The impact of natural climate variability on the global distribution of Aedes aegypti: a mathematical modelling study

Background: Aedes aegypti spread pathogens affecting humans, including dengue, Zika, and yellow fever viruses. Anthropogenic climate change is altering the spatial distribution of Ae aegypti and therefore the locations at risk of vector-borne disease. In addition to climate change, natural climate variability, resulting from internal atmospheric processes and interactions between climate system components (eg, atmosphere–land and atmosphere–ocean interactions), determines climate outcomes. However, the role of natural climate variability in modifying the effects of anthropogenic climate change on future environmental suitability for Ae aegypti has not been assessed fully. In this study, we aim to assess uncertainty arising from natural climate variability in projections of Ae aegypti suitability up to the year 2100. Methods: In this mathematical modelling study, we developed an ecological model in which Ae aegypti population dynamics depend on climate variables (temperature and rainfall). We used 100 projections of future climate from the Community Earth System Model, a comprehensive climate model that simulates natural climate variability as well as anthropogenic climate change, in combination with our ecological model to generate a range of equally plausible scenarios describing the global distribution of suitable conditions for Ae aegypti up to 2100. Each of these scenarios corresponds to a single climate projection, allowing us to explore the difference in Ae aegypti suitability between the most-suitable and the least-suitable projections. Findings: Our key finding was that natural climate variability generates substantial variation in future projections of environmental suitability for Ae aegypti. Even for projections generated under the same Shared Socioeconomic Pathway (SSP) scenario (SSP3–7.0), in 2100 climatic conditions in London might be suitable for Ae aegypti for 0–5 months of the year, depending on natural climate variability. Interpretation: Natural climate variability affects environmental suitability for important disease vectors. Some regions could experience vector-borne disease outbreaks earlier than expected under climate change alone. Funding: Engineering and Physical Sciences Research Council and Wellcome Trust.