Simultaneous record heat hits multiple continents

A simultaneous spate of extreme heat events have broken longstanding, all-time records on multiple continents this week.

Why it matters: Extreme heat events are the clearest manifestation of climate change in weather that people and the ecosystem experience on a daily basis.

• Extreme heat can be deadly, causing the most deaths of any weather-related phenomenon in the U.S. during a typical year, according to the National Weather Service.
• Prolonged heat events with sweltering days and little to no relief at night can be particularly hazardous.

Zoom in: The records from the past week are particularly unusual considering these events are occurring in late August, which is past the typically hottest time of year.

• It is in keeping with the theme of what is likely to be the Northern Hemisphere's hottest summer on record, with the hottest global average sea surface temperatures in recorded history.
• Multiple U.S. states during the past week have seen heat indices, a metric that combines heat and humidity to capture how hot it feels to the human body, climb above 115°F, and in some spots, even exceed 125°F.
• In Chicago on Thursday, the heat index rose to an all-time peak of 120°F, as the air temperature hit 100°F for the first time since 2012.

Context: Extreme heat events globally are becoming more frequent, intense and longer-lasting due to the burning of fossil fuels for energy, deforestation and other contributors to climate change.

• Several studies have shown that particularly severe heat events, such as one in the Pacific Northwest in 2021, would have been "virtually impossible" without human-caused climate change.

By the numbers: For the continental U.S., each day during the past seven has seen about 100 or more hot temperature records set or tied. Those include daytime highs and overnight minimum temperatures.

• The ratio of hot temperature records to cold records has been about seven-to-one during that time period.
• New Orleans, for example, tied its all-time high-temperature record of 102°F on Wednesday, while other locations in Louisiana established new benchmarks.

Between the lines: Beyond the U.S., monthly and all-time records have been set this week in France, Spain, Switzerland, Bolivia and Japan, among other nations.

• Several locations in Europe have broken records set during the deadly summer of 2003, which featured one of the worst heat waves on record in France and nearby nations. Geneva, Switzerland broke an August record with a high of 102.7°F (39.3°C) on Thursday.

• In Japan, Sapporo saw its highest temperature on record at 97.3°F (36.3°C). On Twitter, meteorologist Sayaka Mori said that several schools in Hokkaido were closed due to heat for the first time.
• The region is famous for its winter skiing and hosted the 1972 Winter Olympics.

Of note: Like the U.S., parts of Japan have been experiencing a heat wave that has flared off and on for much of the summer.

• Some of the most anomalous heat has struck South America during its winter season.
• This week, for example, Villamontes, in southeastern Bolivia, tied for the warmest winter temperature on record in the Southern Hemisphere, with a high of 113°F (45°C).

The intrigue: None of these heat waves on their own is surprising, particularly during a summer featuring such unusual ocean temperatures, and with a burgeoning El Niño in the tropical Pacific. Both conditions can supercharge global heat extremes.

• However, to see them occur at the same time is unusual, particularly since even countries supposedly in the grips of their winter season are involved.

Jacob Knutson contributed reporting.