Global warning: 2023 will be the hottest year on record

• September's air and ocean temperatures shattered global records, with NOAA and NASA each confirming early data that indicated it was a highly unusual month.

September was the most unusually warm month ever recorded in the agency's 174 years of instrument records, with a temperature anomaly of 1.44°C (2.59°F).

• This beat the previous warmest September by a staggering margin of 0.46°C (0.83°F), and the prior largest temperature anomaly, which occurred in March 2016, by 0.09°C (0.16°F), NOAA stated.
• Last month was the 49th-straight September with temperatures higher than the 20th century average, and the 535th straight month with warmer-than-average temperatures.

What they're saying: "September 2023 was the fourth month in a row of record-warm global temperatures," said Sarah Kapnick, NOAA's chief scientist, in a statement.

• "Not only was it the warmest September on record, it was far and away the most atypically warm month of any in NOAA's 174 years of climate keeping. To put it another way, September 2023 was warmer than the average July from 2001-2010."

Between the lines: Throughout the year, meteorologists and climate scientists have been playing catch-up with global temperatures as the oceans have soared to record warmth, while entire continents have baked.

• Record warm temperatures during September covered 20% of the world's surface, which was the largest area since at least 1951. Less than 1% of the world's surface had a record-cold September, NOAA found.
• When the year began, NOAA projected that 2023 would likely be a top-10 warmest year, but not at the top of the list.
• However, with a building El Niño in the tropical Pacific, record ocean warmth worldwide, and extremely high land surface temperatures, that has rapidly changed.
• The NOAA now pegs the odds of a record warm year in 2023 at greater than 99%, which is near to or matching other global climate centers.

By the numbers: NASA data, which is processed using different methods, also showed that September was a shockingly warm month — with a temperature anomaly of 1.47°C (2.6°F).

• This was the most unusually warm month on record in NASA's data set as well.

• Other data, including from the Japan Meteorological Agency and the Copernicus Climate Change Service, corroborates NASA and NOAA's findings.
• North America, South America, Europe and Africa had their warmest Septembers on record, and for the sixth-straight month, global oceans ranked as the hottest on record, NOAA found.
• September tied August for the highest monthly sea surface temperature departure from average, at 1.03°C (1.85°F), of any month on record.

Of note: The U.S. has already seen two-dozen billion-dollar weather and climate disasters through the end of September, which is an annual record, NOAA reported last week.

The intrigue: Scientists are trying to determine what exactly is driving the extreme heat this year, in addition to human-caused climate change. Some factors are well-understood, such as a sudden flip from a three-year La Niña, which slightly cools the globe, to a warming El Niño. But there may be unknown factors involved as well.

• "What's remarkable is that these record values are happening before the peak of the current El Nino event, whereas in 2016 the previous record values happened in the spring, after the peak," said NASA climate scientist Gavin Schmidt in a statement.

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