April 2020 was the planet's second warmest April since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) on Wednesday. April 2020 came in just 0.07°C below the record set in April 2016, according to NOAA, but was the warmest April on record, 0.04°C above 2016, according to NASA. Minor differences in global temperature rankings between NOAA and NASA often occur because of the the differing ways they handle data-sparse regions like the Arctic. Missing data due to the Covid-19 pandemic caused additional data quality problems in April.

The year-to-date period of January – April ranks as the second warmest such period on record, behind 2016, said NOAA. According to NCEI's annual temperature outlook, the year 2020 has over a 99.9% chance to rank among the five warmest years on record, and a 69% chance of being the warmest year on record. This would make each of the past seven years among the seven warmest years on record.

NOAA classified April 2020 as having the 11th highest monthly temperature departure from average for any month in the 1,683-month record, dating back to 1880: 1.06°C (1.91°F) above the 20th century average. NASA rated April 2020 as having the 8th highest monthly temperature departure from average, with all four months of 2020 ranking in the top ten.

Global temperature records are more likely to be set during the peak of the solar cycle--and during strong El Niño events, due to the extra heat the tropical Pacific Ocean gives up to the atmosphere. The remarkable warmth of 2020 has come in the absence of an El Niño event and during the minimum of one of the weakest 11-year solar cycles in the past century, speaking to the dominant role human-caused global warming has in heating our planet.

Global ocean temperatures during April 2020 were the warmest on record, and global land temperatures were the second warmest on record. Global satellite-measured temperatures in April 2020 for the lowest 8 km of the atmosphere were the fourth warmest in the 42-year record, according to the University of Alabama Huntsville (UAH) and RSS.

Departure of temperature from average
Figure 1. Departure of temperature from average for April 2020, the second warmest April for the globe since record keeping began in 1880. Record-warm April surface temperatures were present across parts of the Atlantic Ocean, Mexico, the Gulf of Mexico, northern South America, Africa, northern Asia, as well as parts of the Indian and western Pacific oceans. Overall, April 2020 had 6.87% of the world's land and ocean surfaces with a record high April temperature. No land or ocean areas had record cold April temperatures. Credit: NOAA National Centers for Environmental Information (NCEI)

Three billion-dollar weather disasters in March 2020; ten for the year

Three billion-dollar weather-related disasters hit the Earth last month, according to the April 2020 Catastrophe Report from insurance broker Aon:

1) A severe weather outbreak on April 6 - 9 in the Midwest, Plains, Southeast, and Mid-Atlantic U.S. brought widespread damage due to hail and high winds, but no deaths. Damage was estimated at $1.9 billion.

2) A severe weather outbreak on April 10 - 14 in the Midwest, Plains, Southeast, and Mid-Atlantic U.S. featured 138 tornadoes, with three EF4 tornadoes and 12 EF3 tornadoes. At least 38 people were killed, and damage was estimated at $1.0 billion. The 32 people killed by tornadoes during the outbreak made it the deadliest tornado outbreak since April 27 – 30, 2014. The April 12, 2020 EF4 tornado that began in Jefferson Davis County, Mississippi was 2.25 miles wide--the widest tornado in Mississippi history, and not far from the world-record 2.6-mile-wide tornado that hit El Reno, Oklahoma on May 31, 2013.

3) Flooding in Iran from late February through the end of April killed 23 people and cost $1.2 billion.

Through the end of April, Earth had seen ten billion-dollar weather disasters in 2020. The Australian wildfires span the boundary between 2019-2020, and may end up being classified as a 2019 disaster, rather than a 2020 disaster, though. Here is the 2020 list:

1.  Wildfires, Australia, 11/8 – 1/17, $2+ billion, 34 killed
2.  Windstorm Ciara, Western & Central Europe, 2/9 – 2/10, $2.3 billion, 14 killed
3.  Severe Weather, Midwest, Plains, Southeast, and Mid-Atlantic U.S., 4/6 – 4/9, $1.9 billion, 0 killed
4.  Severe Weather, Central and Eastern U.S., 3/27 – 3/30, $1.8 billion, 0 killed
5.  Severe Weather, Australia, 1/18 – 1/20, $1.26 billion, 0 killed
6.  Severe Weather, Central and Eastern U.S., 2/3 – 2/8, $1.25 billion, 5 killed
7.  Severe Weather, Central and Eastern U.S., 1/10 – 1/12, $1.2 billion, 12 killed

8.  Flooding, Iran, 2/24 – 4/30, $1.2 billion, 23 killed
9.  Severe Weather/Nashville Tornado, Central and Eastern U.S., 3/2 – 3/4, $1.1 billion, 25 killed
10. Severe Weather, Midwest, Plains, Southeast, and Mid-Atlantic U.S., 4/10 – 4/14, $1.0 billion, 38 killed

The deadliest weather event of April and of 2020 so far was the ongoing flooding in East Africa from the current “Long Rain” season, which runs from March through May. At least 400 people have died in the floods. Kenya has been the hardest-hit, with 194 deaths from mid-April through May 6.

