalves Gresse; Anna Pagnone; Anita Engels; Jochem Marotzke; Beate Ratter; Antje Wiener; Achim Oberg; Martin Döring (2024). Integration and Synthesis of Assessments. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 144-153. transcript Verlag, Bielefeld. DOI: 10.14361/9783839470817-009

Box III

Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (2024). Toward an Inclusive and Connected Repertoire of Climate Action. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 152-153. transcript Verlag, Bielefeld. DOI: 10.14361/9783839470817-010

Chapter 7

Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (2024). Implications for Shaping Climate Futures. In: Engels, Anita; Jochem Marotzke; Beate Ratter; Eduardo Gonçalves Gresse; Andrés López-Rivera; Anna Pagnone; Jan Wilkens (eds.); 2024. Hamburg Climate Futures Outlook 2024. Conditions for Sustainable Climate Change Adaptation. Cluster of Excellence “Climate, Climatic Change, and Society” (CLICCS), pp. 154-159. transcript Verlag, Bielefeld. DOI: 10.14361/9783839470817-011

1

The Hamburg Climate Futures Outlook 2024: Goals and Structure

With global greenhouse gas emissions still on the rise and a new record global mean temperature reached in 2023, public and policy debates focus increasingly on the needs of adaptation to the impacts of climate change. However, adaptation does not happen simply out of necessity. Whether and how local communities succeed in creating greater resilience in a world where climate change leads to more extreme weather and climate events depends on complex social conditions, which in many places are not yet met. The Hamburg Climate Futures Outlook 2024 has the goal to assess under which physical and social conditions sustainable climate change adaptation is plausible. The assessment aims at audiences in different fields and with different degrees of expertise, with Chapter 7 in particular discussing the implications of our assessment for a wider, non-expert readership and for various types of practitioners.

If neither mitigation of climate change nor adaptation to its consequences can be taken for granted, which type of climate future is awaiting human society? We, the authors, try and answer this question by assessing the plausibility of specific scenarios of how the climate changes and society changes with it in times of multiple crises, and with a global temperature rise of 1.4°C already occurring in 2023 (Copernicus, 2023). We organize the assessment into three main parts: First, we investigate if and how the world is moving toward deep decarbonization by 2050 second, we assess physical conditions of regional variability and extreme events; and third, we assess social processes that render sustainable climate change adaptation plausible.

With deep decarbonization we mean a state in which society has come down to net-zero CO2 emissions. Sustainable climate change adaptation is defined as a social, political, and technical process of adjusting to actual and expected climate change and its impacts. Such a process seeks to moderate or avoid harm, reduce vulnerability, and avoid maladaptation, that is, actions that result in negative effects and increased vulnerability, by enhancing synergies and minimizing trade-offs between climate action and other sustainable development goals (Gresse et al., 2023; Juhola and Käyhko, 2023).

In our assessment, the plausibility of deep decarbonization is linked to the dynamics of 10 social drivers from the fields of politics, law, economics, and culture. These drivers are assessed in their global effects: How do these drivers affect the prospects of moving toward or away from, deep decarbonization on a global scale? What changes do we observe in the drivers’ dynamics, and how do these changes affect the plausibility of a net-zero climate future by 2050? The current Outlook provides an update of previous assessments (Stammer et al., 2021; Engels et al., 2023). We will explain in detail in Chapter 3 why, according to our assessment, the world has moved further away from achieving deep decarbonization by 2050, compared to our first assessment in 2021.

Whereas global emissions and the social drivers of decarbonization can be assessed through a global framework, adaptation to the impacts of climate change is always context-specific. Accordingly, the plausibility of sustainable climate change adaptation needs to be assessed specifically for each regional or local case. In Chapter 4, we delve into the interplay between regional variability and extreme events and thereby provide a physical rationale for the varying regional and local demands to adapt to ranges of climate futures and extreme events.

