Earth Had Its 4th Warmest Year on Record in 2018, Say NOAA and NASA

In its annual climate summary released on Wednesday, delayed several weeks because of the government shutdown, NOAA’s National Centers for Environmental Information (NCEI) reported that Earth experienced its fourth warmest surface temperature in records going back to 1880. NASA and the Japan Meteorological Agency also found 2018 to be the fourth warmest year on record. The five warmest years on record are the now past five years—2016, 2015, 2017, 2018, and 2014, in that order.

From 1880 to 1980, a new temperature record in the NOAA database was set on average every 13 years; however, for the period 1981–2018, the frequency of a new record increased to once every three years. The yearly global land and ocean temperature increased at an average rate of 0.07°C (0.13°F) per decade from 1880 - 2018; however, the average rate of increase since 1981 (0.17°C / 0.31°F) has been more than twice as rapid. This acceleration in global warming is an expected result of the ever-increasing amounts of human-emitted greenhouse gases going into the atmosphere.

The 2018 temperatures were slightly cooler than the previous three years, since the year began with La Niña conditions. During a La Niña, the large amount of cooler-than-average water in the tropical Pacific tends to decrease global temperatures. In addition, 2018 fell near the minimum of the 11-year solar sunspot cycle, which exerted a slight cooling influence.

Figure 1. Departure of surface temperature from average for the globe during 2018. Record warm temperatures were measured across much of Europe and the Mediterranean Sea, the Middle East, New Zealand and surrounding ocean, and across parts of Asia, the Atlantic Ocean and the western Pacific Ocean. No regions experienced record cold conditions. The Caribbean region had its coolest year since 2012, while the Atlantic Main Development Region had its coolest year since 2001. For Europe as a whole, 2018 surpassed 2014 as the warmest year on record. Image credit: NOAA.

NOAA calculated that the average global temperature for 2018 was 1.75°F (0.97°C) above the 1880–1900 average, which is a period commonly used to represent pre-industrial conditions. The years 2015 – 2018 were all slightly more than 1°C above this pre-industrial baseline. The Paris Agreement on climate change seeks to keep global temperatures at no more than 2°C above the pre-industrial threshold, and preferably no more than 1.5°C.

Last year was the sixth warmest on record for satellite-based estimates of temperature through the lowest five miles of the atmosphere, as calculated by the University of Alabama in Huntsville (UAH) and RSS. Because these satellite calculations are large-scale estimates of temperature averaged through a layer well above ground level, they differ from ground-based measurements of surface temperature taken at particular points and from air temperatures over the ocean inferred from sea-surface temperatures. Satellite-based estimates are much more strongly affected by El Niño events.

Notable global heat and cold marks in 2018

Hottest temperature in the Northern Hemisphere: 53.0°C (127.4°F) at Ahvaz, Iran, 2 July
Coldest temperature in the Northern Hemisphere: -61.5°C (-78.7°F) at Geo Summit, Greenland, 6 January
Hottest temperature in the Southern Hemisphere: 49.3°C (120.7°F) at Marble Bar, Australia, 27 December
Coldest temperature in the Southern Hemisphere: -82.4°C (-116.3°F) at Vostok, Antarctica, 27 August

A remarkable 431 major weather stations with a long period of record (POR exceeding 40 years) broke (not tied) their all-time heat record in 2018. In contrast, only 40 major weather stations with a long period of record (POR exceeding 40 years) broke (not tied) their all-time cold record in 2018.

(Courtesy of Maximiliano Herrera.)

Six all-time national heat records tied or broken in 2018

In 2018, six nations broke or tied an all-time record for hottest temperature in recorded history:

Palau: 95°F (35°C) at Koror on March 22
Algeria: 124.3°F (51.3°C) at Ouargla on July 5
Taiwan: 104.5°F (40.3°C) at Tianxiang on July 10
Japan: 106.0°F (41.1°C) at Kumagaya on July 23
South Korea: 105.8°F (41.0°C) at Hongcheon on August 1
Kiribati: 96.0°F (35.6°C), Kanton Island on November 20 (ties previous record)

No nations set an all-time cold temperature record in 2018.

