September 2015: Earth's Warmest Month in Recorded History, Says NOAA

September 2015 had the largest departure of temperature from average of any month among all 1629 months in the record that began in January 1880, said NOAA's National Centers for Environmental Information (NCEI) on Wednesday. (Note that since July and August are typically the warmest months globally in absolute terms, September was not Earth's warmest month in that regard.) NASA rated September 2015 slightly cooler, as the 2nd warmest September on record, falling below September 2014's mark. September 2015's warmth makes the year-to-date period (January - September) the warmest such period on record, according to both NOAA and NASA. September 2015 was the fifth consecutive month a monthly high temperature record has been set in NOAA's database, and the seventh month of the nine months so far in 2015. A potent El Niño event in the Eastern Pacific that crossed the threshold into the "strong" category in early July continues to intensify, and 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 assured that 2015 will be Earth's second consecutive warmest year on record--with 2016 a good bet to exceed even 2015's warmth.

NOAA's top ten warmest global monthly departures from average
1) 0.90°C, Sep 2015
2) 0.89°C, Aug 2015
2) 0.89°C, Mar 2015
2) 0.89°C, Feb 2015
2) 0.89°C, Jan 2007
6) 0.87°C, Jun 2015
7) 0.86°C, Feb 1998
8) 0.85°C, May 2015
8) 0.85°C, Mar 2010
10) 0.84°C, Dec 2014


Figure 1. Departure of temperature from average for September 2015, the warmest September for the globe since record keeping began in 1880. Record warmth was observed across northeastern Africa stretching into the Middle East, part of southeastern Asia, most of the northern half of South America, and parts of central and eastern North America. Record warmth was also over much of the world's oceans, including the Eastern Mediterranean Sea, most of the Arabian Sea, and the waters surrounding Hawaii, where the warm waters are expected to cause a significant coral bleaching episode resulting in a large-scale die-off of coral. Record warm waters were also observed between the Bahama Islands and Bermuda, which helped fuel Hurricane Joaquin's rapid intensification into a Category 4 storm in mid-September. A loss of 10 - 20% of all coral worldwide over the next few months is expected due to the record warm ocean temperatures causing a global bleaching event. Image credit: National Centers for Environmental Information (NCEI) .

Global satellite-measured temperatures in September 2015 for the lowest 8 km of the atmosphere were tied for 3rd warmest in the 37-year record, according to the University of Alabama Huntsville (UAH), and were the 5th 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 several months. The two warmest Septembers occurred during the El Niño events of 1998 and 2010.



Three billion-dollar weather disasters in September 2015
Three billion-dollar weather-related disasters hit the Earth last month, according to the September 2015 Catastrophe Report from insurance broker Aon Benfield: wildfires in Indonesia ($4 billion in losses, though more recent estimates put the damage at $14 billion); wildfires in California that cost at least $2 billion; and drought in Western Canada that has cost at least $1 billion through the end of September. With eighteen billion-dollar weather disasters through September 2015, and two more already during the first half of October--flooding in South Carolina of at least $2 billion, and at least $4.2 billion in damage from China's Typhoon Mujigae--Earth is on pace for an average number of such disasters, compared to statistics from the past ten years.


Disaster 1. Multiple wildfires raged across California during much of September, with the Valley Fire, northwest of San Francisco, and the Butte Fire, southeast of Sacramento, the most destructive of the fires. The Valley Fire--the third most damaging in state history, at $1.5 billion--left four people dead and destroyed 1,958 homes and other structures. The Butte Fire left two people dead and destroyed 475 homes, and was the seventh-most damaging wildfire in state history, at $450 million. This year is now the costliest and damaging year for wildfires in the United States since 2007. In this image, we see burned out cars from the Valley Fire's rampage through Lake County, California; the fire started on September 12, 2015. Image credit: wunderphotographer noneinc.


Disaster 2. As discussed in detail in the Jeff Masters October 13 post, "Costliest (and Deadliest?) Disaster of 2015: Indonesia's $14 Billion Fires", the El Niño event of 2015 has brought devastating drought and fires to Indonesia and neighboring countries. This year's fires in Indonesia are on track be their most expensive disaster in history, beating the $9.3 billion price tag of the 1997 - 1998 fires. In this photo, we see buildings blanketed with thick smog in Singapore on September 24, 2015. Singapore's air quality reached 'very unhealthy' levels on September 24, forcing schools to close, as thick smog from agricultural fires in Indonesia's neighboring Sumatra Island choked the city-state. Image credit: ROSLAN RAHMAN/AFP/Getty Images.


Disaster 3. Drought conditions continued to intensify across western Canada during September as a lack of rainfall wreaked havoc on agricultural interests. The province of Alberta was particularly affected, where a disaster was declared after more than 80 percent of farmers reported sustaining crop loss during the year. Damage estimates were $1 billion and growing. In this image, we see smoke from drought-aided forest fires over British Columbia settling into valleys on July 8, 2015. Image credit: NASA.

Arctic sea ice falls to 4th lowest September extent on record
Arctic sea ice extent during September 2015 was the 4th lowest in the 36-year satellite record, according to the National Snow and Ice Data Center (NSIDC). Sea ice extent reached its annual minimum extent on September 11, bottoming out at the 4th lowest extent on record. Unfavorable winds resulted in large losses of thick, multi-year ice in 2015; there was a 31% depletion of the multi-year ice cover this summer for the Arctic as a whole, compared to only 12% in 2013 and 38% during the record sea ice loss year of 2012.

Notable global heat and cold marks set for September 2015
Hottest temperature in the Northern Hemisphere: 47.8°C (118.0°F) at Mitribah, Kuwait, September 15
Coldest temperature in the Northern Hemisphere: -42.8°C (-45.0°F) at Geo Summit, Greenland, September 30
Hottest temperature in the Southern Hemisphere: 43.0°C (109.4°F) at Villamontes, Bolivia, September 15
Coldest temperature in the Southern Hemisphere: -82.9°C (-117.2°F) at Dome Fuji, Antarctica, September 13

Major stations that set (not tied) new all-time heat or cold records in September 2015
Krosno (Poland) max. 34.5°C, September 1
Anguilla Airport (Anguilla, United Kingdom) max. 33.7°C, September 9. New Territorial record high for Anguilla. Improved to 33.8°C on September 12.
Charlotte Amalie (U.S. Virgin Islands,USA) max. 35.6°C, September 11. New Territorial record high for the U.S. Virgin Islands.
Havana (Cuba) max. 38.2°C, September 12
Ibague (Colombia) max. 36.8°C, September 16
Lerida (Colombia) max. 39.4°C, September 22
Goias (Brazil) max. 41.9°C, September 24
Peixe (Brazil) max. 40.7°C, September 26
Posse (Brazil) max. 38.4°C, September 26
Jerusalen (Colombia) max. 41.8°C, September 26
Jabalcon (Colombia) max. 42.4°C, September 27



New all-time national and territorial heat records set or tied in 2015
As of October 15, 2015, fourteen 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 September 2015" and "Major stations that set (not tied) new all-time heat or cold records in September 2015" sections.

Jeff Masters