Neutral El Niño conditions reign

NOAA’s May 14 monthly discussion of the state of the El Niño/Southern Oscillation (ENSO) stated that neutral ENSO conditions existed, with neither an El Niño nor a La Niña event in progress. Over the past month, sea surface temperatures (SSTs) in the benchmark Niño3.4 region of the eastern tropical Pacific were about 0.2°C above-average, well below the 0.5°C above-average threshold needed to be considered El Niño conditions. 

Forecasters at NOAA and the International Research Institute for Climate and Society (IRI) are calling for a roughly 65% chance of neutral conditions continuing through the Northern Hemisphere summer. They put the odds of an El Niño forming by the August-September-October peak of the hurricane season at about 10%, and the odds of a La Niña event at 38% (an increase from the 30% chance given a month ago). Atlantic hurricane seasons tend to be much more active during La Niña conditions than during El Niño conditions, due to weaker upper-level winds creating lower amounts of wind shear.

As far as the difference between La Nina (ENSO cold phase) and ENSO-neutral for the Atlantic hurricane season goes, this 2007 paper (https://journals.ametsoc.org/doi/pdf/10.1175/JCLI4063.1) found: "ENSO cold-phase landfall frequencies are only slightly larger than neutral-phase landfall frequencies along the Florida and Gulf coasts. However, for the East Coast, from Georgia to Maine, a significant decrease in landfall frequency occurs during the neutral ENSO phase as compared to the cold phase. Along the East Coast, two or more major (category 3 or above) hurricanes never made landfall in the observational record (1900–2004) during a single hurricane season classified as an ENSO neutral or warm phase." Addendum: during the 2005 - 2018 period, there were no Cat 3 hurricanes making landfall in the Georgia to Maine region. 

Departure of temperature from average
Figure 2. Departure of sea surface temperatures (SSTs) in the benchmark Niño 3.4 region (in the equatorial Pacific) ending on May 13, 2020. During the first two weeks of May, SSTs were near average—neutral conditions. Credit: Levi Cowan tropicaltidbits.com

Arctic sea ice: fourth lowest April extent on record

Arctic sea ice extent during April 2020 was the fourth lowest in the 42-year satellite record, according to the National Snow and Ice Data Center (NSIDC). The amount of first-year ice (0- to 1-year old) is close to the same level as last year’s, at about 70 percent of the Arctic Ocean ice cover, much higher than during the mid-1980s, when only 35 to 40 percent of the ice was less than a year old. 

An intense March storm, whose 970 mb central pressure was the lowest ever recorded in the Arctic in March, created large ice rubble piles near Utqiaġvik, Alaska (formerly called Barrow), and caused difficulties for Indigenous hunters along the northwestern Alaskan coast during April.

Antarctic sea ice extent in April 2020 was near the 1981 – 2010 average.

Notable global heat and cold marks for April 2020

Hottest temperature in the Northern Hemisphere: 48.8°C (119.8°F) at Gallinas and Tamuin, Mexico, 12 April
Coldest temperature in the Northern Hemisphere: -43.0°C (-45.4°F) at Summit, Greenland, 5 April
Hottest temperature in the Southern Hemisphere: 43.0°C (109.4°F) at Knysna, South Africa, 19 April
Coldest temperature in the Southern Hemisphere: -74.8°C (-102.6°F) at Dome Fuji, Antarctica, 11 April

Highest 2020 average temperature to date (1 Jan-30 Apr) worldwide: 32.9°C (91.2F) at Telfer, Australia 
Highest 2020 average temperature to date (1 Jan-30 Apr) in the Northern Hemisphere: 32.1°C (89.8°F) at Yelimane, Mail

(Courtesy of Maximiliano Herrera.)

Major weather stations that set (not tied) new all-time heat or cold records in April 2020

Among global stations with a period of record of at least 40 years, 34 set (not just tied) a new all-time heat record in April, and 0 set all-time cold records:

Bougouni (Mali) max. 44.2°C, 3 April
Navrongo (Ghana) max. 44.0°C, 6 April: New national record high for Ghana 
Bissau (Guinea Bissau) max. 41.4°C, 6 April

Birni N'Konni (Niger) max. 47.2°C, 6 April
Naranjo (Costa Rica) max. 35.2°C, 7 April
Tapachula (Mexico) max. 41.0°C, 8 April
La Esperanza (Honduras) max. 31.9°C, 10 April
Palo Seco (Cuba) max. 39.2 °C, 10 April: New national record high for Cuba  
Jovellanos (Cuba) max. 38.7°C, 10 April  
Las Tunas (Cuba) max. 38.3°C, 10 April
Camaguey (Cuba) max. 38.2°C, 10 April
Colon (Cuba) max. 38.2°C, 10 April
Santo Domingo (Cuba) max. 37.8°C, 10 April
Isla de la Juventud (Cuba) max. 36.1°C, 10 April
Florida (Cuba) max. 38.1°C, 11 April

