Extreme Temperature Diary- Saturday September 27th, 2025/Main Topic: Another Ominous Milestone Hit from Ocean Acidification – Guy On Climate
Dear Diary. According to a group of scientists, the Earth has hit another horrible milestone in relation to our environmental health as a species. If the ocean’s acidification gets too high due to its uptake of our excess carbon pollution, then many species of marine organisms will die off, upsetting a food chain that includes us. Many societies rely on fish as a main part of their diets. If these are gone millions of people may go hungry or at the very least will need to adjust to more land-based diets, which will in turn put even more stress on our environment.
Here are details from Grist:
The oceans just hit an ominous milestone
A new report sounds the alarm on ocean acidification as Earth breaches the seventh of nine "planetary boundaries."
grist.org/oceans/the-o...
#Climate #Oceans #Heat #Seas #Fish #MarineLife #Environment #Water — Grist (@grist.org) 2025-09-26T17:05:10.430Z
The oceans just hit an ominous milestone | Grist
The oceans just hit an ominous milestoneA new report sounds the alarm on ocean acidification as Earth breaches the seventh of nine “planetary boundaries.” Bernd Wüstneck / Picture Alliance via Getty Images
Matt Simon Senior Staff Writer
Published Sep 24, 2025
Topic Climate + Oceans
You’re the product of stability on a planetary scale. Around 12,000 years ago, Earth warmed from an ice age into the relatively consistent climate that allowed humans to adopt agriculture, literally putting down roots. That stability, though, is now shattered, as more than 8 billion people rapidly heat the planet, ravage its ecosystems, and plunder its resources.
In a new report, scientists warn that we’ve crossed yet another “planetary boundary,” a threshold that keeps Earth’s systems hospitable to life — a sort of global resilience that allows the planet to absorb shocks. This time, it’s the relentless acidification of the seas that’s crossed into dangerous territory, threatening all manner of marine life, including the organisms at the base of the food web. Of the nine total planetary boundaries, this is the seventh that’s been breached.
“What this health check again and again shows is that we have one interlinked, interconnected Earth system,” said Levke Caesar, co-lead of the Planetary Boundaries Science Lab at the Potsdam Institute for Climate Impact Research and a co-author of the report. “It actually would be fatal if we just concentrate on climate change, because, as we see, there are six other boundaries that have been transgressed. And we’re actually also increasing the pressure on all of these seven boundaries.”
Think of a planetary boundary as a warning sign on a road. At the end of the road is a cliff, representing a tipping point, in which an Earth system dramatically changes, often irreversibly. Researchers are worried, for instance, that parts of the Amazon may be nearing a transformation from rainforests to savannas due to the compounding crises of climate change and deforestation. If that’s the cliff, the concept of a planetary boundary is a big yellow “CLIFF AHEAD” sign, a warning from scientists that we could be approaching a catastrophic shift.
Or to use another metaphor: A planetary boundary is your doctor warning you that you have high blood pressure, and the tipping point is the ensuing heart attack. “We are setting the planetary boundaries in such a way that as long as we are within the safe operating space, we should prevent the crossing of tipping points,” Caesar said.
Before ocean acidification was added to the list this year, the researchers warned that six other boundaries have already been crossed: The climate is changing rapidly; humans are using too much fresh water; we’re driving species to extinction and transforming the biosphere; forests are shrinking; fertilizers are polluting water bodies; and “novel entities” like chemicals and plastics are streaming into the environment.
 PIK Potsdam / GLOBAÏA
Ocean acidification is intimately intertwined with the planetary boundary of climate change because seawater absorbs carbon dioxide from the atmosphere, and indeed has soaked up a quarter of humanity’s CO2 emissions. That’s helped keep the planet from warming even faster, but also creates carbonic acid. Accordingly, the report notes that ocean acidity has grown 30 to 40 percent since widespread burning of fossil fuels started in the industrial era.
