Global Temperature Report for 2024

Berkeley Earth, a California-based non-profit research organization, has been preparing independent analyses of global mean temperature changes since 2013. The following is our report on global mean temperature during 2024.

We conclude that 2024 was the warmest year on Earth since 1850, exceeding the previous record just set in 2023 by a clear and definitive margin. This period, since 1850, is the time when sufficient direct measurements from thermometers exist to create a purely instrumental estimate of changes in global mean temperature.

The last ten years have included all ten of the warmest years observed in the instrumental record.

The warming spike observed in 2023 and 2024 has been extreme and represents a larger than expected deviation from the previous warming trend. The spike has multiple causes, including both natural variability and man-made global warming from the accumulation of greenhouses gases; however, as discussed below, we believe additional factors are needed to explain the full magnitude of this event. Reductions in low cloud cover and man-made sulfur aerosol pollution are likely to have played a significant additional role in recent warming.

Over the previous 50 years, global warming has preceded in an almost linear fashion, consistent with an almost linear increase in the total greenhouse gas forcing. The warming spike in 2023/2024 suggests that the past warming rate is no longer a reliable predictor of the future, and additional factors have created conditions for faster warming, at least in the short-term.

The global annual average for 2024 in our dataset is estimated as 1.62 ± 0.06 °C (2.91 ± 0.11 °F) above the average during the period 1850 to 1900, which is traditionally used a reference for the pre-industrial period. This is first time Berkeley Earth has reported an annual average above 1.6 °C (2.9 °F), and the only second time that Berkeley Earth has reported any year exceeding the key 1.5 °C (2.7 °F) threshold, after slightly doing so in 2023. Due to uncertainties and differences in methodologies, other groups are expected to report 2024 as slightly cooler. The ECMWF’s Copernicus research service joins us in just barely exceeding 1.6 °C (2.9 °F), while other groups are somewhat cooler. The differences between Berkeley Earth’s analysis and that of other groups is discussed at the end of this report.

A goal of keeping global warming to no more than 1.5 °C (2.7 °F) above pre-industrial has been an intense focus of international attention. This goal is defined based on multi-decadal averages, and so a single year above 1.5 °C (2.7 °F) does not directly constitute a failure. However, recent warming trends and the lack of adequate mitigation measures make it clear that the 1.5 °C goal will not be met. The long-term average of global temperature is likely to effectively cross the 1.5 °C (2.7 °F) threshold in the next 5-10 years. While the 1.5 °C goal will not be met, urgent action is still needed to limit man-made climate change. Each increment of additional warming, e.g. 1.6 °C, 1.7 °C, etc., will lead to additional and compounding climate change impacts that can still be avoided if effective mitigation steps are made to reduce man-made greenhouse gas emissions.

During 2024, 24% of the Earth’s surface had a locally record warm annual average, including 32% of land areas and 21% of ocean areas. These areas coincided with a number of major population centers. We estimate that 3.3 billion people — 40% of Earth’s population — experienced a locally record warm annual average in 2024. This includes 2/3 of the population of China, and a majority of the populations of Brazil, Nigeria, Ethiopia, Mexico, 1/3 of the United States, and much of South and Central America, and Eastern Europe.

None of the Earth’s surface had a record cold annual average in 2024.

Due to natural cooling patterns that have recently begun in the oceans, it is expected that 2025 will be moderately cooler than 2024. The most likely outcome is that 2025 ranks as roughly the 3^rd warmest year since 1850, though warmer or cooler outcomes are also possible.

In addition, 2024 was notable for:

• New national record high annual averages for an estimated 104 countries, including Brazil, Canada, China, Greece, Malaysia, Mexico, and South Korea
• Record annual average warmth in both the land-average and ocean-average
• Record warmth in most ocean basins
• The end of the 2023/2024 El Niño and a likely transition to modestly cooler conditions in 2025.

Annual Temperature Anomaly

In Berkeley Earth’s analysis the global mean temperature in 2023 is estimated to have been 1.62 ± 0.06 °C (2.91 ± 0.11 °F) above the average temperature from 1850-1900, a period often used as a pre-industrial baseline for global temperature targets. This is ~0.08 °C (~0.14 °F) warmer than the previous record high observed in 2023. As a result, 2024 is the warmest year to have been directly observed using thermometer measurements, and stands out well-above all previous years.