Jucarito (Cuba) max. 39.2°C, 11 April
Pinares de Mayari (Cuba) max. 33.5°C, 11 April
Indio Hatuey  (Cuba) max. 39.3°C, 2 April
Havana (Cuba) max. 38.5°C, 12 April

Veguitas (Cuba) max. 39.7°C, 12 April: New national record high for Cuba
Trevani (Mayotte, France dependancy) max 36.4°C, 14 April : New territorial high for Mayotte
La Palma (Cuba) max. 37.1°C, 14 April  
Ouagadougou (Burkina Faso) max. 44.2°C, 17 April

Bobo Dioulasso (Burkina Faso) max. 42.0°C, 17 April
Sikasso (Mali) max. 42.5°C, 17 April
Zamboanga (Philippines) max. 37.9°C, 18 April

Caibarien (Cuba) max. 37.0°C, 20 April
Cayo Coco (Cuba) max. 36.8°C, 20 April
Lom Sak (Thailand) max. 42.3°C, 21 April
Takfa (Thailand) max. 42.0°C, 21 April
Chainat (Thailand) max. 42.0°C, 21 April

Toungoo (Myanmar) max. 44.7°C, 22 April
Santa Rosa de Copan (Honduras) max. 37.0°C, 24 April  

Ouesso (Congo Brazzaville) max. 38.7°C, 25 April
Bahia Honda (Cuba) max. 36.3°C, 25 April

Four all-time national/territorial heat record set or tied in 2020

As of May 21, four nations had set an all-time national heat record in 2020:

Colombia: 42.6°C (108.9°F) at Jerusalen, 19 February (tie)
Ghana: 44.0°C (111.2°F) at Navrongo, 6 April
Cuba: 39.2°C (102.6°F) at Palo Seco, 10 April; broken again on 11 April with 39.3°C (102.7°F) at Veguitas, and again on 12 April with 39.7°C (103.5°F) at Veguitas
Mayotte, France dependancy: 36.4°C (97.5°F) at Trevani, 14 April

No all-time national cold records have been set thus far in 2020.

(Courtesy of Maximiliano Herrera.)

Fifty-one other monthly national/territorial heat record beaten or tied in 2020 as of May 25

In addition to the four all-time national heat records, 51 other national monthly heat records have been set thus far in 2020, for a total of 55 national monthly heat records:

January (12): Norway, South Korea, Angola, Congo Brazzaville, Dominica, Mexico, Indonesia, Guinea Bissau, Gambia, Sao Tome and Principe, Cuba, British Indian Ocean Territory
February (10): Spain, Antarctica, Azerbaijan, Costa Rica, The Bahamas, Switzerland, Maldives, Gambia, Russia, Seychelles
March (7): Paraguay, Cabo Verde, Mozambique, Seychelles, United States, Thailand, Northern Marianas Islands
April (14): Paraguay, Niger, St. Barthelemey, Honduras, Guernsey, Haiti, Congo, Brazzaville, Kyrgyzstan, Mongolia, China, Saba, Northern Marianas Islands, U.S. Virgin Islands
May (8): Niger, Greece, Saba, Cyprus, Israel, Solomon Islands, Turkey, Haiti

One monthly national cold record has been beaten or tied in 2020:

April: St. Eustatius

(Courtesy of Maximiliano Herrera.)

Hemispherical and continental temperature records in 2020

Highest minimum temperature ever recorded the Northern Hemisphere in January: 29.1°C (84.4°F) at Bonriki, Kiribati, 17 January. 

Highest maximum temperature ever recorded in North America in January: 42.0°C (107.6°F) at Vicente Guerrero, Mexico, 21 January.

Highest temperature ever recorded in continental Antarctica and highest February temperature ever recorded in Antarctica plus the surrounding islands: 18.4°C (65.1°F) at Base Esperanza, 6 February.

Highest minimum temperature ever recorded in February in Antarctica: 7.6°C (45.7°F) at Base Marambio, 9 February.

Highest minimum temperature ever recorded in March in the Northern Hemisphere: 32.0°C (89.6°F) at Yelimane, Mali on 23 February.

Highest minimum temperature ever recorded in April the Southern Hemisphere: 31.1°C (88.0°F) at Argyle, Australia on 2 April.

Highest minimum temperature ever recorded in May in Europe: 30.1°C (86.2°F) at Emponas, Greece, on 17 May.

 (Courtesy of Maximiliano Herrera.)