Even though an increase in the prevalence of heat waves has been projected by many climate studies in the past, few had looked into the potential of humidity to amplify the negative outcomes even further.
Now, a new global study finds that humidity is likely to increase dramatically in many areas of the world, impacting on humans’ ability to work and spend leisure time outside.
In the study, researchers used global climate models to map current and projected “wet bulb” temperatures, which reflect the combined effects of heat and humidity.
Based on the data, wet-bulb readings that now occur approximately once a year, could arise 100 to 250 days of the year in areas with prevailing humid weather conditions, affecting hundreds of millions of people.
“Lots of people would crumble well before you reach wet-bulb temperatures of 32 C [threshold beyond which normal activities become near-impossible], or anything close,” said co-author on the study Radley Horton from Lamont-Doherty Earth Observatory.
Some parts of the southern Mideast and northern India could even see 35 wet-bulb degrees Celsius (or 76 C) by late century, which is literally off the charts with respect to the heat index (another related measure of the “real feel” of moist summer weather), which caps at 58 C.
Very few events of such extremity have been recorded, with most taking place in areas where people have access to clean water and air-conditioning.
According to Horton, extreme spikes in temperature would have a tremendous effect on all fields of human activity, including economy, agriculture, military efforts, and recreation.
“It’s not just about the heat, or the number of people. It’s about how many people are poor, how many are old, who has to go outside to work, who has air conditioning,” said co-author Alex deSherbinin of the Center for International Earth Science Information Network at Columbia University.
Even if the heat doesn’t kill people directly, many would go on to develop life-threatening kidney problems and other medical conditions.
While the scientist behind the 35-degree survivability limit, Steven Sherwood, is not convinced it will be reached as soon, he contended the point still stands.
“We move toward a world where heat stress is a vastly greater problem than it has been in the rest of human history. The effects will fall hardest on hot and humid regions.”