State of the climate: 2024 will be first year above 1.5C of global warming
This year is now virtually certain to beat 2023 as the hottest year on record, Carbon Brief analysis shows.
It will also be the first full year to surpass 1.5C above pre-industrial levels across the majority of observational records.
In this latest “state of the climate” quarterly update, Carbon Brief finds:
- The year 2024 has seen record warm temperatures for seven of the nine months of the year where data is so far available.
- The world, as a whole, has warmed approximately 1C since 1970 – and 1.2C to 1.4C since the mid-1800s.
- A strong El Niño event contributed to exceptionally high global temperatures early in the year, but record or near-record temperatures persisted despite the fading of El Niño in recent months.
- Record global temperatures have been seen across many regions of the planet over the first nine months of the year.
- Global temperatures are closely aligned with the projections from climate models.
- Global sea ice extent is currently at record lows and Antarctic sea ice has spent much of the year at near-record lows – second only to those seen in 2023.
§ The warmest year on record
In this latest quarterly state of the climate assessment, Carbon Brief has analysed records from five different research groups that report global surface temperature records: NASA’s GISTEMP; NOAA’s GlobalTemp; Hadley/UEA’s HadCRUT5; Berkeley Earth; and Copernicus/ECMWF.
The figure below shows Carbon Brief’s estimate of where 2024 temperatures will end up in each of the groups, based on the year to date and expected El Niño-Southern Oscillation (ENSO) conditions in the tropical Pacific for the remainder of the year.
The dots reflect the best estimate, while the whiskers show the two sigma (95%) confidence interval of the projections. The prior record year (2023 in all groups) is shown by the coloured square.
In all cases, the projected global average temperature for 2024 is virtually certain to exceed the prior record set in 2023.
Three of the five groups (Hadley, Berkeley and Copernicus/ECMWF) are very likely to show annual temperatures exceeding 1.5C above pre-industrial levels (defined here as the 1850-1900 period), while the NASA record has a roughly 40% chance of exceeding 1.5C. Only NOAA’s record is unlikely to show global temperatures above 1.5C this year.
These differences in warming since pre-industrial across different datasets primarily result from choice of ocean records used, as well as differences in approaches to filling in gaps between observations in the early part of the records (e.g. pre-1900s). It reflects the uncertainty in the degree of warming since the mid-1800s, with projected 2024 temperatures ranging from 1.44C (NOAA) to 1.61C (Berkeley Earth).
The figure also provides a composite average of the five different datasets, following the approach used in the sixth assessment report (AR6) from the Intergovernmental Panel on Climate Change (IPCC) and by the WMO. Carbon Brief’s analysis finds that 2024 will be the first year above 1.5C in the composite average.
This provides a way to determine the first year where we can reasonably say that the world has passed that warming level – even though 2023 exceeded 1.5C in the Berkeley Earth dataset and 2024 will not exceed 1.5C in the NOAA dataset.
(It is important to note that exceeding 1.5C in a single year is not equivalent to breaching the Paris Agreement limit. The goal is generally considered to refer to long-term warming – typically over two or three decades – rather than annual temperatures that include the short-term influence of natural fluctuations in the climate, such as El Niño.)
The figure below shows the annual temperatures from each of these groups between 1970 and present, with the year-to-date 2024 temperatures for each record shown as individual points.
There is strong agreement between the different temperature records, with all of them showing approximately 1C warming between 1970 and present. Global temperatures have been around 1.3 above pre-industrial levels in recent years (with a range of 1.2C to 1.4C across the different temperature datasets, reflecting that the differences between them are larger in the 1800s and early 1900s).
As the chart below shows, 2024 (purple line) started out remarkably warm as a result of a strong El Niño event that built in 2023 (red) and peaked near the beginning of the year.
However, global temperatures have remained quite elevated despite the fading of El Niño conditions, setting records through June and remaining quite close to 2023’s exceptional highs in recent months.
Overall, 2024 has set or tied all-time records for seven of the 10 months available to-date in the ERA5 record. (This record uses weather model-based reanalysis to combine lots of different data sources over time.)
While human emissions of CO2 and other greenhouse gases are responsible for effectively all of the Earth’s long-term warming, temperatures in any given year are strongly influenced by short-term variations in the Earth’s climate that are typically associated with El Niño and La Niña events.
