The following is a summary of global temperature conditions in Berkeley Earth’s analysis of July 2023.
- Globally, July 2023 was the warmest July — and the warmest month of any kind — since records began in 1850.
- The previous record for warmest month was broken by a large margin.
- Both land and ocean individually also set new records for the warmest July, with the ocean showing a particularly large margin over the previous record.
- The combined effect of global warming and a strengthening El Niño primarily helped to produce this record, but were likely also aided by additional warmth from other factors discussed below.
- Particularly warm conditions occurred in the North Atlantic, Eastern Equatorial Pacific, Northern South America, Northern Africa, Mexico, and Northern Canada.
- Unusually cool conditions were present in parts of Antarctica.
- The North Atlantic reached all-time record warmth by a large margin.
- El Niño continues to strengthen and is expected to continue into next year.
- 2023 is now virtually certain to become a new record warm year (99% chance).
Global Summary
Globally, July 2023 was the warmest July — and the warmest month of any kind — since directly measured instrumental records began in 1850, breaking the record previously set in July 2019. In addition, this July exceeded the previous record by 0.26 °C (0.47 °F), a surprisingly large margin, well outside the margin of uncertainty.
The global mean temperature in July 2023 was 1.54 ± 0.09 °C (2.77 ± 0.16 °F) above the 1850 to 1900 average, which is frequently used as a benchmark for the preindustrial period.
This is the 11th time in the Berkeley Earth analysis that an individual month has exceed 1.5 °C (2.7 °F) over the preindustrial benchmark. All other such occurrences have happened during December to April, i.e. during the traditionally more variable months of Northern Hemisphere winter and spring. This is the first time that a 1.5 °C anomaly has occurred during Northern Hemisphere summer. Such a temperature excess coming during the already hot summer months is more likely to lead to extreme temperatures and all-time records than if it had occurred at other times of the year.
One of the Paris Agreement goals is 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 of climate over many years, so a few individual months above 1.5 °C do not automatically mean that the target has been exceeded. However, isolated 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 2030s unless significant reductions in greenhouse gas emissions are achieved soon.
Earth’s average temperature in July 2023 was estimated at 17.2 °C (63.0 °F). This the highest temperature on record for any month of the year, and the first monthly average ever observed over 17.0 °C (62.6 °F).
The Earth’s average temperature has a seasonal cycle that peaks during Northern Hemisphere summer. This is because land temperatures experience greater seasonal temperature changes, and there is far more land in the Northern Hemisphere than the Southern Hemisphere.
The global mean temperature anomaly in July 2023 exhibited an increase relative to June 2023, rising more than 0.08 °C (0.14 °F). Such an increase is unsurprising during the strengthening phase of a new El Niño event.
Though setting a record for July, the temperature anomaly in July was not as large as in March 2023. Northern Hemisphere summer months are less variable than Northern winter and early spring months, so it is normal to see larger anomalies during Northern winter. That said, this July’s anomaly is the most extreme ever observed during Northern summer.
Temperatures in July were above the long-term trend line, but recent fluctuations can still be considered consistent with natural variability within the ongoing pattern of global warming.
Spatial Variation
July 2023 continues the ongoing pattern of widespread warmth, though with a few exceptions. Particularly warm conditions were present in the North Atlantic, Eastern Equatorial Pacific, Northern South America, Northern Africa, Mexico, and Northern Canada.
Particularly cool conditions were present in parts of Antarctica.
We estimate that 10.8% of the Earth’s surface experienced their locally warmest July average, and 84% of the Earth’s surface was significantly warm when compared to their local average during the period 1951 to 1980. In addition, 0.01% of the Earth’s surface had their locally coldest July.
The Equatorial Pacific in July is showing strengthening El Niño conditions. Above average temperatures are present in much of the Pacific, with record warm temperatures for this time of year developing in some areas of the Eastern Equatorial Pacific. An El Niño condition was officially declared by NOAA in early June.
Over land regions, 2023 was also the warmest July ever observed, and warmed modestly relative to June. The land average was 1.97 ± 0.13 °C (3.54 ± 0.23 °F) above the 1850 to 1900 average. This beats the previous record for July, which was jointly held by 2021 and 2022.