Though the availability of thermometers limits direct measurements to the period since 1850, indirect evidence suggests that the Earth is currently at its warmest global average temperature for at least several thousand of years, and possibly the warmest since the last interglacial ~120,000 years ago.

The abrupt increase in temperatures from 2022 to 2024 is the largest two year increase since the 1870s.

This is the second time in Berkeley Earth’s analysis that an annual average temperature has exceeded the pre-industrial baseline period by more than 1.5 °C (2.7 °F), having previously done so by a small margin in 2023. It is the first time that an annual average has exceeded 1.6 °C (2.9 °F) in our analysis. As discussed at the end of this report, other research groups have slightly different estimates, some of which also cross these thresholds and others are slightly cooler.

Under the Paris Agreement, many countries have set an aspirational goal of limiting long-term global warming to no more than 1.5 °C (2.7 °F). That target is based on the state of the climate averaged over many years, so it is not automatically considered to have been breached by one or two years exceeding 1.5 °C of warming. However, it is clear that this 1.5 °C (2.7 °F) threshold is no longer avoidable and the long-term average of global warming will likely cross this threshold in the next 5-10 years. Urgent efforts to reduce greenhouse gas emissions would be needed to avoid even higher levels of warming, and the potential for even greater negative impacts. Every increment of warming will matter, so even after 1.5 °C is passed, continued efforts to avoid 1.6 °C, 1.7 °C, etc., will still be needed.

The last ten years stand out as the ten warmest years to have been directly observed.

The temperature uncertainties can be visualized using the schematic below where each year’s temperature estimate is represented by a distribution reflecting its uncertainty. In the analysis that Berkeley Earth conducts, the uncertainty on the mean temperature of a single year is approximately 0.03 °C (0.05 °F) for recent years. The global mean temperature in 2024 lies well above the previous record high set in 2023 and all other years.

The last ten years have been part of a period of significant warmth well above all previous years since 1850. This reflects the long-term trend towards man-made global warming.

Are these changes faster than expected?

Since 1970, global warming has proceeded at a roughly linear pace. This roughly linear pace has been consistent in both rate and magnitude with the expected effects of increasing greenhouse gases during this period.

However, the warming spike in 2023/2024 appears to have deviated significantly from the previous trend. If we were to assume that global warming was continuing at the same rate as during the 50-year period 1970-2019, then the 2023/2024 excursion would be by far the largest deviation from that trend, with only a roughly 1-in-100 chance of occurring solely due to natural variability.

While 1-in-100 chance events do sometimes occur, we consider it more likely that the recent rate of global warming has been larger than expected, exceeding both the previous trend and what would be expected when considering only the observed pattern of greenhouse gas emissions.

As discussed below, it appears that changes in low cloud cover and reductions in man-made aerosol pollution may be responsible for additional recent warming.

Land Average Temperature in 2024

On land, 2024 was also the warmest year directly observed, reaching 2.28 °C / 4.11 °F above the 1850 to 1900 average. This is the second year with a land-average of more than 2.0 °C, and sharply beats the previous record set in 2023 by 0.20 °C / 0.35 °F.

The 0.6 °C / 1.1 °F increase in land-average temperatures over the last two years (2022 to 2024) is the largest two year increase since the 1870s.

As discussed below, many territories and people saw local record warm annual averages in 2024.

Ocean Average Temperature in 2024

On the ocean’s surface, 2024 was also the warmest year directly observed, reaching 1.15 °C / 2.07 °F. This is the second year with a ocean-average above 1.0 °C, and beats the previous record set in 2023 by a small margin, 0.05 °C / 0.08 °F.

The two year increase in ocean-average temperatures, 2022 to 2024, is the largest two year increase in the instrumental record.

Berkeley Earth’s data for the oceans is adapted from the UK Hadley Centre’s HadSST4 data product after interpolation.

Temperature Distribution in 2024

This map shows how local temperatures in 2024 have increased relative to the average temperature in 1951-1980. Prominent warmth over Asia, Africa, North America, and South America is visible this year, as is warmth in the Atlantic, North Pacific, and Southern Ocean.

As can be expected from the global warming caused primarily by greenhouse gases, the temperature increase over the globe is broadly distributed, affecting nearly all land and ocean areas. In 2024, 95.2% of the Earth’s surface was significantly warmer than the average temperature during 1951-1980, 4.6% was of a similar temperature, and only 0.2% was significantly colder.

