Climate Change Blamed in Heat Waves: Science or Simulation?

As Europe and much of North America endured record heat, headlines quickly appeared claiming that the heat wave was "virtually impossible" without human-caused climate change. Really?

Mark Keenan | July 6, 2026

As Europe and much of North America endured record heat in recent days, headlines quickly appeared claiming that the heat wave was "virtually impossible" without human-caused climate change.

To many readers, that sounds like a conclusion drawn directly from observations. It is not. It is the product of a branch of climate research known as extreme weather attribution, which relies heavily on computer models rather than direct measurements.

This was not an isolated claim. Whenever a major storm, wildfire, flood, or heat wave occurs, similar headlines soon follow. We are told that climate change made an event "twice as likely," "35 times more likely," or even "virtually impossible" without human influence. These figures are widely repeated by politicians, journalists, and activists as though they were direct scientific observations.

They are not. They are estimates derived from computer models.

This distinction matters because modern climate policy is increasingly being built not upon observed evidence, but upon simulated realities generated by mathematical models.

The growing field of "extreme weather attribution" illustrates this transformation perfectly. Rather than simply studying weather events after they occur, attribution studies attempt to calculate how much more likely an event supposedly became because of human emissions of CO2. The numbers appear precise and authoritative, yet they rest upon assumptions that deserve far greater scrutiny than they usually receive.

Extreme weather attribution did not emerge in isolation. It represents the next stage of the same modelling paradigm that produced speculative emissions scenarios such as RCP 8.5. Once those scenarios were accepted as plausible descriptions of the future, it became possible to use similar modelling techniques to attribute individual weather events to human emissions with apparently precise numerical confidence. In other words, attribution science is not a departure from the climate modelling enterprise—it is its logical extension.

Most people assume these studies compare today's weather with historical observations. In reality, they compare the present world with a hypothetical world that never existed—a computer-generated version of Earth's climate in which industrial carbon dioxide emissions never occurred. The difference between the two simulations is then presented as the human contribution to the event [i].

Attribution studies typically compare today's climate with a simulated pre-industrial climate to estimate how human emissions altered........

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