January 2021 Temperature Update

The following is a summary of global temperature conditions in Berkeley Earth’s analysis of January 2021.

  • January 2021 was the 6th warmest January since records began in 1850.
  • Moderate La Niña continue in the Pacific and are likely to keep 2021 cooler than other recent years.
  • Very warm conditions occurred over much of the Arctic and North America.
  • Based on January, this year is currently positioned to be around the 5th warmest year overall, with only a remote (~6%) chance of it being a new warmest year.

Global Summary

Globally, January 2021 has been the sixth warmest January since records began in 1850. This is similar to other recent years, including 2018 and 2019, but appreciably cooler than in 2020 and 2016.

The global mean temperature in January 2021 was 0.87 ± 0.06 °C (1.57 ± 0.11 °F) above the 1951 to 1980 average.

This is equivalent to being 1.18 ± 0.07 °C (2.12 ± 0.13 °F) above the 1850 to 1900 average, which is frequently used as a benchmark for the preindustrial period.

The global mean temperature anomaly in January 2021 was similar to that in December 2020, though still cooler than every other month in 2020. The current values are slightly below the long-term trend line associated with recent global warming, but remain consistent with the overall pattern that we expect given natural variability.

Spatial Variation

January 2021 continues the ongoing pattern of wide-spread warmth, though with some notable exceptions. Particularly warm conditions were present in parts of North America, Western Europe, the Middle East, and North Africa. Record setting warmth was also present in parts of the mid-latitude Pacific. Significantly cool temperatures occurred in Northern Asia, the Eastern Tropical Pacific, and part of Antarctica.

The cool temperatures across Northern Asia contrast strongly with the record-breaking conditions present in this region during 2020.

We estimate that 4.7% of the Earth’s surface experienced their locally warmest January average, and 62% of the Earth’s surface was significantly warmer when compared to their local average during the period 1951 to 1980. In addition, 0.2% of Earth’s surface had their locally coldest January.

The cool area in the Eastern Pacific, first observed in June 2020, continues to be indicative of La Niña conditions. The La Niña state is likely to have contributed to the relatively cool global average in January 2021.

Over land regions, 2021 was the 11th warmest January, coming in as 1.21 ± 0.12 °C (2.18 ± 0.22 °F) above the 1951 to 1980 average.

Influenced by La Niña, January 2021 was the 9th warmest January in the oceans, recorded as 0.53 ± 0.04 °C (0.95 ± 0.07 °F) above the 1951 to 1980 average.

Arctic Ocean

In January 2021, highly elevated temperatures were present across much of the Arctic Ocean, up to more than 8 °C (14 °F) above the 1950-1980 average, including some regions that were at or near records for the month.

Conditions this January contrast sharply with January 2020, when a strong polar vortex kept most of the cold air bottled up over the Arctic Ocean. This year the polar vortex has been less robust and outbursts of Arctic air have been more common. In January, the Arctic air was displaced onto Asia. Though not covered by the time frame of this report, we note that a similar Arctic outburst affected North America in February 2021.

La Niña

January 2021 showed the continuation of La Niña conditions in the Pacific Ocean. This weather phenomenon is characterized by the emergence of relatively cool ocean water in the Eastern Central Pacific and is expected to have a cooling impact on global weather patterns over the next several months. La Niña remains at moderate intensity. It is expected to peak this winter, and a transition to ENSO neutral conditions is considered likely before or during Northern Hemisphere summer.

The La Niña conditions occurring now are expected to reduce global mean temperature during the first half of 2021, and make it very unlikely that 2021 will be a record warm year. Most models expect either La Niña or neutral conditions during the rest of 2021, with a return of El Niño not considered likely.

February model forecast from IRI/CPC showing the likely evolution of La Niña conditions during 2021.

Rest of 2020

The ongoing La Niña event makes it likely that 2021 will be cooler than other recent years, though it is nearly certain to remain within the top ten warmest years overall. As La Niña is expected to ease in the 2nd half of the year, the annual average might be expected to warm some during the rest of the year compared to January, but it is unlikely to challenge the previous record warm years.

The statistical approach that we use, looking at conditions in January and prior months, believes that 2021 has only a 6% likelihood of surpassing 2016 and becoming the warmest year that has been directly measured. The most likely outcome would place 2021 as around the 4th or 5th warmest year in the instrumental record. It is unlikely that 2021 would be colder than 7th warmest, which means that it would still surpass all years prior to 2015.

Likelihood of final 2021 ranking, based on January 2021:

  • 1st place (6%)
  • Top 3 overall (14%)
  • 4th place (29%)
  • 5th place (23%)
  • 6th place (14%)
  • 7th place (19%)
  • Top 7 overall (>99%)


The current report marks the first of our reports to transition to HadSST4 rather than HadSST3.

This new version of the sea surface temperature data set produced by the UK Met Office / Hadley Centre includes a number of significant improvements. Most notable are adjustments to uncertainty during the World War II period and corrections related to the transition from ships to automated buoys as the primary means of measuring sea surface temperature.

From this point forward, Berkeley Earth’s Land and Ocean data set will utilize HadSST4. This transition does not require any change in our analysis methods, though the empirically-determined interpolation parameters were recalculated for the new data set. Overall the results of the two data sets are very similar, with the HadSST4 version resulting in a very slightly higher global warming trend than its predecessor.

The effect of this transition will be discussed in more detail in a forthcoming post.

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