Humans can tolerate some extremes of hot and dry temperatures by sweating, which lowers our body temperature via evaporative cooling. However, this ability is greatly reduced when high temperatures are accompanied by high humidity. When people are exposed to a combination of higher temperatures and increased humidity, heat stroke can lead to untimely deaths.

Existing climate models have shown that a global temperature increase to the threshold of human survivability would be reached in some regions of the globe at a point in the distant future. However, a new paper published by Jeremy Pal and Elfatih Eltahir in Nature Climate Change presents evidence that this deadly combination of heat and humidity increases could occur in the Persian Gulf much earlier than previously anticipated.

These regions are critical suppliers of oil and fossil fuels, so if they become inhospitable to humans, the global consequences could be dire—assuming we’re still using these fuels as these effects kick in.

According to climate researcher Christoph Schar, this region is particularly vulnerable to extremely hot and humid climates due to its proximity to warm seas. The Persian Gulf is a relatively shallow body of water, which allows it to absorb more heat than typical oceanic inlets.

Pal and Eltahir used an assembly of climate model simulations with a 25km resolution to predict the impacts of future climate change on the region. They adopted two commonly used greenhouse gas concentration scenarios, one that represents the projected concentration of greenhouse gases in a business-as-usual scenario and one that assumes measures are taken to reduce their production.

In the business-as-usual scenario, the threshold of temperature and humidity risk would be reached in the business-as-usual 30 year model in the countries of Iran, Saudi Arabia, Qatar, Dubai, and the United Arab Emirates. Pal and Eltahir suggest that this rise in temperature and humidity is likely to cripple further development in this region and may even handicap oil and fossil fuel production.

Were these high temperature and humidity conditions to occur, we could see a spike in temperature-related mortality. But there could also be indirect effects on health through climate-dependent infectious diseases, such as those transmitted by mosquitoes, as these insects thrive in warm, moist climates.

There is one computational limitation in this study. The data that is used for atmospheric measurements is at relatively high resolution, covering units 25km square, whereas the data used for future oceanic conditions is from a lower-resolution data set. While this doesn’t invalidate the results of these models, models from data with matched resolution would be more compelling.

Nevertheless, the findings of this paper are striking, and they draw attention to the alarming situation that we could find ourselves in if we continue with business-as-usual emissions.

Nature Climate Change, 2015. DOI: 10.1038/NCLIMATE2833 (About DOIs).