Under the Paris Agreement of 2015^[1], every five years countries review their progress in limiting greenhouse gas emissions. The key aim is to curb the rise in global average near-surface temperature, holding it to well below 2°C above pre-industrial levels, and to pursue efforts to limit the increase to 1.5°C. Consistent with this regular stocktake, C3S provides a global temperature^[2] indicator by averaging values over successive 60-month periods.

This averaging reduces the signal from shorter-term natural variability, such as that associated with El Niño events and volcanic eruptions. It also reduces the differences between the available temperature datasets. However, longer-term variations in temperature, such as those associated with decadal and multi-decadal fluctuations in sea surface temperatures, are still seen.

Global average temperature

Figure 1. Global average near-surface temperature for centred running 60-month periods, relative to the average for the 1991–2020 reference period and as an increase above the 1850–1900 average, according to six datasets. The average temperature for 1991–2020 from ERA5 is 14.4°C. Data sources: ERA5 (C3S/ECMWF), JRA-3Q (JMA), GISTEMPv4 (NASA), HadCRUT5 (Met Office Hadley Centre), NOAAGlobalTempv6 (NOAA) and Berkeley Earth. Credit: C3S/ECMWF.
DOWNLOAD DATA

Six widely-used datasets^[3] show the latest five-year-average global temperature (2019–2023) to be the highest on record and 2023 to be the warmest year on record. The next warmest years are 2016 and 2020. The lower temperatures in 2021 and 2022 coincided with a prolonged La Niña event. All datasets show that the nine years from 2015 to 2023 are the warmest nine years on record, even if the ranking of some of the individual years differs.

The increase in five-year-average temperatures since the second half of the 19th century is estimated to be 1.2–1.3°C. There has been an average increase of 0.1°C approximately every five years since the mid-1970s, but this rate of warming has not been steady. For example, the five-year averages centred on the years from 2003 to 2012 show hardly any change, then rise sharply due to the record warmth of the years from 2015 onwards.

The average rate of temperature increase, according to ERA5, is 0.20°C per decade from 1979 to 2023, with a 95% confidence interval^[4] of ±0.03°C.

Temperature over all land

Figure 2. Average temperature over all land for centred running 60-month periods, relative to the average for the 1991–2020 reference period and as an increase above the 1850–1900 average, according to six different datasets. The average temperature for 1991–2020 from ERA5 is 9.2°C. Data sources: ERA5 (C3S/ECMWF), JRA-3Q (JMA), GISTEMPv4 (NASA), HadCRUT5 (Met Office Hadley Centre), NOAAGlobalTempv6 (NOAA) and Berkeley Earth. Credit: C3S/ECMWF.
DOWNLOAD DATA

The average increase in temperature since the 1970s has been around 1.4–1.5°C over all land, compared with around 1.0°C for the global average. According to ERA5, the average rate of increase over land is 0.32 ± 0.03°C^[4] per decade from 1979 to 2023. The temperature rise over ice-free seas is about half that over land, but nevertheless accounts for about half of the rise in global average temperature, as the area of Earth’s surface covered by sea is much larger than the area covered by land.

Gaps in the coverage of the observations available to ERA5 and JRA-3Q are significant in the early decades of these datasets, and their temperatures over land are lower than those from other datasets for much of the period from 1940 to 1980. This is compensated to a large degree in global average values by differences in sea surface temperatures and air temperatures over sea ice.

European temperature

Figure 3. Average temperature over European land for centred running 60-month periods, relative to the average for the 1991–2020 reference period and as an increase above the 1850–1900 average, according to six different datasets. The average temperature for 1991–2020 from ERA5 is 9.2°C. Data sources: ERA5 (C3S/ECMWF), JRA-3Q (JMA), GISTEMPv4 (NASA), HadCRUT5 (Met Office Hadley Centre), NOAAGlobalTempv6 (NOAA) and Berkeley Earth. Credit: C3S/ECMWF.
DOWNLOAD DATA

The average temperature over European land was only a little warmer in the early 1980s than it had been a hundred years earlier, but has risen sharply over the past forty or so years. The average value for the last five years is around 2.3°C higher than typical values for the latter half of the 19th century. This temperature increase for Europe is about 1°C larger than the corresponding increase for the globe as a whole. Europe has also warmed faster overall than any other continent in recent decades. This is the case for both boreal winter, when European warming is most pronounced at northern latitudes, and summer, when the warming is largest over central and southeastern Europe and around the Mediterranean^[5]. Warming is larger for Asia than Europe in boreal spring, and similar for North America and Europe in autumn. The average rate of temperature increase over Europe, according to ERA5, is 0.47 ± 0.09°C per decade from 1979 to 2023.