We estimate that 24% of the Earth’s surface set a new local record for the warmest annual average. This includes 32% of the land surface and 21% of the ocean’s surface. Particularly extreme conditions were observed over Central and South America, Africa, parts of Asia, Eastern Europe, the Atlantic Ocean, Indian Ocean, and Western Pacific Ocean.

As discussed below, these locations with record warm annual averages are home to approximately 3.3 billion people, including particularly large population centers in Asia, Africa, and South America.

In 2024, no places on Earth experienced a record or near-record cold annual average.

Land areas generally show about twice as much warming as the ocean. When compared to the 1850-1900 averages, the land average in 2024 has increased 2.28 ± 0.12 °C (4.11 ± 0.22 °F) and the ocean surface temperature, excluding sea ice regions, has increased 1.15 ± 0.07°C (2.07 ± 0.12 °F). Most of this warming has occurred since 1970.

Both land and ocean individually set new observational records in 2024. The following figure shows land and ocean temperature changes relative to the average from 1850 to 1900. The tendency for land averages to increase more quickly than ocean averages is clearly visible.

Both the tendency for land to warm faster than ocean and the higher rate of warming over the Arctic are expected based on the understanding of how increases in greenhouse gas concentrations will impact the Earth’s climate. As has been reported by the Global Carbon Project and other observers, 2024 saw a new record for the level of carbon dioxide in the atmosphere. This is due to the continued accumulation of carbon dioxide from human activities. The annual amount of carbon dioxide emitted in 2024 was 0.8% higher than 2023 and set a new all-time high.

End of the Recent El Niño

The emergence of the El Niño weather phenomenon in the middle of 2023 had a significant influence on temperatures during both 2023 and 2024, and is likely the largest short-term contributor to the 2023/2024 temperature spike. This El Niño peaked just before the end of 2023 and ended in June 2024. Central Pacific Ocean cooling continued during the rest of 2024. A new La Niña has begun in January 2025 but is expected to be weak.

El Niño is characterized by the emergence of a large area of relatively warm water in the eastern equatorial Pacific. In addition to the immediate warming in the Pacific, El Niño can have far-reaching effects on global circulation and weather patterns. This disruption of weather patterns tends to be associated with an extended period of somewhat increased global average temperatures that can last for months beyond the peak of the El Niño in the Pacific. Its counterpart, La Niña, is associated with relative cooling the Pacific and somewhat decreases global average temperatures.

Notably, the monthly time series of ocean average temperatures shifted sharply higher in the middle of 2023 — including the largest January to June ocean warming ever observed — due to dissipation of a strong La Niña and its replacement with El Niño. This warmth peaked late in 2023 but persisted well-above the long-term trend until late in 2024. As discussed below, this temperature excursion is not solely due to El Niño in the Pacific, but was also influenced by unusual warming in other ocean basins, especially the North Atlantic.

Prior to 2023, the equatorial Pacific maintained La Niña conditions since mid-2020. This long-lived La Niña contributed to making 2021 and 2022 relatively cooler than other previous years. By contrast, the rapid transition from a La Niña at the start on 2023 to a strong El Niño by the end of 2023, contributed to the temperature records observed in 2023 and 2024.

The 2023/2024 El Niño can be described as “strong” based on the temperatures observed in the Pacific. However, if adjusted for the average level of ocean warming in 2023/2024 (as shown above), it might be considered more “moderate”. The large-scale weather changes associated with El Niño are driven by the contrast between the El Niño region and other regions, so the direct weather impacts of this El Niño may be somewhat less extreme than in 2016 or 1998.

Roughly speaking, we expect each 1 °C (2 °F) temperature shift in the main El Niño / La Niña region to drive a corresponding ~0.1 °C (~0.2 °F) variation in the global mean temperature, with a lag of 3-6 months. For example, we expect the effect of La Niña in 2022 was roughly to make the annual average ~0.1 °C (~0.2 °F) colder than it might otherwise have been. By contrast, rapidly transitioning into El Niño from an La Niña may have contributed ~0.2 °C (~0.4 °F) to the global average.

The second year after an El Niño emerges is often warmer than the first. This was in fact observed to be the case in 2023/2024. Historically, we observe an average of 0.08 °C additional warming in the second year, though with a wide range of variation. With the exception of El Niño years that were also perturbed by large volcanic eruptions, almost every moderate to strong El Niño since 1950 has warmed in the second year compared to the year that it began. However, no other El Niño since 1950 has been associated with as extreme an anomaly in the year of its emergence as 2023. Given the unusual characteristics of 2023 it is somewhat surprising that 2024 was still able to warm further.

