• Economic impacts: Multiple areas of the economic sector experience reduced worker productivity during heatwaves, especially agriculture and construction. Globally, 2% of total working hours is projected to be lost every year, either because it is too hot to work or because workers have to work at a slower pace. Lost productivity from heat stress at work, particularly in developing countries, is expected to be valued at $4.2 trillion dollars per year by 2030, driving more inequality.²⁰  The agricultural sector, where 940 million people earn their livelihood, is set to be harder hit by hotter temperatures, pushing workers, crops and livestock past their physiological heat and drought tolerances.^21 22 This will result in lost labour, in smaller harvests for farmers, higher prices for consumers, and negative impacts on livelihoods. For example, during the 2012 heatwave in the United States, maize yields dropped by 13%, resulting in a sharp increase in global corn prices because the United States supplies 40% of global production. In the short term, such weather events resulting in food price volatility put low-income countries, and those with high crop import dependency ratios, at risk of food insecurity.²³

In parts of India, changes to weather patterns and the resulting impacts on agriculture and other sectors are expected to translate into a 9% decrease in standards of living by 2050 assuming no adaption.²⁴ A World Bank report suggests that by 2050, about 600 million Indians will live in places that could experience loss of living standards, which could cost 2.8% of the GDP, stalling efforts to pull large parts of the population out of poverty.²⁵ Increasing energy demand for cooling also comes as an extensive economic cost to residents, businesses, and governments. Often energy grids are unable to supply the required power for air conditioning in cities during heatwaves.^26 27 This results in not only increased emissions from carbon-based energy sources, but the failure of power grids, loss of power to businesses, hospitals, and critical infrastructure – compounding loss of productivity, increased costs for the energy sector, and reduced access to life-saving cooling and medical care. New power infrastructure is needed to support this demand in some areas and new lower-emission lower-heating technologies are critical. With these extreme heat events, the need for access to cooling should be viewed as a basic necessity – not just for health and productivity reasons but, in some cases, even for survival.²⁸

• Ecological impacts: Heatwaves, without concomitant increases in precipitation, can lead to water shortages and increased stress for plants, particularly in arid regions.²⁹ This has the effect of reducing plant growth, the basis of energy production and the food chain, with an overall drying-out of the landscape. In Europe, the 2003 heatwaves caused tree damage, increased leaf fall and turned carbon-sink landscapes into carbon-sources, releasing more CO2 into the atmosphere than was absorbed.³⁰ These hot and dry conditions are favourable to the start and rapid spread of forest fires, which now regularly accompany heatwaves. In 2010, during the heatwave in Russia – which was the hottest in 130 years – more than 15 million hectares of forest, vegetation and peat land areas burnt, and importantly in areas without fire-tolerant species.³¹ Heatwaves can also dry up shallow aquatic ecosystems and accelerate glacier melt. For example, the 2003 European heatwave resulted in a 10% loss in glacier mass in Europe, which was five-times more than the average annual loss.²⁷ Similar impacts were reported for the French Alps in 2019. Over time, such deep permafrost warming and thawing could cause landslides and rock falls, continuing the negative ecological impacts.²⁷

Heatwaves and health: a new opportunity for innovation and research

As the effects of heatwaves become more frequent and visible, funding and research targeting heat and health is a high global priority. For example, the September 2019 UN Climate Action Summit coalition on social and political drivers is advocating for key actions that cities and governments can invest in like heat protection. It is also encouraging development banks, philanthropy, and private sector to commit funds for climate-informed health surveillance and response systems for heatwaves. Similarly, the Belmont Forum has prioritized heat and health as one of three themes for the 2019 funding call on Climate, Environment, and Health where €11M in cash and in-kind resources is committed to support up to 12 research projects. The European Commission’s Horizon 2020 has committed around 35% of it €80B research fund for climate-related expenditure, including health research to better understand current and future heat risks for the EU.

On the research and application front, the World Climate Research Programme studies global climate systems evolution to inform societal understanding of risks. The World Weather Research Programme advances society’s ability to cope with high impact weather by focusing on improving the accuracy, lead time and utilization of weather prediction. The Global Heat Health Information Network is a group of scientists, professionals and policy-makers working to enhance research to action and promote science-based decision tools to better manage heat risks. Regular events and an online learning center provide resources on heat health including case studies of heat management tools and models already in practice. The Climate Services for Resilience Development is a public-private initiative that focuses on heat (and other risks), developing new guidance and online decision tools.

And at Future Earth, heat is a cross-cutting theme across the work of our Health, Urban, and Risk Knowledge-Action Networks, that seek to generate multi-faceted knowledge to inform solutions for complex societal issues.