Saharan Africa (Gascoigne et al., forthcoming). For drought we consider a much less frequent and presumably more severe event, so the loss in consumption may be higher.

Although there are productivity losses associated with extreme heat (Kjellstrom et al., 2018, Foster et al., 2021), here we focus on the loss of life and morbidity associated with extreme heat (without considering the potential major effect of higher temperatures and heat on quality of life and average labor productivity). A WBGT threshold of 33 degrees Celsius corresponds with the reference upper limit for healthy, acclimatized humans at rest to keep a normal core temperature, based on international standard ISO 7243 used to assess heat stress on workers (International Organization for Standardization, 2017). Heat-related mortality and hospital visits increase significantly around this level, disproportionately affecting outdoor workers and the elderly for whom WBGT does not have to exceed 33 degrees Celsius to reach a dangerous level (Cheng, Lung, and Hwang, 2019; Tuholske et al., 2021).

To determine the number of people exposed to any one of the four shocks considered we take the maximum number of people exposed in each 1km grid cell to either of the four hazards (Figure 5). This is done to avoid double-counting. Note that we do not assume everyone in a 1km grid is either exposed or not exposed to flooding by overlaying the data in this way since we first calculate the population exposed to flood using the relevant higher resolution flood and population data.

# 4 MEASURING VULNERABILITY

In this section we motivate the choice of indicators used to identify households that are vulnerable and discuss the data and methods used to measure them.

## 4.1 CHOICE OF INDICATORS

As highlighted above we consider two key aspects of vulnerability: (i) the physical propensity to experience severe income, asset or health loss and (ii) the inability to cope with and recover from the losses. Multiple dimensions are considered within each of these. We introduce the proposed indicators for measuring each dimension.

### Physical propensity to experience severe loss

Access to electricity and a certain standard of drinking water are critical for economic activity and survival and as such are included in the World Bank’s multidimensional poverty measure (World Bank 2018). Additionally, when shocks hit, access to these services is an important determinant of the impact of the shock on welfare. For example, with access to improved drinking water, contaminated water from flooding and storms, or lack of water due to drought has less of an impact. Nevertheless, it is essential to acknowledge that the current indicator of access to improved drinking water, often represented by covered wells in low-income countries, may not sufficiently reflect susceptibility to contamination during extreme events such as floods or droughts. Therefore, there is a need for future work to refine this indicator by considering a potentially higher threshold. Metrics such as “improved piped water” can offer a more precise assessment of the infrastructure safeguarding against water-related risks in the event of shocks. With access to electricity, households are more likely to have assets such as fans that can help with heatwaves. A fuller discussion is available in the World Bank’s Lifelines report (Hallegatte et al, 2019). Whilst not a final selection of assets and infrastructure that matter for determining the initial loss of the shock, these measures provide a good first estimate to stimulate discussion. Access to markets and 15