In Chapter 5, we empirically scrutinize the contextual conditions that affect the plausibility of sustainably adapting to climate change in various geographical localities and regions. We look at nine case studies in urban, rural, and coastal settings across different regional contexts. The case studies—Hamburg, São Paulo, Ho Chi Minh City, Lower Saxony (Germany), Kunene (Namibia), the Nepal Highlands, the German North Sea coast, Taiwan and the Maldives—examine barriers to sustainable climate change adaptation in order to find locally specific answers to the question:

“Under which conditions is sustainable climate change adaptation plausible?”

Chapter 6 synthesizes and integrates the findings from the three different assessments of Chapters 3 to 5, and Chapter 7 concludes with a reflection on the implications they may bear for different types of practitioners.

The assessment provided in this Outlook thus contains three different parts that are closely interrelated. Chapter 2 explains how we integrate the different elements into a coherent whole: the plausibility of deep decarbonization, the interplay between regional variability and extreme events, and the conditions under which sustainable climate change adaptation becomes plausible.

Authors:

Eduardo Gonçalves Gresse, Andrés López-Rivera, Anna Pagnone, Jan Wilkens, Anita Engels, Jochem Marotzke, Beate Ratter

2

The Plausibility of Climate Futures: Explaining the Methodology

This chapter contains a brief introduction to key concepts of the current Outlook. Our focus here is on how the different elements of the overall assessment relate to each other while the following chapters will provide deeper justifications of conceptual choices for the Social Plausibility Assessment Framework (Chapter 3), for the analysis of internal climate variability and extremes (Chapter 4), and for assessing plausibility conditions for sustainable adaptation to climate change (Chapter 5). All three parts of the overall assessment are based on a combination of literature review and our own empirical research.

Worldwide efforts toward deep decarbonization are on the rise, but structural challenges for the attainment of the Paris Agreement temperature goal persist and have, in some cases, even deepened. Our past assessments came to the conclusion that limiting global warming to 1.5°C—corresponding to the most ambitious part of the Paris Agreement temperature goal—is not plausible. This lack of plausibility also applies to the scenario that global warming will only temporarily exceed but thereafter again fall below 1.5°C. Such a scenario of limited overshoot requires deep decarbonization by around 2050, which we do not deem plausible. Furthermore, increased ambition and speed to achieve deep decarbonization is required for limiting global warming to below 2°C or to prevent even larger global temperature rises. Already under current climate conditions, engaging in climate change adaptation is increasingly important, and this need will aggravate if the Paris Agreement temperature goal is missed. Therefore, exploring sustainable ways of adapting to climate change is key to promote climate-resilient and sustainable development, in addition to efforts at decarbonization.

We have already shown in previous Outlooks that deep decarbonization depends on a complex interplay of social drivers and their enabling and constraining conditions. Agreeing on the necessity of deep decarbonization as a precondition for the attainment of the 1.5°C temperature goal of the Paris Agreement by no means guarantees that society will actually move in this direction. Along the same lines, agreeing on the necessity to prepare for negative impacts of climate change and to engage in adaptation measures does not guarantee that society will actually plan, finance, and implement climate change adaptation, least of all in a sustainable manner. Moreover, if the global mean temperature rises more than 2°C compared to pre-industrial times, the physical conditions for achieving sustainable climate adaptation will have become more challenging. Therefore, drawing on the interplay between deep decarbonization (mitigation) and adaptation, the current Outlook edition addresses the overarching question:

Under which conditions is sustainable climate change adaptation plausible?

This overarching question combines an updated assessment of the social plausibility of deep decarbonization by 2050 (Chapter 3), an assessment of the physical challenges that internal climate variability and extremes pose for adaptation (Chapter 4), and the plausibility of sustainable climate change adaptation in specific regions, organized around nine case studies (Chapter 5).

Key concepts

Climate Futures: CLICCS research is organized around the concept of climate futures, by which we mean potential future states of the co-evolution of the physical climate system and society. Physical boundary conditions influence but in no way determine the way in which society will evolve. Complex social dynamics, in turn, contribute in many ways to changes in the physical boundary conditions, for example by altering the chemical composition of the atmosphere or by changing the net functions of land and water masses as sinks or sources of greenhouse gases. How these changes affect both global temperature changes and local manifestations of climate and weather is to a certain degree dependent on internal variability of the climate system.