This is perilous news for oceanic lifeforms. Many organisms, like corals, mollusks, and crustaceans, build shells for protection, but carbonic acid reduces the amount of calcium carbonate available for them to do so. And what they do manage to build will be continuously eroded by the increasing acidity of seawater, requiring them to add new layers to their homes to keep up. “Acidification affects a lot of marine organisms physiologically,” said Peter Roopnarine, curator of geology at the California Academy of Sciences, who wasn’t involved in the report. “Whether that’s for a properly functioning respiratory system, or for building an external or internal skeleton. It affects everything from the larvae, or the development of these organisms, all the way up to the adults.”
Acidification and rising water temperatures also cause coral bleaching, when the organisms get stressed and release the symbiotic algae that provide them energy. Because scientists have evidence that organisms are already being harmed in this way, the new report confirms that we’ve crossed the planetary boundary for ocean acidification. “There’s some real concern that as our water acidifies, that there will be fairly significant ecosystem impacts to the marine calcifying species,” said Jennie Rheuban, a research specialist at the Woods Hole Oceanographic Institution, who wasn’t involved in the report.
This acidification could also shake the very foundation of the oceanic food web. Phytoplankton are tiny photosynthetic organisms that soak up CO2 and expel oxygen, just like plants on land. Indeed, these plankton gobble up half of the CO2 sequestered worldwide by photosynthesis, and produce half of Earth’s atmospheric oxygen.
Unfortunately, many species of phytoplankton build shells and may struggle as the oceans relentlessly acidify. These organisms sequester loads of carbon and serve as a critical food source for small creatures known as zooplankton, which in turn are consumed by larger animals like fish.
But not all oceans are acidifying the same way. Colder locales, like the Arctic or Southern Ocean that encircles Antarctica, more readily acidify than tropical waters. That means the polar regions — which may be remote but host a bevy of species like whales — could be approaching a tipping point where organisms aren’t able to build shells. “The Southern Ocean is about to tip,” said Ken Johnson, a senior scientist who studies the region at the Monterey Bay Aquarium Research Institute but wasn’t involved in the report. “The water is changing faster. We’re creeping right up to the edge of that tipping point.”
Further complicating matters, planetary boundaries often reinforce one another. In addition to acidification, ocean life is dealing with the breaching of the climate boundary, as the seas have absorbed around 90 percent of the excess heat that humans have added to the atmosphere. That’s steadily raised the average ocean temperature, but is also driving extreme marine heat waves, further stressing the organisms there. (Oxygen concentrations also drop as temperatures rise, compounding their pain.) They’re also dealing with the “introduction of novel entities” boundary being breached, as chemicals and plastic pollution injure and kill oceanic species.
Those overlapping crises are not only making it more difficult for organisms to survive, but may also be making it more difficult for the ocean to keep sequestering carbon. That’s what Caesar and her colleagues will be exploring next. “What is happening under these different stressors?” Caesar said. “Because it’s not just ocean acidification. The ocean is also losing oxygen. It’s warming. How is this impacting this ocean buffering capacity?”
The good news is that by rapidly reducing greenhouse gas emissions, we can pull back from the cliff of ocean acidification. In fact, human intervention is why 2 of the 9 planetary boundaries haven’t been crossed. Levels of ozone in the stratosphere are now within safe levels, the report notes, thanks to international agreements banning ozone-depleting substances. And atmospheric aerosols are also within the safe operating space, thanks to countries better regulating the burning of dirty fuels like coal and switching to renewable power like solar and wind.
The number of overlapping and reinforcing problems makes the ocean a particular challenge. But by doing things like restoring coastal ecosystems and reducing plastic pollution, humans can reduce the pressures we’re putting on them. “That can be really hard to tackle, addressing these problems when there isn’t sort of a silver bullet where you change one thing and you fix all the problems,” Rheuban said. “There’s quite a number of different issues that need to be solved.”
Here are more “ETs” recorded from around the planet the last couple of days, their consequences, and some extreme temperature outlooks, as well as any extreme precipitation reports:
In the Republic of Congo nearly 100% of the stations broke their monthly records.