North Atlantic Warmth

The Northern Hemisphere portion of the Atlantic Ocean experienced an extreme warming event during the summer and fall of 2023. A large portion of this warmth has persisted into 2024. Based on historical observations, a deviation from the long-term trend of the size observed in 2023 should occur less than once per century, with the last similar event reported during the super El Niño of 1877/1878.

While North Atlantic warming can occur with El Niño, the event observed in 2023 appears to have occurred before El Niño was strongly developed, and is likely to be only weakly connected.

We believe that variability in the North Atlantic and other regions is largely responsible for the surge in global mean temperatures in the middle of 2023, before the 2023 El Niño event had gathered strength.

The surge is mid-2023 in the North Atlantic appears to have been caused, in significant part, by unusually low levels of Saharan dust at that time. However, as discussed below, a reduction in man-made sulfur aerosols is likely also contributing to the persistent warmth in the North Atlantic.

The persistence of warming in the North Atlantic, which was not generally anticipated, may have contributed to the persistence of high global average temperatures in 2024 even after the El Niño had ended. Recent changes may indicate that North Atlantic is also cooling a bit, but the basin remains at temperatures that are warmer than ever observed prior to 2023.

National Average Temperature

Though the focus of our work is on global and regional climate analysis, it is also possible to use our data to estimate national temperature trends.

In Berkeley Earth’s estimation, 2024 had the warmest nation-wide annual averages since instrumental records began in the following 104 countries:

Albania, Algeria, Antigua and Barbuda, Austria, Barbados, Belarus, Belize, Bosnia and Herzegovina, Brazil, Brunei, Bulgaria, Cambodia, Cameroon, Canada, Central African Republic, Chad, China, Colombia, Comoros, Croatia, Cyprus, Czechia, Democratic Republic of the Congo, Djibouti, Dominica, El Salvador, Equatorial Guinea, Eritrea, Ethiopia, Federated States of Micronesia, Fiji, Gabon, Germany, Ghana, Greece, Grenada, Guatemala, Guinea, Guinea-Bissau, Guyana, Haiti, Honduras, Hungary, Indonesia, Italy, Ivory Coast, Jamaica, Kenya, Kiribati, Kosovo, Laos, Liberia, Libya, Liechtenstein, Lithuania, Macedonia, Malawi, Malaysia, Malta, Mexico, Moldova, Mongolia, Montenegro, Mozambique, Netherlands, Nicaragua, North Korea, Oman, Palau, Paraguay, Philippines, Poland, Republic of Serbia, Republic of the Congo, Romania, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Samoa, San Marino, Seychelles, Sierra Leone, Singapore, Slovakia, Slovenia, Solomon Islands, Somalia, South Korea, South Sudan, Sri Lanka, Suriname, Sao Tome and Principe, Taiwan, Thailand, Togo, Trinidad and Tobago, Tunisia, Uganda, Ukraine, Venezuela, Vietnam, Yemen, Zambia, Zimbabwe

Further, the averages for the continents of North America, South America, Asia, Africa, and Europe each set new annual average records in 2024.

This list of countries having record warmth in 2024 is estimated from Berkeley Earth’s gridded temperature data set. Due to uncertainties and methodological differences, national weather agencies may give slightly different estimates of temperatures in 2024. In some cases, this may cause disagreements over whether a record national average was truly reached in 2024.

In addition, we note that the United States as a whole only just missed setting an annual average record in our analysis, though the contiguous lower 48 states did set a new annual average record.

Looking at the specific cities and sub-national locations where record annual averages occurred, we estimate that approximately 3.3 billion people — 40% of Earth’s population — live in places that observed their locally warmest year during 2024. This was concentrated in Asia, South and Central America, Africa, and Eastern Europe. It includes 2/3 of the population of China, as well as most of the population of Brazil, Nigeria, Ethiopia, Mexico, and 1/3 of the population of the United States.

The following chart provides a summary of the warming that countries/regions experienced in 2024 relative their 1951 to 1980 averages. Countries setting annual average records are outlined in black.

It is also worth noting from the above chart that a majority of ocean basins set new records in 2024, with the exception of the Arctic Ocean, South Pacific Ocean, and Southern Ocean.