Plausibility: Climate futures cannot be determined in a probabilistic way due to the manyfold internal complexities and irreducible uncertainties of the co-evolution of climate and society. Acknowledging the limited feasibility of a robust probabilistic assessment, we have developed an alternative framework to assess the plausibility of climate futures (Stammer et al., 2021). “Our understanding of plausibility assessment is based on theoretical or mental models of social dynamics and physical processes. Once these models are established, we hold available empirical evidence against the main assumptions of these models and come to a conclusion whether the world is moving toward or away from a predefined climate future [scenario]. In light of this conclusion, we provide a conjecture on the plausibility of the climate future” (Engels et al., 2023, p. 14, emphasis by authors). What was developed with regard to social dynamics also makes sense for physical processes for which deep uncertainty exists and hence no agreed-upon quantitative measure of uncertainty can be formulated. For uncertainty that is not deep, probability distributions can be agreed upon, and plausibility is then defined such that an event may happen with appreciable probability. Whether an event will indeed occur depends not only on the future evolution of global warming but also on chance. Plausibility in any of these senses does not relate to the desirability of specific climate futures. We strive for a matter-of-factly approach to assessing climate futures, adopting a sense of sober realism because we think that it is important to know where society stands, globally speaking, compared to both overly hopeful and fatalistic expectations of the future.

Social Plausibility Assessment Framework: The Framework starts from a model of transformational change, further elaborated in Section 3.1, which acknowledges the importance of history, context, and agency (Aykut et al., 2021; Wiener et al., 2023). Plausibility refers to the level of confidence and to the strength of our knowledge judgments (Janasik, 2021), based on theoretical models of change and available empirical evidence. We understand this as a learning assessment, where repeated applications help improve the models and help them stand the test of time. We use the framework to look at the social plausibility of a specific climate future, in this case the scenario that global society will have achieved deep decarbonization by 2050. In the first Outlook, published in 2021, we identified 10 social drivers as key elements of potential change toward deep decarbonization (see Table 2.1), each influenced by specific enabling and constraining conditions and by specific relations to other drivers. In each new edition of the assessment, we screen newly available empirical evidence for changes in these conditions that might affect each driver’s direction and how the drivers relate to each other. Of special interest is the generation and use of globally visible resources for climate-related societal engagement, such as new legal norms, discursive frames, or funding possibilities. Such resources form the basis of novel climate action “scripts”, for example when activists develop new contentious practices, companies engage in new forms of climate reporting, or innovative climate litigation cases diffuse across national jurisdictions. New resources and scripts broaden existing repertoires of climate-related engagement and contribute to the “densification” of the global opportunity structure for climate action (see Section 3.1).

Interplay of internal climate variability and extreme events: Internal climate variability arises from the chaotic interactions within and between components of the climate system such as atmosphere, ocean, cryosphere, and land (see also Section 4.1). Since the existence of internal climate variability potentially obscures signals of anthropogenic climate change, it is important to quantify, understand, and project internal climate variability. Specific tools to address this challenge are required, such as single-model initial-condition large ensembles. Global warming exacerbates many extremes, but on the regional or local scale the distribution of internal climate variability is often wider than the anthropogenic effect. The interplay of regional variability and extremes poses particular challenges to the science supporting sustainable adaptation to climate change, for instance the capability of climate models to represent extremes, the attribution of extreme events to human influence, and the probability of compounding extreme events.

