Killer Heat Forever, From Our Fossil-Fueled Inertia

Tule Lake bed. Photo: Jeffrey St. Clair.

Sometime between 2070 and 2099, assuming “business as usual” between now and then as regards the use of fossil fuels, the following will occur:

+ For the equivalent of a week or more each year, about 120 million people across the U.S.A. will be exposed to conditions so hot, the heat index (or “feels like” temperature, which is produced by the combination of heat and humidity) will surpass the limits of the National Weather Service’s heat index charts. Depending on locality at that time, the upper limit of the heat index scale could be at or above 127°F (52.8°C);

+ In 47 of the lower 48 U.S. states, these “off-the-charts” conditions will occur in at least one county at least once a year. Historically, “off-the-charts” conditions have only occurred in the Sonoran Desert region, along the California-Arizona border, and only for a few days each year.

Last week, the Union of Concerned Scientists released Killer Heat, a report analyzing how the frequency of days with a dangerously hot heat index — the combination of temperature and humidity the National Weather Service calls the “feels like” temperature — will change in response to the global emissions choices we make in the coming decades.

Kristy Dahl, a climate scientist with the Union of Concerned Scientists (UCS), briskly describes this quite likely hot late 21st century for the U.S.A. in (1); she was the lead scientific author of the research paper that arrived at the detailed geographical distribution and frequency of occurrence of these future high temperature conditions (2); and she was part of the team of Union of Concerned Scientists people who produced that agency’s report (3) and interactive website (4) for the informational benefit of the general public, about these looming national and regional climatic changes (for the worse),

The expected temperature conditions are reported for seven regions (in sum covering the 48 contiguous states): Northeast, Southeast, Midwest, Southern Great Plains, Northern Great Plains, Southwest, Northwest; and are also broken down with great specificity for each of the 3,109 counties of the contiguous U.S.

Kristy Dahl and the Union of Concerned Scientists have done a marvelous job of presenting the data very clearly, and of making its implications compellingly explicit.

Two lessons are available from this work:

1) The sooner we cease using fossil fuels to generate energy, and the more quickly and significantly we reduce our emissions of carbon dioxide, methane and other greenhouse gases, the lower the excessive climatic heating we — and our descendants — will have to suffer through in the future. And that future will last a long time (200,000 years) because nature removes CO2 from the atmosphere very slowly;

2) Local and regional governments and public service agencies must devise strategies, programs, and procedures to provide public“heat relief” methods for the people living in the regions they serve (or ‘supervise’), and they must also create or expand facilities for achieving that end. Basically, we have to evolve our current system of episodic emergency services(like fire departments, rescue teams, and ambulance transports) into a public (i.e. free) system of chronic emergency services. “Help” will be needed widely “all the time.”

The reports produced by Kristy Dahl and her UCS colleagues give a vivid picture of an imminent swelteringly uncomfortable (and unhealthy) mid-range future — see them. The vividness of the image of that future discomfort is undoubtedly the most useful result of this work and its reporting, because that vividness may motivate more serious governmental efforts to swerve American society away from its mindless fossil-fueled consumerist (and militarist) obsession, which is increasingly cooking us and our children and grandchildren, etc.


(1) Will the U.S. Be a Dystopian Hellscape in 2100 if Emissions Keep Rising?, Kristy Dahl 22 July 2019, [news release and summary of findings in UCS report, (3)]

(2) Increased frequency of and population exposure to extreme heat index days in the United States during the 21st century, Kristy Dahl, et. al., 16 July 2019, [science paper]

(3) Killer Heat in the United States: Climate Choices and the Future of Dangerously Hot Days (2019), Union of Concerned Scientist [report for the general public, based (2)]

(4) Killer Heat in the United States: The Future of Dangerously Hot Days, [Interactive Maps, from (3)]

Manuel Garcia Jr, once a physicist, is now a lazy househusband who writes out his analyses of physical or societal problems or interactions. He can be reached at

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