Decadal-scale variations can be much more prominent for particular regions than for the globe as a whole. For Europe, the contrast between the warm conditions of the 1930s and the cold conditions of the early 1940s is a particularly striking feature.

Arctic temperature

Figure 4. Average Arctic temperature over land for centred running 60-month periods, relative to the average for the 1991–2020 reference period and as an increase above the 1850–1900 average, according to six different datasets. The average temperature for 1991–2020 from ERA5 is -12.7°C. Data sources: ERA5 (C3S/ECMWF), JRA-3Q (JMA), GISTEMPv4 (NASA), HadCRUT5 (Met Office Hadley Centre), NOAAGlobalTempv6 (NOAA) and Berkeley Earth. Credit: C3S/ECMWF.
DOWNLOAD DATA

Temperatures over the Arctic have risen much more rapidly than those over most of the rest of the globe. From the mid-1920s onwards, the datasets are generally in good agreement for temperatures over Arctic land. They show a warmer-than-average period in the 1930s and 1940s, cooler temperatures in the 1960s and 1970s that are only a little higher than the average for 1850–1900, and a rise in temperature of about 2.5°C since the mid-1970s. Current temperatures are around 1.8°C higher than those of the warmer-than-average years around 1940. The average rate of temperature increase over Arctic land, according to ERA5, is 0.65 ± 0.09°C per decade from 1979 to 2023.

Long-term temperature change over the Arctic Ocean is more uncertain, but most datasets indicate a warming over the Arctic as a whole of close to 3°C since the late 1970s. This is a little larger than the warming over Arctic land alone and about three times larger than the corresponding global average warming over the same period.

Note

[1] Read more about the Paris Agreement on the United Nations Framework Convention on Climate Change (UNFCCC) website.

[2] The global temperature datasets used here are either a combination of surface air temperatures (temperatures at a nominal height of two metres) over both land and sea, or of surface air temperatures over land and sea surface temperatures over ice-free sea. For simplicity these are referred to here as ‘temperature’ or ‘surface temperature’.

[3] The six datasets are as discussed by Simmons et al. (2021), apart from the use here of the newer JRA-3Q reanalysis rather than JRA-55, and version 6.0 rather than version 5.0 of NOAAGlobalTemp. The JRA-3Q data are downloaded at 1.25° resolution and processed in the same way as documented for JRA-55. Further details are given in the Climate Indicators ‘About the Data’ section.
The differences in annual average global temperature anomalies derived from the six datasets are mostly smaller than 0.1°C over the period since 1948 for which all six provide values. The spread among datasets averages 0.06°C over this period, and ranges from 0.01°C (in 2012) to 0.14°C (in 1976). The spread has nevertheless been relatively large for recent years, averaging 0.05°C for 2016–2023. This is partly because the datasets are aligned to have the same average temperature for 1991–2020.

[4] For further information on the methodology, see the Climate Indicators ‘About the data’ section.

[5] Maps showing how seasonal warming rates vary geographically have been presented by Simmons (2022), based on data from March 1979 to February 2022. Several processes may be important in determining these variations, depending on region and season. They include planetary-scale adjustments of temperature and wind patterns, but may also involve local feedbacks, such as arise from changes in sea ice extent, snow cover and soil moisture.

References

Simmons A., et al., 2021: Low frequency variability and trends in surface air temperature and humidity from ERA5 and other datasets, ECMWF Technical Memoranda 881. dx.doi.org/10.21957/ly5vbtbfd

Simmons A., 2022: Trends in the tropospheric general circulation from 1979 to 2022, Weather Clim. Dynam., 3, 777–809. doi.org/10.5194/wcd-3-777-2022