It's the harshest and most extreme heat event ever seen in Western Africa.
Never happened anything like this before in the rainy season.
100% of all tropical countries in the world are breaking records: never happened — Extreme Temperatures Around the World (@extremetemps.bsky.social) 2025-09-27T18:42:52.864Z
EXTRAORDINARY
National monthly record broken also in Central African Republic with 37.0C at Bangui
Hundreds of thousands of square km with record heat allover the area in CAF,both Congos,Gabon,Angola
Absolutely historic and unprecedented event.
African climatic history rewritten — Extreme Temperatures Around the World (@extremetemps.bsky.social) 2025-09-27T18:53:43.207Z
TANZANIA AGAIN
Every single tropical country is breaking records:
Never happened anything like this
Today historic heat at Dar Es Salaam with 34.0C,
Hottest September day in history, few days after having its hottest night
Tanzania has been with relentless record heat since 2018 — Extreme Temperatures Around the World (@extremetemps.bsky.social) 2025-09-26T18:52:16.619Z
RELENTLESS RECORD HEAT IN SRI LANKA
Record heat has been going on for years in Sri Lanka,specially for high minimums.
Minimums continue to be widespread in the range of 27C/28C in coastal areas with records broken systematically, last ones were
28.2C at Mannar, 28.0C at Galle — Extreme Temperatures Around the World (@extremetemps.bsky.social) 2025-09-27T15:44:23.498Z
INSANE EAST ASIA HEAT WAVE COMING
The calendar will say October in few days, but for hundreds of millions of people will be like August.
Full summerlike conditions are expected in China,Mongolia,Siberia,Japan and Koreas.
Records of October highest temperatures will be
THOUSANDS. — Extreme Temperatures Around the World (@extremetemps.bsky.social) 2025-09-27T12:35:05.977Z
Record heat in INDONESIA never ends:
Since March 2023 records are falling every single today.
Tonight it was the September hottest night in the airports of Jakarta and Semarang with Minimums of
26.1C and 28.0C. — Extreme Temperatures Around the World (@extremetemps.bsky.social) 2025-09-27T02:33:50.603Z
🌡️HISTORIC HEAT WAVE IN SOUTH AMERICA
Yesterday 37.4C Tranque Lautaro 🇨🇱 It ties
CHILE HOTTEST SEPTEMBER DAY IN HISTORY
Today Records smashed in BOLIVIA🇧🇴
MAX
40.6 Ascension de Guarayos
39.1 San Javier
HIGH MINS
27.6 San Jose
25.7 San Javier
Brutal contrasts heat/cold 👇 — Extreme Temperatures Around the World (@extremetemps.bsky.social) 2025-09-26T21:21:08.479Z
EXTRAORDINARY HEAT IN THE CARIBBEAN
Brutal heat with >37C in Curacao,36C Martinique.
Stfling hot nights with widespread Minimums of 28/30C.
It's the harshest heat wave the Caribbean has ever seen,worse than 2023 and 2024. — Extreme Temperatures Around the World (@extremetemps.bsky.social) 2025-09-27T10:26:36.404Z
They survived Hurricane Helene. Here’s how they’re doing a year later.
The powerful storm caught many people off guard as it drove through six US states. As devastating as it was, did Helene truly change anything?
grist.org/extreme-weat...
#Hurricane #Disaster #Weather #NC #Florida #Georgia — Grist (@grist.org) 2025-09-26T09:57:56.685Z
Trump raised $8 million for Hurricane Helene survivors. Where did it all go?
grist.org/accountabili...
#Disaster #Trump #Climate #Hurricane #Evangelical #FEMA #GoFundMe — Grist (@grist.org) 2025-09-26T14:16:05.933Z
#ClimateCrisis "...promises don’t reclaim land in atolls. They don’t develop mangrove defenses, shore up our hospitals and schools against rising seas or preserve cultural stability tied to land that is slipping under waves...”
news.un.org/en/story/202... — Silicon Valley North - Citizens Climate Lobby (@cclsvn.bsky.social) 2025-09-27T16:59:41.081Z
Ahead of COP, Africa aims to become the continent of climate solutions.
