October 2015: Earth's Warmest Month on Record by a Huge Margin

Earth’s surface temperature has surged high into uncharted territory, thanks to a record-strength El Niño event combined with the long-term rise in temperatures due to human-caused global warming: October 2015 was Earth’s warmest month on record by a huge margin, according to data released by NOAA's National Centers for Environmental Information (NCEI) on Wednesday. October 2015 was the second consecutive month with a new all-time warmest month record: September 2015 previously held the record for the largest positive departure of temperature from average of any month among all 1630 months in the historical record that began in January 1880. As shown in the table below, October 2015's 0.98°C (1.76°F) departure from the 20th Century average beat the next ten runners-up by an unusually large margin, underscoring how unusual and extreme the current surge in global temperatures is. NASA also rated October 2015 as the warmest month in the historical record by a large margin, again defined as the largest positive departure from average (note that in an absolute sense, Earth's warmest month is July, but NOAA and NASA do not keep track of global temperature records in an absolute sense.) October 2015's warmth makes the year-to-date period (January - October) the warmest such period on record, according to both NOAA and NASA. October 2015 was the sixth consecutive month a monthly high temperature record has been set in NOAA's database, and the eighth month of the ten months so far in 2015. The potent El Niño event in the Eastern Pacific that crossed the threshold into the "strong" category in early July continued to intensify into mid-November. Strong El Niño events release a large amount of heat to the atmosphere, typically boosting global temperatures by at least 0.1°C. This extra bump in temperature, when combined with the long-term warming of the planet due to human-caused emissions of heat-trapping gases like carbon dioxide, makes it virtually certain that 2015 will be Earth's second consecutive warmest year on record. The lingering warmth from El Niño is likely to make 2016 a good bet to exceed even 2015's warmth.

NOAA's top ten warmest global monthly departures from the 20th Century average:
1) 0.98°C, Oct 2015
2) 0.91°C, Sep 2015
3) 0.89°C, Mar 2015
4) 0.88°C, Feb 2015
4) 0.88°C, Jan 2007
6) 0.87°C, Aug 2015
6) 0.87°C, Jun 2015
8) 0.86°C, Feb 1998
9) 0.85°C, May 2015
10) 0.85°C, Mar 2010


Figure 1. Departure of temperature from average for October 2015, the warmest October for the globe since record keeping began in 1880. Record warmth was observed across the entire southern half of Australia, part of southern and southeastern Asia, much of central and southern Africa, most of Central America and northern South America, and parts of western North America. Record warmth was also over much of the world's oceans. This includes the Pacific waters near the Mexican coast, where Hurricane Patricia exploded into the most intense Western Hemisphere hurricane on record on October 23, with 200 mph winds. Record warm waters were also observed over the portion of the Arabian Sea where Category 4 Tropical Cyclone Chapala and Category 3 Megh tracked in October--the first time two major tropical cyclones had ever been observed in the Arabian Sea in the same year. Record warm waters were also observed around Hawaii, where the warm waters caused the worst coral bleaching episode in Hawaii's history, which will likely result in a large-scale die-off of coral. A loss of 10 - 20% of all coral worldwide is expected due to the global bleaching event currently underway, due to the extensive record-warm ocean temperatures worldwide. Image credit: National Centers for Environmental Information (NCEI) .


Figure 2. Departure of the global surface temperature from average for the year-to-date period January - October, for all years from 1880 to 2015. This year is on pace to easily beat last year as the warmest year on record. Image credit: NOAA.

Global satellite-measured temperatures in October 2015 for the lowest 8 km of the atmosphere were the warmest October readings in the 37-year record, according to the University of Alabama Huntsville (UAH), and were the 2nd warmest on record, according to RSS. The lowest 8 km of the atmosphere heats up dramatically in response to moderate to strong El Niño events, with a time lag of about six months.



Three billion-dollar weather disasters in October 2015
Three billion-dollar weather-related disasters hit the Earth last month, according to the October 2015 Catastrophe Report from insurance broker Aon Benfield: flooding in South Carolina of at least $2 billion, $4.2 billion in damage from China's Typhoon Mujigae, and $1 billion in damage from flash flooding in France. With 21 billion-dollar weather disasters through October 2015, Earth is on pace for a below-average number of these disasters, compared to the average of 28 recorded during the previous 10-year period, 2005 - 2014.


Disaster 1. Typhoon Mujigae hit the Philippines as a tropical storm on October 2 before rapidly intensifying and striking China on October 4 as a Category 3 storm. Mujigae killed two in the Philippines and at least 20 in China. Economic losses in Philippines were estimated at $1.3 million, and were $4.2 billion in China, making Mujigae the costliest tropical cyclone of 2015. In this image, we see a rapidly intensifying Typhoon Mujigae approaching China at 03:05 UTC October 3, 2015. Image credit: NASA.


