Extreme heat belt to cover more than 100 million people by 2053

An area of intensely warm weather - a so-called extreme heat belt - with at least one day per year in which the heat index hits 52 degrees Celsius - is expected to cover a US region of more than 100 million people by the year 2053, according to a new study.

The research, carried out by the nonprofit First Street Foundation, used a peer-reviewed model built with public and third-party data to estimate heat risk at a hyper-local scale of 30 sq m.

The mission of the First Street Foundation is to make climate risk modeling accessible to the public, government and industry representatives, such as real estate investors and insurers.

The findings showed that heat exceeding the threshold of the National Weather Service's highest category - Extreme Danger or above 52 degrees Celsius - was expected to impact 8.1 million people in 2023 and grow to 107 million people in 2053, a 13 fold increase.

This would include a geographic region stretching from northern Texas and Louisiana to Illinois, Indiana and Wisconsin inland areas far from the more temperate weather often seen near the coasts.

When relative humidity is combined with air temperature, the heat index, also known as the apparent temperature, is what the outside temperature feels like to the human body.

To understand the exact relationship between the two measurements, the research team examined satellite-derived land surface temperatures and air temperatures between 2014 and 2020.

This information was further examined by factoring in elevation, how water is absorbed in the area, the distance to surface water and the distance to a coast.

The model was scaled to future climate conditions, using a middle of the road scenario proposed by the Intergovernmental Panel on Climate Change, in which carbon dioxide levels start falling by mid-century, but don't reach net zero by 2100.