Recent emissions are making heat waves worse

A new Stanford study found that greenhouse gases released since the 2015 Paris Agreement have significantly intensified Europe's heat waves, including the continent's hottest weeks every year since 2021.

“We found that the emissions released since the signing of this Paris Agreement in 2015 have substantially and significantly increased the intensity of Europe's recent individual heat waves.”

This summer's heat waves killed tens of thousands

Europe experienced back-to-back heat waves in summer 2025 and 2026 that broke records, with temperatures exceeding 40 degrees Celsius in several countries and reaching 46 degrees in Spain and Portugal. At least 35,000 excess deaths were attributed to these events.

The Paris Agreement target is already slipping away

The 2015 Paris Agreement aimed to limit warming to 1.5 degrees Celsius above pre-industrial levels, but the world is now expected to reach 1.8 degrees under current climate policies. Beyond 1.5 degrees, impacts intensify dramatically.

Europe is heating twice as fast as the world

The continent is warming at more than double the global average rate, making it particularly vulnerable to climate change impacts including extreme weather, ecosystem loss, and threats to food security.

AI model reveals the emissions' hidden impact

Researchers used a machine learning diffusion model trained on climate data to simulate how Europe's heat waves would have unfolded under 2015 emission levels versus today's. They found recent emissions increased heat wave intensity by roughly one-third of a degree Celsius.

“This is a purpose built machine learning model that we trained on large amounts of climate model data…to make predictions about how individual heat waves might have unfolded differently if those same weather patterns had occurred under different levels of human emissions.”

A third of a degree causes outsized damage

While one-third of a degree Celsius seems small, scientific research shows even tiny temperature increases on hot days cause disproportionately large impacts on heat wave deaths and other damages.

“That third of a degree might seem very small, maybe imperceptible to us walking around, but there's a large body of scientific literature that suggests that even small increments of temperature on a hot day can have these disproportionate impacts on the damages caused by those heat waves.”

More warming is already locked in

Emissions already released into the atmosphere will continue warming the climate regardless of future climate action. Even under the most optimistic emissions reduction scenarios, more heat wave intensification is unavoidable.

“Even in the context of the most optimistic, ambitious future for reducing emissions, there's still more intensification of extremes that is essentially committed.”