July 2023 was also the warmest July in the oceans, recorded as 1.22 ± 0.11 °C (2.19 ± 0.19 °F) above the 1850 to 1900 average. This beats the previous record for July, which occurred in 2019, by a large margin.
The temperature anomaly for July is also — by far — the largest ocean-average temperature anomaly observed in instrumental measurements for any month of the year. This surpasses the previous record set last month.
Causes of Recent Warmth
This month’s record, and the longer recent period of warmth, are driven by a collection of several man-made and natural factors acting together.
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, 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 slightly higher. As a result, record highs for global average temperature tend to be set during El Niño years. This year, a new El Niño officially began in June after a multiple year period of La Niña.
These two factors, global warming and El Niño, are the primary factors responsible for the present high temperatures. However, three additional factors are worth highlighting.
Firstly, the solar activity cycle is still ramping up towards a peak in 2024 or 2025. Such cycles are a natural part of the dynamics of the sun and follow an ~11-year pattern. During the active phase, the associated modest increase in solar radiation can lead to slightly warmer conditions.
Further, the massive eruption of Hunga Tonga–Hunga Haʻapai in January 2022 may be contributing to current warming and other weather effects. Unlike most volcanoes, the eruption of Hunga Tonga was rich in water vapor and low in sulfur. Usually, a large eruption results in a temporary period of cooling due to excess sulfur in the atmosphere, but the Hunga Tonga eruption may have contributed warming instead due to its large water vapor contribution.
Hunga Tonga injected ~150 million tonnes of water vapor into the stratosphere. This is small compared to the atmosphere’s total water vapor content, but unusually large for the stratosphere. This eruption raised the water vapor content of the upper atmosphere by ~15%. This plume, which will take at least several years to dissipate, has been estimated by Jenkins et al. to warm the Earth by about +0.035 °C (0.063 °F). However, the magnitude of warming remains highly uncertain as does the possibility of more impactful regional variations.
Lastly, in 2020, the International Maritime Organization adopted new rules on the allowable sulfur content in marine fuels. These new rules, adopted to reduce air pollution and protect human health, had the effect of cutting the sulfur emissions from marine shipping by 85% almost overnight. Because sulfur aerosols have short-lived cooling effect, the removal of these aerosols likely warmed regions with heavy shipping activity. This is discussed further in the next section on the North Atlantic. For the global average, the effect of removing marine aerosols may have added about 0.02 °C (0.03 °F).
While the primary drivers of recent temperature change are global warming and El Niño, those additional factors may also be acting in concert to add a bit more warmth to the global average temperature and create the present record warm conditions.
North Atlantic
The North Atlantic Ocean has been record warm in June and July 2023, beating the previous July by an enormously large margin (more than 0.6 °C/1.1 °F), and contributing substantially to the record global average in July. The present anomaly developed rapidly, increasing more than 0.35 °C (0.6 °F) since May, and is highly unusual. No previous July average in the North Atlantic has deviated this far from the long-term trend.
We believe that the warmth in North Atlantic is due to a combination of extreme internal variability and man-made factors. On the internal side, we have the early stages of El Niño, the low Saharan dust discussed last month, and an unusual high pressure system in the northwest portion of the North Atlantic in July. The man-made factors include global warming, but also the recent reduction in marine sulfur pollution.
In 2020, new international rules governing heavy fuels for marine shipping abruptly reduced sulfur emissions from large ships by ~85%. This change was made to preserve human health, due to the toxic nature of sulfur aerosols. However, such aerosols also reflect sunlight, and as a result have a cooling effect. These sulfur aerosols are believed to have masked some of the effects of global warming, especially in the heavily trafficked North Pacific and North Atlantic regions. Because marine aerosols are short-lived, there impact is largest close to where they are released, including areas with large number of cargo ships, such as the North Atlantic. An analysis suggests that removing the sulfur aerosols may have added ~0.25 °C (~0.5 °F) to the North Atlantic region.
