Climate extremes such as heat waves, droughts, river floods, crop failures, forest fires and tropical cyclones are increasing under the influence of human-induced climate change. Although it is clear that the intensity, frequency and duration While the frequency of some of these events will increase with continued atmospheric warming, it is not yet clear how this will translate into cumulative, so-called unprecedented lifetime exposure (ULE). ULE is defined in this study as exposure to climate extremes exceeding the 99.99 percentile of exposure expected in a pre-industrial climate.

A new study, combining climate and impact models with demographic data, examined this unprecedented lifetime exposure to six climate extremes across different birth cohorts and global warming scenarios. The findings show that The proportion of people born in 2020 who will face unprecedented lifetime exposure to climate extremes will at least double compared to those born in 1960, with current mitigation policies leading to 2.7°C warming by 2100.

Projections indicate that younger generations will face significantly higher cumulative exposure to extremes over their lifetimesFor example, in Brussels, people born in 1960 are projected to experience three heat waves in their lifetime, while those born in 2020 are projected to experience almost 11 in a 1.5°C warming scenario, 18 in a 2.5°C warming scenario, and 26 in a 3.5°C warming scenario by 2100. These numbers significantly exceed the ULE threshold, which is defined here as six heat waves.

At the global level, the proportion of the cohort born in 1960 experiencing ULE to heat waves is estimated to be around 16%. This proportion increases towards younger generations. Under a 1.5°C warming scenario, the proportion of the cohort born in 2020 experiencing ULE to heat waves stabilizes at an average value of 52% (62 million people)However, under a 3.5°C warming scenario, this share almost doubles to reach 92% (111 million people)This means that 111 million children born in 2020 will experience unprecedented life in terms of exposure to heat waves in a world that warms by 3.5°C, compared to 62 million in a 1.5°C warming scenario.

Although the ULE for other extremes, such as heat waves, is generally lower, it still affects a large proportion of the population. Under a 3.5°C warming scenario, 29% people born in 2020 face unprecedented exposure to crop failure. River floods will follow, to which people will be exposed to unprecedented levels of 14%Exposure to tropical cyclones is lower due to their geographical limitations, however, when considering only regions that may experience them, the estimate for the 2020 birth cohort increases from 6% to 11% in the 1.5°C scenario and from 10% to 19% in the 3.5°C scenario.

The study also found that The risk of facing unprecedented lifetime exposure to heat waves is significantly higher among population groups characterized by high socioeconomic vulnerability. Analysis using the Global Relative Deprivation Index (GRDI) showed that the most vulnerable part of the 2020 birth cohort has a significantly higher chance of facing ULE to heat waves (95%) compared to the least vulnerable part (78%). These socio-economically vulnerable groups have lower adaptive capacity and greater constraints in implementing adaptation measures, which underlines disproportionate risk to disadvantaged communities.

These findings clearly call for deep and sustainable reductions in greenhouse gas emissions to reduce the burden of climate change on current young generationsMore ambitious policies towards achieving the Paris Agreement goal of limiting global warming to 1.5°C would bring direct benefits to children. It is estimated that A total of 613 million children born between 2003 and 2020 would thus avoid heat wave exposureFor crop failures it would be 98 million, for river floods 64 million, for tropical cyclones 76 million, for droughts 26 million and for forest fires 17 million.

It is important to note that the analysis focuses on local exposure and does not include cascading non-local impacts (such as disruption of supply chains or impacts on the economy), nor potential adaptation or maladaptation measures. It also does not take into account demographic factors such as migration, mortality or heterogeneity within grid cells. Despite these limitations, the study highlights the urgent need for measures to protect the future of young generations from escalating climate extremes. Spring

The entire study was published in the journal Nature

Glossary of key terms

• Anthropogenic climate change: Climate change caused by human activity, especially the release of greenhouse gases.
• Unprecedented Lifetime Exposure (ULE): Experiencing cumulative lifetime exposure to climate extremes that exceeds the 99.99th percentile of exposure expected in a pre-industrial climate.
• Global Mean Temperature (GMT): The average temperature on the Earth's surface. The increase in GMT is used as a measure of global warming.
• GMT trajectory: The projected path of change in global average temperature over time, often associated with different emissions scenarios.
• Birth cohort: A group of people born in the same year or within a specific time period.
• Cohort fraction (CF): The percentage of people in a given birth cohort who will experience unprecedented lifetime exposure to a given climate extreme.
• Pre-industrial climate: The climate that existed before large-scale human influences usually refers to the period before 1850.
• Model projections: Outputs of climate and impact models that simulate future climate conditions and their impacts based on different scenarios.
• Socioeconomic vulnerability: The vulnerability and inability of socio-economic groups to cope with the adverse impacts of climate change, often linked to factors such as poverty, access to resources and adaptive capacity.
• Global Gridded Relative Deprivation Index (GRDI): An indicator of relative deprivation and poverty based on multiple socio-economic factors at the network level.
• GDP per capita: Gross domestic product divided by population, often used as an indicator of economic prosperity.
• Inter-Sectoral Impact Model Intercomparison Project (ISIMIP): An initiative to compare models for projecting the impacts of climate change in different sectors.
• Heat Wave Magnitude Index daily (HWMId): An index used to quantify the severity of heat waves.