Dr. Jeff Masters ·

Above: Temperature percentiles for land and ocean areas across Earth for the year 2017, as compared to the entire period from 1880 to 2017. Areas in darkest red had the warmest annual temperatures in 2017 of any year on record. Image credit: NOAA.

In 2017, Earth experienced its third warmest surface temperature in records going back to 1880—and its warmest year on record without an El Niño event—according to NOAA. El Niño tends to increase global air temperature by transferring heat from the ocean into the atmosphere, which helped push global readings to record levels in 2015 and 2016. However, there was no El Niño in 2017.

In its annual climate summary released on Thursday, NOAA’s National Centers for Environmental Information (NCEI) calculated that the average global temperature across both land and ocean surfaces for 2017 was 1.51°F (0.84°C) above the 20th-century average of 13.9°C (57.0°F). This made 2017 the third warmest calendar year on record, coming in 0.18°F (0.10°C) below the record set in 2016.

Using a slightly different technique, the Japan Meteorological Agency also found that 2017 was the third warmest year in this 137-year period. Update: NASA data published at midday Thursday ranked 2017 as the second warmest year on record, behind 2016 but just ahead of 2015. Small differences in analysis technique can lead to slightly different rankings in the results from these three agencies. NASA's technique incorporates more of the Arctic, which was extremely warm in 2017.

The past year breaks the remarkable three-year string of consecutive global heat records set by 2014, 2015, and 2016. It’s worth noting that 2017 was considerably warmer than 2014, which was a record-breaking year at the time (see Figure 1). This illustrates just how exceptional the past four years have been, amid the continuing warming effects of human-produced greenhouse gases.



Last year was also the third 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). In the UAH dataset, 2017 came in at 0.38°C above the 1981–2010 average, behind first-place 2016 (0.51°C) and 1998 (0.48°C). Both 2016 and 1998 began with very strong El Niño events in progress, but 2017 did not. Because these calculations are indirect, large-scale estimates of temperature well above ground level, derived from satellite data, they need not correspond to trends in direct ground-based measurements of surface temperature.

Figure 1. Departure from the 20th-century average for the global January-through-December temperature for the years 1880 - 2017. Last year saw the third warmest temperatures on record. Image credit: NOAA/National Centers for Environmental Information (NCEI).

Figure 2. Monthly departures from 20th-century average temperature for the period 1980 through 2017, colored to indicate whether an El Niño (red) or La Niña (blue) event was under way. Gray bars indicate neutral months. The year 2017 saw the highest monthly departures from average on record for any neutral months, as well as the highest annual temperatures for any year without an El Niño event. Image credit: NOAA/NCEI.

December 2017 in review

December 2017 tied as Earth's third warmest December since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI). NOAA rated the five warmest Decembers since 1880 as being 2016, 2015, 2017 and 2014, and 2010. Global ocean temperatures last month were the 6th warmest on record for any December, according to NOAA, and global land temperatures were the 2nd warmest on record.

Figure 3. Temperature percentiles for land and ocean areas across Earth in December 2017, as compared to all Decembers from 1880 to 2017. Areas in darkest red had the warmest monthly temperatures of any December on record. No land or ocean areas experienced record-cold December temperatures. Image credit: NOAA/NCEI.

One billion-dollar weather disaster in December 2017

One billion-dollar weather disaster hit the Earth last month, according to the December 2017 Catastrophe Report from insurance broker Aon Benfield: wildfires in Southern California that cost at least $1 billion. For the year 2017, Earth had 28 billion-dollar weather events, which is the sixth most in a year since Aon Benfield began tabulating disasters in 1990. The average from 1990 - 2016 was 22 billion-dollar weather disasters; the greatest number was 41, set in 2013. Last year, there were 31 billion-dollar weather disasters. We’ll have a full summary of 2017’s billion-dollar weather disasters by January 24, when Aon Benfield releases their annual review. Preliminarily, here are 2017’s billion-dollar weather disasters:

Hurricane Harvey, U.S., 8/25 – 9/2, $90 billion, 84 killed

Hurricane Maria, Caribbean, 9/18 – 9/21, $60 billion, 98+ killed

Hurricane Irma, Caribbean/Bahamas/SE U.S., 9/5 – 9/12, $55 billion, 124 killed

Wildfires, U.S. (California), 10/8 – 10/30, $9.4+ billion, 43 killed

Flooding, China, 6/22 – 7/5, $7.5 billion, 141 killed

Drought, Southern Europe, 1/1 – 7/31, $6.6 billion, 0 killed

Flooding, China, 7/13 – 7/17, $4.5 billion, 20 killed

Typhoon Hato, Macau/Hong Kong/China, 8/23 – 8/24, $3.5 billion, 22 killed

Severe Weather, U.S. Rockies/Plains, 5/8 – 5/11, $3.4 billion, 0 killed

Flooding, Peru, 1/1 – 4/1, $3.1 billion, 120 killed

Severe Weather, U.S. Plains/Southeast/Midwest, 3/26 – 3/28, $2.75 billion, 0 killed

