Modelling health futures
Authors: None The Lancet Planetary Health
Journal: The Lancet Planetary Health (2021)

Nils Bohr famously said that “Prediction is very difficult, especially if it's about the future!” This aphorism neatly encapsulates the challenges of building models that extrapolate observed patterns out of sample, something which is unavoidable when investigating future events. That the future is inherently uncertain does not free us from needing to plan and find ways to consider possible futures though. Fortunately, we have more and better tools for considering the future than ever before, so that while we cannot predict what will happen with certainty, we can gain useful insights into the likely consequences of some of the key choices that are open to us. These are tools we sorely need because the growing and highly dynamic nature of human activities and their impacts means that understanding the past is increasingly insufficient for guiding future actions. For example, records of past flood frequency and magnitude only take you so far in understanding future risk when the climate is changing, sea levels are rising, and infrastructure is expanding. Throughout the history of climate change as a societal concern, a great deal of energy has been spent arguing about the merits and shortcomings of various climate and climate impact models and how much faith we should put into them. Notably, an important component of this originated from politically motivated public relations campaigns designed to deny climate change science and delay policy responses. Nevertheless, this tactic was successful, in part, because of the real challenges in capturing important aspects of the atmosphere, ocean, and biosphere in computer models and understanding the sources and magnitude of uncertainties in the future projections they generate. One of the chief ways in which this challenge is being met is through systematic model improvement, comparison, and evaluation. In the climate science community this is orchestrated through the Coupled Model Intercomparison Projects (CMIP) which are synchronised to inform the IPCC Assessment Reports. This coordination allows model developments such as improved spatial resolution or cloud physics representation to be evaluated in consistent model runs between modelling groups to explore common emissions scenarios and generate a spread of climate projections for various potential futures. Uncertainties inherent in projecting the future state of the climate system are propagated into climate impact model outputs that simulate things like freshwater resource availability or crop yields, and contain their own additional assumptions and uncertainties. Similar coordinated modelling efforts have consequently emerged to facilitate model improvement and evaluation and uncertainty quantification for a number of climate impacts. So far the health impacts of climate change have not seen a high degree of coordinated modelling effort despite the fact that human health is a key concern that can motivate climate policy and has been shown to be sensitive to many climatic parameters, thus requiring adaptation to those changes that are already here or now locked in. A lack of coordination makes model projections of climate impacts on health hard to compare and overall effects very difficult to estimate. Greater cross-discipline cooperation and collaboration is certainly warranted and coordinated modelling frameworks and associated research structures potentially offer an important shared goal and coordinating mechanism to facilitate more joined up research and policy on the health effects of climate change. This issue is largely given over to a series of papers which use harmonised input data and common simulation protocols from the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) to investigate the impacts of climate change on: temperature-related mortality in Europe and globally, enteric pathogens, dengue and malaria transmission, vibriosis, and labour supply and productivity. Each Article is summarised and contextualised in a linked Viewpoint which highlights the benefits of this approach and outlines some priority areas that would strengthen the evidence base for modelling health burdens under climate change. Climate change is a health risk multiplier, primarily increasing existing risks rather than creating entirely new ones; consequently, many of the interventions needed to reduce vulnerability are not new either. However, as with the case of flooding, a dynamic situation means that past priorities are not on their own reliable indicators of future ones. Coordinated impact modelling efforts such as those presented in this issue are a powerful tool to help plan for human health in our uncertain climate future. Projections of temperature-attributable mortality in Europe: a time series analysis of 147 contiguous regions in 16 countriesThe increase in heat attributable fraction will start to exceed the reduction of cold attributable fraction in the second half of the 21st century. This finding highlights the importance of implementing mitigation policies. These measures would be especially beneficial in the Mediterranean, where the high vulnerability to heat will lead to an imbalance between the decreasing cold and increasing heat-attributable mortality. Full-Text PDF Open AccessGlobal, regional, and national burden of mortality associated with non-optimal ambient temperatures from 2000 to 2019: a three-stage modelling studyNon-optimal temperatures are associated with a substantial mortality burden, which varies spatiotemporally. Our findings will benefit international, national, and local communities in developing preparedness and prevention strategies to reduce weather-related impacts immediately and under climate change scenarios. Full-Text PDF Open AccessGlobal projections of temperature-attributable mortality due to enteric infections: a modelling studyTemperature-attributable mortality could increase under warmer climate and unfavourable sociodemographic conditions. Mitigation policies for limiting global warming and sociodemographic development policies for low-income and middle-income countries might help reduce mortality from enteric infections in the future. Full-Text PDF Open AccessProjecting the risk of mosquito-borne diseases in a warmer and more populated world: a multi-model, multi-scenario intercomparison modelling studyRising global mean temperature will increase the climatic suitability of both diseases particularly in already endemic areas. The predicted expansion towards higher altitudes and temperate regions suggests that outbreaks can occur in areas where people might be immunologically naive and public health systems unprepared. The population at risk of malaria and dengue will be higher in densely populated urban areas in the WHO African region, South-East Asia region, and the region of the Americas, although we did not account for urban-heat island effects, which can further alter the risk of disease transmission. Full-Text PDF Open AccessFuture scenarios of risk of Vibrio infections in a warming planet: a global mapping studyOur projections anticipated an expansion of both the temporal and spatial disease burden for Vibrio infections, in particular at high latitudes of the northern hemisphere. However, the largest extent occurred from 1980 to 2020 and a more moderate increase is expected for the future. The most positive outcome is that the projections showed that Vibrio morbidity will remain relatively stable over the coming decades. Full-Text PDF Open AccessEffects of climate change on combined labour productivity and supply: an empirical, multi-model studyBoth labour supply and productivity are projected to decrease under future climate change in most parts of the world, and particularly in tropical regions. Parts of sub-Saharan Africa, south Asia, and southeast Asia are at highest risk under future warming scenarios. The heterogeneous regional response functions suggest that it is necessary to move away from one-size-fits-all response functions to investigate the climate effect on labour. Our findings imply income and distributional consequences in terms of increased inequality and poverty, especially in low-income countries, where the labour effects are projected to be high. Full-Text PDF Open AccessTaking globally consistent health impact projections to the next levelDespite intensive research activity within the area of climate change, substantial knowledge gaps still remain regarding the potential future impacts of climate change on human health. A key shortcoming in the scientific understanding of these impacts is the lack of studies that are conducted in a coordinated and consistent fashion, producing directly comparable outputs. This Viewpoint discusses and exemplifies a bottom-up initiative generating new research evidence in a more coordinated and consistent way compared with previous efforts. Full-Text PDF Open Access