Monthly Temperature Patterns

The year 2024 began with six months of continuous record high monthly-average temperatures. This is partly due to the El Niño event that peaked in late 2023. However high temperatures persisted well beyond the end of El Niño in June 2024. Similar warmth occurred in the second half on 2024, though only August set a new record as the other five months each ranked behind the records set in 2023. In 2024, our analysis placed every month at least 1.5 °C (2.7 °F) above the 1850-1900 average for that month.

Causes of Warmth in 2024

The warming pattern in 2023/2024 has been extraordinary. It appears to have been caused by a combination of natural and man-made factors.

Over the long-term man-made global warming has been responsible for gradually increasing temperatures at a rate of ~0.20 °C / decade. Greenhouse gas emissions, which are the underlying cause of global warming, reached record highs in 2024.

While global warming controls the long-term trend, it changes only gradually. Short-term fluctuations in global mean temperature are primarily driven by internal variations in the climate system, such as the state of the El Niño / La Niña oscillation. To a lesser extent, they can also by affected by external processes such as the solar cycle and volcanic eruptions.

A large portion of the temperature change from 2022 to 2023 can be ascribed to the effect of the transition from La Niña to El Niño, alongside other sources of natural variability (e.g. the North Atlantic) and combined with modest warming from several additional factors. In 2024, this El Niño contributed warmth in the first half of the year before dissipating in June. Due to a lag between peak El Niño and the peak impact on global temperatures, it is often the case that the year after an El Niño emerges is warmed more by the event than the year in which it began. This is consistent with 2024 being warmer than 2023.

The North Atlantic variations appear to be a mix of random natural variability and forced changes due to a reduction in man-made sulfur aerosols discussed below. In contrast to El Niño cycles, the random component of North Atlantic variability has been largely unpredictable.

Other factors likely influencing 2023/2024 climate include the ~11-year solar cycle, which is now near its expected peak, and very modestly increases the energy coming from the sun. The current solar cycle appears to be modestly stronger than the previous cycle, but has an intensity close to 20^th century averages.

In addition, we consider it possible that the January 2022 Hunga Tonga eruption is contributing to unusual weather in 2023 and 2024. 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 the greenhouse effect caused by its large water vapor contribution to the upper atmosphere.

The total effect of the Hunga Tonga eruption is uncertain with arguments for both warming and cooling having been made. In addition, the excess water vapor may have had hard to predict indirect effects on upper atmospheric dynamics or chemistry. At present approximately half of the water vapor injected into the upper atmosphere by Hunga Tonga remains there.

Another likely factor in the warmth witnessed during 2023/2024 is the reduction in man-made sulfur aerosols. In 2020, new international rules (IMO2020) 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. The aerosols can also serve a condensation centers aiding in the formation of cloud cover. This latter effect may be particularly important in oceanic regions due to the typically high relative humidity and low abundance of other condensation centers such as dust.

In general, sulfur aerosols are believed to have masked some of the effects of global warming. Reducing them from shipping could explain some of the excess warming, especially in the heavily trafficked North Atlantic and North Pacific regions.

Increased attention has recently been paid to the question of marine aerosols and their impact on climate. This has led to a diversity of estimates of the net effect.

Energy Imbalance and Cloud Cover

In order to understand the high rates of warming in 2023 and 2024 it is useful to examine Earth’s energy imbalance (EEI). The energy imbalance is the difference between how much energy the Earth absorbs from the Sun and how much subsequently escapes back into space as thermal radiation. It is a direct measure of how much extra energy is being trapped in the Earth system as a result of changes in greenhouse gases and other factors. As long as the energy imbalance is positive, we can expect the Earth to continue warming.

In the decades since satellites began reliably measuring Earth’s energy imbalance, the values observed in 2023 are the largest on record. This imbalance has subsequently reduced somewhat in 2024.

Spatially, the recent change in Earth’s energy imbalance is concentrated over the North Atlantic, South Atlantic, North Pacific, Europe, and the Southern Ocean. The change in the Southern Ocean is primarily related to record low sea ice cover in recent years. The changes in other ocean basins may be directly related to the reduction in marine sulfur aerosol emissions, which would be expected to allow more sunlight to reach the Earth’s surface.

Recent work by Goessling and colleagues has found that the changes in Earth’s energy imbalance are in large part the result of recent decreases in low cloud cover. This leads to a corresponding decrease in Earth’s albedo and allows a greater portion of incoming sunlight to be absorbed rather than reflected back into space.

