September 2021 was Earth’s fifth-warmest September since global record-keeping began in 1880, 0.90 degree Celsius (1.62°F) above the 20th-century average (and just 0.04 degree Celsius below the record held jointly by 2020, 2019, 2016, and 2015), NOAA’s National Centers for Environmental Information, NCEI, reported October 14. NASA reported September 2021 as the second-warmest September on record, 1.16 degrees Celsius (2.09°F) above the 1880-1920 period, which is its best estimate of preindustrial temperature. Minor differences in rankings between the two agencies result from the different ways they treat data-sparse regions such as the Arctic.

The month’s heat was focused more on land areas than ocean areas, thus impacting society more directly: September 2021 global ocean temperatures were the sixth warmest on record, according to NOAA, with global land areas experiencing their second warmest September on record. Africa and South America had their warmest September on record; North America, its third warmest; and Asia, its ninth warmest. As detailed in our post last week, the contiguous U.S. experienced its fifth-warmest September on record in 2021. Satellite-measured September temperatures of the lower atmosphere were the sixth-warmest in the 43-year-long record, according to the University of Alabama, Huntsville.

Figure 1. Departure of temperature from average for September 2021, the fifth warmest September for the globe since record keeping began in 1880. Record-warm September temperatures were present across parts of Africa, the Atlantic Ocean, the British Isles, southern Asia, South America, and the Pacific Ocean. (Image credit: NOAA/NCEI)

January-September ranked as Earth’s sixth warmest such period on record. According to NCEI’s annual temperature outlook, the year 2021 is highly likely to rank among the 10 warmest years on record, and more than 95% likely to fall in the range of sixth- to seventh-warmest on record. These odds are based on statistical averages and do not take into account the arrival of La Niña (see below), which tends to reduce global temperature slightly.

One billion-dollar weather disaster in September; 35 so far in 2021

Earth experienced one billion-dollar weather disaster in September 2021, according to Aon: category 1 Hurricane Nicholas, which hit Texas on September 14, causing $1 billion in damage. In addition, four other weather disasters earlier in the year accumulated enough damages by the end of September to exceed the $1 billion threshold, giving the Earth 35 billion-dollar weather disasters so far in 2021. The most in an entire year is 50 billion-dollar weather disasters, set in 2020. In the U.S., Aon catalogued 17 billion-dollar weather disasters so far in 2021, while NOAA counted 18 (NOAA lumps all wildfires into one disaster, while Aon treats individual fires as separate disasters).

Figure 2. Billion-dollar weather disasters in January through September 2021, according to Aon.

La Niña has arrived

La Niña conditions have overtaken the Eastern Pacific, NOAA reported in its October monthly discussion of the state of the El Niño/Southern Oscillation, or ENSO.

Over the past week, sea surface temperatures in the benchmark Niño 3.4 region of the eastern tropical Pacific (5°N-5°S, 170°W-120°W) were 0.6 degree Celsius below average. The range for “weak” La Niña conditions is 0.5-1.0 degree Celsius below average; the range for a “moderate” La Niña is 1.0-1.5 degrees Celsius below average.

The NOAA and Columbia University International Research Institute for Climate and Society forecast for the December-January-February period is for an 87% chance of La Niña, 13% chance of ENSO-neutral, and a 0% chance of El Niño.

At its peak, the La Niña event is expected to be at moderate strength (57% chance). Historically, about half of all northern hemisphere winter La Niña events (such as that during the previous 2020-2021 winter, also of moderate strength) have continued into or re-emerged during the following winter.

Figure 3. 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). Temperatures were 0.4-0.7 degree Celsius below average over the past month. (Image credit: Tropical Tidbits)

The predicted moderate-strength La Niña event is potentially bad news for the drought-stricken U.S. Southwest and Southern Plains, where reduced wintertime precipitation is more common during La Niña events. In order 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.

A La Niña event forming at this point in the year could foster an active end to the Atlantic hurricane season – particularly since ocean temperatures in the typical October/November breeding grounds for tropical cyclones (the Caribbean, Gulf of Mexico, and off the Southeast U.S. coast) are much above average. While there is currently little to be concerned about in the Atlantic, the GFS ensemble model has been predicting in recent runs that the Caribbean may be an area to watch for tropical cyclone development beginning on Wednesday.

Figure 4. Departure of sea surface temperature from average for October 14, 2021. Temperatures were more than one degree Celsius (1.8°F) above average over a large portion of the Caribbean, Gulf of Mexico, and waters along the Southeast U.S. coast. (Image credit: Tropical Tidbits)

Arctic sea ice: 12th-lowest September extent on record

Arctic sea ice extent during September 2021 was the 12th-lowest in the 43-year satellite record, according to the National Snow and Ice Data Center (NSIDC). Low pressure and cloudy skies dominated the Arctic this summer, leading to the highest September ice extent since 2014.

Despite September total ice extent being higher than in recent years, the amount of multiyear ice was at a near-record low, with an extent of only 1.29 million square kilometers (498,000 square miles), just slightly above the record-low value of 1.27 million square kilometers (490,000 square miles) at the end of the 2012 melt season. Arctic ice thickness and volume were also at near-record low values in September 2021.

