Scenarios have been recognised as a useful tool for planning, which have resulted in a strong increase in the number of (multiscale) scenarios in climate change research. This paper addresses the need for methodological progress and testing of conceptual considerations, by extending the global shared socioeconomic pathways (SSPs). We present a set of four European SSPs until 2100 and a novel method to develop qualitative stories for Europe equivalent to the global SSPs starting from an existing set of European scenarios. Similar to the global SSPs, the set includes a sustainable future with global cooperation and less intensive lifestyles (We are the World; Eur-SSP1); a future in which countries struggle to maintain living standards in a high-carbon intensive Europe (Icarus; Eur-SSP3); a world in which power becomes concentrated in a small elite and where Europe becomes an important player (Riders on the Storm; Eur-SSP4); and one where a lack of environmental concern leads to the overexploitation of fossil fuel resources addressed by technological solutions (Fossil-fuelled Development; Eur-SSP5). We conclude that the global SSPs are a good starting point for developing equivalent continental scale scenarios that, in turn, can serve multiple purposes. There are, however, methodological challenges related to the choice for equivalence and the exact methods by which scenarios are constructed that need to be tested further.

Whether and how long-term energy and climate targets can be reached depend on a range of interlinked factors: technology, economy, environment, policy, and society at large. Integrated assessment models of climate change or energy-system models have limited representations of societal transformations, such as behavior of various actors, transformation dynamics in time, and heterogeneity across and within societies. After reviewing the state of the art, we propose a research agenda to guide experiments to integrate more insights from social sciences into models: (1) map and assess societal assumptions in existing models, (2) conduct empirical research on generalizable and quantifiable patterns to be integrated into models, and (3) build and extensively validate modified or new models. Our proposed agenda offers three benefits: interdisciplinary learning between modelers and social scientists, improved models with a more complete representation of multifaceted reality, and identification of new and more effective solutions to energy and climate challenges.

The Paris Agreement established the 1.5 and 2°C targets based on the recognition Bthat this would significantly reduce the risks and impacts of climate change^. We tested this assertion by comparing impacts at the regional scale between low-end (< 2°C; RCP2.6) and high-end (> 4°C; RCP8.5) climate change scenarios accounting for interactions across six sectors (agriculture, forestry, biodiversity, water, coasts and urban) using an integrated assessment model. Results show that there are only minor differences in most impact indicators for the 2020s time slice, but impacts are considerably greater under high-end than low-end climate change in the 2050s and 2080s. For example, for the 2080s, mitigation consistent with the Paris Agreement would reduce aggregate Europe-wide impacts on the area of intensive agriculture by 21% (on average across climate models), on the area of managed forests by 34%, on water stress by 14%, on people flooded by 10% and on biodiversity vulnerability by 16%. Including socioeconomic scenarios (SSPs 1, 3, 4, 5) results in considerably greater variation in the magnitude, range and direction of change of the majority of impact indicators than climate change alone. In particular, socioeconomic factors much more strongly drive changes in land use and food production than changes in climate, sometimes overriding the differences due to low-end and high-end climate change. Such impacts pose significant challenges for adaptation and highlight the importance of searching for synergies between adaptation and mitigation and linking them to sustainable development goals.

The stability and resilience of the Earth system and human well-being are inseparably linked1–3, yet their interdependencies are generally under-recognized; consequently, they are often treated independently4,5. Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, water and nutrient cycles, and aerosols at global and subglobal scales. We propose ESBs for maintaining the resilience and stability of the Earth system (safe ESBs) and minimizing exposure to significant harm to humans from Earth system change (a necessary but not sufficient condition for justice)4. The stricter of the safe or just boundaries sets the integrated safe and just ESB. Our findings show that justice considerations constrain the integrated ESBs more than safety considerations for climate and atmospheric aerosol loading. Seven of eight globally quantified safe and just ESBs and at least two regional safe and just ESBs in over half of global land area are already exceeded. We propose that our assessment provides a quantitative foundation for safeguarding the global commons for all people now and into the future.