Earth had its sixth-warmest year on record in 2021, 0.84 degree Celsius (1.51°F) above the 20th-century average, NOAA reported January 13. NASA also rated 2021 the sixth-warmest year on record (tied with 2018), 1.12 degrees Celsius (2.02°F) above the 1880-1920 period, which is its best estimate for when preindustrial temperatures occurred. NASA rates the margin of error of its annual temperature measurement at .05 degree Celsius.

The European Copernicus Climate Change Service rated 2021 as the fifth warmest year on record; Berkeley Earth rated it the sixth warmest year on record, as did the Japan Meteorological Agency. Minor differences in rankings often occur among various research groups, the result of different ways they handle data-sparse regions such as the Arctic. Global satellite-measured temperatures in 2021 for the lowest eight kilometers of the atmosphere were not yet available at the time of this writing.

Global ocean temperatures in 2021 were the seventh warmest on record, and global land temperatures the sixth warmest on record. As shown in Figure 1, temperatures over land have been warming about 2.5 times more rapidly than temperatures over the oceans.

Figure 1. Yearly departure (1880-2021) of NASA global temperatures from preindustrial temperatures; 12-month average (thin lines) and 132-month (thick lines) are shown. (Image credit: James Hansen)

The Northern Hemisphere had its sixth-warmest year on record in 2021 and the Southern Hemisphere its ninth-warmest. By continent, here are the 2021 temperature rankings:

Europe: ninth warmest;
Asia: seventh warmest, and China’s warmest year on record;
South America: sixth warmest;
Africa: third warmest;
Australia (and Oceania):  18th warmest; and
North America: seventh warmest.

As detailed in a January 10 post at this site by Bob Henson, 2021 for the U.S. was the fourth-warmest year in history going back to 1895. Thirty-five states had a top-10 warmest year on record, and none of the contiguous 48 states was below average in temperature in 2021.

The two main human-emitted heat-trapping gases — carbon dioxide and methane — both reached all-time highs in 2021, with the methane growth rate hitting its highest level on record.

Figure 2. Departure of temperature from average for 2021, the sixth-warmest year the globe has seen since record-keeping began in 1880, according to NOAA. Record-high annual temperatures occurred across parts of northern Africa, southern Asia, southern South America, as well as across parts of the Atlantic and Pacific Oceans. No land or ocean areas had a record-low temperature for 2021. (Image credit: NOAA National Centers for Environmental Information)

According to NOAA and NASA, the 2021 global temperature ranking means that the eight warmest years on record since 1880 were the most recent eight years — 2014 through 2021. The European Copernicus Climate Change Service rates the past seven years — 2015 through 2021 — as being the seven warmest years on record, with 2010 slightly beating out 2014 as the eighth warmest year on record.

The global warmth in 2021 is all the more striking as it occurred near the minimum of the weakest solar cycle in more than 100 years and during a year dominated by La Niña conditions — factors which tend to cool the globe. The warmth of 2021 is a testament to how significantly human-caused global warming is heating the planet.

Warmest year on record for total ocean heat content

When a La Niña is in progress, as was the case during much of 2021, a slight dip in global air temperature is typically balanced by a tiny bump-up in global ocean heat content, so it’s no surprise that the total heat content of the world’s oceans in 2021 was the warmest in recorded human history, according to a January 11, 2022 paper by Cheng et al., Another record: Ocean warming continues through 2021 despite La Niña conditions, published in Advances in Atmospheric Sciences. In the uppermost 2,000 meters of the oceans, there were 227-235 zettajoules more heat in 2021 than the 1981-2010 average, and 2021 had 14-16 zettajoules more ocean heat content than in 2020, equal to 145 times world electricity generation in 2020 (a zettajoule is one sextillion joules — ten to the 21st power). To put those numbers into context, understand that humans use a total of about 0.5 zettajoules of energy per year.

More than 90% of the increasing heat from human-caused global warming accumulates in the ocean as a result of its large heat capacity. The remaining heating manifests as atmospheric warming, a drying and warming landmass, and melting land and sea ice. Increasing ocean heat content, OHC, causes sea-level rise through thermal expansion of the water and melting of glaciers in contact with the ocean, resulting in higher coastal erosion and more damaging storm surges. OHC also produces stronger and more rapidly intensifying hurricanes; causes more intense precipitation events that can lead to destructive flooding; contributes to “marine heat waves” that damage or destroy coral reefs; and disrupts atmospheric circulation patterns.

