In this extract from “The Pocket Guide to Planetary Peril” (WH Allen, 2025), author Jakob Thomä, a professor at the University of London’s SOAS Centre for Sustainable Finance, examines an existential threat facing us all: heat. As the impacts of climate change take hold, Thomä argues that heat will become the risk no one can avoid.
We live in places that will be flooded by rising sea levels. We have food production systems dependent on specific climates. And we have built economic structures, trade relationships and social dynamics contingent on certain temperatures.
What’s more, we are not alone in this world, and the rapidly changing climate is a threat to the flora and fauna with whom we share this planet. Some of us think this is a problem — although admittedly not all of us.
The key questions then are: How fragile are systems to a changing climate? What are the costs of the impacts or shocks to the system (such as relocating people from places underwater, or victims of extreme weather events that are made more likely by climate change)? What are the costs of adapting to these impacts? How do we negotiate the equity and distributional impacts of these effects? And crucially, what are the costs of preventing these impacts to begin with?
That is the climate discourse in a nutshell. Except for heat. Heat is a different story because we cannot live above a certain heat level.
Of course, the heat story is driven by climate change, so at first glance it may seem I am making an artificial distinction here. Global warming is heat and heat is global warming. But the reason is that it creates an almost unmanageable risk, one incapable of being mitigated by adaptation, at least within the current technological paradigm.
This is different to almost any other effect from climate change. We can maintain habitats below sea level, the Netherlands being a perfect example, through dams and adaptation. Perhaps we would not be able to do this everywhere, and perhaps we would decide that we couldn’t be bothered — economically speaking — to do this, but we at least have the means.
We can change food production patterns, our economic activity cycles, we can irrigate, we can create water, we can do all these things. Some have prohibitive price tags and come with dramatic non-financial costs to health, cultural capital and societal welfare. But they can be done.
Related: 200,000 Americans could die of temperature-related causes each year if global warming hits 3C
Heat is the final boss. Heat is a different beast. Heat deaths in and of themselves may not appear as a particularly new or novel phenomenon. They happen everywhere, as the frail, the ill and the old are unable to regulate their body temperatures during hot summers.
And heat deaths can also happen to the young. One of the first “proven” victims of climate change is a 6-year-old boy from Toyota, Japan, who collapsed in a park on a morning field trip, and was dead by the afternoon.
When I think of the heartbreak of our indifference, I think of him. These kinds of deaths will increase in frequency through climate change but, of course, as any self-respecting climate sceptic or denialist will tell you, we can also expect fewer deaths from cold temperatures.
Indeed, there is some reason to believe that from a pure temperature perspective, temperature-related mortality has in fact decreased in the past decades, not just because of improved adaptation, but also because of warmer winters.
Over time, that pendulum — as we near 1.5 and 2 degrees Celsius (2.7 to 3.6 degrees Fahrenheit) global warming above pre-industrial levels — will swing in the other direction, with up to 10 million annual climate deaths by the end of the century, according to some estimates (not counting the indirect deaths from climate poverty, conflict and so on).
What will be new about heat deaths is the extent to which the lived environment will become physically uninhabitable for everyone, old and young, middle-aged, healthy and ill.
Extracted from “The Pocket Guide to Planetary Peril” by Jakob Thomä (WH Allen, £16.99)