Though changes in low cloud cover can explain changes in absorbed solar radiation, they aren’t really a primary cause. Cloud cover responds to other changes in the environment and can reasonably be understood as a sort of feedback or amplifier of other changes. Knowing that cloud cover changes are playing an important role in recent warming is very useful, but then requires one to determine why the cloud cover has changed.

Most climate models do expect absorbed solar radiation to increase as global warming progresses. This would be due to a reduction in low cloud cover, a reduction in snow and ice at the surface, and an increase in water vapor, all of which favor an increase in absorbed solar radiation. However, the observed changes indicated by the CERES program are far more rapid than typically expected by climate models given the current pace of global warming.

The change in cloud cover and rapid increase in absorbed solar radiation may be due, in part, to the recent reduction is man-made sulfur and other aerosols that have historically served to block a portion of the incoming solar radiation and facilitate cloud formation. In essence, recent efforts to reduce smog and other air pollution may have inadvertently accelerated global warming. It is also possible that some of the changes in cloud cover are due to natural variability or other feedback processes. Better understanding the recent changes in cloud cover and the associated increases in absorbed solar radiation will be vital for ensuring accurate forecasts of the future.

Given the known reductions in man-made air pollution, and the evidence of an increasing energy imbalance, it is also reasonable to anticipate that global warming may continue to accelerate if additional reductions in sulfur air pollution are undertaken.

Future Long-term Trend

Though it is interesting to understand the characteristics of individual years, global warming is ultimately about the long-term evolution of Earth’s climate. The exceptional nature of the warming in 2023/2024 makes future forecasting more difficult, since it likely points to a deviation from the historical trend.

Since 1980, the overall trend has been about +0.20 °C/decade (+0.36 °F/decade). The extreme warmth in 2023/2024 likely points to a period of greater warming. However, whether that greater warming rate persists over the long-term or is only present briefly is hard to predict. To the extent that excess recent warming is likely driven by reductions in man-made aerosol pollution, future warming from this source will also depend directly on human choices regarding the regulation of such aerosols.

That said, our long-term trend estimate (a 30-year LOESS smooth) has already crossed 1.4 °C (2.5 °F) above the average temperature from 1850-1900. Given recent rates of warming is may take only ~5 years for our long-term trend to reach 1.5 °C (2.7 °F).

The Paris Agreement on Climate Change aims to keep the long-term average global temperature rise to well below 2 °C (3.6 °F) and encourages parties to strive for warming of no more than 1.5 °C (2.7 °F). It has been clear for sometime that the 1.5 °C (2.7 °F) goal will not be achieved. Too little time remains and efforts at mitigation fall far short of what would have been needed to meet that target.

Nonetheless, effective mitigation can still limit global warming and reduce the severity of negative outcomes. The increasing abundance of greenhouse gases in the atmosphere due to human activities is the primary cause of recent global warming. If the Paris Agreement’s goal of no more than 2 °C (3.6 °F) warming is to be reached, significant progress towards reducing greenhouse gas emissions needs to be made soon.

Global Mean Temperature Prediction for 2025

Based on historical variability and current conditions, it is possible to roughly estimate what global mean temperature might be expected in 2025. Our current estimate is that 2025 is likely to be cooler than 2024. With the end of the 2023/2024 El Niño and the shift towards a weak La Niña, it is likely that 2025 will cool relative to 2024 and 2023. As a result, we expect that 2025 will be roughly the 3^rd warmest year in the instrumental record. However, the newly formed La Niña is expected to be weak, and a return to El Niño by the end of 2025 is possible. The swings from El Niño to La Niña and back again are the largest source of predictable interannual variability in the global temperature record.

Estimated probabilities of annual average rank in 2025:

• 1st place: 6%
• 2nd place: 19%
• 3rd place: 63%
• 4th – 6th place: 11%
• 7th place or lower: 1%

At the start of 2024, we foresaw a 58% chance that 2024 would become a record warm year. The actual evolution of 2024 appears to have been broadly consistent with the forecast. Statistically, we expect global mean temperature to fall within our predicted forecast range ~95% of the time.

Comparisons with Other Groups

When preparing our year-end reports, Berkeley Earth traditionally compares our global mean temperature analysis to the results of four other groups that also report global mean surface temperature. The following charts compares Berkeley Earth’s analysis of global mean temperature to that of the NASA’s GISTEMP, NOAA’s GlobalTemp, the UK’s HadCRUT, and ECMWF‘s reanalysis. All of these groups produce a similar understanding of recent climate change.

