The Middle East and North Africa are already some of the hottest places on Earth. In Riyadh, Saudi Arabia daily high temperatures can exceed 40°C (104°F) for the entire summer. Unfortunately, it’s about to get a whole lot hotter. A paper from the Max Planck Institute for Chemistry and the Cyprus Institute in Nicosia today warns that by the end of the century parts of the region could be too hot for humans to survive.

The authors examined the possible impact of climate change using two different projections of greenhouse gas concentration. The first assumes that carbon emissions will be curbed by mid-century while the latter assumes that they will continue to increase. Both projections predict that by 2050 the global temperature will be close to or have already exceeded the 2°C (3.6°F) target set last year in Paris.

In the milder of the two scenarios, the number of days per year that would qualify as part of a heat wave would increase from the 15 per year on average for the region during the years 1986 to 2005, to 83 per year by mid-century. In the more drastic scenario there would be 118 heat wave days per year. By the end of the century those would increase to 104 days and 204 days, respectively.

That’s a more than fivefold increase in the number of heat wave days—at a minimum. Such an occurrence would have a devastating effect on the half a billion people living in the region. A heat wave day occurs after temperatures have exceeded the 90th percentile temperature set between baseline years of 1961-1990 for six or more days.

This is not the first study to warn about the effects of climate change on the Middle East and North Africa. Organizations from the World Bank to the US National Intelligence Council (pdf) have cited the particular vulnerability of the region. One paper published last year predicted that by the end of the century the temperature in the oil-producing countries around the Persian Gulf could exceed the limits of human adaptability, even for healthy adults (pdf).

The Middle East and North Africa are already incredibly hot. Fresh water is limited. Local food crops are vulnerable to reduced rainfall. The drier it gets, the more sandstorms will force people indoors. These changes are in addition to the global effects of climate change: more severe weather, more war, and rising sea levels.

In the Middle East, climate change already has been blamed for pushing rural populations into cities, making them more dependent on imported food and vulnerable to running out of safe drinking water. Larger temperature changes could push people out of the region entirely.

The last couple years have shown that the world is pretty bad at managing large-scale migration, but that may turn out to be a mere trial-run for things to come.