Earth likely briefly passed critical warming threshold on Friday and Saturday

The planet likely briefly exceeded a key warming threshold on Friday and Saturday for the first time since at least the beginning of instrument records, new data shows.

Driving the news: The indication that Friday and Saturday were the first two days on record to have a global average surface temperature above 2°C when compared with preindustrial levels, emerged first from a dataset maintained by the European Center for Medium-Range Weather Forecasts (ECMWF).

• "Our best estimate is that this was the first day when global temperature was more than 2°C above 1850-1900 (or pre-industrial) levels, at 2.06°C," Samantha Burgess, the deputy director of the Copernicus Climate Change Service stated on X, formerly known as Twitter, on Sunday.
• She also noted the Saturday record in a post on Monday, stating: "Now two Nov 2023 days where global temperature exceeded 2°C in ERA5."
• When compared with the 1991-2020 average, Friday's global mean was a record-setting 1.17°C (2.1°F) above average.
• In a post on X on Monday, the ECMWF found that Friday was a bit warmer, at 2.07°C above preindustrial levels, while Saturday reached an anomaly of 2.06°C.

Why it matters: A daily global average surface temperature climb to greater than 2°C above preindustrial levels indicates just how quickly the planet is warming, including some of the extremes that are now possible.

Yes, but: Breaching the 2-degree threshold for two days does not mean that the Paris Agreement's target of holding global warming to "well below" such a mark has been exceeded.

• The agreement refers to the long-term average over two or more decades rather than one day, month or even year.

Between the lines: The dataset that shows the record, known as ERA5, comes from a process known as reanalysis, in which a computer model uses surface temperature readings from land and ocean sources as well as algorithms to arrive in near time at an accurate global temperature reading for each day.

• The new record is considered provisional since it is subject to adjustment for accuracy. Subsequent information from other reanalysis sources and surface-based data sets and other reanalysis methods may confirm it or diverge slightly.

The big picture: News of the record is in keeping with the record-shattering year so far.

• This year is on track to be the hottest on record globally in all surface weather datasets and saw both the hottest month on record (September) but also the largest margin for any monthly record in history.
• Each month since May has set monthly global temperature records, and heat waves have scorched large parts of the globe, from the Southern U.S. to Africa, South America, China and Japan.
• Last summer, the global average surface temperature first rose into record territory and eclipsed the 1.5-degree Paris target. That caught some scientists off guard, and the failure of the planet to cool back down below all-time record territory has stood out.

• November, too, is now likely to be the hottest such month on record.

The intrigue: The 1.5 and 2-degree targets were set by political leaders, but scientific research bolsters the case that if warming were to exceed even the more stringent target, the likelihood of devastating and potentially irreversible climate calamities would increase dramatically.

• A report released last week shows the ways that climate change is already wreaking havoc on the U.S., for example.
• While human-caused climate change is viewed as the larger driver of the long-term increase in temperatures and record warmth this year, a strong El Niño event in the tropical Pacific Ocean is helping to pump added heat into the climate system.
• This is further increasing temperatures, easily vaulting them into record territory.

Of note: To keep tabs on the long term and when 1.5°C and 2°C may be reached for real, Copernicus has created an app that can be viewed here.

What's next: This record, like some others so far this year, is likely to be cited in the fraught negotiations at the COP28 climate summit in Dubai, which begins Nov. 30.

Go deeper... Climate change report: Heat-related deaths on track to rise 370% by mid-century

Editor's note: This article has been updated with the news of Saturday's global average temperature, a Copernicus ECMWF image and details of Copernicus' app.