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The unprecedented heat in mid-November is scorching Brazil and other parts of South America, creating a record-breaking hot spell for the planet.
The heat in Rio de Janeiro, a city of nearly 7 million people, has proven disruptive and deadly. A woman died at a Taylor Swift concert in sweltering heat on Friday evening. It was so hot on Saturday that Swift postponed her concert planned for that evening. “The safety and well-being of my fans, fellow artists and crew must and will always come first,” read a message posted to Swift’s Instagram Story Saturday afternoon.
Although it is still spring in the Southern Hemisphere, temperatures have risen far above normal even in summer, which is more than a month away.
A stagnant anticyclone, El Niño and human-caused climate change have combined to produce this excessive heat.
Rio has been experiencing an oppressive combination of heat and humidity for days. On Friday, when the woman died at the Taylor Swift concert, midday temperatures were above 100 degrees and the dew point, a measure of humidity, was above 70 degrees. At dew points above 75 degrees, the humidity is oppressive.
At a dew point of 77, there are about 23 grams of water, or about 1.55 tablespoons, in each cubic meter of atmosphere. That’s the weight of about nine pennies.
Friday’s heat indices – a measure of how it feels taking humidity into account – topped 120 degrees. Climate historian Maximiliano Herrera tweeted The heat index reached up to 137 degrees in Rio’s suburbs on Saturday.
The higher the heat index, the less sweat can evaporate from our body. That’s because the air is already closer to its ability to hold moisture. When heat indices are high, less heat can evaporate from our skin, thereby cooling us down. This can lead to difficulty regulating our body temperature. If left unchecked, heat exhaustion and heat stroke can occur.
Temperatures around Rio on Saturday were both dangerously high and record-breaking. Rio’s Jacarepaguá-Roberto Marinho Airport reported a heat index of 131 degrees Saturday morning, the product of a temperature near 97 degrees and a dew point of 86 degrees. Most of the city’s other airports recorded high temperatures between 105 and 107 degrees.
Herrera said the town of Seropédica, a suburb about 25 miles west-northwest of Rio and 15 miles inland, hit 108.7 degrees, a November record.
Record high temperatures also spread to Peru and Bolivia. On Saturday, highs of 102.6 degrees in Tingo de Ponaza, Peru, and 102.2 degrees in Cobija, Bolivia, set November records. according to Herrera.
About a week ago the heat moved to Brazil for the first time. The BBC reported that a red alert has been issued for almost 3,000 towns due to “unbearable” heat. On November 12th, Rio reached 108.5 degrees, a record high for this month.
The intensity of the heat is expected to ease somewhat after Sunday, but temperatures in central South America are expected to remain warmer than normal through next week.
What drives the heat?
Contributing to the heat was the counterclockwise rotating surface high pressure system just off the coast of Brazil. This creates warm, moist northerly winds that bring in the same humidity that is characteristic of the Amazon rainforest. At higher elevations there is also a “heat dome,” or ridge of hot, sinking air. While deflecting the jet stream as well as bad weather and cloud cover, it promotes hot sunshine.
What Drought in the Amazon Means for the Planet
The heat is also being compounded by a strengthening El Niño, the climate pattern associated with warmer than average ocean waters in the tropical Pacific.
Furthermore, the frequency, intensity and duration of extreme heat events like this are increasing due to human-caused climate change. The planet just experienced its warmest 12-month period on record, and the last five months have all been the warmest on record.
According to the United Nations, Brazil has warmed by 0.9 degrees in the last few decades alone. Land use changes, including deforestation in the Amazon, are expected to accelerate the pace of warming.