One billion more people now face at least one day of extreme heat stress annually compared to about five decades ago, a direct consequence linked to the burning of fossil fuels, including coal, oil, and gas, according to new research published Monday in the journal Nature Climate Change.
Mexico, Kenya, Italy, and other nations around the world are experiencing one to two more months of heat stress than they were several decades ago, the study found. Some areas are seeing even greater increases in heat stress, and regions previously untouched by these conditions are now affected.
The research utilized "feels-like" temperatures to assess heat stress on individual humans, accounting for temperature, humidity, wind speed, and other factors. This methodology, employing the Universal Thermal Climate Index, modeled the human body’s response to environmental conditions.
The study categorized heat stress into three levels: strong, defined as index temperatures of greater than or equal to 32 degrees Celsius (89.6 degrees Fahrenheit); very strong, at 38 degrees Celsius (100.4 degrees Fahrenheit) or higher; and extreme, at 46 degrees Celsius (114.8 degrees Fahrenheit) or higher.
Jennifer Francis, a climate scientist at the Woodwell Climate Research Center, stated that the study "adds stark details about increasing dangers to billions of humans." Francis further noted that the analysis shows "not only is temperature rising, but so is humidity, which makes high temperatures more deadly because our body’s air conditioning system — sweating — struggles to keep up."
Capital's Cost: A Billion More Suffer
Places that might see around 50 more days per year of at least strong heat stress compared with the 1970s include parts of Southern Africa, specifically Namibia and Angola, and Eastern Africa, including parts of Tanzania, Kenya, and Uganda. Parts of Mexico and Central America also fall into this category.
In Southern Spain, Italy, Greece, and Turkey, some areas will experience up to 40 additional days with strong heat stress compared with the 1970s. Much of Southern Europe is now seeing almost a full month of additional strong heat stress days from decades ago.
Within the U.S., much of the country experiences 15 or more days of at least strong heat stress, while southern parts, including Texas and Florida, are seeing close to 25 or more days with very strong heat stress.
These heat stress seasons are also lasting longer, intensifying the burden on workers and communities. Rebecca Emerton, the study’s lead author and a senior scientist at the European Centre for Medium-Range Weather Forecasts, described it as striking "to see heat stress not only intensifying in those places that we already consider as being hot or used to experiencing heat waves ... but also to see this, we call it, expanding footprint of heat stress expanding into regions where it’s historically been rare or non-existent."
Global Reach of Extraction's Impact
The feels-like temperatures on the ten warmest nights of each year have increased faster, by 0.32 degrees Celsius (0.58 degrees Fahrenheit) per decade, than the ten warmest days, which have increased by 0.27 degrees Celsius (0.49 degrees Fahrenheit) per decade. For tropical nights, the researchers considered a minimum temperature of 20 degrees Celsius (68 degrees Fahrenheit), indicating that people might not be recovering properly from daytime heat in the overnight hours.
Extreme feels-like temperatures, heat stress days, and tropical nights have all become dramatically more frequent, longer, and more severe over the past six decades. These changes are directly linked to the systematic burning of fossil fuels, including coal, oil, and gas, which continues to drive capital accumulation for energy corporations.
Managing Symptoms, Not Systemic Disease
Emerton stated that the work highlights the urgent need to mitigate future warming and ensure adaptation strategies, heat health action plans, early warning systems, and climate risk assessments are in place. These proposals, while presented as solutions, do not address the foundational economic structures that incentivize the continued extraction and burning of fossil fuels, thus managing the symptoms of a system designed for profit at the expense of human and planetary well-being.