A man tried to cool himself with a water bottle during the first heat wave on June 9 in New York City
The western United States is experiencing extreme temperatures these days due to a heat wave caused by the high pressure system in the atmosphere that traps hot air, according to scientists.
The climate crisis is increasing the severity and recurrence of these phenomena, with serious health consequences.
US authorities define a heat wave as a phenomenon when, for at least two days, the lowest recorded temperature is 85% higher than the average temperature for the region in July and August.
The temperature often drops to this lower level at night, which is a key point, because after very high temperatures during the day, the human body rests at night, if the temperature drops sufficiently.
Heat waves are formed more often with high pressures in the atmosphere that generate a state of entrapment and lead to the formation of a thermal dome that can be compared to a greenhouse placed under sunlight and without ventilation.
Higher pressures stop clouds from forming and push air down by compression, resulting in a rise in temperature.
Overhead air currents usually push these air masses into the atmosphere but sometimes they expand and slow down, leaving these thermal domes in place.
Heat is the cause of more deaths in the United States than any other extreme weather event such as torrential rains, floods and hurricanes, according to official data.
Hundreds of people died in Canada and the United States last year when the thermal dome raised temperatures to 49.6 degrees Celsius.
Such hot air limits the body’s ability to stay at the right temperature and can cause a “chain” of adverse effects, as the World Health Organization points out, such as convulsions, fatigue, heart attacks and hyperthermia.
The World Health Organization stresses that “hospitalization and death due to heat can occur very quickly (on the same day) or delayed” by a few days, and is particularly affected by the most vulnerable groups.
People with heart or respiratory problems are especially at risk.
This intense heat also affects homeless people who live on the streets and those who work outside in the middle of the day, as well as those who live near a source of pollution, such as highways.
The climate crisis is making heat waves, like all weather phenomena, more intense. By emitting greenhouse gases, humanity has caused the planet to be warming on average by 1.2 degrees Celsius compared to the pre-industrial period.
Since the 1960s in the United States, heat waves have become longer, hotter and more frequent with decade after decade, according to official data.
The Federal Environmental Protection Agency (EPA) says heat waves “increased in frequency sharply, from an average of two heat waves per year during the 1960s to six heat waves per year during the 2010s and 2020s”.
The climate crisis has increased the probability of a heatwave that hit Canada and the United States in 2021 by 150 times, according to estimates by the World Weather Attribution Initiative, a network of weather scientists who attribute extreme events to the climate crisis.
About Author
