On 21 July 2024, the daily global average temperature reached a new record high in the ERA5 dataset, at 17.09°C, slightly exceeding the previous record of 17.08°C from 6 July 2023.

Based on preliminary data released by C3S on 23 July, Sunday 21 July was the hottest day since at least 1940, by a small margin of 0.01ºC.

While it is almost indistinguishable from the previous record, what really stands out is the difference between the temperatures since July 2023 and all previous years.

The data can be explored in Climate Pulse, the C3S application that provides historical and near real-time temperature data from the ERA5 reanalysis dataset.

Before July 2023, the previous daily global average temperature record was 16.8°C, on 13 August 2016. Since 3 July 2023 there have been 57 days that have exceeded that previous record, distributed between July and August 2023, and during June and July so far in 2024.

According to C3S Director Carlo Buontempo: "On July 21st, C3S recorded a new record for the daily global mean temperature.  What is truly staggering is how large the difference is between the temperature of the last 13 months and the previous temperature records. We are now in truly uncharted territory and as the climate keeps warming, we are bound to see new records being broken in future months and years." 

Analysis of the years with the highest annual maximum daily global temperatures shows that both 2023 and 2024 have seen annual highs substantially above those recorded in previous years.

Another sign of the global warming trend is the fact that the ten years with the highest daily average temperatures are the last ten years, from 2015 to 2024.

The difference in the highest daily average temperature between the lowest ranked of those ten years (2015) and the previous record before 2023 (13 August 2016) was 0.2°C.

What caused this new record global average temperature?

The global average temperature tends to reach its 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 temperatures. The large land masses of the northern hemisphere warm up faster than the oceans of the southern hemisphere can cool down during the northern summer months.

The global average temperature was already at near-record levels in recent days, slightly below the levels of 2023, after being at record levels for the time of year for more than a year.

Our analysis suggests that the sudden rise in daily global average temperature is related to much above-average temperatures over large parts of Antarctica. Such large anomalies are not unusual during the Antarctic winter months, and also contributed to the record global temperatures in early July 2023.

Was this expected?

As the global average temperature was already at near-record levels during the first half of July, close to the temperatures seen at this time of year in 2023, and the global average temperature typically reaches its peak at this time of year, it is not completely unexpected that we are seeing a similar, if marginally higher, global average temperature.

Is 2024 likely to be the warmest year on record?

The ranking for 2024 will largely depend on the development and intensity of the next phase of the El Niño Southern Oscillation (ENSO) (i.e. when and how strongly La Niña develops).

To date, 2024 has been sufficiently warm for it to be quite possible that the full year will be warmer than 2023, but the exceptional warmth of the last four months of 2023 makes it too early to predict with confidence which year will be the warmer.

What was the previous record?

The previous highest daily global average temperature was 17.08°C, a record set on 6 July 2023 as part of a long streak of record-breaking daily global average temperatures in July and August 2023.

Prior to the long streak of record-breaking temperatures in July and August 2023, the highest daily global average temperature in the ERA5 dataset was 16.80°C, on 13 August 2016.