Most nations do not maintain official databases of extreme temperature records, so the national temperature records reported here are in many cases not official. I use as my source for international weather records researcher Maximiliano Herrera, one of the world's top climatologists, who maintains a comprehensive list of extreme temperature records for every nation in the world on his website. If you reproduce this list of extremes, please cite Maximiliano Herrera as the primary source of the weather records.

Sixty-seven monthly national/territorial heat records were set in 2018

January: Marshall Islands
February: Marshall Islands, Falkland Islands, Kuwait, Qatar, Saudi Arabia, Palau, Ethiopia, Angola
March: Marshall Islands, Qatar, Armenia, Madagascar, Pakistan, Iraq, UAE, Turkmenistan, Tajikistan, Uzbekistan, Saba
April: Albania, Montenegro
May: Hong Kong, Norway, Tonga
June: Oman, Marshall Islands, Cocos Islands, Tonga, Isle of Man
July: Iran, Namibia, Indonesia, El Salvador, Jordan, Netherlands, South Korea, Comoros, Bangladesh
August: Japan, Fiji, Falkland Islands, Liberia
September: Iraq, Comoros, Myanmar, Sao Tome and Principe
October: Japan, Finland, Thailand, Switzerland, Guam, Angola
November: Hungary, Albania, Slovakia, Poland, Guam, Seychelles, Myanmar
December: Marshall Islands, Japan, Taiwan, Cabo Verde, Angola, Thailand, India
(Courtesy of Maximiliano Herrera.)

One national monthly cold record set in 2018

September: Iceland

Continental/hemispheric records in 2018

Highest temperature ever recorded in April in Asia: 50.2°C (122.4°F) at Nawabshah, Pakistan, 30 April
World record of the highest reliably-measured minimum temperature in 24 hours: 42.6°C (108.7°F) at Qurayyat, Oman, 26 June
African record of highest temperature: 51.3°C (124.3°F) at Ouargla, Algeria, 5 July
African record of the highest minimum temperature: 39.5°C (103.1°F) at Salah, Algeria, 29 July
Northern Hemisphere record of the highest minimum temperature ever recorded in November: 30.5°C (86.9°F) at Yelimane, Mali, 9 November
Northern Hemisphere record of the highest minimum temperature ever recorded in December: 29.0°C (84.2°F) at Bangkok, Thailand, 4 December

Figure 2. The Annual Climate Extremes Index (CEI), updated through 2008, shows that the contiguous U.S. climate has been getting more extreme since the early 1970s. On average since 1910, 20% of the U.S. has seen extreme conditions in a given year (thick black line). In 2018, 33% of the U.S. had extreme conditions (upper 10%). The most extreme year on record was 2012. Image credit: NOAA/NCEI.

Ninth most extreme weather year on record for the contiguous U.S.

In 2018, the U.S. had its 14th warmest and 3rd wettest year on record, said NOAA. See the roundup from weather.com's Brian Donegan for other U.S. highlights. The year was the ninth most extreme weather year for the contiguous U.S. since 1895, according to NOAA’s Climate Extremes Index. Approximately 33% of the nation experienced extremes (top 10%) in temperature, precipitation, or drought, compared to the 1895 – 2018 average of 20%. The Climate Extremes Index (CEI) is based upon three parameters:

1) Monthly maximum and minimum temperature
2) Daily precipitation
3) Monthly Palmer Drought Severity Index (PDSI)

The temperature data is taken from 1100 stations in the U.S. Historical Climatology Network (USHCN), a network of stations that have a long period of record, with little missing data. The temperature data is corrected for the urban heat island effect, as well as for station and instrument changes. The precipitation data is taken from 1300 National Weather Service Cooperative stations. The Climate Extremes Index defines "much above normal" as the highest 10% of data, "much below normal" as the lowest 10%, and is the average of these five quantities:

1) The sum of (a) percentage of the United States with maximum temperatures much below normal and (b) percentage of the United States with maximum temperatures much above normal.

2) The sum of (a) percentage of the United States with minimum temperatures much below normal and (b) percentage of the United States with minimum temperatures much above normal.

3) The sum of (a) percentage of the United States in severe drought (equivalent to the lowest tenth percentile) based on the Palmer Drought Severity Index (PDSI) and (b) percentage of the United States with severe moisture surplus (equivalent to the highest tenth percentile) based on the PDSI.

