First Three Weeks of July 2023 Warmest on Record, Breaking Global Temperature Records
The high ocean surface temperatures are coinciding with the development of El Niño conditions, a period of warmer-than-average SSTs in the tropical Pacific. Declared by the WMO on 4 July, this naturally occurring climate pattern leads to higher likelihood of extreme heat across many regions and in the ocean. Alongside this are continuing record high SSTs in the North Atlantic Ocean. In June, average SSTs across the whole North Atlantic were there warmest in the ERA5 record for the time for year by an average of 0.91°C.
“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.
Once ERA5 data for the whole month of July are available, they will be published together with an analysis of the temperatures in the C3S monthly climate bulletin around 8 August.
Technical Information
1. Highest daily global mean surface air temperatures on record
According to the ERA5 dataset, the global mean surface air temperature reached its highest daily value (17.08°C) on 6th July 2023. This value was within 0.01°C of the values recorded on 5th and 7th July. As shown in the chart above, all days since 3rd July have been hotter than the previous record of 16.80°C from 13th August 2016.
2. Highest daily global mean surface air temperatures on record
According to the ERA5 dataset, the global mean surface air temperature averaged for the first 23 days of July 2023 was 16.95°C. This is well above the 16.63°C recorded for the full month of July 2019, which is currently the warmest July and warmest month on record. At this stage, it is virtually certain that the full monthly average temperature for July 2023 will exceed that of July 2019 by a significant margin, making July 2023 the warmest July and warmest month on record.
Note that the current ranking for the warmest July from NOAA based on the NOAAGlobalTemp dataset differs from the ranking based on ERA5. NOAA puts July 2021 as the warmest July whereas it is July 2019 in ERA5 (ERA5 ranks July 2021 as the 4th warmest). This difference in rankings can be explained by differences in spatial coverage between the two datasets. While ERA5 provides temperature estimates over the entire globe, vast portions of the polar regions are not covered by NOAA’s dataset, as can be seen in this figure.
3. Hottest three weeks on record
The fact that the first 3 weeks of July (3rd to 23rd July) have been the 3 hottest weeks on record can be inferred from the chart of daily temperature time series included in the main body of the statement as well as from Figure S1 (the 21 days since 3rd July are the hottest 21 days in the ERA5 dataset). Furthermore, if we compare the average temperature for the first 23 days of July 2023 (for which we have data from ERA5) with the same average for all months of July going back to 1940, July 2023 clearly stands out as the warmest month on record, as shown in Figure S3.
4. 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 figure used in the main body of the statement. 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 3rd to 12th July and then again from 17th to 22nd 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 (as reported by C3S) when the daily global temperature rose above the threshold for the first time during that month (as reported in a C3S article).
5. Well above-average global sea surface temperatures
Daily sea surface temperatures (SSTs) averaged over the global extrapolar oceans (60°S–60°N) have stayed at record values for the time of year since April 2023. Most notably, since about mid-May, global SSTs have risen to unprecedented levels for the time of year. According to ERA5 data, on 19th July, the daily SST value reached 20.94°C, only 0.01°C shy of the highest value recorded for 29th March 2016 (20.95°C).
6. 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.