These fluctuations in temperature between the ocean and atmosphere in the tropical Pacific help make some individual years warmer and some cooler.
The figure below shows a range of different ENSO forecast models produced by different scientific groups. The values shown are sea surface temperature variations in the tropical Pacific – the El Niño 3.4 region – for three-month periods.
Most models expect neutral conditions in the tropical Pacific, with only a few crossing the -0.5C Niño 3.4 sea surface temperature (SST) anomaly that represents the development of a formal La Niña event.
This should result in relatively cooler temperatures in 2025, though it is possible that the year ends up warmer than anticipated given the continuation of high temperatures in recent months – despite the absence of El Niño conditions.
§ Large areas of record warmth
While global average temperatures are an important indicator of changes to the broader climate system over time as a result of human activities, these impacts will differ as some regions experience more rapid warming or extreme heat events than is reflected in the global average.
The figure below shows the parts of the world that saw record warm or cold temperatures over the first three quarters of 2024 (January through to September) in the Berkeley Earth dataset compared to all prior years since global temperature record began in 1850.
Notably, no area on Earth saw record cold (or even the second, third, fourth or fifth coldest temperatures on record). Nearly all of Central America and large parts of South America saw their warmest year to date on record, as did much of eastern Europe, Africa, China, south-east Asia, and Korea.
The figure below shows the temperature anomaly over the first nine months of the year compared to the 1951-80 baseline period used by Berkeley Earth. Warming was particularly pronounced over land regions, with many areas already showing warming of 1.5C or 2C above that baseline.
§ Temperatures are tracking climate model projections
Climate models provide physics-based estimates of future warming given different assumptions about future emissions, greenhouse gas concentrations and other climate-influencing factors.
The figure below shows the range of individual models forecasts featured in AR6 – known collectively as the CMIP6 models – between 1970 and 2030, with grey shading and the average projection across all the models shown in black. Individual observational temperature records are represented by coloured lines.
While global temperatures were running below the pace of warming projected by climate models for much of the period between 2008 and 2022, the past two years have been closer to the model average.
However, the CMIP6 models may be biassed a bit too warm, with a subset of “hot” models pushing up the average. The IPCC used an approach that weighted models based on how well they reproduced historical temperatures, rather than simply averaging all the models together.
Excluding these hotter models from the analysis results in observations over recent years much closer to the multi-model average and near the centre of the uncertainty range across all models. It also reveals that the past two years – 2023 and 2024 – have been near the upper end of the model range.
§ Record low global sea ice extent
Highly accurate observations of Arctic and Antarctic sea ice have been available since polar-observing satellites became available in the late 1970s.
Arctic sea ice extent during the first three-quarters of 2024 has been below or at the low end of the historical 1979-2010 range, but has not seen any record daily lows.
Antarctic sea ice, on the other hand, set new all-time low records for a few days in July and September, and has generally been the second lowest on record (after 2023) from June onwards.
The figure below shows both Arctic (red) and Antarctic (blue) sea ice extent in 2024, the historical range in the record between 1979 and 2010 (shaded areas) and the record lows (dotted black line).
Unlike global temperature records (which only report monthly averages), sea ice data is collected and updated on a daily basis, allowing sea ice extent to be viewed through to the present day.
Global sea ice extent is estimated by combining both Arctic and Antarctic sea ice extent. The figure below shows global sea ice extent in each year, with 2024 shown in red. Currently global sea ice extent is at record-low levels, below the prior record for this date set in 2023.
§ Methodological note
A statistical multivariate regression model was used to estimate the range of likely 2024 annual temperatures for each group that provides a temperature record. This model used the average temperature over the first six months of the year, the average ENSO 3.4 region value during the first nine months of the year and the average predicted ENSO 3.4 value during the last three months of the year to estimate the annual temperatures.
The model was trained on the relationship between these variables and annual temperatures over the period of 1950-2023. The model then uses this fit to predict both the most likely 2024 annual value for each group, as well as the 95% confidence interval. The predicted ENSO 3.4 region values for the last three months of 2024 are taken from the IRI plume forecast.
The percent likelihood of different year ranks for 2024 is estimated by using the output of the regression model, assuming a normal distribution of results. This allows Carbon Brief to estimate what percent of possible 2024 annual values fall above and below the temperatures of prior years for each group, as well as the likelihood of the year exceeding 1.5C in each record.