Figure 3. Total ocean heat content (OHC) in the top 2000 meters from 1958-2021. (Credit: Cheng et al., 2022, Another record: Ocean warming continues through 2021 despite La Niña conditions, Advances in Atmospheric Sciences)

A slew of heat records in 2021

International weather records researcher Maximiliano Herrera keeps the pulse of the planet in remarkable detail, and he logged 10 nations or territories that set or tied their all-time reliably measured heat records in 2021. This total falls well short of the record of 24 such records in 2019. One nation set an all-time cold record in 2021. Here are the all-time heat records set in 2021 (note that Herrera does not consider the official U.S. all-time heat record of 56.7°C (134°F) at Death Valley in 1913 to be reliably measured):

United Arab Emirates:  51.8°C (125.2°F) at Sweihan, June 6 (tie);
Oman: 51.6°C (124.9°F) at Joba, June 16;
Canada: 49.6°C (121.3°F) at Lytton, June 29 (record beaten three consecutive days);
U.S.: 54.4°C (130°F) at Death Valley Furnace Creek, California, July 9 (tie);
Morocco: 49.6°C (121.3°F) at Sidi Slimane, July 10 (tie);
Turkey: 49.1°C (120.4°F) at Cizre, July 20;
Taiwan: 40.6°C (105.1°F) at Taimali, July 25;
Tunisia: 50.3°C (122.5°F) at Kairouan, August 11;
Italy: 48.8°C (119.8°F) at Siracusa (Syracuse), August 11; and
Dominica: 35.8°C (96.4°F) at Canefield Airport, August 12.

One all-time national/territorial cold record set or tied in 2021

United Arab Emirates (for places at low elevations): -2.0°C (28.4°F) at Raknah, January 9.

Among global weather stations having at least 40 years of record-keeping, Herrera documented 404 that exceeded (not just tied) their all-time heat record in 2021; 54 stations with a long-term period of record set an all-time cold record. For comparison, 348 stations set their all-time heat record in 2020 and eight set their all-time cold record.

106 monthly national/territorial heat records beaten or tied in 2021

In addition to the all-time national/territorial records listed above, 106 nations or territories set monthly all-time heat records in 2021, for a total of 116 monthly all-time records:

– January (10): Mexico, Bangladesh, Nigeria, Japan, Malta, Tunisia, Turkey, Russia, Georgia, Spain;
– February (12): Iraq, Uzbekistan, Mongolia, South Korea, Liechtenstein, Slovenia, Croatia, Slovakia, Poland, Sweden, Pakistan, Northern Mariana Islands;
– March (14): Northern Mariana Islands, Qatar, Saudi Arabia, Bahrain, Kuwait, Pakistan, Oman, Jersey, Guernsey, Germany, Netherlands, Luxembourg, Belgium, US Virgin Islands;
– April (4): South Africa, Northern Mariana Islands, Hong Kong, Tajikistan;
– May (8): Northern Mariana Islands, Taiwan, Russia, Qatar, Turkmenistan, Uzbekistan, Dominica, Saba;
– June (8): Cocos Islands, Congo Brazzaville, Mexico, Belarus, Estonia, Malta, Tunisia, Botswana;
– July (1): Cocos Islands;
– August (10): Qatar, Mexico, Morocco, Spain, Andorra, Iceland, Gabon, Botswana, Kenya, Philippines;
–  September (9): Hong Kong, Norway, Saba, Central African Republic, Maldives, Botswana, Dominica, Angola, Kenya;
– October (11): Iran, Morocco, China, South Korea, Taiwan, Botswana, Bangladesh, Antigua and Barbuda, French Southern and Antarctic Lands, Peru, Malaysia;
– November (7): United Arab Emirates, Bulgaria, Botswana, Cyprus, Taiwan, Solomon Islands, Haiti; and
– December (12): Bangladesh, Azerbaijan, Canada,  Kazakhstan, Kyrgyzstan, Nepal, Comoros, Reunion, British Indian Ocean Territory, Paraguay, Mexico, Portugal.

Five monthly national/territorial cold records beaten or tied in 2021

Six nations or territories set all-time monthly cold records (including the all-time cold record set in the United Arab Emirates, listed above):

– April (2): Slovenia, Switzerland;
– June (2): Saba, Paraguay; and
– July (1): Namibia.

Notable global heat and cold records for 2021

Hottest temperature in the Northern Hemisphere: 54.4°C (130.0°F) at Death Valley, U.S., July 9;
Coldest temperature in the Northern Hemisphere: -64.1°C (-83.4°F) at Summit, Greenland, March 25;
Hottest temperature in the Southern Hemisphere: 47.9°C (118.2°F) at Mardie, Australia, December 20;
Coldest temperature in the Southern Hemisphere: -81.9°C (-115.4°F) at Dome Fuji, Antarctica, June 14;
Highest 2021 average temperature worldwide: 32.4°C (90.3°F) at Yelimane, Mali; and
Highest 2021 average temperature in the Southern Hemisphere: 29.7°C (85.5°F) at Surabaya Airport, Indonesia.

Earth’s record for hottest yearly average temperature was 32.9°C (91.2°F) at Makkah, Saudi Arabia, in 2010 and 2016.

