Recently, a study published in the journal Nature, "Global emergence of unprecedented lifetime exposure to climate extremes", pointed out that if global warming continues to intensify, the current young generation will encounter extreme climate events far exceeding pre-industrial levels in their lifetime. If children born in 2020 live in a world with a temperature rise of 3.5℃, 92% of them will experience "unprecedented" heat waves.

The study quantified the climate risks of future generations from a "lifetime perspective", highlighting the profound and unfair impacts of different warming paths on the younger generation and vulnerable groups in society, providing a new perspective for measuring the benefits of emission reduction and adaptation, and also sounding the alarm for policymakers and all sectors of society.

The intensity of emission reduction determines the fate of future generations

Based on the global climate model (CMIP5) and population data, the study quantified the risk of human lifetime exposure to extreme climate events under different warming paths.

1. Heatwaves

The study uses Brussels as an example to show lifetime exposure to heatwaves under different global mean temperature (GMT) paths. The study shows that high warming paths (2.5℃, 3.5℃) significantly increase exposure risk and trigger threshold crossings in advance.

• People born in 1960 experience an average of 3 heatwaves in their lifetime, far below the 6 ULE (Unprecedented Lifetime Exposure) threshold.
• People born in 1990 exceed the threshold in scenarios with global warming of 2.5°C and above.
• People born in 2020 will experience 26 extreme heatwaves in their lifetime if global warming rises by 3.5℃, far exceeding the pre-industrial threshold (6 times); and even if global warming is controlled at 1.5℃, people born in 2020 will still experience 11 extreme heatwaves in their lifetime (still exceeding the threshold).

(Image source: Global emergence of unprecedented lifetime exposure to climate extremes)

Globally, intergenerational risk has jumped:

• People born in 1960: Regardless of the warming path, CF_heatwaves (the proportion of birth cohorts facing unprecedented lifetime exposure to heat waves (ULE)) is about 16% (13 million people), and the risk faced by early groups is lower and the path differences are small.
• People born after 1980: CF_heatwaves begin to depend significantly on the warming path.
• People born in 2020: Under the 1.5°C path, 52% of people born in 2020 (62 million people) face heat wave ULE; under the 3.5℃ path, this proportion soars to 92% (111 million people).

In addition, from a regional perspective, under the low warming path (1.5℃), the risk of heat waves in tropical regions is the highest; but as warming intensifies, extreme events will sweep the world, and under a global warming of 3.5℃, the entire population of 113 countries will face heat wave ULE.

2. Multi-hazard risk: threats to crops, floods, and hurricanes coexist

Except for heat waves, the cohort proportion (CF) of other climate extreme events is relatively low in all birth years and GMT paths, but still affects a large number of people.

Under the scenario of global warming of 3.5℃, 29% of the population born in 2020 will experience unprecedented crop yield reductions and 14% will experience river flood ULE; droughts, wildfires, and tropical cyclones also show a significant increase in the probability of ULE with increasing temperature, but the base is lower than that of heat waves.

Vulnerable groups bear greater risks

In addition to the global threat of heat waves, other extreme climate events also have a significant impact on specific regions and groups, and socioeconomic status further amplifies this risk.

The study links climate risk with socioeconomic vulnerability, combines the Global Gridded Relative Deprivation Index (GRDI) with per capita GDP levels, and reveals the inequality crisis. Compared with the least vulnerable people in their generation, people with higher socioeconomic vulnerability are always more likely to face unprecedented lifetime heat wave exposure.

For example, in the 2020 birth cohort, 95% of the high-deprivation (high socioeconomic vulnerability) group (or 23 million people) face unprecedented lifetime heatwave exposure (ULE), compared with 78% (19 million people) of the low-deprivation group.

The results show that a large proportion of the global birth cohort is expected to face unprecedented heatwaves, river flooding, drought, crop failure, wildfires and tropical cyclones. As the world warms, the frequency of these extreme climate events increases, and the proportion of the population facing ULE also increases.

To achieve the goals of the Paris Agreement, we need to adopt more aggressive policies. Under current policies, the global temperature rise is expected to reach 2.7℃. The younger generation will bear an unprecedented burden of climate extreme events, and the intensity of emission reduction will directly determine their lifetime exposure risk.

Author：Qinger