Adaptation: Conceptually, we classify adaptation responses into three analytical categories (Fedele et al., 2019): First, coping strategies: short-term reactive responses that aim at immediate reactions to climatic impacts in socio-ecological systems. Second, incremental adaptation: a stepwise approach along beaten paths, focusing on sectoral or context-specific adjustments with minor systemic stability disturbance. And third, transformative adaptation: fundamental changes that encompass broader and deeper actions directed at the root causes of vulnerabilities while at the same time envisioning long-term systemic shifts (for more details and concrete examples, see Chapter 5). Coping and incremental adaptation strategies are the most frequent types of adaptation and are characterized by lock-ins and unsustainable adaptation pathways. Transformative strategies, in turn, are a key enabling, but not necessarily sufficient, condition for sustainable climate change adaptation. Responses that aim at reducing risk but create adverse effects or increase vulnerabilities are called maladaptation (for further elaboration on these concepts, see Section 5.1).

Sustainable climate change adaptation: Adapting to climate change in a sustainable manner means accounting for the broader spectrum of societal goals and socio-ecological transformations involved when designing, planning, and implementing adaptation responses. Drawing on Gresse et al. (2023), we define sustainable climate change adaptation as the process of adapting to actual and expected climate change and its impacts by significantly reducing actual and potential conflicts and exploiting synergies between climate action and other sustainable development goals. Hence, a sustainable adaptation response necessarily has to extrapolate the various ranges of climate action while also fostering sustainability transformations, that is, multi-sectoral and system-wide shifts that foster human development while protecting and upholding the Earth’s life-support systems’ resilience (see also Section 5.1).

Context conditions for the plausibility of sustainable climate change adaptation: Organized around nine local and regional case studies, we focus on the interaction of societal systems with their various social, cultural, spatial, temporal, and natural environments. Based on an inductive rationale, the investigation builds on a commonly structured and joint assessment of empirical studies and conceptual reflections taken from these case studies. They examine, analyze, and assess the barriers to and the possibilities for sustainable climate change adaptation across different regional contexts. To account for locally specific and diverse ways of knowing (cf. Petzold et al., 2021; Wiener et al., 2023), the case studies were written by interdisciplinary groups of authors and in co-authorships with local experts situated in the respective case study context. This was implemented in accordance with calls to integrate various knowledge forms alongside current adaptation strategies, as for example acknowledged in the fifth and sixth Assessment Reports by the Intergovernmental Panel in Climate Change (IPCC). This integration is not merely seen to enhance the efficacy of adaptation efforts but also deemed essential for fostering ethical and sustainable adaptation practices (Nakashima et al., 2018; de Coninck et al., 2018, Petzold et al., 2020). In light of these assessments, we empirically reconstruct the conditions that make sustainable climate change adaptation plausible in each specific and place-based case.

Integrating the building blocks of the Outlook 2024

Assessing the plausibility of deep decarbonization by 2050 creates a first important building block for the overarching question of the plausibility conditions for sustainable climate change adaptation. If it is not plausible, or—as the assessment in Chapter 3 will show—even becoming less plausible that deep decarbonization will be achieved by 2050, this implies a global warming of more than 1.5°C that will persist until the end of the century; a warming level that, in turn, affects the physical boundary conditions for the future of human society. Understanding these physical boundary conditions helps define the challenges for adaptation to climate change impacts in different regional and local settings.

Global warming exacerbates many extremes, but on the regional or local scale the distribution of internal climate variability is often wider than the anthropogenic effect. Therefore, the interplay of internal climate variability and extreme events is the second important building block that affects the plausibility conditions for sustainable climate change adaptation. Each example discussed in Chapter 4 illustrates a particular fundamental point relevant for the plausibility of sustainable climate change adaptation: the capability of climate models to represent extremes (here: precipitation), the attribution of extreme events to human influence (here: marine heatwaves), and the probability of compounding extreme events (here: extreme heat in multiple breadbasket regions). In this fundamental sense, these examples foreshadow the relevance of the physical processes and results for the adaptation challenges that are assessed in Chapter 5.

