As the world gears up for COP28, there is alarming data on the horizon. The year 2023 is on course to possibly becoming the warmest year in recorded history, with temperatures nearing 1.4°C above the pre-industrial era average.
In September 2023, global temperatures reached a record high. The average surface air temperature was 16.38°C, which is 0.93°C higher than the September average between 1991 and 2020. Moreover, it was 0.5°C warmer than the earlier record set in September 2020.
Chart 1 | The chart shows the globally averaged surface air temperature anomalies relative to 1991–2020 for each September from 1940 to 2023.
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The month of September 2023 was approximately 1.75°C above the average temperature of September during the 1850-1900 span, which is considered the pre-industrial benchmark.
From January to September 2023, the global surface air temperature was 0.52°C above the 1991-2020 average and 0.05°C higher than the same period in 2016, the warmest year. During this time frame in 2023, the world’s average temperature was 1.40°C higher than the baseline period of 1850-1900.
According to the Copernicus Climate Bulletin, in September 2023, the majority of Europe experienced temperatures significantly higher than the average from 1991 to 2020. A region stretching from France to Finland and extending to north-western Russia reported its hottest September ever. Notably, both Belgium and the U.K. faced unparalleled heatwave conditions at the start of the month.
Chart 2 | The chart shows the average global surface air temperatures for the 30 warmest months between 1940 and 2023, arranged in ascending order. The temperatures for June, July, August, and September of 2023 are highlighted.
The hottest-ever September of 2023 followed the warmest-ever two months on record — July and August 2023 — when the global mean temperature reached monthly records of 16.95°C and 16.82, respectively. The notable increase in these two months, especially compared to the July 2019 record of 16.63°C, is evident in Chart 2. Moreover, September 2023 is the sole September represented in this chart. The warmest September before 2023 recorded an average surface air temperature 15.88°C, which is not high enough to be included in chart 2.
Chart 3 | The chart shows the global daily surface air temperature (°C) from January 1, 1940 to September 30, 2023, plotted as a time series for each year. The line for 2023 is highlighted.
Other years are marked in grey. The thick black line represents the 1.5°C threshold above pre-industrial levels. For more than 80 days in 2023, the global temperature was at least 1.5° higher than pre-industrial levels. The year 2023 holds the record for the highest number of such days.
In a worrying update, the extent of sea ice has stayed at very low levels for this time of the year in the Antarctic region. Sea ice extent refers to the total area of an ocean where there is at least some sea ice present. Satellite records for September reveal that both daily and monthly extents have plummeted to their lowest annual peaks, with the monthly extent dropping 9% below the norm.
Chart 4 | The chart shows the daily Antarctic sea ice extent from 1979 to September 2023. The year 2023 is highlighted; the median for 1991–2020 is shown as a dotted line.
Meanwhile, the monthly average Arctic sea ice extent in September 2023 reached its annual minimum of 4.8 million km2, about 1.1 million km2 (or 18%) below the 1991-2020 average for September. This value is the fifth lowest in the satellite data record.
Source: European Union’s Copernicus Climate Change Service
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