Environment

July 2023 ranked hottest month on record in past 170 years

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NASA and NOAA have declared that July 2023 was the hottest month on record
NASA and NOAA have declared that July 2023 was the hottest month on record
A heat map illustrating temperature anomalies in July 2023 across the globe
NASA’s Goddard Institute for Space Studies
A graph illustrating the temperature anomalies since 1880, as deviations from the 20th century average
NASA’s Goddard Institute for Space Studies / NASA's Earth Observatory
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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.

A heat map illustrating temperature anomalies in July 2023 across the globe
NASA’s Goddard Institute for Space Studies

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.

Sources: NASA, NOAA

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6 comments
David F
NASA has also announced recently that the Tongo subsea volcano January 2022 released 10% more water vapour into the stratosphere, and that its warming effect could last a few years. With water vapour being Earth's dominant greenhouse gas, is this year's warming due to H2O or CO2.
P51d007
170 years....and how old is the earth again?
Bob809
What about the high temperatures prior to the last 170 years? Were they not higher, many times? Or is it just not convenient to let people know that much higher temperatures than this year were experienced on the planet prior to the last 170 years. As David F points out, the biggest 'so called offender' of greenhouse gases is water vapour, not CO2. CO2 is what keeps us alive, the trees take care of it. Anyone notice how much greener everything is this year?
Old J Hawthorne
David F, what's the big idea? You're not supposed to mention anything but human activity when talking about "climate change". Don't mention solar flares, the ever-changing magnetic field, the tilt of the Earth...and don't mention that the climate has been changing continuously through time. After all, they are using 39 whole years as a baseline, we aren't supposed to think about how old the Earth is, and how ridiculous it is to use 39 years to prove anything. Now, stop breathing, you're destroying the planet when you exhale.
Robbie Price
... and out come the trolls again...


Water vapour is much more complex than CO2 which has no negative feedbacks - you add more to the atmosphere the planet will warm up. In contrast, H2O in its some of it's states actually functions to keep the planet cooler than it would be otherwise be (it provides both positive and negative feedbacks). Essentially, despite the effectiveness of water vapour as a GHG it is not driving the system but responding to it (except, yes, perhaps, when it gets spat into the stratosphere by a volcano).

The flora and fauna of previous hot periods bear little resemblance to that of today, the continents are even in different places and so things were living at entirely different latitudes than we find their fossils in.
Nelson Hyde Chick
I'll bet August beats it.