World temperature records shattered not once, but twice this week

This week the world sweltered as the record for hottest-ever global temperature was shattered, first on Monday, then again on Tuesday.

On July 4, Independence Day in the U.S., the average global temperature reached 62.9 degrees Fahrenheit (17.82 degrees Celsius), according to data collected by the U.S. National Centers for Environmental Prediction. That temperature surpassed the old record of 62.6 degrees F (17.01 C) that was set on Monday.

The number was calculated based on global temperatures across both land and sea, then averaged together, though it's not likely to be certified as an official record.

Randy Cerveny, who serves as a rapporteur on extreme records for the United Nations/World Meteorological Organization, says the unofficial data provided by NCEP is correct, but records certifiers don't use this metric. They look at specific temperatures at a given location, rather than a global average.

“What they have done is taken all the available observations from land and sea — we have tons of sea buoys and station across the land — and they have a particular set of equations that will aggregate that down to one value,” he said. “They have come up with a value that is the hottest we have recorded using that method since 1979."

Tuesday’s global high was nearly 1.8 degrees Fahrenheit (a full degree Celsius) higher than the 1979-2000 average, which already tops the 20th- and 19th-century averages.

Other heat-records have been shattered across the globe this week. Both Quebec and Peru surpassed record-high temperatures. Beijing reported nine straight days last week when the temperature exceeded 95 degrees Fahrenheit. And in the U.S., cities like Medford, Oregon and Tampa, Florida have been hovering at all-time highs.

Phoenix posted a high Monday of 116 degrees, one degree shy of the record for the date. Tuesday's high at Sky Harbor International Airport was 113 degrees.

Experts believe more heat records will be broken this summer, because of the culmination of rising summer temperatures and the El Niño conditions in the equatorial Pacific.

El Niño is the warm phase of the El Niño-La Niña Southern Oscillation pattern. This phenomenon happens in a naturally occurring cycle when sea surface temperatures across the east-central equatorial Pacific Ocean reach above-average temperatures. They are typically associated with extreme weather and above-average precipitation in the western U.S.

This year, El Niño conditions have already developed across the Pacific and have the potential to bring above-average precipitation and increase the likelihood of extreme weather events.

Before this record-hot week, the hottest global-average day on record was set in 2016, during the last El Niño global weather event. El Niño plays a significant role in global average temperatures, and experts say it likely contributed to these record hot days.

“The short-term aspect of this particular data is because of the development of the El Niño,” said Cerveny, who is a professor at Arizona State University’s School of Geographical Sciences and Urban Planning. “Because the Pacific Ocean is so big, when it warms up, it has a dominating impact on the global temperatures around the entire Earth.”

And even with this year’s El Niño, ocean temperatures are warmer than usual.

Earlier this summer: Phoenix was 1 degree off from tying a record temperature set in 1907

In April, NOAA's Climate Prediction Center found that global ocean temperatures reached record highs, at 1.55 degrees Fahrenheit above the average over the years 1982-2011. This marked the second-highest monthly ocean temperature for any month on record, just 0.02 of a degree shy of the record-warm ocean temperatures set in January 2016, during the last El Niño.

The Pacific Ocean is the world’s largest ocean and covers roughly one-third of the Earth’s surface, making it significantly larger than all of Earth’s landmasses combined. Cerveny says it makes sense that global temperatures have reached record highs when these 64 million square miles of water warm up.

“If the Pacific Ocean gets hot, that has an enormous impact on global temperatures,” he said.

Cerveny said while the El Niño is a short-term cause of the record-breaking temperatures, rising temperatures caused by climate change are also fueling the heat.

“The long-term aspect of this particular value is associated with global warming,” Cerveny said. “Year after year, temperatures on Earth are getting hotter.”

The eight warmest years on record have now occurred since 2014, according to the European Union's Copernicus Climate Change Service, with 2016 the hottest year ever.

Scientists say the planet is the hottest it has been in roughly 125,000 years. Experts believe more heat records will be broken this summer because of the culmination of rising summer temperatures, accompanied by El Niño.

Cerveny says the impacts of these new record-shattering numbers cannot yet be quantified, but they will likely cause a spike in heat waves and exacerbate heat-related illnesses and death.

Heat deaths have skyrocketed across Arizona and Maricopa County in recent years. In 2022, a record 425 people died of heat-related causes in Maricopa County. A decade ago, the county reported 75 heat deaths.

“We're in uncharted territory,” Cerveny said. “Humankind has never seen these types of temperatures, so we are going to be seeing effects that we haven’t felt before in modern society.”

Jake Frederico covers environment issues for The Arizona Republic and azcentral. Send tips or questions to jake.frederico@arizonarepublic.com.

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This article originally appeared on Arizona Republic: Climate change, El Niño help fuel back-to-back global heat records