The nine case studies and the combination of empirical analyses and theoretical reflection create the third important building block for assessing the plausibility conditions for sustainable climate change adaptation. The case studies analyze different types of adaptation responses (or lack thereof) and address the extent to which social systems are able to adapt to climate change, that is, the context-specific limits and limitations of adaptation. While the scenario for the plausibility assessment of the first building block—achieving deep decarbonization by 2050—has a clear time horizon, the scenario for sustainable climate change adaptation spreads into many different place-specific scenarios, each depending on the particular local manifestations of climate change, the expected climate extremes including their inherent uncertainties, and unclear time horizons. Which combination of sustainability goals, which level of adaptation, and which limits of adaptation make a good scenario for assessing the plausibility conditions in a specific local or regional setting is always subject to negotiation. Therefore, the nine case studies apply a common set of questions but are in themselves inductive in defining which type of climate change impact is most socially relevant, and what would actually constitute criteria for adapting to these impacts in a sustainable way.

Considering the challenges of such diverse geographical and temporal scales as well as the context-specific understandings of what it means to adapt to climate change in time, we come to a very differentiated answer to the overarching question of the plausibility conditions for sustainable climate change adaptation (Chapter 6).

Who are we? How do we work?

“We” are a group of 73 authors working together in the Cluster of Excellence Climate, Climatic Change, and Society (CLICCS) at the Universität Hamburg, its partner institutions, chiefly among them the Max Planck Institute for Meteorology and the Helmholtz-Zentrum Hereon, and from within the regions assessed in the nine case studies, contributing with practical knowledge and local perspective to climate change adaptation efforts in these different regions. While our goal is to provide a global assessment, we are aware of the risk of over-representing northern European views and understandings of the dynamics we are observing and of marginalizing views and voices from the Global South, or simply from places other than Northern Europe, as well as from epistemic perspectives other than the ones typically employed in mainstream climate science. In order to minimize this risk, we explicitly include assessments of dynamics in countries of the Global South. We made specific efforts to represent different epistemic perspectives in the literature reviews to also draw from scientific fields that are typically not represented in mainstream climate science, and to include diverse ways of knowing by including authors and perspectives from the Global South. We invited authors from outside of CLICCS to make sure that we write on specific regions together with authors from these regions (Brazil, Maldives, Nepal, Taiwan, and Vietnam). Finally, we invited authors from the Global South to review two previous versions of this Outlook. As we rely on different combinations of original data produced in CLICCS, existing data bases on many different topics, and deep literature reviews, we explain in every chapter the specific data foundation that the assessment contained therein is based on.

Learning assessment: Conceptual developments between Outlook versions

We have introduced a number of conceptual developments in this new Outlook version. Table 2.1 summarizes how key conceptual choices have been refined, added, and deepened. Each Outlook is organized around a new overarching question, which also guides us in the way we integrate the different assessment parts. While Outlook 2021 focused on deep decarbonization and temperature changes, Outlook 2023 added a new framework for Sustainable Climate Change Adaptation, which is now, in this Outlook, applied to 9 case studies. The number of authors has risen continuously from 43 to 73.

Authors:

Anita Engels, Jan Wilkens, Andrés López-Rivera, Eduardo Gonçalves Gresse, Anna Pagnone, Beate Ratter, Martin Döring, Jochem Marotzke, Stefan C. Aykut, Antje Wiener

TABLE 2.1

Learning Assessment: Conceptual developments between Outlook versions

Outlook 2024

Outlook 2023

Outlook 2021

Overarching question

Under which conditions is sustainable climate change adaptation plausible?

What affects the plausibility of attaining the Paris Agreement temperature goals?

Is it plausible that the world will reach deep decarbonization by 2050?

