The following is a summary of global temperature conditions in Berkeley Earth’s analysis of October 2024.
- Globally, October 2024 was nominally the second warmest October since records began in 1850, though by so small a margin as to be effectively tied with October 2023 as the warmest.
- Both the land and ocean averages were also nominally the second warmest for October, though the land-average was less than the record by a not significant margin.
- Particularly warm conditions were present in parts of Asia, North Africa, North America, South America, the Arctic, the western North Atlantic, and North Pacific.
- We estimate that 24 countries set new national monthly-average records for October.
- A weak La Niña is considered likely to develop before the end of 2024, but is not certain.
- The 12-month moving-average continues to be near record warm at 1.64 ± 0.07 °C (2.95 ± 0.13 °F) above the 1850-1900 average.
- 2024 is almost certain to be the warmest year on record.
Global Summary
Globally, October 2024 was nominally the second warmest October since directly measured instrumental records began in 1850. October 2024 was measured as 1.69 ± 0.09 °C (3.04 ± 0.17 °F) above the corresponding 1850-1900 average. This is 0.02 °C (0.04 °F) cooler than the October 2023 record, but as this difference is much smaller than the corresponding uncertainty, October 2024 was effectively tied with 2023 for the warmest October. All other October averages prior to 2023 have been at least 0.25 °C (0.45 °F) cooler.
Sixteen of the last seventeen months have set or effectively tied the monthly global temperature record, with only September 2024 serving as an exception. In addition, October 2024 marks the sixteenth consecutive month at least 1.5 °C warmer than the corresponding 1850 to 1900 monthly average.
One of the Paris Agreement ambitions has been to limit global warming to no more than 1.5 °C (2.7 °F) above the preindustrial baseline. That goal is defined in reference to the average climate over many years, so a year or two above 1.5 °C does not automatically mean that the target has been exceeded. However, recent anomalies above 1.5 °C are a sign that the Earth is getting close to that limit. It is likely that global warming will cause the long-term average to exceed 1.5 °C during the late 2020s or early 2030s unless significant reductions in greenhouse gas emissions are achieved soon.
The global mean temperature anomaly in October 2024 was significantly warmer than September 2024, though still cooler than January through April.
The 12-month moving average of global mean temperature now stands at 1.64 ± 0.07 °C (2.95 ± 0.13 °F) above the 1850-1900 average. We are likely at or near the peak for this warming event, as relative cooling is expected soon following the recent end of El Niño.
Compared to the long-term trend, the current deviation is one of the largest on record. Other recent large El Niño events, such as 2016 and 1998, produced somewhat smaller deviations above trend. Only the 1878/88 Super El Niño clearly presented a larger deviation above the trend line than the current event.
Spatial Variation
October 2024 continues the ongoing pattern of widespread warmth, with a few important exceptions. Particularly warm conditions were present in parts of Asia, North Africa, North America, South America, the Arctic, the western North Atlantic, and North Pacific.
We estimate that 7.2% of the Earth’s surface experienced their locally warmest October average (including 7.6% of land areas), and 85% of the Earth’s surface was significantly warm when compared to their local average during the period 1951 to 1980. By contrast, none of the Earth’s surface had their locally coldest October.
The El Niño event in the equatorial Pacific ended in June with sea surface temperatures falling below the El Niño threshold. The now-ended El Niño was officially declared by NOAA in early June 2023 and thus lasted about a year. Conditions in the equatorial Pacific are currently neutral. As discussed below, a weak La Niña is now expected to develop soon which will bring with it some relative cooling. The initial phase of this development is visible near South America in the equatorial Pacific, but remains weak and unconsolidated.
Over land regions, 2024 was nominally the second warmest October ever observed. The land average was 2.47 ± 0.20 °C (4.44 ± 0.35 °F) above the 1850 to 1900 average. This was cooler than the previous October record, set in 2023, by 0.08 °C (0.14 °F). Given the margin of uncertainty, October 2023 and 2024 can also be regarded as effectively tied in the land-average.
In total, we estimate that 24 countries had their warmest national-average October on record, these were:
Algeria, Antigua and Barbuda, Argentina, Chile, Cuba, Djibouti, Dominica, East Timor, Eritrea, Ethiopia, Federated States of Micronesia, Jamaica, Japan, Libya, Mexico, Nepal, Pakistan, Palau, Saint Kitts and Nevis, Seychelles, Solomon Islands, Somalia, United States of America, and Yemen
In addition, North America set a continent-wide record average for October.
October 2024 was the second warmest October in the ocean average behind only October 2023. The ocean average temperature in October 2024 was recorded as 1.10 ± 0.07 °C (1.99 ± 0.12 °F) above the 1850 to 1900 average.
The ocean temperature anomaly for October is slightly cooler than September, and the coolest month in over a year, as El Niño related warmth appears to be dissipating.
According to the European ERA5, daily global ocean average temperatures are now somewhat below the records set during the same days of the year in 2023. The oceanic warmth over the last year is due primarily to the combination of El Niño and extremely unusual warmth in the Atlantic. As El Niño has now ended, it is likely that the daily ocean average temperatures will continue lower than during 2023 and remain somewhat below 2023 for the rest of the year. Even so, ocean averages during the rest of 2024 appear likely to remain warmer than 2022 and all other previous years.
