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.