Antarctica: a near-record cold winter and a significant ozone hole

According to NSIDC, “For the interior of the Antarctic continent, specifically the region near the South Pole, the winter of 2021 was among the coldest on record. At the National Science Foundation’s Amundsen-Scott South Pole Station, temperatures for June, July, and August were 3.4 degrees Celsius (6.1 degrees Fahrenheit) lower than the 1981-to-2010 average at -62.9 degrees Celsius (-81.2 degrees Fahrenheit).”

These temperatures make the 2021 winter the second coldest winter (June-July-August) on record, behind only 2004 in the 60-year weather record at the South Pole Station. For the polar darkness period, from April through September, the average temperature was -60.9 degrees Celsius (-77.6°F), a record for those months.

The unusual cold was attributed to two extended periods of stronger-than-average encircling winds around the continent: Those winds tend to isolate the ice sheet from warmer conditions. A strong upper-atmosphere polar vortex was observed also, leading to a significant ozone hole, in the upper quartile (top 25 percent) of ozone reduction events since 1979. Had the world not greatly reduced its emission of ozone-depleting chemicals since the 1990s, the ozone loss in this year’s cold Antarctic would have been far worse.

Antarctic sea ice extent during September was near-average.

Figure 5. Global food prices averaged over the year 2021 are the highest since 1975, after adjusting for inflation. (Image credit: United National Food and Agriculture Organization)

Food prices hit a 46-year high

Global food prices in September were at their highest level since September 2011, said the United Nations Food and Agriculture Organization (FAO) in its monthly report on October 7. After adjusting for inflation, 2021 food prices averaged for the first nine months of the year were the highest since 1975.

The September increase was driven by a surge in the price of grains and vegetable oil, with wheat prices a dominant driver; drought in Russia and Canada contributed to the high wheat prices. However, total global production of grains in 2021 is expected to set an all-time record: 1.1% more than the previous record set in 2020. Unfortunately, because of higher demand (in part, from an increased amount of wheat used to feed animals), the 2021 harvest was not expected to meet consumption requirements in 2021/2022, resulting in a drawdown in global grain inventories to their lowest levels since 2015/2016.

While the impact of Hurricane Ida on U.S. grain exports did cause “upward pressure” on corn prices, the report said, that pressure was countered by improved global crop prospects and the start of harvests in the U.S. and Ukraine.

The surge in food prices this year is concerning: High wheat prices in 2011 (in the wake of export restrictions triggered by drought in Russia) helped lead to massive civil unrest and the toppling of multiple governments (the “Arab Spring”). See my in-depth 2016 analysis, Food System Shock: Climate Change’s Greatest Threat to Civilization.

Notable global heat and cold marks for September 2021

The information below is courtesy of Maximiliano Herrera. Follow him on Twitter: @extremetemps:

– Hottest temperature in the Northern Hemisphere: 50.1°C (122.2°F) at Jahra, Kuwait, September 1;
– Coldest temperature in the Northern Hemisphere: -46.3°C (-51.3°F) at Summit, Greenland, September 9;
– Hottest temperature in the Southern Hemisphere: 43.9°C (111.0°F) at Corumba, Brazil, September 20;
– Coldest temperature in the Southern Hemisphere: -79.4°C (-110.9°F) at Vostok, Antarctica, September 30;
– Highest 2021 average temperature to date (Jan.-Sep.) in the Southern Hemisphere: 29.7°C (85.5°F) at Surabaya Airport, Indonesia; and
– Highest 2021 average temperature to date (Jan.-Sep.) in the Northern Hemisphere: 33.0°C (91.4°F) at Makkah, Saudi Arabia.

September 2021 major weather stations’ new all-time heat or cold records: 6 all-time heat records, no all-time cold records

Among global stations with a record of at least 40 years, six set, not just tied, all-time heat records in September; no stations set an all-time cold record:

Puerto Casado (Paraguay) max. 43.0°C, September 19;
Corumba (Brazil) max. 43.9°C, September 20;
Tres Lagoas (Brazil) max. 43.1°C, September 20;
Valparaiso (Brazil) max. 42.3°C, September 21;
Jales (Brazil) max. 42.4°C, September 21; and
Correntina (Brazil) max. 41.2°C, September 22.

10 all-time national/territorial heat records set or tied in 2021

As of September 30, 2021, 10 nations or territories had set or tied an all-time reliably-measured national heat record:

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 3 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, 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

As of September 30, 2021, one nation or territory had set or tied an all-time national cold record:

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

Seventy-six monthly national/territorial heat records beaten or tied as of September 30

In addition to the all-time national/territorial records listed above, 76 nations or territories have set monthly all-time heat records; five have set all-time monthly cold 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; and
–  September (9): Hong Kong, Norway, Saba, Central African Republic, Maldives, Botswana, Dominica, Angola, Kenya.

Five monthly national/territorial cold records beaten or tied as of September 30

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

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, 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.

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...