Different groups use different data and methods, but arrive at broadly similar conclusions. All of the monitoring agencies concur that 2024 is the warmest year in the observational record, and by a significant margin. Several groups conclude that 2024 was at least 1.5 °C above their own estimates of the 1850 to 1900 baseline.

That said, the estimates of the total amount of warming in 2024 relative to the 1850 to 1900 baseline period do vary somewhat among the groups. This is primarily due to different estimates of global mean temperature during the baseline period.

In the modern period, slight disagreements between groups mostly reflect the simple measurement uncertainties in these estimations and the differences in how various research programs look at the Earth. Each uses a somewhat different selection of source data and different methods of interpolation and correcting for measurement errors. Some methods are more limited than others. Berkeley Earth is notable for incorporating more weather station data than any other project.

Unfortunately, there are larger disagreements regarding the earliest part of the observational temperature history. If we align each time series for a pre-industrial baseline, it becomes clear that some of the series imply a slightly larger or smaller change in the present day due to their differing estimates of the pre-industrial period.

Smoothing each series makes this even clearer.

Estimating global mean temperature in the late 19^th century is always going to be more challenging than during the recent period due to less data and the less reliable nature of the data that does exist. Much of the disagreement between analysis groups derives from the choice of ocean dataset employed. NASA and NOAA rely on NOAA’s ERSST data product, while Berkeley Earth and HadCRUT use the HadSST data set. These two data products are the only widely used instrumental reconstructions of the long-term changes in the ocean and they disagree to an appreciable degree.

The primary reason that ERSST and HadSST differ is due to different estimates of the biases introduced by changing methods and instrumentation over time. Early ocean temperature observations relied on hauling buckets of water onto the ship’s deck in order to be measured. Over time this was replaced, first with measurements at an engine cooling intake, and later with automated buoys. It is known that each of these processes measures the ocean slightly differently (e.g. sampling at slightly different depths), and will give slightly different answers at the level of a fraction of a degree Celsius. Untangling these differences and correcting the resulting biases is an important aspect of ocean temperature analysis. Unfortunately ERSST and HadSST disagree on the magnitude of these corrections. These problems are well-known and have led to calls for new approaches to understood past ocean biases. In the future, new efforts to analyze ocean temperature records and the associated biases may help to reduce this disagreement.

Ultimately, each research group strives to produce the best possible estimate, but these methodological differences make understanding of the changes since the pre-industrial period more difficult. Different research groups disagree on the amount of warming that has occurred since the pre-industrial by more than 0.1 °C (0.2 °F).

This large difference between analysis groups is sometimes described as the “structural uncertainty” in the estimate of long-term temperature change, and limits humanity’s ability to say for sure how much warming has occurred. Most groups provides an error estimate of how confidently climate can be reconstructed within their own set of bias and uncertainty assumptions. However, the structural disagreement between groups is often larger than the individual uncertainty estimates of the groups, indicating that disagreements about the underlying assumptions themselves are likely a significant source of uncertainty.

Berkeley Earth Methodology

In reconstructing the changes in global mean temperature since 1850, Berkeley Earth has examined 22 million monthly-average temperature observations from 50,746 weather stations. Of these 18,447 stations and 186,000 monthly averages are available for 2024.

The weather station data is combined with sea surface temperature data from the UK Met Office’s Hadley Centre (HadSST). This ocean data is based on 483 million measurements collected by ships and buoys, including 14.2 million observations obtained in 2024. We reprocess and interpolate the HadSST data to provide a more complete picture of the oceans. After combining the ocean data with our land data, we arrive at a global picture of climate change since 1850.

Uncertainties arise primarily from the incomplete spatial coverage of historical weather observations, from noise in measurement devices, and from biases introduced due to systematic changes in measurement technologies and methods. The total uncertainty is much less than the long-term changes in climate during the last 170 years.

This report is based on such weather observations as had been recorded into global archives as of early January 2024. It is common for additional observations to be added to archives after some delay. Consequently, temperature analysis calculations can be subject to revisions as new data becomes available. Such revisions are typically quite small and are considered unlikely to alter the qualitative conclusions presented in this report.

Copyright

This report was prepared by Berkeley Earth. The contents of this report, including all images not attributed to a specific third-party author, may be reused under the terms of the Creative Commons BY-NC 4.0 copyright license for any non-commercial purpose and in any forum, consistent with the terms of that license. 

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Data

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