September 2015: Warmest September on Record for Planet Earth

Our global temperature continued its upward trend last month with September 2015 marking the warmest September ever recorded for the entire planet.

According to a report by NOAA’s National Centers for Environmental Information, Earth’s combined average temperature for the month – over both land and sea surfaces – was 60.62°F, which is 1.62°F above the 20th century average. It surpassed the previous record set just last year by 0.19°F and marked the highest departure from average for any month on record. September was also the fifth consecutive month this year to break a monthly temperature record.

Although strong El Niño conditions – a natural climate phenomena that boosts oceanic and atmospheric temperatures – helped fuel September’s record warmth, it does not tell the whole story. The long-term trend of human-caused climate change was also a key factor. NOAA reports that fourteen of the fifteen warmest years on record have occurred since 2000 and they were not all El Niño years. This September, the globally averaged sea surface temperature was 1.46°F above the 20th century average of 61.1°F.  That is the highest temperature departure for any September on record. And, as NOAA points out, “This departure from average is also 0.45°F higher than the global ocean temperature for September 1997, when the last strong El Niño occurred.”

While heat dominated most of the planet last month, some places were particularly warm, including most of North America. Here in the contiguous United States, it was our second warmest September on record. With a monthly temperature of 68.5°F, which is 3.7°F above the long-term norm, only September 1998 was warmer. In fact, most of the lower forty-eight states experienced exceptionally warm conditions and nine  – Connecticut, Colorado, Maine, Michigan, Minnesota, New Mexico, Rhode Island, Utah, and Wisconsin – were record warm.

Year to date, the first nine months of 2015 were the warmest of any year on record. That puts 2015 well on track to becoming Earth’s warmest year ever recorded. Global temperature records date back to 1880.