Drought, U.S. Plains/Rockies, 3/1 – 9/30, $2.5 billion, 0 killed

Drought, China, 5/1 – 8/31, $2.5 billion, 0 killed

Tropical Cyclone Debbie, Australia, 3/27 – 4/5, $2.4 billion, 14 killed

Severe Weather, U.S. Midwest/Plains/Southeast, 3/6 – 3/10, $2.1 billion, 0 killed

Wildfires, U.S. West, 6/1 – 9/30, $2.0 billion, 0 killed

Severe Weather, U.S. Midwest, 6/11, $2.0 billion, 0 killed

Severe Weather, U.S. Midwest/Plains/Southeast/MS Valley, 4/28 – 5/01, $2.0 billion, 20 killed

Drought, Somalia, Ethiopia, Kenya, 1/1 – 3/31, $1.9 billion, hundreds killed

Severe Weather, U.S. South, 2/27 - 3/2, $1.9 billion, 4 killed

Severe Weather, U.S. Plains/Midwest/Northeast, 6/27 – 6/30, $1.55 billion, 0 killed

Severe Weather, U.S. South, 1/18 - 1/23, $1.3 billion, 21 killed

Typhoon Damrey, Vietnam, Philippines, 11/1 – 11/8, $1.0 billion, 114 killed

Typhoon Lan, Japan/Philippines, 10/18 – 10/23, $1.0 billion, 17 killed

Tropical Storm Nanmadol, Japan, 7/4 – 7/6, $1.0 billion, 37 killed

Winter Weather, U.S. Plains/Midwest/Southeast/Northeast, 3/13 – 3/15, $1.0 billion, 11 killed

Severe Weather, U.S. Plains/Rockies, 6/12 – 6/14, $1.0 billion, 0 killed

Wildfires, U.S. (California), 12/8 – 12/30, $1 billion, 2 killed

December Billion-Dollar Disaster 1. The largest wildfire in California history, the Thomas Fire, erupted on December 6, as powerful Santa Ana winds fanned the blaze. Wildfires in Southern California during December 2017 killed 2 and caused at least $1 billion in damage. Above: Firefighters monitor a section of the Thomas Fire along U.S. Highway 101 northwest of Ventura, California, in the predawn hours on Thursday, December 7, 2017. Image credit: Mario Tama/Getty Images.

La Niña continues

La Niña conditions strengthened over the past month, said NOAA’s Climate Prediction Center (CPC) in its January 11 monthly advisory. They predicted that a weak to moderate La Niña event would peak during the Northern Hemisphere winter of 2017-18, with a transition to neutral conditions likely to occur during the mid-to-late spring. Over the last few weeks, sea surface temperatures (SSTs) in the benchmark Niño 3.4 region (in the equatorial Pacific) have remained below the 0.5°C-below-average benchmark that is required to qualify as La Niña. The 3-month average SSTs must hold at these levels for five consecutive months (with an accompanying La Niña-like atmospheric response) in order to qualify as a La Niña event in the NOAA historical database.

During moderate La Niña conditions, the SSTs remain at least 1.0°C below average. The La Niña of late 2016 barely qualified as a minimal weak event, according to the NOAA database. Our last moderate La Niña event was in 2011-12.

Figure 4. Sea surface temperatures (SSTs) in the benchmark Niño 3.4 region (in the equatorial Pacific) have been well below the threshold of at least 0.5°C below the seasonal average, as required for La Niña conditions. Image credit: Levi Cowan, tropicaltidbits.com.

Arctic sea ice extent the second lowest on record for December

Arctic sea ice extent during December 2017 was the second lowest in the 38-year satellite record, according to the National Snow and Ice Data Center (NSIDC). By the end of the month, sea ice extent began tracking into record-low territory, a trend that continued during the first half of January. As of Jan. 17, the sea ice extent was back in second place behind the record seasonal lows of January 2017.

Sea ice surrounding Antarctica saw its fourth lowest December extent on record. On Jan. 17, it was running in second place, behind only the record lows of early 2017.

Figure 5. Arctic sea ice extent for the last few years (colored traces) has been running well below the 30-year climatological range from 1981–2010 (shaded bands). Image credit: NSIDC.

Notable global heat and cold marks set for December 2017

Hottest temperature in the Northern Hemisphere: 40.0°C (104.0°F) at Matam, Senegal, 2 December and at Am Timan, Chad, 21 December

Coldest temperature in the Northern Hemisphere: -59.3°C (-74.7°F) at Summit, Greenland, 29 December

Hottest temperature in the Southern Hemisphere: 47.4°C (117.3°F) at Birdsville, Australia, 29 December

Coldest temperature in the Southern Hemisphere: -45.6°C (-50.1°F) at Concordia, Antarctica, 1 December

(Courtesy of Maximiliano Herrera.)