Social Plausibility Assessment Framework

Relationality (push/pull dynamics) between social drivers

Densification of climate action (scripts and repertoires of Global Opportunity Structure)

10 social driversEnabling and constraining conditions and resources of Global Opportunity Structure

Social drivers

Stronger emphasis on drivers as processes:

▶Transnational Initiatives -> Transnational Cooperation

▶Climate Protests and Social Movements -> Climate Activism and Social Mobilization

▶Consumption Patterns -> Consumption Trends

Widening of one driver:

▶Journalism -> Media

10 social drivers

▶UN Climate governance

▶Transnational initiatives

▶Climate-related regulation

▶Climate protests and social movements

▶Climate litigation

▶Corporate responses

▶Fossil-fuel divestment

▶Consumption patterns

▶Journalism

▶Knowledge production

Physical processes

Three example interplays of regional variability and extremes:

▶Precipitation

▶Marine heatwaves

▶Extreme heat in multiple breadbasket regions

Physical Plausibility Assessment Framework. Six example physical processes:

▶Permafrost thaw

▶Arctic sea-ice decline

▶Polar ice-sheet melt

▶Atlantic Meridional Overturning Circulation instability

▶Amazon Forest dieback

▶Regional climate change and variability

Temperature trends for the 21st century

Sustainable Climate Change Adaptation

Inductive model of conditions of sustainable climate change adaptation via nine case-studies

Distinction between coping-incremental-transformative. Definition of sustainable climate change adaptation

Not discussed

Authors

73 from CLICCS and external partners from Brazil, Maldives, Nepal, Taiwan, Vietnam

63 from CLICCS only

43 from CLICCS only

3

The Plausibility of Achieving Deep Decarbonization by 2050

3.1

The Social Plausibility Assessment Framework

The Social Plausibility Assessment Framework is a central contribution to scenario-driven research on climate futures. It was first developed in the Outlook 2021 (Aykut et al., 2021) and refined in the Outlook 2023 (Wiener et al., 2023) as a robust qualitative approach to assess if a particular climate future appears plausible or not, given what we know about relevant social dynamics. The assessment draws on in-depth analyses of processes that act as social drivers of the climate future in question, with a view to examining past, present, and emergent dynamics of these processes, as well as context conditions that might enable or constrain them in the future. In doing so, we do not adopt a normative approach that focuses on what should happen to make a desirable scenario plausible. Instead, we use an analytical approach that aims to systematically explore the social plausibility of a given climate future and understand what processes, institutions, and agencies shape this plausibility.

What do we mean when we say that we assess the plausibility of a particular climate future? Indeed, there is a vivid debate on how to conceptualize possible, feasible, probable, and plausible climate futures in the IPCC and elsewhere (Brutschin et al., 2021; Jewell and Cherp, 2023; Glette-Iversen et al., 2022; Pielke Jr. et al., 2022; Riahi et al., 2022; Schipper et al., 2021). There is also a strong call to quantify the probability of climate futures. However, looking at the probability of deep transformational change by 2050 would require prioritizing quantified trend extrapolations over the recognition of deep uncertainties inherent in social dynamics and of complex interrelations between them (Selin and Guimarães Pereira, 2013). While it may be possible to apply probability reasoning to much more narrow dynamics such as demographic change or energy demand, we do not think it is possible to establish a robust quantitative assessment of the probability of deep decarbonization by 2050. Instead, our assessment is based on a much more holistic, but also in many ways more modest, understanding of the complexities of transformational change over a long period of time, in which we acknowledge the importance of history, context, and agency (Aykut et al., 2021; Wiener et al., 2023; Engels and Marotzke, 2023). We define plausibility as a state in which an internally consistent future—or qualitative scenario—and a theory-based model of change are assessed vis-à-vis available empirical evidence on relevant social dynamics that can be held against this model of change. Plausibility in this sense is suitable for assessing processes of deep uncertainty, and it involves an inherently qualitative knowledge judgment (Glette-Iversen et al., 2022). We are therefore not far away from Jewell’s and Cherp’s (2023, p. 3) definition of plausible as “occurable in exploratory scenarios with internally-consistent assumptions”, but go beyond their interest in feasible options that can be implemented by specific groups of actors. We also depart from Pielke Jr. et al.’s understanding of plausible emission scenarios, which use growth rates consistent with observations and near-term projections without employing an underlying theory or model of social change (Pielke Jr. et al., 2022).

