After two consecutive years (2019 and 2020) that ranked among the top three warmest on record, Earth was a slightly cooler planet in 2021. But not by much.
According to an analysis by scientists at NOAA's National Centers for Environmental Information (NCEI), 2021 ranked sixth on the list of warmest years on record, dating back to 1880.
Earth’s average land and ocean surface temperature in 2021 was 1.51 degrees F (0.84 of a degree C) above the 20th-century average.
It also marked the 45th consecutive year (since 1977) with global temperatures rising above the 20th-century average. The years 2013-2021 all rank among the ten-warmest years on record.
The Northern Hemisphere’s land and ocean surface temperature was also sixth highest on record, at 1.96 degrees F (1.09 degrees C) above average. Looking at the Northern Hemisphere’s land areas only, the temperature was third warmest on record, behind 2016 (second warmest) and 2020 (the warmest).
Ocean heat content (OHC), which describes the amount of heat stored in the upper-levels of the ocean, was record high in 2021, surpassing the previous record high set in 2020. The seven highest OHCs have occurred in the last seven years (2015-2021). High ocean-heat content can contribute to sea-level rise.
2021 as ranked by other scientific organizations
NASA scientists, who conducted a separate but similar analysis, also determined that 2021 was the sixth-warmest year on record, tied with 2018.
Scientists from Europe’s Copernicus offsite link, however, ranked 2021 as the globe’s fifth warmest on record.
Additional NOAA findings
- Polar sea ice: The average annual sea ice cover in the Arctic was approximately 4.08 million square miles — the ninth-smallest annual average cover in the 1979-2021 record. The last seven years (2015-2021) had an annual sea ice extent that ranked among the 10 smallest on record, according to data from the National Snow and Ice Data Center offsite link. In the Antarctic, annual sea ice cover was slightly below average at 4.42 million square miles, the 18th smallest on record.
- Global tropical cyclones: There was an above-average number of tropical cyclones around the world in 2021, with a total of 94 named storms. This value ties with 1994 as the tenth-highest number of named storms in the 41-year record. However, there were only 37 hurricane-strength tropical cyclones worldwide — the lowest number on record, just surpassing the now second-lowest record of 38 set in 2009.
- December 2021 warmth: December’s average temperature across global land and ocean surfaces was 1.49 degrees F (0.83 of a degree C) above the 20th-century average. This value was tied with 2016 as Earth’s fifth-warmest December in 142 years. Regionally, South America saw its third-warmest December on record, while Africa and Oceania ranked among the eight warmest on record. Both North America and Europe had an above-average December temperature, but it was their coolest December since 2016.