The heat has been unusually pronounced for more than two weeks in Argentina, where temperatures topped 100 degrees to round out December. Areas south of the equator are experiencing summer at present, but readings are still wildly off base for what would typically be observed this time of year.
Buenos Aires Ezeiza Airport hit 104.2 degrees on Dec. 29, its highest December temperature on record and, at the time, highest overall temperature since 1999. The city’s observatory spiked to 41.1 degrees Celsius, or 106 degrees Fahrenheit, on Tuesday. Only one day — in January 1957 — had snagged a higher temperature in nearly 115 years of record-keeping.
Maximiliano Herrera, a climate historian who tracks international temperature records, described Tuesday as “a historic day in Buenos Aires.” The recent heat wave also represents the first time since 1995 that the Argentine capital has seen temperatures exceeding 40 degrees Celsius (104 Fahrenheit), meaning nobody there under the age of 26 has experienced temperatures this high before.
Argentina’s National Meteorological Service noted that 11 records had been smashed Tuesday. Five major cities — Punta Indio, Buenos Aires, Las Flores, El Palomar and San Fernando — registered both their highest January temperatures on record and their highest readings in at least 50 years.
The agency issued red alerts for much of the country, writing that the “extreme temperatures” would have “very dangerous” health effects.
Córdoba, a city of 3.3 million in the strip of flat plains that stretches through central Argentina, climbed to 108.5 degrees Monday.
Farther to the west in San Juan, a city in the lee of the Andes Mountains east of the border with Chile, temperatures unofficially may have reached 111 degrees.
San Antonio Oeste, 500 miles southwest of Buenos Aires and on the water, made it to 109 degrees, the station’s second-highest reading on record. Westerly winds helped blow extremely warm air all the way toward the coast, fending off the more moderate marine layer.
Tres Arroyos, east of Bahía Blanca, set a record at 105.3 degrees, and nearby Coronel Pringles, about 45 miles to the west-northwest, also managed a record at 103.3 degrees.
“Wear light clothing and light colors,” the weather service tweeted. “Eat lightly. Don’t expose yourself to the sun.”
It was also exceptionally hot in neighboring Paraguay and Uruguay, where temperatures soared above 104 degrees (40 Celsius).
Unlike in many North American heat waves, relative humidities across central Argentina were very low. That meant the air where the hottest conditions were ongoing was bone dry.
In scorching environments characterized by dry conditions, people outdoors won’t actively notice sweat accumulating on their bodies — instead, the atmosphere will evaporate it before it can collect, desiccating an individual before they even notice they’re dry. That makes the heat especially dangerous.
The extreme temperatures are the result of a heat dome, or a sprawling ridge of high pressure, that brings hot temperatures and sinking air. Parcels of air that sink are subject to a process called adiabatic compression, which squeezes air pockets and causes them to heat up even more. Air that “downslopes,” or slides down the Andes, experiences the same phenomenon, magnifying the effect.
Since air expands when it’s heated, heat domes can cause the lower atmosphere to bulge and expand vertically. The heat dome over Argentina thus far has boosted the atmosphere’s “halfway” mark of density about 415 feet higher than average.
The heat wave could eventually affect agriculture, too; Argentina is among the world’s top exporters of soybean and corn.
A climate connection
Heat waves are among the deadliest weather phenomena, surpassing tornadoes, flooding and hurricanes in their human toll in many areas. Quantifying their exact human impact is difficult because of the issue of “excess mortality,” which occurs when the elderly, those with preexisting health conditions and other vulnerable populations die prematurely because of the heat.
Overnight minimum temperatures, which in some places may not drop below 75 or 80 degrees, can prevent the body from having an opportunity to cool down and reset before the next day of heat.
Human-induced climate change is amplifying the frequency and intensity of heat domes and, subsequently, bolstering the impacts of extreme heat. Last year was the fifth-hottest on record globally, according to the Copernicus Climate Change Service of the European Union, and ocean warmth hit a record because of the uptake of greenhouse gases spewed by human activity.
While the heat in Argentina looks likely to subside by this weekend, it’s the latest episode to fit into an alarming pattern illustrating the effects of human-induced climate change.