The equinox on September 22 marked a seasonal milestone for planet Earth. It signified a rapid progression into autumn for those of us in the Northern Hemisphere and spring for those “down under” in the Southern Hemisphere.
Let’s dive deeper into our monthly analysis to see how the planet fared for the month and the year to date:
Climate by the numbers
The average global temperature set in September 2017 was 1.40 degrees F above the 20th-century average of 59.0 degrees, according to scientists from NOAA’s National Centers for Environmental Information. This average temperature was the fourth highest for September in the 1880-2017 record. This marked the 41st consecutive September and the 393rd consecutive month with temperatures above the 20th-century average.
Year to date | January through September 2017
The year-to-date average temperature was 1.57 degrees F above the 20th-century average of 57.5 degrees. This was the second warmest for this period, 0.23 of a degree behind the record set in 2016. Nine of the 10 warmest January-September global temperatures have occurred since 2005, with 1998 as the only exception.
Other notable climate events and facts around the world last month included:
Below-average sea ice at the poles persists
The average Arctic sea ice coverage in September was 25.5 percent below the 1981-2010 average, the seventh smallest on record. On September 13, Arctic sea ice reached its annual minimum extent (coverage) at 1.79 million square miles, the eighth smallest in the 1979–2017 satellite record.
Antarctic sea ice extent in September was 4.2 percent below average, the second smallest on record.
Warmer-than-average lands and oceans
The globally averaged land-surface temperature ranked as third warmest for the month of September and second highest for the year to date (January to September).
The globally averaged sea-surface temperature ranked fourth warmest for September and third highest for the year to date.
Africa leads the continents in September warmth rankings
Africa had its warmest September on record; South America, its fifth; Asia, its seventh; North America, its eighth; Oceania, its 12th; and Europe, its 19th.
Edited for WeatherNation by Meteorologist Mace Michaels