Jul 27, 2023 - Energy & Environment

Scientists declare July world's hottest month and warn future will be worse

Daily global mean surface air temperatures
Data: Copernicus Climate Service/ERA5; Chart: Axios Visuals

Scorching heat waves on three continents, unprecedented ocean temperatures along with global average temperature records are prompting scientists to predict July will clinch the title of Earth's hottest month.

Why it matters: Five days short of August, extreme weather across multiple continents has proven deadly and costly as they upend precedent. Some, like the U.S. heat wave, are expected to continue into next month.

  • So far, July has featured the warmest three weeks yet recorded worldwide, according to the EU-funded Copernicus Climate Change Service and the World Meteorological Organization, a U.N. agency.
  • A separate analysis from independent researchers also released Thursday came to the same conclusion.
  • Based on paleoclimate records from tree rings and other sources, scientists said it is likely the hottest month since at least 100,000 years ago.

The big picture: The month has featured scorching heat across the U.S., Europe and China, with records falling daily like bowling pins.

  • The human toll is not yet fully known, but emergency room visits for heat-related illness have spiked in some U.S. cities.
  • Axios Austin's Nicole Cobbler reports that heat-related illnesses doubled in that city from June last year, and EMS calls in July have dramatically increased, per officials.
  • This past week has seen temperature records fall in Greece and Italy, with wildfires striking popular tourist spots and prompting large evacuations.
  • One study released this week found that the U.S. and European heat waves would have been "virtually impossible" without human-caused climate change.

By the numbers: According to one widely-used climate data set, known as ERA5, the global mean surface air temperature averaged during the first 23 days of July was 16.95°C (62.51°F), well above the 16.63°C (61.9°F) set during the full month of July 2019.

  • "At this stage," Copernicus and the WMO stated, "It is virtually certain that the full monthly average temperature for July 2023 will exceed that of July 2019 by a significant margin."

The intrigue: Typically, monthly records are exceeded by a tiny fraction of a degree. However, the ERA5 data set's margin between the first 23 days of July 2023 and July 2019 has been about 0.32°C (0.57°F), and about 1.5°C above preindustrial levels. This closely matches an independent analysis from climate scientist Karsten Haustein at Leipzig University.

  • "What we've experienced during the first three weeks of July is so exceptionally warm that it would take a large asteroid impact, or something of that magnitude, to prevent July from being the warmest July on record," climate scientist Zeke Hausfather, who did not participate in the new temperature assessments, told Axios in an email.
  • However, July did not breach the Paris Agreement's temperature target, which refers to a long-term average.

The intrigue: Ocean temperatures have been even more unusual than air temperatures this month, reaching unprecedented levels since mid-May.

  • While some of the ocean heat can be attributed to an El Niño event brewing in the tropical Pacific Ocean, it is not the only factor.
  • "There are many contributing factors to this historically hot July — with human-caused climate change of course being the driving factor in reaching this new record," Zack Labe, a researcher at Princeton and NOAA told Axios in an email.

Zoom in: Across the U.S., relentless heat waves have affected tens of millions this month.

  • In Phoenix, the city blew past its record of 18 consecutive days with high temperatures of 110°F or above, with at least 27. Phoenix is on course to become the first large city in the U.S. to have a monthly average temperature at or above 100°F.
  • "I've been waiting until 10 pm or later to walk my dog, and it's still over 100°F, which has me worried about her paws and my hydration," reports Jessica Boehm of Axios Phoenix.
  • In Miami, which is experiencing its worst heat wave on record, Axios Miami's Deirdra Funcheon reports: "Miami is always steamy in summer, but this one has felt particularly punishing."
  • "The only tolerable thing to do outside is swim — and I wait until around sunset to do that," she says.

Blanketed by warm moisture from the Gulf and high humidity, the Houston area has recorded at least three heat-related deaths since June, with the city's Fire Department reporting a sharp increase in heat-related illness calls.

  • In the city, there were 442 calls in June and 323 from July 1-20, compared to 264 calls in June and 342 calls during the comparable 2022 time frame, official data show.

What they're saying: WMO secretary-general Petteri Taalas called July's extreme weather events, "The harsh reality of climate change and a foretaste of the future."

--Axios Houston's Shafaq Patel contributed to this article.

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