4) Twice the value of the percentage of the United States with a much greater than normal proportion of precipitation derived from extreme (equivalent to the highest tenth percentile) 1-day precipitation events.

5) The sum of (a) percentage of the United States with a much greater than normal number of days with precipitation and (b) percentage of the United States with a much greater than normal number of days without precipitation.

Figure 3. Temperature percentiles for land and ocean areas across Earth in December 2018, as compared to all Decembers from 1880 to 2018. Areas in darkest red had the warmest monthly temperatures of any December on record. Record warm temperatures were present across much of the Southern Hemisphere, specifically across much of Australia, the southwestern Indian Ocean and across parts of the northwestern Indian Ocean, and the south Atlantic, off the eastern coast of Argentina. According to Australia's Bureau of Meteorology, Australia had its warmest December on record with a mean temperature that was 2.13°C (3.83°F) above the 1961–1990 average. Notable cool temperatures were present across much of central Asia and Far East Russia where temperature departures were -3.0°C (-5.4°F) or lower. However, no land or ocean areas had large-scale record cold December temperatures. Image credit: NOAA/NCEI.

December 2018 summary

December 2018 was Earth's second warmest December since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) and NASA. Only 2015 had a warmer December. Global ocean temperatures were the second warmest on record for any December, according to NOAA, and global land temperatures were the eighth warmest on record. Satellite-measured temperatures for the lowest 8 km of the atmosphere were the sixth or fourth warmest in the 40-year record, according to the University of Alabama Huntsville (UAH) and RSS, respectively.

The December report for the contiguous U.S. has not yet been released by NCEI.

Figure 4. Departure of sea surface temperatures (SSTs) in the benchmark Niño 3.4 region (in the equatorial Pacific). Over the past two months, SSTs have been near the 0.5°C above-average threshold needed for an El Niño event. Image credit: Levi Cowan, tropicaltidbits.com.

Odds of an El Niño event decrease

NOAA’s Climate Prediction Center (CPC) kept an El Niño Watch in place in its January 10 monthly advisory, but reduced its odds of an El Niño event happening this year. Over the past week, sea surface temperatures (SSTs) in the benchmark Niño 3.4 region (in the equatorial Pacific) were about 0.4°C above average. Temperatures of at least 0.5°C above average are needed to be classified as an El Niño event, with the 3-month average temperature staying more than 0.5°C above average for five consecutive months. Oceanic conditions have been near the weak El Niño threshold since late September, but the atmosphere has not responded, leading NOAA to classify the state of the atmosphere as neutral.

In the January 10 advisory, NOAA set the odds for an El Niño event to form at 65% for the coming winter and spring months (February through May), the time of year when El Niño events are typically at their strongest. These odds have decreased from the 90% chance given in NOAA’s December advisory. If an El Niño event does form, it is expected to be a weak one.

Arctic sea ice: fourth lowest December extent on record

Arctic sea ice extent had the fourth lowest average December extent in the 40-year satellite record, according to the National Snow and Ice Data Center (NSIDC).

Notable global heat and cold marks set for December 2018

Hottest temperature in the Northern Hemisphere: 40.3°C (104.5°F) at Diourbel, Senegal, 6 December
Coldest temperature in the Northern Hemisphere: -56.6°C (-69.9°F) at Summit, Greenland, 1 December
Hottest temperature in the Southern Hemisphere: 49.3°C (120.7°F) at Marble Bar, Australia, 27 December
Coldest temperature in the Southern Hemisphere: -44.1°C (-47.4°F) at Concordia, Antarctica, 3 December
(Courtesy of Maximiliano Herrera.)

Major weather stations that set (not tied) new all-time heat or cold records in December 2018

Rabbit Flat (Australia) max. 47.1°C (116.8°F), 12 December
Marble Bar (Australia) max. 49.3°C (120.7°F), 27 December
Wittenoom (Australia) max. 47.8°C (118.0°F), 27 December
Skukuza (South Africa) max. 46.3°C (115.3°F), 27 December
Alice Springs (Australia) max. 45.6°C (114.1°F), 29 December
Curtin Springs (Australia) max. 46.9°C (116.4°F), 30 December

Bob Henson contributed to this post.