# **1. Introduction**

on nearly all aspects of urban life, including health, the economy and infrastructure. Extreme periods of hot temperatures are associated with increased deaths and illnesses (Gasparrini et al, 2017), reduced productivity within heat-exposed sectors of the workforce (Kjellstrom 2016), increased suicide and accident rates (Park, Pankratz, and Behrer 2021), higher operating costs and reduced asset lifespans for energy and transport infrastructure (Chapman et al, 2013) and reduced learning outcomes for schoolchildren (Zivin et al. 2016). Global air temperatures may increase by up to 3.2°C by 2100 depending on global emission trends, but the frequency, duration and intensity of heatwaves is projected to increase even if global warming is limited to 1.5°C (Masson-Delmotte et al 2021). A national assessment conducted by the Indian government on climate change projects increasing temperatures for India through the 21st century, including increasing extreme heat events (Krishnan et al, 2020). India faces particularly acute challenges due to the projected increase in heat stress since limited access to domestic water sources, insulated buildings and air conditioning makes it harder for a significant portion of the 1.4 billion population to cope during periods of high heat stress (Azhar 2019, World Bank 2022).

Since the early 2000s, improved quantification of the losses caused by flooding, seismic risk and landslides have helped strengthen the global disaster risk management agenda and underpin increased investment in measures to reduce the losses they cause. By contrast, heatwaves have been described as a “hidden hazard” whose impacts often remain under-counted (Roberts et al 2023). Whereas storms, floods and earthquakes destroy physical assets such as houses, factories, roads and hospitals whose replacement cost can be quantified quickly, the most important channels through which heat waves cause harm are their impacts on human bodies: either through ill health or loss of productivity at work. Methods to assess heat hazard and quantify its health and economic impacts are well established, but their uptake has remained confined to research settings – such as geography and public health departments of universities – to a greater degree than with flood or seismic risk assessment (property-centered hazards for which the insurance and real estate industries have created a large market for risk assessment services). Mortality related to heat waves is known to be significantly under-counted in official statistics (Azhar et al 2014). This has contributed to a relatively low prioritization of heat risks among scientific stakeholders, policy stakeholders and the public.

With studies suggesting that parts of the Indian subcontinent will increasingly experience heat and humidity conditions that approach limits of human survivability by the late 21<sup>st</sup> century (Im et al 2017), heatwave preparedness and mitigation actions are an increasingly urgent consideration. Fortunately, resilience to heatwaves is a challenge that South Asian cities can address decisively and effectively given policy actions that are feasible at the urban scale. Indeed, focusing on these cities is strategic, as urban regions are more accessible, easier to govern, and efficient for implementing interventions compared to rural areas. India’s first city-level Heat Action Plan was developed in Ahmedabad, a city of 7.6 million people in the western state of Gujarat, where researchers documented a tripling of the daily all-cause mortality rate during the 2