Effective and rapid action is needed to achieve global climate change mitigation goals, presenting an opportunity to ensure that any actions taken are also beneficial to human health . The potential health co-benefits of climate actions are significant and could prevent many millions of premature deaths annually. The size of these health co-benefits can vary depending on the sector, level of policy ambition and mode of implementation, as well as by country. More research is needed to understand what additional environmental, social or economic benefits these actions might have.
As part of the Pathfinder Initiative, researchers carried out an umbrella review to synthesise empirical and modelled evidence on climate mitigation actions to investigate their effects on both greenhouse gas emissions and human health .
What is an umbrella review?
An umbrella review is a review of systematic literature reviews, including where available meta-analyses that combine estimates of effect sizes (the strength of the relationship between modelled variables) from different studies. Umbrella reviews can therefore bring together and synthesise all the available evidence on a topic . They may be qualitative (synthesising non-numeric information, such as interviews on how people feel about climate change) or quantitative (synthesising numeric information, such as the amount of carbon dioxide emitted from a factory).
Our umbrella review is a quantitative synthesis of systematic reviews on climate mitigation actions with health co-benefits.
What is the value of this umbrella review?
This review determines the most effective actions for global climate change mitigation and promoting good health based on the best scientific evidence available . The data we collected allows us to assess:
- The types of climate change mitigation actions with defined health co-benefits that have been reported in the literature and their pathways of impact on health (e.g. air pollution, diet, physical activity)
- The change in magnitude of health exposure or outcome and GHG emissions from specific actions across sectors, pathways to health, and contexts
- How the evidence is spread within and between different sectors, type of action and contextually, for example between regions of the world and socio-economic status.
How can our data be used?
Below is the data that has been gathered through the umbrella review. The data has been split into three tables according to GHG type: cumulative CO2 equivalents (CO2eq); individual greenhouse gases (CO2, N2O, and CH4); and particulate emissions from Black Carbon and Black Smoke. Health outcomes are reported in terms of change in years of life lost (YLL) per year per 100,000 people. All outcomes have been reported at the national scale; actions are assumed to be implemented maximally across the country they were modelled or implemented within.
There are three tables, separated based on the type of GHG reported:
- Table 1: GHG emissions are reported for each individual action in terms of metric tonnes CO2eq/year/capita, with global warming potentials of CH4 (GWP25) and N2O (GWP298) . This enables the reader to consider and compare the overall impact of mitigation actions.
- Table 2: GHG emissions are reported separately for each gas in terms of metric tonnes CO2eq/year/capita. This enables the reader to compare actions within and between gases. Note that, in the case where multiple gases were reported for a single action, the health outcomes will be repeated.
- Table 3: particulate emissions which could not be converted to the standard measure of ‘tonnes CO2eq’ were reported here, as their actions are useful to investigate despite the difficulty of standardisation.
CO2 equivalents (CO2eq) - A carbon dioxide equivalent or CO2 equivalent, abbreviated as CO2-eq is a metric measure used to compare the emissions from various greenhouse gases on the basis of their global-warming potential (GWP), by converting amounts of other gases to the equivalent amount of carbon dioxide with the same global warming potential.
- Papatheodorou S. Umbrella reviews: what they are and why we need them. European Journal of Epidemiology 2019; 34: 543–6.
- 2 Belesova K, Green R, Clercq-Roques R, et al. Quantifying the effectiveness and health co-benefits of climate change mitigation actions across sectors: a protocol for an umbrella review. Wellcome Open Research 2022; 7: 98.