Climate Scenarios Get a Health Check: 63 Experts Redraw Humanity’s Possible Futures

For roughly a decade, climate scientists and policymakers have relied on a set of five storylines about how the world might evolve, known as the Shared Socioeconomic Pathways, or SSPs. These scenarios, first published around ten years ago, sketch how socioeconomic development could unfold in futures marked by very different levels of challenge for climate adaptation and mitigation. One pathway, called Sustainability, imagines a collective pivot toward green energy, shrinking economic inequities and sustained investment in research and development. Another, Regional Rivalry, describes a world fractured by nationalism and resource conflict, where strife suppresses economic development, wealthy countries see slowing population growth and birth rates climb in poorer nations. A third, Fossil-Fueled Development, pictures a world doubling down on hydrocarbons and enjoying rapid economic growth that, in the scenario’s logic, drives new investments in education and health even as rising emissions degrade the environment and amplify health risks.

Those narratives have proven indispensable for projecting how today’s choices shape tomorrow’s climate, and they now feature in global processes such as United Nations climate conferences, where negotiators from around the world debate and agree on approaches to build resilience and sustainability. But for a subject as intricate as public health, the intentionally simple scenarios leave too much out. Under Fossil-Fueled Development, for instance, the canonical storyline says growth funds better education and health systems while emissions worsen environmental hazards. It says nothing about whether hospital systems would actually be prepared for the resulting caseload, or whether more frequent heat waves would push people indoors for longer stretches, deepening mental health burdens by cutting them off from the outdoors and from one another.

That gap is precisely what a large international group of researchers set out to close. Last year, 63 experts in climate change and health convened in Vienna with the goal of extending the SSPs so that they better reflect the dynamic nature of public health across the rest of the century. The expanded narratives they produced, published in The Lancet Planetary Health on October 5, 2026, offer comprehensive visions of how population health and health systems might develop under each pathway, and they probe how communities could better prepare for shifting future health risks. Lead authorship of the accompanying paper fell to Carole Green, a doctoral student in environmental and occupational health sciences at the University of Washington, who attended the workshop and distilled the collective work into the publication.

The original SSPs, Green explains in a University of Washington News interview, are a narrative framework used alongside greenhouse gas emissions pathways to project climate impacts out to the year 2100. They describe the societal choices that determine the magnitude and pattern of interventions protecting human health and well-being. Each of the five pathways represents a fundamentally different version of the future, and researchers use them in health research to estimate the possible magnitude and geographic pattern of climate-driven health impacts over decades. At the University of Washington, for example, projects use future warming levels to analyze potential wildfire impacts on Washington residents through the Climate Impacts Group. The pathways have even been downscaled to describe what the future might look like in particular countries and regions.

What the original pathways quantified, however, was narrow: GDP and population change. The new work adds layers of complexity specifically designed to capture how public health could evolve under each storyline. Heat waves illustrate the problem. Climate modeling alone can project how the planet warms, but it cannot say how access to hospitals and healthcare might change by 2100, nor how concurrent societal shifts might interact with a changing climate to shape people’s well-being. Current heat wave modeling captures the climate interactions that drive health impacts, but leaves open the questions that matter most to health planners: whether the systems meant to care for the sick will keep pace, and how altered daily life will feed back into physical and mental health.

Once that complexity was added, the picture that emerged was strikingly nuanced. The drivers of health impacts, the experts found, are complex, and many are neither entirely good nor bad. Prioritizing sustainability, mitigation and adaptation will not necessarily produce the best world for every future health outcome, even though those choices clearly shape the trajectory of health and well-being. Perhaps the most consequential conclusion is that global health futures are not predetermined. Different pathways could lead to vastly different health outcomes, with governance, health-system capacity, resources, equity and cross-sectoral factors such as water and energy playing critical roles in determining which future unfolds.

One scenario makes the trade-offs vivid. In that storyline, societies do not prioritize cutting greenhouse emissions, focusing instead on adapting to the changing climate. Heavy investment in technology generates considerable wealth, and that wealth benefits some health outcomes. But the bargain carries hidden costs: as heat burdens grow, people must spend more time indoors, reducing their connection to the outdoors and to nature. It is, in Green’s assessment, a scenario you really do not want to live in. The overall message is that each future is a mix, a blend of gains and losses that resists easy categorization, which is exactly what makes the expanded scenarios challenging and useful at the same time.

The payoff from this effort is a far more sophisticated toolkit for understanding future health risks from climate change. Researchers and policymakers can now add a layer of analysis that goes beyond warming levels and population numbers, asking instead what access to healthcare looks like in a given future, what the extent of food insecurity might be, and how societies would guarantee access to clean air and water. When decision-makers can see how those variables interact under different storylines, the argument goes, they are better positioned to develop appropriate policies. That is the practical purpose of scenario planning: not prediction, but a structured way to explore consequences before they arrive.

The next phase takes the work global and local at once. The team will apply the narratives in six countries where research using the SSPs has so far been limited: Brazil, Senegal, South Africa, India, Vietnam and the Solomon Islands. Key in-country leads have already been identified, and Green notes there is considerable appetite for the research. All countries are required to develop national health adaptation plans and to conduct vulnerability and adaptation assessments, and many are interested in modeling future health risks. The project aims to test how well the global narratives fit each national context, how they would look different, and how local knowledge and local experts can be brought together to talk through possible futures.

Quantification is also on the roadmap. The researchers plan to measure specific disease burdens, universal healthcare access, water and sanitation infrastructure, and digital health under the expanded pathways, with some analyses pairing SSPs with particular warming levels to project impacts. For Green, leading the writing of a paper produced by dozens of the world’s leading experts on climate and health was deeply meaningful, an opportunity she credits to the support of her advisor, Kristie Ebi, who encouraged her to take it on. Her own description of the role is disarmingly simple: listening to experts and writing down what they say. The result is a framework that could shape how the world plans for health in an uncertain century, one carefully drawn future at a time.

Subject of Research: Expanding Shared Socioeconomic Pathways to model future public health outcomes under climate change

Article Title: Q&A: UW doctoral student on expanding climate models to better capture the complexities of public health

Article References: Q&A: UW doctoral student on expanding climate models to better capture the complexities of public health. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Shared Socioeconomic Pathways, climate change, public health, health systems, University of Washington, The Lancet Planetary Health, heat waves, climate scenarios, health adaptation, global health, sustainability, greenhouse gas emissions