News•October 18, 2016

Hottest Months on Record Have Something in Common

On Tuesday, the National Oceanic and Atmospheric Administration (NOAA) released its global temperature data for September. It shows that the month was a scant 0.07°F (0.04°C) below September 2015’s record, making it the second-warmest September on record.

That ends a streak of 16 consecutive record-setting hot months in NOAA’s dataset, a record-setting streak itself. The run of planetary heat has rewritten the record books.

The year-to-date heat has the world on track for its hottest year on record.

The run of record-setting months means 15 of the most abnormally warm months have occurred since March 2015. Accounting for ties, the only exception is January 2007 which came in tied for 11th. There has never been a run of hot months like this in the 1,641 months (or 136-plus years) of data at NOAA’s disposal.

March 2016 tops the list with a global temperature 2.21°F (1.23°C) above the 20th century average. Even though September 2016 is the second-warmest September on record, it’s still on the list clocking in at 11th with temperatures 1.6°F (0.89°C) above average.

To find the most recent record cold month, you have to look all the way back to February 1929 when the global average temperature was 1°F (0.54°C) below the norm. The rest of the top 15 coldest months compared to average are peppered throughout the early 20th and late 19th century.

Oh, and the planet hasn’t had a cooler-than-normal month — nevermind record-setting cool — in 381 months (nearly 32 years).

The global average temperature is the clearest indicator of climate change and each month on record is a testament to what’s happening to the planet because of human carbon pollution. With all the record-warm months, it’s no surprise that NOAA still projects 2016 will be the hottest year in at least 137 years.

Even if the next three months are merely equivalent to the 21st century average temperature — something that’s unlikely given the recent hot streak — 2016 would still beat 2015 for the hottest year on record.

The year-to-date temperature anomaly using the 1891-1910 baseline.

NASA, which also keeps a tab on the global average temperature, had this September as the warmest on record compared to their 1951-1980 baseline. Climate Central has blended both datasets and used an 1881-1910 baseline, which reflects pre-industrial temperatures and is a way to assess of how close we are to the 1.5°C climate threshold that’s been outlined in the Paris Agreement.

According to that analysis, the year-to-date has been 1.27°C (2.3°F) above normal. That’s down from a peak hit in March where temperatures crossed the 1.5°C threshold, but still a sobering reminder of what’s at stake ahead of the next round of international climate talks in Morocco early next month.