How will Climate Change affect Heatwaves, Wildfires and Air Quality across the UK and northern Europe?

Climate change is projected to amplify both the frequency and intensity of heatwaves. These heatwaves are often accompanied by other extreme events, such as wildfires and air pollution episodes, which together create significant risks to public health. Many of the UK's record extreme temperatures have occurred in the last decade and the chance of a 40°C heatwave, such as the one in summer 2022 that led to over 3,000 deaths, will become increasingly common (Chiristidis et al 2020). Wildfire risk is also anticipated to increase, potentially doubling under a 2°C global warming scenario, leading to an extended wildfire season over the UK (Perry et al., 2022).

Air pollution events are associated with heat waves through weather conditions that favour reduced dispersion of emitted pollutants due to low winds speeds, and through temperature-driven impacts on emissions and chemistry that produce air pollutants such as ozone and secondary organic aerosols (Vieno et al. 2010). Our recent work suggests that with global warming levels of ~4°C, particulate matter (PM_2.5) concentrations in summer will increase by 25% across northern Europe (Doherty et al. in prep). Wildfires, triggered by heatwaves, are a further source of air pollution. Whilst wildfires tend to occur at rural-urban boundaries and in agricultural regions, increases in the severity, duration and extent of wildfires mean compound hazard events of heat, wildfire and air pollution will be greater in the future (Perry et al. 2022). Moreover, several studies have suggested that longer heat waves lead to a greater likelihood of intense wildfires and extreme air pollution levels (Schnell and Prather 2017; Hegedűs et al. 2024)

This project will use high spatial resolution measurement and model datasets and Earth System Modelling to further our understanding of compound heat, wildfire and air pollution events for present-day and future. This project contributes and is supported by a newly funded, multi-institution research hub that brings together experts from a wide range of disciplines to examine extreme events in the context of our future transition to Net Zero. The outcomes of this project will contribute to improved quantitative understanding of co-occurring extremes on regional climate, air quality and health.

Research questions

1.   How frequently do heat, wildfire and air pollution events co-occur across the UK and northern Europe?

2.   What is the relationship between them and what are their key drivers?  

3.   How have these compound events changed over the 20th century?  

4.   What are the health implications of co-occurring events?

5.   How will compound events change in the future under different policy-relevant global warming scenarios? What are the main drivers of such changes?

Methodology

The student will use a range of existing environmental datasets for the historical period (1960-present-day) and for the future under different emission scenarios, and perform model simulations with a state-of the-art Earth System Model. They will use statistical clustering techniques applying machine learning to identify compound events (e.g. Hegedus et al 2024, Schnell and Prather 2017).

The climate datasets include the ERA5 reanalysis for Europe and the HadUK-Grid for the UK. For wildfires, fire risk indices will be derived from these climate datasets and supplemented with burned area data from MODIS satellite observations. For air pollution, there are measurements from the AURN UK network and estimates generated by the EMEP4UK chemistry transport model. For future climate projections at policy-relevant global warming levels, the student will make use of UKCP18 and IPCC CMIP6 model results, in addition to state-of-the-art CMIP7 model results which will become available within the next couple of years. The student will have the opportunity to analyse or perform simulations with the UK Earth System Model (UKESM2), developed for the latest IPCC assessments, that includes dynamic fire representation with the INFERNO fire model to simulate wildfire emissions and air pollution in response to climate change and to evaluate changes in these compound heat, wildfire and air quality events and their key driving processes for the first time.

Using statistical and clustering techniques the student will identify extreme events and episodes using different metrics applied to existing 20th century datasets examining their overlap and progression, lags in space and time, and their trends for present-day and future accounting for the uncertainty in policy-relevant global warming levels. Depending on the student’s interests, the health effects of heat and air pollution could be estimated by performing health impact calculations using existing dose-response relationships (e.g. Gasparrini et al. 2015).

For further details see: https://geosciences.ed.ac.uk/study/degrees/research-degrees/phd-projects/physical-sciences?item=1740