Finally, our framework differs from research on social tipping points toward decarbonization (Otto et al., 2020; Fesenfeld et al., 2022). Studies in this tradition typically identify social fields or dynamics which can bring about radical transformational change once a critical threshold has occurred (Winkelmann et al., 2022; Lenton et al., 2023). The assumption is that from then on the unfolding dynamic becomes so strong and self-reinforcing that a new normality is firmly locked-in, leading to rapid decarbonization with limited reversibility of the process (Milkoreit, 2023). The typical S-curve of a technological innovation is the mental model here: It starts with only a few early adopters, but over time the number of adopters rises to a critical point at which the new technology very rapidly, and sometimes even disruptively, replaces an older technology (Kucharavy and Guio, 2011). We depart from this mental model for a number of reasons (Wilkens et al., 2023; Aykut et al., 2021). Mainly, our focus does not lie on identifying invariable social tipping points in social systems, but on understanding context-dependent social processes and the set of relevant context conditions of these processes that would actually have an effect on future shifts in social dynamics. This allows us to get a more realistic understanding of where current social dynamics and constellations of enabling and constraining conditions point to, given the available empirical evidence. Knowing that social dynamics very often follow the shape of recurrent waves or cycles rather than clear-cut S-curves, and knowing that it is often only possible to determine in hindsight whether some threshold has changed the direction of a dynamic permanently, we prefer a realistic assessment over providing optimistic narratives.

The past Outlook editions have applied the Social Plausibility Assessment Framework to assess the plausibility of deep decarbonization by 2050 and of limiting global warming to 1.5°C, relative to pre-industrial levels, based on the analysis of 10 selected social drivers (Stammer et al., 2021; Engels et al., 2023). As we understand it here, deep decarbonization describes a transition to net-zero carbon emissions, leading to a very low carbon intensity in all sectors of the economy, a reduced energy demand (Méjean et al., 2019), and very low demand for carbon-intensive consumer goods. Deep decarbonization can thus be thought of as reducing carbon emissions to as close to zero as possible, with residual emissions compensated by active carbon dioxide removal from the atmosphere (IPCC, 2018; Deep Decarbonization Pathways Project, 2015; Wimbadi and Djalante, 2020; UN Climate Action; IPCC 2021, Annex VII, Glossary). Such a transition also implies a profound social transformation, including changes in norms, regulations, institutions, individual behaviors, and personal values (Shove and Walker, 2010; O’Brien, 2018; Beckert, 2024). The scenario must be clearly distinguished from other, less constrained futures in which decarbonization is only partially achieved by 2050. However, it must also remain generic enough to allow for a broad range of emissions trajectories and technology pathways so as to place the analytical focus on the social transformations that enable deep decarbonization (Held et al., 2021, p. 25; see Figure 3.1).

The Social Plausibility Assessment Framework consists of a series of key concepts—social drivers, context conditions, resources, and the global opportunity structure—that allow us to capture and describe the continuous interplay of historical dynamics and path dependencies, structural and institutional conditions for social change, and the creative work of societal agency (Aykut et al., 2021; Wiener et al., 2023). Social drivers are defined as overarching social processes that generate change toward or away from a given scenario and its characteristics. As social processes, drivers mediate between agency and structure and span micro-, meso-, and macro-scales of global society (Jordan et al., 2018). They reflect societal multiplicity and the agency of a plurality of stakeholders (Wiener, 2022), but also economic and socio-technical dynamics (Geels et al., 2017). Social drivers capture a broad and multifaceted range of political and societal engagement with the climate problem, which facilitates or hinders decarbonization and generates “climatizing” effects by diffusing climate concerns in new policy fields, governance arenas, and societal spheres (Aykut et al., 2017). As in previous Outlooks, we analyze 10 social drivers, which represent relevant existing and emergent social processes that generate change away or toward a scenario of deep decarbonization by 2050. This list (see Table 2.1) represents an analytical choice based on the literature and our own expert elicitation. Given the intrinsic complexity of social systems and foreseeable changes in the dynamics of low-carbon transformations worldwide, this list may be subject to changes in the future (we address some newer developments below).