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Assessing the Global Climate in September 2017

Globe had its fourth warmest September and second warmest year to date on record

Courtesy of Pixabay.com

The globally averaged temperature over land and ocean surfaces for September 2017 was the fourth highest for the month of September in the NOAA global temperature dataset record, which dates back 138 years to 1880. The year-to-date global temperature was second-warmest on record.

This monthly summary, developed by scientists at NOAA's National Centers for Environmental Information, is part of the suite of climate services NOAA provides to government, business, academia and the public to support informed decision-making.

September 2017 Temperature

  • The September temperature across global land and ocean surfaces was 1.40°F above the 20th century average of 59.0°F, the fourth highest value for September in the 138-year period of record, behind 2015 (highest), 2016 (second highest), and 2014 (third highest). The 10 warmest Septembers have occurred during the 21st century, specifically since 2003. September 2017 also marks the 41st consecutive September and the 393rd consecutive month with temperatures at least nominally above the 20th century average.
  • The September globally averaged land surface temperature was 2.11°F above the 20th century average of 53.6°F. This value was the third highest September land global temperature in the 1880–2017 record, behind the record set in 2016, and 2015 (second highest). The 10 warmest Septembers have occurred during the 21st century, specifically since 2005. This was the 24th consecutive September and the 283rd consecutive month with land temperatures at least nominally above the 20th century average.
  • The September globally averaged sea surface temperature was 1.13°F above the 20th century monthly average of 61.1°F. This was the fourth highest global ocean temperature for September in the record, behind 2015 (highest), 2014 (second highest), and 2016 (third highest). Compared to previous monthly values, the September 2017 global ocean temperature was the lowest monthly temperature departure from average since December 2016. September 2017 also marks the 41st consecutive September and the 492nd consecutive month with ocean temperatures at least nominally above the 20th century average. The last six Septembers (2012–2017) are the six warmest on record. Nine of the 10 warmest September global ocean temperatures occurred during the 21st century (since 2003), with only one year from the 20th century (1997) among the top 10.

September 2017 Sea Ice

  • On September 13, Arctic sea ice reached its annual minimum extent at 1.79 million square miles, the eighth smallest minimum extent in the 1979–2017 satellite record, according to the National Snow and Ice Data Center using data from NOAA and NASA. This was 471,000 square miles below the 1981–2010 average, but the largest Arctic sea ice minimum since 2014. In parts of the Beaufort Sea, the location of the sea ice edge was farther north than any point in the 39-year record. For the entire month of September, the average Arctic sea ice extent was 650,000 square miles (25.5 percent) below the 1981–2010 average, the seventh smallest September sea ice extent on record.
  • The Antarctic sea ice extent for September was 6.96 million square miles, 310,000 square miles (4.2%) below average, the second smallest September sea ice extent since records began in 1979.

Year-to-Date (January–September 2017)

  • The year-to-date temperature across global land and ocean surfaces was 1.57°F above the 20th century average of 57.5°F. This was the second highest value for January–September in the 1880–2017 record, behind the record year of 2016 by 0.23°F. Nine of the 10 warmest January–September global land and ocean temperatures occurred during the 21st century (since 2005), with only one year from the 20th century (1998) among the top 10.
  • The year-to-date globally averaged land surface temperature was 2.47°F above the 20th century average of 48.7°F. This was also the second highest for January–September in the 138-year record, behind 2016 by 0.38°F.
  • The year-to-date globally averaged sea surface temperature was 1.22°F above the 20th century average of 61.1°F. This was the third highest for January–September in the record, behind 2016 and 2015.

For a more complete summary of climate conditions and events, see our September 2017 Global Climate Report.