Researchers have claimed that global warming could make many cities around the world too hot to host the Summer Olympic Games in the coming decades.

The team concludes that in just 70 years, only eight Northern Hemisphere cities outside Western Europe will be cool enough to host the games, making it increasingly hard for organisers to continue with their current system.

" Climate change could constrain the Olympics going forward," said lead researcher Kirk Smith from the University of California, Berkeley. "And not just because of rising sea levels."

Smith and his colleagues came to this conclusion by analysing heat radiation, humidity, temperature, and wind data from two separate climate models focused on possible Olympic Games sites, which combined make up a model they call the wetbulb globe temperature (WBGT).

Using the WBGT, the team predicted the temperatures of various cities in the Northern Hemisphere in the coming decades, with populations of over 600,000 people - one of the current stipulations for a city to host the games.

They then looked at which of these cities had a 10 percent chance of having to cancel their outdoor marathon events because temperatures would be at unsafe levels in the future.

Right now, this '10 percent' criterion is used to choose which cities will host the games, because the marathon is extremely dependent on weather conditions, and cancelling it on short notice would drastically impact the overall games.

"If you're going to be spending billions of dollars to host an event, you're going to want have a level of certainty that you're not going to have to cancel it at the last minute," says Smith.

With all of these criteria in place, the team used their model to see which cities would likely be unfit for future Olympic events, concluding that only eight out the 543 viable countries in the Northern Hemisphere would fit the bill by 2085.

"The findings indicate that by 2085, Istanbul, Madrid, Rome, Paris and Budapest – all cities that are or were in contention for either the 2020 or 2024 Summer Olympics – would be unfit to host the games," the team said. "Tokyo, the city that has secured the 2020 summer Olympiad, would also be too hot to ensure athlete safety, should these projections come to pass."

The cities that would still be viable, according to the researchers projections, are St. Petersburg (Russia), Riga (Latvia), Bishkek (Kyrgyzstan), Ulaanbaatar (Mongolia), Calgary (Canada), Vancouver (Canada), and San Francisco. In Western Europe, up to 25 smaller cities would be viable, but no country in Latin America or Africa would.

The team says that even though these findings are specifically looking at future Olympic events, they show just how much global warming could potentially impact our society.

"Climate change is going to force us to change our behaviour from the way things have always been done," says Smith. "This includes sending your kids outside to play soccer or going out for a jog. It is a substantially changing world."

The team isn't alone in this opinion, either. Back in May, an international team of researchers found evidence that climate change might trigger a mass exodus from the Middle East and Northern Africa by 2065 because temperatures will reach a dangerous level.

But it's important to point out that the current study is a commentary only based on modelling. Much more research needs to be done before we can have a better idea of what our future could look like. 

And there are definitely work-arounds for the Olympics to continue, even if this bleak forecast bears out, such as having more events inside, or hosting certain events in different parts of the world in the same yea. So climate change isn't necessarily the end of the games, but it's definitely something worth thinking about.

The commentary was published in The Lancet.