By a U.S. Climate Research Scientist

Over the past two decades, heat waves have broken records across the United States and around the globe. From the Pacific Northwest’s deadly heat dome to the searing temperatures in the South, these events are no longer anomalies — they’re signatures of a warming planet.

A major new study published in Nature analyzed 213 historic heat waves between 2000 and 2023, concluding that climate change has made such extremes significantly more frequent and more intense, and even traced the contribution of the world’s largest industrial emitters — known as “carbon majors.”
Read the full study in Nature

How Scientists Link Heat Waves to Human Activity

Attribution science works by comparing two simulated worlds:

  1. one with current greenhouse gas emissions, and
  2. one without human influence.

By measuring the difference in likelihood between the two, researchers can estimate how much climate change increased the probability or intensity of a given heat event.

In the latest Nature study, researchers combined advanced climate models with a global emissions database to determine which companies contributed most to rising background temperatures. The findings are striking: emissions traced to the top 80–100 “carbon majors” are responsible for roughly half of the observed increase in the severity of heat waves since the pre-industrial era.

Background on attribution methods — ScienceDirect overview

What the Data Show

  • Between 2000 and 2009, human-driven warming made severe heat waves about 20 times more likely.
  • By the 2010s, that multiplier had increased to nearly 200 times.
  • For 55 of the 213 analyzed heat waves, scientists concluded such events would have been “virtually impossible” without the added heat from greenhouse gases.

These findings are consistent with regional analyses in North America, such as the World Weather Attribution study of July 2023, which found that record-breaking temperatures across the western United States were “virtually impossible without climate change.”

What It Means for the United States

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  1. Health and safety: The number of days above 100°F has grown steadily, straining energy systems and increasing heat-related mortality, especially among outdoor workers and the elderly.
  2. Infrastructure: Roads, power grids, and agriculture face stress from prolonged heat. Understanding how human activity amplifies these risks helps states prioritize adaptation — from cooling centers to resilient design codes.
  3. Accountability and innovation: Linking emissions to physical outcomes doesn’t just identify responsibility; it also highlights where clean-energy innovation can have the greatest effect in preventing future extremes.

A Scientific Foundation, Not a Political Argument

This new body of evidence doesn’t point fingers at governments or political leaders. Instead, it strengthens the scientific foundation for understanding our shared impact on climate extremes. Attribution science provides something rare in public debate — a measurable, evidence-based connection between cause and consequence.

The message for Americans is clear: the physics are unambiguous, and the data keep aligning. Heat waves are no longer just weather; they are quantifiable symptoms of a changing atmosphere — and a call for resilience, adaptation, and smarter energy choices.

Editorial Note – Climate Project
Sources: Nature (2025), ScienceDirect, World Weather Attribution, NOAA Climate Program Office, NASA Earth Science Division.