New analysis has revealed that the Gulf region has the most hot and humid weather anywhere on Earth – and it is set to get warmer still.
More than half of the most extreme temperature and humidity readings recorded on land have occurred on the Arabian Peninsula, the study revealed.
Researchers looked at wet-bulb temperature (TW) data from more than 10,000 weather stations across the globe.
TW is the reading given by a thermometer wrapped in a piece of saturated muslin and reflects the air temperature and the level of humidity.
A figure above 35°C – which can be produced by, for example, an air temperature of 46°C and a humidity level of 50 percent – is too extreme for the human body to cope with for extended periods, because heat cannot be dissipated by sweating.
The new survey revealed that there have only ever been 14 occasions on land when the TW exceeded 35°C, all of which happened in the past two decades.
Eight of these instances took place in the Gulf region, with the record being reached in Dhahran, Saudi Arabia, in July 2003.
Two others were recorded at a weather station in Ras Al Khaimah, while there was a single instance in Abu Dhabi. Others in the region happened in Oman, Qatar and Saudi Arabia.
"Our findings indicate that reported occurrences of extreme TW have increased rapidly at weather stations … and that parts of the subtropics are very close to the 35°C survivability limit," the researchers wrote in their paper, published this month in the journal Science Advances.
“We project that TW will regularly exceed 35°C over 50km x 50km land areas and for three to six hours’ duration at land grid points with less than 2.5°C of warming since preindustrial [times] – a level that may be reached in the next several decades.”
The study – The emergence of heat and humidity too severe for human tolerance –showed that instances of extreme humid heat have doubled since 1979.
“In the past 40 years, with increases in global temperatures of about 1°C [since preindustrial times], there have been very strong upward trends of extreme temperature and humidity,” said Dr Colin Raymond, a Nasa scientist and first author of the study.
“There’s been more of these events, whether you’re talking about 29°C, 31°C or 33°C. There’s every reason to believe, as global temperatures go up, there will be a rapid increase in these kind of events.”
Events of extreme humidity and heat are, he said, set to become more frequent and widespread, and will last longer.
Higher temperatures will mean that the atmosphere has more water vapour, which, because it is a greenhouse gas, will cause further temperature increases.
“It’s a very strong relationship between the magnitude of these extremes and changes in the global temperature rise,” Dr Raymond said.
A wet-bulb temperature of 35°C is exceeded more often over the waters of the Arabian Gulf than on land, as indicated by reports from weather stations on ships.
Another of the study’s authors, Dr Tom Matthews, of Loughborough University in the UK, said the Gulf region was the area of the world with the greatest amount of energy in the atmosphere.
“Over the waters of the Gulf is the hottest and most humid place on Earth,” Dr Matthews said. “The Gulf is head and shoulders above everywhere else.”
The latest study follows a paper published in 2015 by other researchers that predicted that wet-bulb temperatures would more often exceed 35°C in future.
Dr Matthews said the results of the research showed the importance of cutting carbon emissions to limit temperature increases.
“The solution is to stop increasing the concentration of greenhouse gases in the atmosphere. The only practical way to do that is to cut the emissions,” he said.
“The concentration of greenhouse gases is still going up. The total is still growing. It needs to stop growing. It needs to halt completely.”