Disaster 2. Torrential 1-in-1000 year rains of over two feet, associated with a plume of moisture wrapping around Hurricane Joaquin, brought tremendous flooding across much of South Carolina during the first week of October. At least 21 people were killed, and damage was conservatively estimated at $2.0 billion, including $300 million in damage to crops. In this photo, we see a church surrounded by flood waters on October 5, 2015 in Columbia, South Carolina. Image credit: Sean Rayford/Getty Images.


Disaster 3. At least 19 people were killed along the southeast coast of France by a flash flood on October 3 - 4. Cannes received a record 107 mm (4.21”) in just one hour; the previous one-hour record was 70 mm (2.76”). In this photo, we see a man walking past damaged cars in Mandelieu-la-Napoule, southern France, on October 5, 2015. Cars are often stacked in this manner in the aftermath of flash floods, as was the case during the catastrophic Rapid City, SD, flood of 1972 (scroll page for photo). Image credit: Anne-Christine Poujoulat/AFP/Getty Images.

Arctic sea ice comes in at 6th lowest October extent on record
Arctic sea ice extent during October 2015 was the 6th lowest in the 36-year satellite record, according to the National Snow and Ice Data Center (NSIDC).

Notable global heat and cold marks set for October 2015
Hottest temperature in the Northern Hemisphere: 46.0°C (114.8°F) at Bassora Airport, Iran, October 3.
Coldest temperature in the Northern Hemisphere: -60°C (-76.0°F) at Geo Summit, Greenland, October 24. This is a new record of minimum temperature in the Northern Hemisphere for the month of October.
Hottest temperature in the Southern Hemisphere: 48.4°C (119.1°F) at Vredendal, South Africa, October 27. This is a new world record of maximum temperature for the month of October.
Coldest temperature in the Southern Hemisphere: -72.3°C (-98.1°F) at Vostok, Antarctica, October 22.

Major stations that set (not tied) new all-time heat or cold records (for any month) in October 2015
Nevis Airport (Saint Kitts and Nevis) max. 34.1°C, 2 October
Canefield Airport (Dominica) max. 35.5°C,  3 and 4 October:  new national record high for Dominica
Gustavia (Saint Barthelemy, France) max. 35.5°C,  5 October: new territorial record high for Saint Barthelemy
Sal (Cape Verde) max. 36°C, 5 October
Peixe (Brazil) max. 41.4°C,  5 October
Picos (Brazil) max. 41.5°C, 5 October; broken again with 41.9°C on 21 October
Januaria (Brazil) max. 41.3°C,  5 October
Monte Azul (Brazil) max. 40.7°C,  5 October
Posse (Brazil) max. 39.1°C,  5 October
Aragarcas (Brazil) max. 42.6°C, 6 October
Xavantina (Brazil) max. 42.3°C, 6 October
Golden Rock Airport (Saint Kitts and Nevis) max. 34.1°C, 6 October
The Valley (Anguilla,United Kingdom) max. 34.2°C, 10 October:  new territorial record high for Anguilla;  this was broken on 11 October with a reading of 34.4°C (but this reading is suspect)
Pedro Afonso (Brazil) max. 40.9°C, 17 October
Palu (Indonesia) max. 38.5°C,  20 October
Pirapora (Brazil) max. 40.8°C, 21 October
Montes Claros (Brazil) max. 39.6°C, 21 October
Maripasoula (French Guiana, France) max. 37.5°C, 21 October
Saint Laurent du Moroni (French Guiana, France) max. 37.8°C, 22 October: new territorial record high for French Guiana
Saint Georges de L'Oyapock (French Guiana, France) max. 37.0°C, 22 October
Paracatu (Brazil) max. 40.2°C, 22 October
Arinos (Brazil) max. 42.3°C, 22 October
Peixe (Brazil) max. 41.5°C,  22 October
Monte Azul (Brazil) max. 41.1°C, 22 October
Taua (Brazil) max. 38.8°C,   22 October
Posse (Brazil) max. 39.2°C,  22 October
Semarang Airport (Indonesia) max. 39.5°C, 28 October: Tied national record high for Indonesia
Vredendal (South Africa) max. 48.4°C, 27 October



New all-time national and territorial heat records set or tied in 2015
As of November 15, 2015, sixteen nations or territories tied or set all-time records for their hottest temperature in recorded history in 2015, and two (Israel and Cyprus) set all-time cold temperature records. For comparison, only two nations or territories set all-time heat records in 2014, and nine did in 2013. The most all-time national heat records held by any year is nineteen in 2010. 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. Wunderground's weather historian Christopher C. Burt maintains a database of these national heat and cold records for 235 nations and territories on wunderground.com's extremes page.

Kudos also to Mr. Herrera for supplying the data for the "Notable global heat and cold marks set for October 2015" and "Major stations that set (not tied) new all-time heat or cold records in October 2015" sections of the post.

Jeff Masters