Yet another unwanted temperature record may have been set in 2023. According to a preliminary estimate, the global average surface temperature on 17 November was more than 2°C above pre-industrial levels for the first time.
“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,” tweeted Sam Burgess at the Copernicus Climate Change Service. The finding is provisional, she said.
While exceeding this milestone on one day shows how rapidly the planet is warming as a result of rising greenhouse gas levels, it doesn’t mean that the 2°C warming limit has been breached.
“Hopefully it will prove transitory, but it’s a worrying sign,” tweeted Zeke Hausfather of Berkeley Earth.
The Paris Agreement established a goal to limit the increase in the global average temperature to “well below 2°C above pre-industrial levels” and pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels. It didn’t clearly define what was meant by limiting warming to 1.5°C or 2°C above pre-industrial, but climate scientists generally regard it as being when the long-term average exceeds 1.5°C or 2°C compared with the late 19th century. The nature of averages means it will not be clear when the world passes these limits until several years afterwards.
The definition of pre-industrial matters too. Human-caused warming actually began as early as the mid-18th century, according to Michael Mann at the University of Pennsylvania, and had already raised temperatures by 0.3°C before the late 19th century.
2023 has been the hottest year in recorded history so far, with numerous maximum temperature records smashed around the world and yet more extreme weather. It could be the first year with an average temperature more than 1.5°C above pre-industrial times.
2024 could be even hotter, in part because the climate has entered an El Niño phase, which transfers more ocean heat into the atmosphere.
However, the long-term global average is not expected to exceed 1.5°C until the early 2030s, according to the last report by the Intergovernmental Panel on Climate Change (IPCC).
Preventing this would require limiting future emissions to less than 220 gigatonnes of carbon dioxide, an almost impossible goal given that annual global emissions are around 40 gigatonnes and still rising.
The world is currently on course to pass 2°C of warming in the 2040s or 2050s, according to the IPCC.
Global warming does appear to be accelerating, according to Hausfather, but is still in line with the projections of global climate models.