Every month of 2023 has so far has exceeded 1.2°C above pre-industrial times [note], according to the HadCRUT dataset.

These high values are influenced by the ever-rising temperatures driven by human-induced climate change, as well as the influence of the developing El Niño – a cycle of natural climate variation in the tropical Pacific which imparts warmth from the ocean to the atmosphere which temporarily raises global temperature.

If the relatively high monthly temperatures recorded this year continue, the year is on track to exceed the annual temperature of 2016 – which is currently the warmest year in the HadCRUT series.

HadCRUT5 provides a series of global annual and monthly temperature values from January 1850. In the series the first time a monthly value of 1.2°C exceeded was February 1998 – also another El Niño year.

The record month in the series is February 2016, very marginally ahead of September 2023.

What does all of this mean for global temperature trends?

Colin Morice is a Met Office Climate Monitoring and Research Scientist.He said: “Human influence continues to be the dominant driver of increasing global temperatures. “2023 has been further influenced by the onset of El Niño in the tropical Pacific and has seen notably warm temperatures over land and sea. 2023 is on track to be the warmest year on record if the current conditions continue to the end of the year.”

The above graph shows the difference from the 1850-1900 (°C) average for each calendar month. 2023 months (January to September) are shown in red.

March 1990 was the first calendar month to exceed 1.0°C in the HadCRUT5 series. The last month to be below the long-term 1850 to 1900 average was October 1976.

The coldest calendar month in the series was January 1893 when temperatures were -0.62°C below average.

[Note]:  The global temperature for pre-industrial times is taken as an average of the period between 1850-1900.