Following the hottest June on record and a series of extreme weather events, including heatwaves in Europe, North America and Asia, and wildfires in Canada and Greece, ERA5 data from the Copernicus Climate Change Service (C3S*) show that July 2023 was the hottest month on record globally and broke several records within the month.
Global daily surface air temperature (°C) from 1 January 1940 to 31 July 2023, plotted as time series for each year. 2023 and 2016 are shown with thick lines shaded in bright red and dark red, respectively. Other years are shown with thin lines and shaded according to the decade, from blue (1940s) to brick red (2020s). The dotted line and grey envelope represent the 1.5°C threshold above preindustrial level (1850–1900) and its uncertainty. Data: ERA5. Credit: C3S/ECMWF.
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The month started with the daily global mean surface air temperature record being broken on four days in a row, from 3-6 July. All days throughout the rest of July were hotter than the previous record of 16.80°C, set on 13 August 2016, making the 29 days from 3-31 July the hottest 29 days on record. The hottest day was 6 July, when the global average temperature reached 17.08°C, and the values recorded on 5 and 7 July were within 0.01°C of this. During the first and third weeks of the month, temperatures also temporarily exceeded the 1.5°C threshold above preindustrial level – a limit set in the Paris Agreement, the first time this has happened during July.
As anticipated in a C3S press release on 27 July, C3S data now confirm that July 2023 has been the hottest July and hottest month in the ERA5 data record, which goes back to 1940 (See Supplementary Information section 2). The monthly average temperature was 16.95°C, well above the previous record of July 2019 (16.63°C) and virtually identical to our best estimate of the 1.5°C warming above preindustrial level for July (16.96°C).
Globally averaged surface air temperature for all months of July from 1940 to 2023. Shades of blue indicate cooler-than-average years, while shades of red show years that were warmer than average. Data: ERA5. Credit: C3S/ECMWF.
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Contributing to the exceptionally warm July for the globe as a whole is a long period of unusually high sea surface temperatures (SSTs). Since April, the global average daily SST has remained at record values for the time of year. From mid-May onwards, global SSTs values have reached unprecedented levels for the time of year. According to ERA5 data, on 31 July, the daily SST value reached a record high of 20.96°C, 0.01°C above the previous highest value ever recorded, of 20.95°C on 29 March 2016. Further analysis of record high SSTs in July 2023 can be found in a C3S web article.
Daily global sea surface temperature (°C) averaged over the 60°S–60°N domain plotted as a time series for each year from 1 January 1979 to 31 July 2023. The years 2023 and 2016 are shown with thick lines shaded in bright red and dark red, respectively. Other years are shown with thin lines and shaded according to the decade, from blue (1970s) to brick red (2020s). Data: ERA5. Credit: C3S/ECMWF.
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Carlo Buontempo, Director of C3S, comments: “Record-breaking temperatures are part of the trend of drastic increases in global temperatures. Anthropogenic emissions are ultimately the main driver of these rising temperatures”. He added, “July’s record is unlikely to remain isolated this year, C3S’ seasonal forecasts indicate that over land areas temperatures are likely to be well above average.”
“The extreme weather which has affected many millions of people in July is unfortunately the harsh reality of climate change and a foretaste of the future,” said World Meteorological Organization’s Secretary-General Prof. Petteri Taalas. “The need to reduce greenhouse gas emissions is more urgent than ever before. Climate action is not a luxury but a must.” Since April, the global average daily sea surface temperature has remained at record values for the time of year.
*C3S is implemented by the European Centre for Medium–Range Weather Forecasts with funding from the European Commission.
- 1. Highest daily global mean surface air temperatures on record
According to the ERA5 dataset, all days since 3 July have been hotter than the previous record of 16.80°C, from 13 August 2016.
Ranking of the top 40 warmest days in the ERA5 dataset based on globally averaged surface air temperature. Days in July 2023 are highlighted in bold. Data: ERA5. Credit: C3S/ECMWF.
- 2. Highest monthly global mean surface air temperature on record
The ranking of the 30 warmest months globally in the ERA5 dataset highlights how much warmer July 2023 was relative to the previous warmest month (July 2019).
- 3. Global mean temperature temporarily exceeded the 1.5° C threshold
The 1.5°C warming threshold above preindustrial level (1850–1900) is shown in the first figure of this article. In this figure, the dashed line represents the best estimate of the threshold while the grey envelope represents the uncertainty range around this estimate. The methodology used to produce daily estimates of the 1.5°C threshold and its uncertainty is outlined in a C3S article and a C3S About the data and analysis webpage.
According to ERA5 data, the daily global mean surface air temperature temporarily surpassed the best-estimate line once from 3 to 12 July and then again from 17 to 22 July. While the threshold had been previously exceeded in other months (most notably during winter 2015-2016 and spring 2016), this was the first time the threshold was exceeded in July. This was also the case in early June 2023 when the daily global temperature rose above the threshold for the first time during that month.
- 4. New national temperature records
National meteorological and hydrological services have reported a number of daily and station temperature records and are responsible for verifying any new national temperature records. Thus, China set a new national temperature record of 52.2°C on 16 July (Turpan city in China's Xinjiang province), according to the China Meteorological Administration. WMO’s provisional State of the Global Climate 2023 report, which will be presented to COP28 in December, will incorporate details of new national temperature records.
The temperature record for continental Europe of 48.8°C (119.8°F), measured in Sicily on 11 August 2021, was not broken during the July heatwaves, according to provisional information.
Temperature records in the United States of America are maintained by the US National Oceanic and Atmospheric Administration’s National Centers for Environmental Information.