NASA and NOAA have confirmed what many people have felt firsthand – July 2023 was the hottest month in recorded history, which goes back about a century and a half. The finding follows a worrying trend that has a decent chance of setting 2023 as the hottest year on record.
NASA, NOAA and other organizations keep track of global temperatures using tens of thousands of weather stations around the world, with records stretching back as far as 1850. “Normal” temperatures are calculated by averaging data over multi-decade periods – for instance, NASA uses 1951 to 1980 as a baseline. Temperature swings are then determined as deviations from that average.
Globally, July tends to be the hottest month in any given year, due to it being the peak of summer in the Northern Hemisphere, where there's more land mass. This year’s was a clear leader – NASA’s data indicates the global average air temperature was 1.18 °C (2.1 °F) warmer than the average July. It edged out the previous record-holder, July 2019, by 0.24 °C (0.43 °F). In fact, the top five hottest Julys on record have been the last five.
Since they use different datasets, NASA and NOAA usually end up with slightly different figures, but still come to a consensus. NOAA reports that this July was 1.12 °C (2.02 °F) warmer than average, marking the 47th consecutive July – and the 533rd consecutive month – to record temperatures above the 20th century average.
Sea surface temperatures also saw a record-high temperature anomaly of 0.99 °C (1.78 °F) above the long-term average, according to NOAA data. This likely contributed to record low sea ice coverage, both globally and in Antarctica, while the Arctic also saw below average coverage.
Perhaps unsurprisingly, the outlook for the rest of the year isn’t too rosy, with an El Niño effect expected to last into 2024. NOAA ranks it higher than 99% certain that 2023 will finish in the top five warmest years on record, with an almost 50/50 chance of taking out the number one spot.