The continent’s 54 nations outline a bold vision for climate action and pledges to present a unified position at the global meeting later this year.
grist.org/climate/ahea...
#Climate #Africa #Kenya #Nigeria #SouthAfrica — Grist (@grist.org) 2025-09-26T19:36:44.101Z
Here's your daily dose of climate fiction.
We Cast Our Eyes to the Unknowable Now
Deep in the fissures that plague Koreatown, Christina’s search for her sister reveals something new.
grist.org/climate-fict...
#ClimateFiction #Fiction #Lit #BookSky #Solarpunk #GreenSky — Grist (@grist.org) 2025-09-26T19:33:21.856Z
Solid shift east - out to sea - on many models and even the new NHC forecast. These are the Google AI ensembles. What’s happening here - partly - is #Humberto is now forecast to be a Cat 5 monster #Hurricane & is exerting an even bigger influence on #Imelda, helping to pull it away like a magnet 1/ — Jeff Berardelli (@weatherprof.bsky.social) 2025-09-27T13:11:15.297Z
#Humberto is making a run to Cat 5 status. There’s plenty of lightning around the eye, showing it has the vertical motion needed for further intensification. By days end - or before- we could have 160 mph! That would make it the 2nd cat 5 of the season. Warmer climate = more rapid intensification! — Jeff Berardelli (@weatherprof.bsky.social) 2025-09-27T16:17:35.506Z
Friday night update: Double hurricanes off the East Coast next week with #Humberto and #Imelda. #Hurricane Humberto may reach 150 mph! And #Imelda may dump feet of rain if it stalls. Here’s more… — Jeff Berardelli (@weatherprof.bsky.social) 2025-09-27T01:44:45.930Z
Wild to see #94L and #Humberto juxtaposed like this: much more Pacific-ish than Atlantic-ish.
Big forecast headaches loom, possibly for days to come, with #94L sandwiched between #Humberto + a cutoff low in the SE US. Unusual setups are tough for models.
yaleclimateconnections.org/2025/09/whil... — Bob Henson (@bhensonweather.bsky.social) 2025-09-26T19:00:50.061Z
My quote on NWS job application loyalty questions: “You’re going to discourage qualified employees from applying because of these questions that have nothing to do with how well you can make a forecast, or if you are able to put out a proper weather warning. It’s not relevant to the job.” — Dr. Jeff Masters (@drjeffmasters.bsky.social) 2025-09-27T18:06:25.081Z
#SFBay. First rain storms arrive in the Bay Area. A preview.
www.sfchronicle.com/weather-fore... — Silicon Valley North - Citizens Climate Lobby (@cclsvn.bsky.social) 2025-09-27T17:03:54.366Z
#EVs Tesla said it “respectfully encourages EPA not to rescind the Endangerment Finding, as that finding is lawful, based on a robust factual and scientific record, and has been an established part of federal law...”
www.mercurynews.com/2025/09/26/t... — Silicon Valley North - Citizens Climate Lobby (@cclsvn.bsky.social) 2025-09-27T17:09:11.951Z
#Pollution “Nobody knows what they’re dealing with because it’s subsurface” The Orphan Oilfield Problem.
www.hcn.org/articles/new... — Silicon Valley North - Citizens Climate Lobby (@cclsvn.bsky.social) 2025-09-27T17:21:40.972Z
Just visited Antelope Canyon, AZ. The colors and rock shapes were exquisite! Foreign tourism is going well in AZ; I was the only American in my group of 16. Lots of Germans and Japanese here, and at the Grand Canyon. — Dr. Jeff Masters (@drjeffmasters.bsky.social) 2025-09-27T17:16:19.309Z
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