Marine sulfur reduction would not explain all of the present North Atlantic spike, but may have added to its severity. The current North Atlantic temperature anomaly is much further from the trend line than any previously observed North Atlantic anomaly. However, if we assume that approximately 1/3 of that warming was due to the recent reduction of marine sulfur emissions, then the remaining warming spike would be consistent with a large — but not unprecedented — natural variation from the trend. Thus we consider it plausible that the North Atlantic warmth is due to a combination of large natural variability (contributing about 2/3) and the man-made reduction in marine sulfur pollution (contributing about 1/3).
The reduction in marine sulfur aerosols from shipping, though regionally significant in areas with high shipping volumes, has likely only added a few hundredths of a degree to the global average temperature.
Antarctica
Another feature of the temperature distribution in July 2023 was unseasonably warm conditions around the periphery of Antarctica. Though Antarctica remains well-below freezing, and is in the middle of Southern Hemisphere Winter, temperatures in July were not as cold as is typically expected. The sea ice around Antarctica is refreezing far more slowly than in any previously observed year in the satellite record (starting in 1979), running roughly a month behind the typical schedule. Recently led to the largest Antarctic sea ice anomaly on record.
It is unclear to what extent the unusual evolution of Antarctic sea ice this year may be related to climate change or to other unusual factors such as the Hunga Tonga eruption.
El Niño Outlook
July 2023 saw the strengthening of the new El Niño that began in July. The current CPC/IRI analysis suggests that El Niño conditions will persist for the foreseeable future, at least until next year. Models currently disagree on the likely intensity of the current El Niño, with some models predicting a very strong event, while others are more mild or moderate. The intensifying warm pool in the Pacific will likely give us a clearer idea of what to expect during the next month or two.
El Niño is likely to moderately boost global average temperatures during the rest of 2023 and into 2024. Due to the lag between the development of El Niño and its full impact being felt on global temperatures, it is likely that the current El Niño will have a greater impact on global temperatures in 2024 than it does in 2023. If other factors remain warm, such as the North Atlantic, that raises the possibility that the annual average in 2024 could be even warmer than 2023.
Year to Date
This year began with a January that was similar to January in 2021 and 2022. However, with the end of La Niña, temperatures diverged markedly in February and March, and are now considerably warmer than in 2021 or 2022. With the development of El Niño and record warmth in the North Atlantic, July warmed significantly relative to May and June.
So far, only June and July have set records for monthly average temperature in 2023, though they have done so by large margins.
The most significant spatial features of year-to-date temperatures are the shift towards El Niño, warmth across much of the northern mid-latitudes, cooling in the Western USA, and several ocean hotspots. Year-to-date, 7.4% of the Earth’s surface has experienced average temperatures that are a local record high. In addition, none of the Earth’s surface has been record cold year-to-date.
Rest of 2023
2023 is on pace to be the warmest year yet observed since instrumental measurements began. The surprisingly strong warming in June and July 2023, combined with the likelihood of a strong El Niño event, have increased the forecast for the rest of 2023. The statistical approach that we use, looking at conditions in recent months, now believes that 2023 is virtually certain to become the warmest year on record (99% chance).
This forecast probability is higher than last month’s report, when the likelihood of a record warm year was estimated at 81%. It also represents a large change from the forecast at the beginning of the year (before the development of El Niño), when only a 14% chance of a record 2023 was estimated.
In this assessment, we also find it nearly certain that 2023 will result in the warmest ocean-average year ever measured (>99% likelihood), boosted by global warming and the presence of El Niño. However, it remains unlikely that the land average will set an annual average record in 2023, with a 3rd place finish being the most likely outcome.
Even with surprising recent warmth and the potential for a strong El Niño, the annual average temperature for 2023 is still unlikely to exceed 1.5 °C (2.7 °F) above the preindustrial benchmark. However, the model has increased the odds of such an event to 20%.
[Note: Because these predictions are based on the statistical relationships observed in past years, they expect June and July to serve as strong predictors of the rest of the year. Given the unusual conditions currently present in the North Atlantic and elsewhere, these predictions may be less accurate than we’d typically expect.]
Because of the lag between the development of an El Niño and its maximum impact on global temperatures, an El Niño that develops during 2023 is likely to have an even larger warming effect on global mean temperature in 2024 than 2023.
Likelihood of final 2023 ranking:
- 1st place (99 %)
- 2nd or 3rd place (1 %)
- Top 3 overall (> 99 %)
