Global temperature records continue to break. This is how we monitor a warming Earth.

World daily temperature records were broken this week, according to preliminary data.

The modeling tools that produced these estimates can provide early warning of extreme heat events, even if they aren’t as accurate as the monthly and annual reports produced by major agencies, experts say.

Who produces the data?

The University of Maine has set up an online tool called Climate Reanalyzer, which shows curves in global average temperature for each day since 1979.

On Monday, July 3, this curve reached a high of 17.01 degrees Celsius (62.62 degrees Fahrenheit). That record was broken on Tuesday with 17.18C (62.92F), and again on Thursday with 17.23C (63.01F).

The European climate change service Copernicus, which has a similar tool, later confirmed Monday and Tuesday’s records, albeit with slightly different figures of 16.88C (62.38F) and 17.03 (62.65F) respectively.

How do they arrive at their figures?

Estimates are produced through a combination of actual temperature measurements from ground stations, satellites and more with computer modeling.

The two tools are conceptually similar but differ in exact sources and methods, leading to slightly different results.

The University of Maine relies on public model output data produced by the US National Oceanic and Atmospheric Administration (NOAA) for forecasts.

NOAA, for its part, said that although it was recording record warm surface temperatures in many locations around the world, it could not “validate the methodology or the conclusion of the University of Maine’s analysis.”

NOAA guarantees its own monthly and annual temperature reports.

The fact that both results converge is reassuring, Zeke Hausfather, a climate scientist at Berkeley Earth, told AFP.

The European instrument is considered “very state-of-the-art” by the wider community, he added.

What are the limits?

“These are estimates, unofficial data,” University of Maine climate scientist Sean Birkel, who developed the Climate Reanalyzer, told AFP.

“The greatest emphasis should be placed on an annual and monthly time scale,” he added, with these reports subject to greater scrutiny and scrutiny than is possible for daily records that rely on near real-time information.

On Thursday, Copernicus separately released its analysis of the past month, announcing it was the warmest June on record. A similar monthly report from NOAA is expected next week.

These reports are based “solely on observations” from land and sea and collect much more data, Hausfather explained.

In general, climate experts prefer to focus on long-term trends and changes in order to eliminate merely weather-related variations.

Also, the concept of global average temperature is a bit abstract and not necessarily that meaningful to the general public.

“Nobody lives on the global average,” Hausfather said.

What is the value of daily record estimates?

Despite these limitations, the value of the daily records is that “we can begin to identify extreme events,” which could have climatic significance, Birkel said.

Although temperature on the daily timescale is meteorological, not climate, adding 40-year data provides important climate context, he says.

“These interim records provide another piece of evidence of changes in the global climate pattern due to climate change and the evolution of the El Nino episode,” said Omar Baddour, head of climate monitoring at the World Meteorological Organization.

“I think this is a sign that we are heading for a very warm period. June was the warmest June on record by quite a large margin,” Hausfather said. “At this point, it seems increasingly likely that 2023 as a whole will be the warmest year since records began in the mid-1800s.”

Agence France-Presse