Global daily heat records were announced in parallel this week, according to instruments that provide preliminary data.

Although they can be the first warning of an episode of extreme heat, they should be treated with caution, climate experts say, quoted by AFP.

Who creates this data?

The University of Maine in the United States has created a website called Climate Reanalyzer that shows the average global temperature for every day of the year since 1979.

On Monday, July 3, this curve reached a record high of 17.01°C. Since then, this record has been broken again on Tuesday (17.18°C) and Thursday (17.23°C).

The European Copernicus Climate Observatory, which has a similar instrument, confirmed Monday’s and Tuesday’s records, albeit with slightly different values ​​(16.88°C and 17.03°C, respectively).

What are they based on?

These estimates are created using so-called “reanalysis” tools, which combine temperature measurements (by weather stations, satellites, etc.) and their interpretation using a computer model.

The different models used explain the differences between the obtained values.

The University of Maine relies on public data from the US National Oceanic and Atmospheric Administration (NOAA).

The agency, which acknowledged that many local temperature records are currently being set around the world, distanced itself from the university’s findings, saying it could not “verify the methodology or conclusions”, preferring to focus on monthly and annual records.

However, the fact that Copernicus produced similar results suggests that the published data can be “taken seriously”, Zack Hausfather, a climate scientist at the University of Berkeley, told AFP.

The European instrument (called ERA5) is considered “the most reliable” by scientists, he added.

Why should these records be treated with caution?

These are estimates that are “not official data,” Sean Birkel, developer of the Climate Reanalyzer website, told AFP.

“I think the focus should be on annual and monthly records,” which are scrutinized, the University of Maine researcher added. Such checks are not possible for near-real-time data due to lack of time.

On Thursday, Copernicus separately published its analysis of last month, announcing that it was the warmest June on record. A similar monthly review from NOAA is expected next week.

These reports are based “solely on observations” from the ground, which are also “much more” than what is fed into the reanalysis instruments, Zack Hausfather explained.

Generally, climatologists prefer to focus on long-term trends and changes to eliminate variations that are simply related to the weather.

Moreover, the global average temperature is an “abstract” number that doesn’t necessarily appeal to the general public, Zack Hausfather notes. “No one lives at the average world level”

How useful is this daily data?

Despite all that’s going on, this daily data “may allow us to start identifying extreme events” that could “be climatically significant,” Sean Birkel said.

Previous records identified can then be checked against other databases, which will allow the study of the factors driving these rising temperatures to begin, he noted.

“These previous records are further evidence of changes in global climate trends due to climate change and the current El Niño episode,” said Omar Baddour of the World Meteorological Organization.

That’s “a sign that we’re headed for a very warm period at the surface of the globe,” Zack Hausfather agreed.

“At this rate, it is increasingly likely that 2023 will be the warmest year since records began” in 1880.

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