Major weather stations that set (not tied) new all-time heat or cold records in December 2017

In 2017, 185 major weather stations beat (not just tied) their all-time highest temperature records, and 17 beat records for their all-time lowest temperature. Here are the major station records for December 2017:

Piripiri (Brazil) max. 41.9°C (107.4°F), 6 December

(Courtesy of Maximiliano Herrera.)

Fourteen all-time national heat records set or tied in 2017

For the year 2017, fourteen nations set or tied all-time national heat records, and two set or tied all-time cold records. The record for most all-time heat records in a year is 22, set in 2016. "All-time" record here refers to the warmest or coldest temperature ever reliably reported in a nation or territory. The period of record varies from country to country and station to station, but it is typically a few decades to a century or more. 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.

All-time national heat records set or tied in 2017:

Comoros: 96.8°F (36.0°C) at Hahaya International Airport, 15 November

Macau: 102.2°F (39.0°C) at Ka Ho, Coloane Island, 22 August (tie)

Hong Kong: 102.2°F (39.0°C) at Wetland Park, 22 August

San Marino: 104.5°F (40.3°C), at Serravalle, 3 and 9 August

Vatican City: 105.3°F (40.7°C) at Roma Macao AWS, 2 August (tie)

United Arab Emirates: 125.2°F (51.8°C), at Mezaira, 30 July

Spain: 117.1°F (47.3°C), at Montoro AEMET, 13 July

Iran: 128.7°F (53.7°C), at Ahwaz, 29 June

Oman: 123.4°F (50.8°C), at Qurayyat on 30 May and at Joba on 31 May (tie)

Pakistan: 128.3°F (53.5°C), at Turbat on 28 May (tie)

Guinea: 113°F (45.0°C), at Koundara, 29 March (tie)

Ghana: 110.8°F (43.8°C), at Navrongo, 26 March

Chile: 113°F (45.0°C), at Cauquenes, 26 January

Cocos Islands (Australia): 91.0°F (32.8°C), at Cocos Island Airport, 23 February (tie with 8 April 2015 and 11 April 1998)

All-time national cold records set in 2017:

United Arab Emirates: 22.3°F (-5.4°C) at Jabel Jais, 3 February

Qatar: 34.7°F (1.5°C) at Abu Samra, 5 February

National monthly maximum temperature records tied or beaten in 2017 (60):

Jan: Comoros, Uganda, Singapore, Mexico

Feb: Iceland

Mar: Kenya, Indonesia, Spain, Chile, Cook Islands

Apr: Ghana, Wallis and Futuna, Honduras, Samoa, Uganda, Pakistan, Cabo Verde, UAE

May: Greece, Iran, Norway, Austria, New Caledonia

June: Mexico, Oman, Iraq, Turkey, Albania, Portugal, UAE

July: Cyprus, Comoros, Mayotte, Saudi Arabia, Indonesia, Niger

August: Iran, UAE, Trinidad and Tobago, USA, French Guiana, Costa Rica, New Caledonia

September: Syria, Saudi Arabia, Iceland

October: Portugal, Hong Kong, Comoros, Brazil, Singapore

November: Kyrgystan, Uzbekistan, Tajikistan, Cabo Verde, China, Mexico

December: Saudi Arabia, Ghana, Kuwait

National monthly minimum temperature records set in 2017 (2):

Jan: St. Eustatius

July: Greenland

Continental/hemispheric records set in 2017

World record of highest minimum temperature for March: 35.6°C at Yelimane, Mali, 31 March

Asian record of highest temperature ever recorded in April: 50.0°C at Larkana, Pakistan, 19 April

World record of highest temperature ever recorded in May (tied): 53.5°C at Turbat, Pakistan, 28 May

Asian record of highest temperature ever recorded in June: 53.7°C at Ahwaz, Iran, 29 June

Northern Hemisphere record of lowest temperature ever recorded in July: -34.3°C at Geo Summit, Greenland, 4 July

Asian record of highest temperature ever recorded in December: 39.4°C at Makkah, Saudi Arabia, 4 December

Notable global heat and cold marks set for 2017

Hottest temperature in the Northern Hemisphere: 53.7°C (128.7°F) at Ahvaz, Iran, 29 June

Coldest temperature in the Northern Hemisphere: -59.6°C (-75.3°F) at Geo Summit, Greenland, 21 March

Hottest temperature in the Southern Hemisphere: 48.2°C (118.8°F) at Tarcoola, Australia, 9 February

Coldest temperature in the Southern Hemisphere: -83.9°C (-119.0°F) at Concordia, Antarctica, 20 June

Bob Henson contributed to this post.