The planet had its warmest July on record “by a long shot” — and very likely also had its warmest-ever month in 174 years of record-keeping — according to NASA and the National Oceanic and Atmospheric Administration.
The striking data, presented Monday by scientists from both agencies, indicate that last month smashed Earth’s previous July record by more than one-third of a degree Fahrenheit — a figure that may seem small but represents a staggering leap in the context of global records.
The new milestone follows what was the hottest June in recorded history, and is just the latest in a series of worrying climate extremes in recent months, including record-warmth across the world’s oceans.
“Last month was way, way warmer than anything we’ve ever seen,” Sarah Kapnick, NOAA’s chief scientist, said Monday in a news briefing, adding that July is typically the planet’s warmest month of the year. Given that, “it’s very likely that July 2023 was hotter than any month in any year since at least 1850,” she said.
NASA and NOAA together found that last month’s average global surface temperature was 2.02 degrees Fahrenheit above the 20th-century average. This was the first time an average July temperature recorded 1.8 degrees Fahrenheit, or 1 degree Celsius, above the long-term average, according to NOAA.
Last month was also the fourth consecutive month that global ocean surface temperatures hit a record high, the scientists said. NOAA said July 2023 had the highest monthly sea surface temperature anomaly, which is a measure of how much warmer or cooler temperatures are from the long-term average, at 1.78 degrees Fahrenheit.
Carlos Del Castillo, chief of the Ocean Ecology Laboratory at NASA Goddard Space Flight Center in Greenbelt, Maryland, said the past 10 years have been the warmest decade for the world’s oceans since the 1880s. This trend in ocean warming carries far-reaching consequences, he said.
"As the oceans heat, the water expands, and when you combine that with the melting of ice over land, that contributes to increases in sea-level rise," Del Castillo said, adding that rising seas can trigger coastal flooding and coastal erosion. Changes in ocean temperatures can also have enormous impacts on marine species and their broader ecosystems, he said.
The new July records were driven by long-term, human-caused global warming but were also amplified by a naturally occurring climate pattern called El Niño. This phenomenon is characterized by warm ocean surface temperatures in parts of the Pacific Ocean and tends to boost global temperatures and influence weather conditions around the world.
Forecasters at NOAA’s Climate Prediction Center have said there is a greater than 95% chance that El Niño will continue through winter in the Northern Hemisphere.
Gavin Schmidt, director of the NASA Goddard Institute for Space Studies in New York, said the biggest impacts of El Niño will likely occur next year.
“So we’re anticipating that not only is 2023 going to be exceptionally warm, and possibly a record-warm year, but we anticipate that 2024 will be warmer still,” he said.
The new July records are stark on their own, but they also follow a broader warming trend that has been playing out in recent decades.
Last month was the 47th consecutive July, and the 533rd consecutive overall month, with temperatures above the 20th-century average, according to NOAA.
“The really important thing to remember is that July 2023 is just the latest in a long run of extremely warm months and years going back several decades,” Kapnick said.
The NOAA chief scientist added that while El Niño events only temporarily warm the planet — compounding background warming from human-caused climate change — the events of 2023 offer a grim outlook on the consequences of such accelerated changes to the world’s climate.
“A year like this gives us a glimpse at how rising temperatures and heavier rains can impact our society and stress critical infrastructure over the next decade,” she said. “It’s important to remember that these years will be cool by comparison by the middle of the century if we continue to warm our planet as greenhouse gas emissions continue.”