Kim Stanley Robinson’s book “The Ministry for the Future” opens with the story of an aid worker struggling to escape an extreme heatwave that knocks out the power grid and kills thousands of people unable to escape the heat. The book is fiction, but it is based on an alarming reality: climate change could make some parts of the world so hot that even in the shade, just being outside can kill even young, healthy people.
Texans got a small taste of that this summer. In temperatures as high as 109°F, officials called us to conserve electricity to protect the electrical grid. If the grid fails, how will we protect ourselves from extreme heat?
Recent research by Daniel J. Vecellio shows that the threshold for dangerous heat used in the past (a wet bulb temperature of 35°C), is too high. Our bodies actually suffer adverse physiological changes at lower temperatures, especially when the humidity is high.
These are the conditions the article says we could see in the subtropics, home to some of the highest population densities on the planet, if we cannot limit our carbon emissions.
The heat the world is facing now is different from the hot weather Texas experienced a century ago, heat that could be managed with a well-ventilated house, sleeping porches, and resting during the hottest part of the day.
When climate scientists raise the alarm about excessive heat in a warming climate, they are talking about deadly conditions where the combination of temperature and humidity makes it impossible for the human body to cool itself off, leading to physiological stress, heat stroke, and even death.
In the article, Vecellio and his team combine new research on the human body’s response to heat with the Coupled Model Intercomparison Project (CMIP) climate model to investigate which areas of the world will see heat and humidity at levels that are uninhabitable by humans for significant parts of the year. They also investigate how the distribution of deadly heat changes with various levels of global warming, from 2°C to 4°C.
At 1.5°C of global warming, the current goal of the international climate community, prolonged periods of deadly heat are limited to northern India and eastern China. But at 4°C of global warming, the parts of the world exposed to dangerous heat covers most of sub-Saharan Africa, the eastern half of China, large portions of South America and Australia, and most of the eastern half of the United States, including Texas.
Alarmingly, the regions which could see the highest incidence of deadly heat have the largest populations of anywhere in the world: India and the Indus River Valley (population: 2.2 billion), eastern China (population: 1.0 billion), and sub-Saharan Africa (population 0.8 billion).
In the highest global warming scenario, a 4°C warmer world, “…2.7 billion persons will experience at least 1 week of daytime (8h) ambient conditions associated with dangerous heat, 1.5 billion will experience a month under such conditions, and 363.7 million will be faced with an entire season (3 months) of life-altering extreme heat.”
The authors note that air conditioning is not a viable long-term adaptation plan. Air conditioning consumes lots of energy, and producing that energy causes more carbon emissions. And, running an air conditioner, while it cools off the inside of a building, transfers the waste heat from inside, to the outside, making it even hotter. Finally, as Texans already know, excessive heat strains the electrical grid. And if the grid fails, we are left with no way of protecting ourselves. This doesn’t even take into consideration the lives of people who have no choice but to live or work outside.
The report emphasizes the importance of limiting global warming to 1.5°C, a goal scientists say is still within reach, if the global community can make deep cuts in carbon emissions. The report is in line with the findings of the Global Stocktake Report, which stresses the importance of limiting warming to 1.5 °C to avoid the most catastrophic impacts of global warming. It also is in line with the comments by Pope Frances in his recent encyclical, Laudate Deum, which reminds us of our moral obligations in the face of the threat of climate change.