Hemispherical and continental temperature records in 2021

– Highest minimum temperature ever recorded in April in the Southern Hemisphere: 31.7°C (89.1°F), at Vioolsdrif, South Africa, April 13;
– Highest minimum temperature ever recorded in May in Europe: 29.4°C (84.9°F), at Zymbragou, Greece, May 2;
– Highest minimum temperature ever recorded in June in North America: 40.3°C (104.5°F), at Stovepipe Wells, U.S., June 18;
– Highest reliable temperature on Earth: 54.4°C (130°F) at Death Valley Furnace Creek, California (U.S.), July 9 (129.9°F measured there in August 2020 was also rounded to 54.4°C);
– Highest minimum temperature ever recorded in North America and the highest minimum temperature in the world in July: 42.0°C (107.6°F) at Stovepipe Wells, California (U.S.), July 11;
– Highest minimum temperature recorded in July in Europe: 34.3°C (93.7°F), Kalymnos, Greece, July 31;
– Highest minimum temperature recorded in August in Europe: 35.2°C (95.4°F), Plakias, Greece, August 3;
– Highest temperature ever recorded in Europe: 48.8°C (119.8°F), Siracusa (Syracuse), Italy, August 11; and
– Highest minimum temperature ever recorded globally in September: 38.9°C (102.0°F) at Badwater Basin (Death Valley), California (U.S.), September 9.

Figure 4. Departure of sea surface temperature from average in the benchmark Niño 3.4 region of the eastern tropical Pacific (5°N-5°S, 170°W-120°W). Sea surface temperatures were approximately one degree Celsius below average over the past month, characteristic of borderline weak-to-moderate La Niña conditions. (Image credit: Tropical Tidbits)

December 2021: Earth’s fifth-warmest December on record

December 2021 was the fifth-warmest December since global record-keeping began in 1880, NOAA’s National Centers for Environmental Information reported January 13. NASA and the European Copernicus Climate Change Service rated the month as the sixth-warmest December on record. Again: Minor differences in rankings often occur among various research groups, the result of different ways they handle data-sparse regions such as the Arctic.

In the U.S., December 2021 was the warmest December on record, as detailed in a January 10 post at this site by Bob Henson.

La Niña conditions remain near the weak-to-moderate threshold

La Niña conditions persisted during December, and they are expected to continue through the Northern Hemisphere spring (67% chance) and transition to neutral conditions by the April-May-June period (51% chance), NOAA reported in its January monthly discussion of the state of the El Niño/Southern Oscillation, or ENSO. To be designated an official La Niña event, La Niña conditions have to be present for at least five consecutive months, with each month representing three-month average conditions. This criterion was met in December.

Over the past month, sea surface temperatures in the benchmark Niño 3.4 region of the eastern tropical Pacific (5°N-5°S, 170°W-120°W) were about 1.0 degree Celsius below average. The range for “weak” La Niña conditions is 0.5-1.0 degree Celsius below average; the range for “moderate” La Niña conditions is 1.0-1.5 degrees Celsius below average.

The NOAA and Columbia University’s International Research Institute for Climate and Society forecast for the upcoming Atlantic hurricane season (August-September-October) is for a 30% chance of La Niña, 45% chance of ENSO-neutral, and a 25% chance of El Niño.

The impact of the current La Niña event may be being boosted by an intensely negative Pacific Decadal Oscillation (PDO). The PDO is an index of sea surface temperatures across the northeast and tropical Pacific Ocean that reflects some of the circulation aspects of the El Niño-Southern Oscillation. The PDO can swing sharply from month to month, but usually it leans positive (warm) or negative (cool) for a few years at a time. Almost every month since 2017 has seen a negative PDO, and the past three months have seen exceptionally negative values; the December PDO index was the lowest for any December in data going all the way back to 1854. When the PDO is negative, La Niña is more common and its impacts are often more pronounced, and the highly negative PDO of December 2021 may have played a role in the intense December weather observed in the United States.

Arctic sea ice: 13th-lowest December extent on record

Arctic sea ice extent during December 2021 was the 13th-lowest in the 44-year satellite record, according to the National Snow and Ice Data Center (NSIDC). This is the highest December extent since 2014, and led the NSIDC to call the results “a good winter, relatively speaking.”

Antarctic sea ice extent in December was approximately tied for second-lowest on record, behind the record-low extent of 2016.

Notable global heat and cold marks for December 2021

– Hottest temperature in the Northern Hemisphere: 41.5°C (106.7°F) at Matam, Senegal, December 3;
– Coldest temperature in the Northern Hemisphere: -61.1°C (-78.0°F) at Delyankir, Russia, December 8;
– Hottest temperature in the Southern Hemisphere: 47.9°C (118.2°F) at Mardie, Australia, December 20; and
– Coldest temperature in the Southern Hemisphere: -45.1°C (-49.2°F) at Concordia, Antarctica, December 3.

Major weather stations’ new all-time heat or cold records in December 2021

Among global stations with a record of at least 40 years, three stations set (not just tied) all-time cold records in December 2021, and two stations set an all-time heat record:

Jiayin (China) min. -44.4°C, December 24;
Wuying (China) min. -43.0°C, December 24;
Fuyuan (China) min. -42.3°C, December 24;
Jurien Bay (Australia) max. 46.0°C, December 25; and
Rottnest Island (Australia) max. 42.5°C, December 26.

(Courtesy of Maximiliano Herrera)

Bob Henson contributed to this post.

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Jeff Masters

Jeff Masters, Ph.D., worked as a hurricane scientist with the NOAA Hurricane Hunters from 1986-1990. After a near-fatal flight into category 5 Hurricane Hugo, he left the Hurricane Hunters to pursue a...