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Whatever side of In the subjective city versus rural debate you find yourself in, the objective laws of thermodynamics dictate that cities lose on at least one front: they tend to get unbearably hotter, more so than the surrounding rural areas. This is thanks to the urban heat island effect, in which buildings and roads easily absorb the sun’s energy and release it well at night. The greenery of rural areas, on the other hand, provides shade and cools the air by releasing water.
Climate change has the effect of an urban heat island all the more terrible in cities around the world, and it will only get worse. Like, much worse. An international team of researchers have used a new modeling technique to estimate that by the year 2100, cities around the world could heat up to 4.4 degrees Celsius on average. For perspective, this figure erases the Optimistic goal of the Paris Agreement for a global average temperature rise of 1.5 ° C from pre-industrial levels. In fact, the team’s figure more than doubles the deal’s tough goal of limiting that global rise to no more than 2 degrees C.
Until now, global climate models have tended to disregard urban areas, and for good reason, as they represent only 3% of the earth’s land surface. Cities are just a failure. Researchers are more interested in the dynamics of things like the ocean, ice, and drafts. “We’re closing that kind of gap,” says Lei Zhao, climatologist at the University of Illinois at Urbana-Champaign and lead author of a recent paper Posted in Nature’s climate change describing the modeling. “We provide city-specific projections for the future.”
His team’s model suggests that warmer cities could spell disaster for urban public health, which is already suffering from the effects of the increased heat. Between 2000 and 2016, according to the World Health Organization, the number of people exposed to heat waves soared by 125 million and extreme heat killed more than 166,000 between 1998 and 2017. And if for the moment half of the world population lives in urban areas, this proportion is expected to increase to 70% by 2050, according to the authors of this new article. People in search of economic opportunities unknowingly rush into peril.
“When I read these newspapers I just don’t know what’s wrong with humanity, to be honest with you. Because it’s like the same song is being sung by different people, ”says climate scientist Camilo Mora of the University of Hawaii at Manoa, who was not involved in the work. “Come on man! When are we going to take this seriously? It’s another person ringing the bell. For some reason, we refuse to hear this thing.
To calculate the city’s temperature rise, Zhao and his colleagues at a number of institutions, including Princeton University and the Lawrence Berkeley National Laboratory, constructed a statistical model for the climate of urban areas, based on focusing on changes in temperature and humidity. These two factors are the conspiratorial threats of extreme heat: Our bodies respond to high temperatures by sweating, which is more colloquially known as evaporative cooling. But humidity makes this process less efficient, because the more humid the air, the less easily it accepts the sweat which evaporates from our body. This is why moist heat is so much more uncomfortable than dry heat.
The heat and humidity are not only uncomfortable; they can be dangerous. Mora identified 27 different ways heat can kill a person. When your body detects that it is overheating, it redirects blood from the organs in the heart of your skin to your skin, thereby dissipating more heat into the air around you. (This is why your skin turns red when you are hot.) In extreme heat, it can get out of hand, causing ischemia or extremely poor blood flow to organs. This can damage crucial organs like the brain or the heart. Additionally, an elevated body temperature can cause cell death, known as heat cytotoxicity. Humidity worsens the risk overheating and organ failure, because you can’t sweat as efficiently to cool off.
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