The brain is negatively affected by environmental heat, even at current levels.

Frontal lobe changes from heat can impede planning, decision-making, and attention.

Cognitive test scores fall as temperatures rise, affecting memory and reaction time.

Although the large majority of climate scientists hold firmly to the belief that the climate is heating up at an unsustainable rate, an undetermined segment of the population is convinced that global warming worries are overblown—a belief that runs counter to demonstrable scientific evidence, as well as everyday observation.

In 1988, experts testified before Congress in the first congressional hearing about climate change. Every year in the 21st century has been hotter than 1988, with each decade hotter than the previous. The last three years, from 2023 to 2025, were the hottest in recorded history, dating from 1850, when sufficient direct measurements by instruments (thermometers) allowed an estimate of temperature. The last 11 years have included all of the warmest years observed using instrumental methods.

But one does not have to look at extreme temperature elevations to encounter convincing evidence that even less extreme examples affect the smooth operation of the human brain. If we stick to temperatures we’ve already experienced, especially in 2023, 2024, and 2025, there is more than enough to worry about.

The Effect of Heat on the Brain

In general, even moderate heat elevation adversely affects the brain’s reasoning power and thought patterns. As the temperature and duration of the heat wave increase, the brain’s neurotransmitters suffer disruptions in their messaging of the signal from one neuron to the next. In reaction, the receiving neurons may fire too rapidly, too slowly, slightly erratically—it doesn’t matter which; the results are disruptive effects on mood, memory, thinking, and sleep. Added to that is the loss of electrolytes due to sweating—leading to weakness, muscle cramps, and in some cases seizures. Additional heat exposure affects perception and behavior, especially clear thinking, sustained attention, memory, and rapid decision-making.

Perhaps most striking of all are the subjective mental experiences. Think back to the last time you were ensnared in a “heat wave,” even one of moderate intensity by today’s standards (90-100 degrees Fahrenheit). You were undoubtedly totally preoccupied with your discomfort; you could hardly think of anything else. In response to your heat-induced lethargy and restlessness, your concentration was almost nil, and you........

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