Impacts and risks from high‐end scenarios: Strategies for innovative solutions

The Paris Agreement states that climate change should be limited to “well below” 2°C and that countries should strive to limit temperature rise even further, to 1.5°C. However, it has been shown that achieving the 2°C target will require more emissions reductions than currently pledged. Thus, without early and drastic emissions reductions, high-end climate scenarios (where the temperature increase is above 2°C and could rise as high as 4-6°C) are very plausible despite international agreements. However, there are few studies that simultaneously assess their potential impacts, the ability of adaptation options to reduce vulnerabilities, and their potential synergies and trade-offs with mitigation. Thus, it is vital that decision‐makers have access to reliable scientific information on these uncertain, but potentially high‐risk, scenarios of the future to inform integrated adaptation and mitigation planning.

The overall objective of IMPRESSIONS was to advance understanding of the consequences of high‐end climate change through the development of an integrated set of multi‐scale, high‐end climate and socio‐economic scenarios and their application to improved models for analysing impacts, vulnerability, adaptation and mitigation. Adaptation and mitigation pathways that address these impacts and vulnerabilities were generated with stakeholders. The pathways were then analysed to assess the need for transformative strategies that take account of potential synergies and trade‐offs between adaptation, mitigation and sustainable development. How the new knowledge gained from the scenarios, impact modelling and pathways can be embedded within decision‐making processes was also evaluated, so that the project outcomes lead to effective climate governance plans that deal with adaptation and mitigation in a synergistic way.

The main approach was to develop new scenarios and models of the impacts of high levels of climate change, and apply these to five case studies at different geographical scales: the continental scale for Europe; the national scale for Scotland; a transboundary river catchment in Iberia; two municipalities in Hungary; and an EU external case study that looks at interactions between Europe, Central Asia, Russia and China. Different adaptation and mitigation options have been assessed for each case study in order to help decision‐makers identify strategies that are robust for a range of possible futures.

This was achieved through the following steps:

  • Establish decisionmaker needs. In‐depth interviews and stakeholder workshops to understand what tools and knowledge decision‐makers need in order to make robust and effective decisions on adaptation and mitigation in the face of highly uncertain scientific information;
  • Develop integrated climate and socioeconomic scenarios. Work closely with stakeholders in the five case studies to create a set of integrated high‐end climate and socio‐economic scenarios that include potential tipping points;
  • Develop robust methods and models to assess climate change impacts and vulnerability. Integrate a wide range of existing and new spatial models of impacts and vulnerability into a single assessment framework, to analyse the complex interactions, synergies and trade‐offs between different sectors such as agriculture, forestry, urban development and tourism as they compete for land, water and energy, and the resulting impacts on health and biodiversity;
  • Develop adaptation and mitigation pathways. Work with stakeholders in each case study to develop adaptation and mitigation pathways which will be tested with the models;
  • Analyse risks, opportunities, costs and benefits of adaptation and mitigation. Evaluate the adaptation and mitigation pathways developed by stakeholders, studying the effectiveness over time of different pathways in the face of high‐end climate and socio‐economic scenarios, which could include non‐linear changes and tipping points. Develop recommendations on robust new policy strategies and pathways, including the risks and opportunities of different policy options, in order to provide integrated and transformative solutions that help society plan for the long‐term in the context of high levels of climate change;

Knowledge exchange and dissemination. Communicate the results to a broad community of stakeholders to maximise their active participation in the research and enhance current approaches to climate change policies and actions.

The main outcomes of the IMPRESSIONS project:

  • The assessment of decision-maker needs revealed that they perceive high-end climate change as having a low probability or distant occurrence and do not routinely account for such scenarios within existing climate actions. While more information about the implications of particular sectoral and cross-sectoral impacts is needed, climate change uncertainty is not a significant barrier to decision-making. Decision-makers also perceive non-climate drivers to be at least as important, in many cases more important, than climate change alone.
  • A set of highly diverse integrated climate and socio-economic scenarios was developed across multiple scales by downscaling the IPCC-related scenario framework of Representative Concentration Pathways (RCPs) and Shared Socio-economic Pathways (SSPs). The scenarios provide a detailed qualitative and quantitative context for testing the robustness of adaptation and mitigation decisions. They are included in the IMPRESSIONS Integrated Assessment Platform (IAP2), an extension of the CLIMSAVE Integrated Assessment Platform (IAP1), which is a unique user-friendly, interactive web-based tool that enables European stakeholders to explore the complex multi-sectoral issues surrounding impacts, vulnerability and adaptation to climate and socio-economic change across Europe within the agriculture, forestry, biodiversity, water, coastal and urban sectors. 
  • The impacts of climate change, and vulnerability to those impacts, will vary greatly across Europe. Benefits in some regions and sectors, such as increasing forest productivity in northern Europe, are offset by detrimental effects in others, such as severe water scarcity, heat stress and loss of productivity in southern Europe and parts of central and eastern Europe, and widespread flood damage.
  • Three common cross-scale pathways for climate action were identified with stakeholders: (i) shifting to sustainable lifestyles through a cultural change in ways of living, commuting, producing, purchasing and learning for a reflexive and sustainability-oriented society; (ii) governance for sustainability and climate resilience that is democratic, flexible, cooperative and transparent; (iii) and new forms of integrated and sustainable resource management that address water, energy, food, land-use and biodiversity holistically, to create synergies and alleviate trade-offs.
  • Analysis of the adaptation and mitigation pathways shows that beyond the 2°C threshold, conventional solutions to adaptation and mitigation may prove not to be enough. Transformative solutions aimed at implementing radically different institutional arrangements, searching for synergies between adaptation and mitigation and linking them to sustainable development become increasingly important.
  • Policy integration is crucial to achieve the Paris Agreement goal and adapt to the impacts of climate and socio-economic change. An integrated perspective that takes into account the links between multiple policy domains, sectors and scales can facilitate synergies and alleviate trade-offs between adaptation, mitigation and other goals.
  • The stakeholder-led approach in IMPRESSIONS ensured that the research was driven by the priorities of decision-makers from key economic and social sectors so that significant co-learning was achieved. This enabled decision-makers to identify robust, innovative and effective solutions for addressing high-end climate change. It also highlights societal and policy innovations and supports transformations needed to realise synergies between adaptation and mitigation and achieve a sustainable green economy. It also builds capacity and understanding so that decision-makers will be able to use the new information on innovative solutions and train others to sustain a lasting legacy into the future.

The projects outcomes are summarised in an accessible format on the IMPRESSIONS Information Hub. Further information is also available in a set of policy briefs, a set of videos (available via the IMPRESSIONS Information Hub or YouTube channel), and other IMPRESSIONS deliverables and publications (available in the project’s online library).

NERC Centre for Ecology & Hydrology


University of Lisbon


Stockholm Environment Institute


Wageningen University


Danish Meteorological Institute


Finnish Environment Institute


University of Edinburgh


Dutch Research Institute for Transitions


Cranfield University


Jill Jäger


Scuola Superiore di Studi universitari e di perfezionamento Sant'Anna




Pensoft Publishers




University of Kassel (DE)


Joan David Tabara Villalba (ES)


Central European University (HU)


University of Paris 1 (FR)


London School of Hygiene and Tropical Medicine


Eidgenössische Technische Hochschule Zurich


Potsdam Institute for Climate Impacts Research




University of Milano-Bicocca


University of Salzburg


University of Oxford