The amplifying effects climate change will have on heatwaves have already been detailed in past research. A new report, however, comes to quantify the cost in human lives if we decide not to take action — millions of people around the world could lose their lives, the team reports.

The findings pose a new warning to officials and the public regarding the price of inaction in climate issues.

Deadly greenhouse

The team from the National Bureau of Economic Research (NBER), a non-profit based in the USA, reports that if greenhouse emissions are not reduced, heatwaves in the future could kill millions of people in all areas of the globe.

Not only will these heatwaves directly kill people (through heat stress and stroke), but they will also indirectly increase mortality by making it harder for our bodies to regulate their temperature. Not only will this heavily impact older people and those with underlying conditions, but excessive heat will also make it harder for everyone to carry out their tasks.

The findings are based on an analysis of past heatwave patterns in eight countries around the globe and the European Union, the number of heat-related deaths caused by them, and projected changes in heatwave patterns and temperatures in the future. From this data, the authors estimated the number of casualties such events will cause in the future.

The authors note that excessive heat is among the deadliest types of extreme weather. Prolonged exposure to high temperatures can lead to heart conditions, heart attack, and a host of other conditions (caused by our bodies working extra hard to keep cool). Such an effect would be much larger in hotter areas of the globe such as those close to the equator.

Future heatwaves could kill 85 in every 100,000 (around 8.5 million) people by 2100 if greenhouse gas emissions continue undisturbed, the team writes. They also “estimate the mean increase in mortality risk is valued at roughly 3.2% of global GDP” by the same date. The poor and the elderly, especially those living in already hot areas, are particularly at risk. The findings are supported by previous research on the topic, which estimated how many Europeans will be at risk from weather-related phenomena in the future.

The availability of air conditioning can help mitigate the effects of heatwaves, the authors note, but it’s a relatively expensive good that these categories have limited access. Wide-scale use of air conditioning can make cities even hotter, however, and they drive an increase in CO2 emissions if their energy is sourced from fossil fuels.

The paper “Valuing the Global Mortality Consequences of Climate Change Accounting for Adaptation Costs and Benefits” is available here.