Considered in terms of the average over the last 12 months (November 2023 to October 2024), record warmth has been widespread, especially in the tropics. Large parts of South America, Africa, Southeast Asia, Europe, Canada, the Atlantic and Indian Ocean have had a 12-month average that is higher than any previous November to October period. No regions have significant relative cooling during this period.
Causes of Recent Warmth
The record warmth over the last 12 months has been due in large part to the El Niño condition in the Pacific, which is a form of natural variability associated with short-term swings in global temperature. This short-term change occurs alongside a background of longer-term man-made and other natural changes mostly also favoring warming during the present time.
Firstly, man-made global warming has been raising the Earth’s temperature by about 0.19 °C/decade (0.34 °F/decade). This is a direct consequence of the accumulation of additional greenhouse gases in the atmosphere, especially carbon dioxide. This is the primary factor responsible for long-term warming.
However, this global warming is a gradual process. It does not explain short-term spikes and fluctuations in Earth’s average temperature. The main reason for such spikes is internal variability in the distribution of heat and circulation of the oceans and atmosphere. The largest and most well-known form of short-term internal variability is the El Niño / La Niña cycle originating in the Pacific. During the El Niño phase, global average temperatures tend to be somewhat higher. As a result, record highs for global average temperature tend to be set during El Niño years. Last year, a new El Niño officially began in June after a multiple year period of La Niña. The rapid transition from a moderately strong La Niña to El Niño played a large role in the warming of 2023.
The recent El Niño has now ended, but there is a lag of a few months between the end of an El Niño and the dissipation of its effects on global temperature. As a result, October temperatures are likely still elevated, in part, due to the recently ended El Niño.
In addition to the natural El Niño variability, it is likely that other variability also contributed to recent high temperatures. One area of special interest is the Atlantic Ocean. The Northern Atlantic was persistently warm during the second half of 2023 and remains warm in October, with some regions continuing to set records. In early 2024, significant warmth also expanded in the Southern Atlantic, though this has since declined. If these changes were entirely natural, the warming spike in the North Atlantic would be rare. However, in previous discussions, we noted that warm anomalies in the North Atlantic are likely to be combination of natural variability and man-made regional warming due to new marine shipping regulations that abruptly reduced maritime sulfur aerosol pollution by ~85%.
The combination of global warming and El Niño are the primary factors responsible for the recent high global average temperature. However, other factors may also be playing a role. In particular, the evolution of oceanic heatwaves in the Atlantic and other areas have played a large role in determining the outlook for 2024.
El Niño / La Niña Outlook
June 2024 saw the end of the recent El Niño event. Conditions in October 2024 are in the neutral regime with continued concern for a possible near-future La Niña event. The recently ended El Niño began in mid 2023 and peaked late in 2023 as roughly the 3rd strongest event of the last 30 years. It has undoubtedly helped to boost global average temperatures over the last 12 months.
Due to the lag between changes in El Niño condition and its full impact being felt on global temperatures, it is plausible that the El Niño will have had a greater impact on global temperatures in 2024 than it did in 2023.
It is now considered likely that a weak La Niña event will soon emerge, this would generate moderately cooler global-average conditions late in 2024 and likely reduce temperatures in 2025 as well. However, it is also possible that the Pacific remains neutral thorough the end of 2024. The possibility of entirely avoiding a La Niña event was considered low just a few months ago, but now has a roughly 25% chance. If a La Niña develops, it would almost certainly ensure than 2025 is cooler than 2024.
Rest of 2024
With ten months completed, 2024 will almost certainly be the warmest year since instrumental measurements began, moderately exceeding the record set in 2023. The first ten months of 2024 started with many large anomalies, though this is expected to cool somewhat at the end of 2024. The El Niño that began in 2023 provided significant warmth for both 2023 and 2024. It is typically true that the second year after an El Niño emerges is warmer than the first, though that is not guaranteed.
The statistical approach that we use, looking at conditions in recent months, now believes that 2024 has a >99% chance of being warmer than 2023, making this outcome almost certain. The ultimate annual average will still somewhat depend on the magnitude and timing of a possible La Niña at the end of 2024, but such an event is expected to be too late and too weak to prevent 2024 from becoming the newest record warm year.
Estimated Probability of 2024 Annual Average final rankings:
- 1st – >99%
- 2nd – <1%
This forecast probability of record warmth is substantially increased from the approximately 50-60% chance previously estimated in January-April, but only slightly changed from the 92% chance of a record estimated in June and the 96% chance estimated in July.
Individually, we estimate an >99% chance that 2024 has the warmest land-only average measured since 1850. Further, we estimate a >99% chance that 2024 has the warmest ocean-only average. In both cases, the current record was set in 2023.
We also consider it almost certain that 2024 will have an annual-average temperature anomaly more than 1.5 °C (2.7 °F) above our 1850-1900 average. The annual average in 2023 slightly exceeded the 1.5 °C (2.7 °F) threshold in our dataset, and this is almost certain to occur again in 2024.
Though the IPCC has set a goal to limit global warming to no more than 1.5 °C above the pre-industrial, it must be noted that this goal refers to the long-term average temperature. A couple years warmer than 1.5 °C does not automatically mean that the goal has been exceeded. However, breaching 1.5 °C does serve to emphasize how little time remains to meet this target. Unless sharp reductions in man-made greenhouse gas emissions occur soon, the long-term average is likely to pass 1.5 °C during the late 2020s or early 2030s.
