Swampy and sweltering — Increasing levels of humidity are here to make heat waves even worse This summer’s heat is only a preview of what’s in store for our future.
Matt Simon, WIRED.com – Jul 28, 2023 11:30 am UTC Enlarge / A tourist refreshes at a vapor barrier in Budapest, Hungary, on July 16, 2023. Arpad Kurucz/Anadolu Agency via Getty Images reader comments 72 with
Because youre a smooth-skinned mammal, no weather feels quite as oppressive as a humid heat wave. The more water vapor in the air, the less efficiently your sweat can evaporate and carry excess heat away from your skin. Thats why 90 Fahrenheit in humid Miami can feel as bad as 110 in arid Phoenix.
Climate change has supercharged this summers exceptionally brutal heat all around the worldheat waves are generally getting more frequent, more intense, and longer. But they are also getting more humid in some regions, which helps extend high temperatures through daytime peaks and into the night. Such relentless, sticky heat is not just uncomfortable, but sometimes deadly, especially for folks with health conditions like cardiovascular disease.
One of the more counterintuitive effects of climate change is that a warmer atmosphere can hold more water vapor than a colder one. A lot of it, in fact: Each 1.8 Fahrenheit bump of warming adds 7 percent more moisture to the air. Overall, atmospheric water vapor is increasing by 1 to 2 percent per decade. That additional wetness is why were already seeing supersize downpours, like the flooding that devastated Vermont earlier this month.
Water vapor is actually a greenhouse gas, like carbon dioxide or methane, responsible for about half of the planet-warming effect. (It’s supposed to be up there, whereas humans have been pumping in way too much extra carbon.) More warming evaporates more water, which causes more warminga climatic feedback loop. Advertisement
In landlocked areas, heat waves evaporate water from plants and soils. But humidity gets especially oppressive near the ocean, where water is more readily available. Coastal regions in general are seeing more humid conditions as ocean temperatures warm, says Alexander Gershunov, a research meteorologist at the Scripps Institution of Oceanography, who studies humidity and heat waves. Air sitting over a water body tends to be close to saturated. It has a lot of moisture in itclose to 100 percent relative humidity.
Sea surface temperatures have been steadily climbing globally, as the oceans absorb something like 90 percent of the excess heat that humans are adding to the atmosphere. But since March, global sea surface temperatures have been skyrocketing above the norm. The North Atlantic, in particular, remains super hot, loading Europes air with extra humidity.
The waters around Florida are also logging truly astonishing sea surface temperatures: On July 24, a buoy recorded a temperature of 101 Fahrenheit. You have incredibly warm Gulf water that warms the atmosphere, which can then absorb more moisture. So it’s kind of a feedback loop, says Kent State University biometeorologist Scott Sheridan. In a lot of the areas around the Mediterranean, where there’s been really bad heat, and then in Florida and the Gulf Coast, those have been the really big driving factors for why the humidity is so high.
Accordingly, in Miami the heat indexa measurement that combines temperature and relative humidityhas been above 100 for over 40 days in a row, smashing the previous record of 32 days in 2020.
Meanwhile in California, Gershunovs research has confirmed that heat waves are getting stickier. It’s not just more frequent, more intense, and longer-lasting heat waves, like is the case all over the world with the warming climate, says Gershunov. Here, the heat waves are also changing flavor. They’re becoming more expressed disproportionately in nighttime temperatures. It turns out it’s because of humidity, and that’s related to the warming of the ocean. Page: 1 2 Next → reader comments 72 with Advertisement Channel Ars Technica ← Previous story Next story → Related Stories Today on Ars