Record-breaking! July 21 is the hottest day on record! Next...

Compiled by: Gong Zixin

According to data from the Copernicus Climate Change Service

July 21st just passed

Earth experiences hottest day on record

The global average daily temperature reached 17.09℃

Breaking the previous record of 17.08°C set on July 6, 2023

Record high

According to preliminary data released by the Copernicus Climate Change Service on July 23, July 21 was the hottest day since 1940, with an error of only 0.01°C. Although this is almost the same as the previous record, what is really striking is the difference between the temperature since July 2023 and previous years.

Global average daily surface temperature for 2024 (red), 2023 (orange), and all years from 1940 to 2022 (grey). Data for 21 July 2024 are preliminary.
Prior to July 2023, the global daily average temperature record was 16.8°C on August 13, 2016. Since July 3, 2023, 57 days have exceeded the previous record, distributed between July and August 2023, and in June and July so far in 2024.

Carlo Buontempo, Director of the Copernicus Climate Change Service, said: “A new record for the global average daily temperature was recorded on 21 July. What is truly striking is the magnitude of the difference between the temperatures of the past 13 months and the previous temperature record. We are in real uncharted territory here and as the climate continues to warm we will certainly see new records broken in the coming months and years.”

An analysis of the years with the highest annual daily temperatures globally shows that the annual maximum temperatures in 2023 and 2024 will be significantly higher than in previous years.

Another sign of a global warming trend is that the 10 years with the warmest daily average temperatures were the most recent 10 years, from 2015 to 2024.

The difference between the decade’s lowest-ranked average daily temperature (2015) and the highest average daily temperature before 2023 (August 13, 2016) is 0.2°C. The jump from the 2016 record to 2023/2024 is about 0.3°C, highlighting just how warm 2023 and 2024 are (see figure below).

Global maximum annual daily average temperatures recorded over the past 50 years (1974 - 2024). The 10 highest annual maximum temperatures are highlighted in dark red. Data for 2024 is current up to 21 July 2024.

What caused the new record global average temperature?

Global average temperatures tend to reach their annual peak between late June and early August, coinciding with the Northern Hemisphere summer. This is because the seasonal patterns of the Northern Hemisphere drive the overall global temperature. During the Northern Hemisphere summer months, large tracts of the Northern Hemisphere's landmass warm faster than the Southern Hemisphere's oceans cool.

Average global temperatures have approached all-time highs in recent days, just below 2023 levels, after more than a year of record-high temperatures.

The analysis showed that the sudden rise in global average daily temperatures was associated with much higher-than-average temperatures over much of Antarctica. Such large anomalies are not uncommon during the Antarctic winter, which also led to the record global temperatures in early July 2023.

What’s more, Antarctic sea ice extent was nearly as low as it was this time last year, leading to well-above-average temperatures in parts of the Southern Ocean.

Surface air temperature anomaly on 21 July 2024 relative to the 1991–2020 reference period mean.

Is this expected?

Since global average temperatures were already close to record highs in the first half of July, close to what they would be at this time in 2023, and global average temperatures typically peak at this time of year, it is not entirely unexpected that we would see similar global average temperatures, even if slightly higher.

Will 2024 be the hottest year on record?

The ranking of 2024 will depend largely on the development and strength of the next phase of the El Niño Southern Oscillation (ENSO) (i.e. the timing and strength of La Niña development). So far, 2024 has been warm enough that it is likely to be warmer than 2023 throughout the year, but the unusual warmth of the last four months of 2023 makes it too early to predict which year will be warmer.