James Rae

Sure! And great work @jfarmersalmanac.bsky.social and @oceanandclimate.bsky.social for the fascinating paper and threads!

Kudos to Maddie for leading this work and many thanks to @willerstorfi.bsky.social @gmacgilchrist.bsky.social @oceanicandrea.bsky.social Casimir de Lavergne & Laurie Menviel for all their help and input, @uniofstandrews.bsky.social for funding Maddie’s PhD, and all of you for reading!

We are psyched about this as the ice ages are cool (sorry!) - but also as figuring out these processes by which the ocean took up 100s of gigatonnes of CO2 from the atmosphere in the past may help us better understand the controls on its capacity for carbon uptake in the future… 📈🌊

Reconstructions of biogeochemistry from the high latitude North Pacific and Southern Oceans share similar structure over the ice ages

This likely acted in concert with other processes (changes in winds, circulation, sea ice, iron) to draw down CO2 during the ice ages.
It can also explain why biogeochemical records from the North Pacific and Southern Ocean share similar structure (Haug & Sigman‘s “polar twins” 👯)

Potential CO2 outgassing anomalies in 4 different sets of model simulations with better ventilated intermediate depth North Pacific

Notably, this is achieved without any change in Southern Ocean upwelling, sea ice or iron supply - it’s simply the result of having less carbon in the upwelled water.

Outgassing anomaly in the Southern Ocean - less carbon is outgassed due to reduced carbon load of waters upwelled from the Pacific

The consequence - shown here - is that less CO2 would be delivered to the Southern Ocean. This by itself reduces Southern Ocean CO2 outgassing by as much as 50%.

Figure showing change in different proxies sensitive to ventilation at the LGM relative to today in the North Pacific. Better ventilation is shown by the red dots - and there is a clear signal of this above 2000m.

In previous papers we and others have shown that these intermediate depth N Pacific waters were better ventilated during glacial periods (e.g. figure here from Rae 2020 and see also Rafter 2022 and Keigwin 1998 among others!) www.science.org/doi/full/10....

Figure showing ocean outgassing potential - the tendency of a parcel of water to give out CO2 to the atmosphere when it surfaces. Red colours in the North Pacific show its high outgassing potential and these isopycnals outcrop in the Southern Ocean, fuelling regional outgassing.

Part of the inspiration for this study was an interesting paper by Haidi Chen showing that much of the CO2 outgassed in the Southern Ocean today is sourced from the intermediate depth North Pacific. As these waters are old and CO2 rich they have huge outgassing potential (red colours below).

Southern Ocean CO2 outgassing and nutrient load reduced by a well-ventilated glacial North Pacific - Nature Communications A better-ventilated North Pacific could have reduced the carbon of water upwelled in the Southern Ocean, reducing outgassing and revealing a remote influence on Southern Ocean biogeochemistry in glaci...

🚨New paper on Southern Ocean CO2🚨
Using a suite of Earth system models, Maddie Shankle et al show that better ventilation of intermediate waters in the North Pacific ends up reducing outgassing of CO2 in the Southern Ocean 🌊🧪⚒️🧵 @earthscista.bsky.social
www.nature.com/articles/s41...

Big congratulations to @mudwaterclimate.bsky.social & team on securing funding to launch the St Andrews Global Research Centre for Changing Climates! 🌍 📈

The centre will take an interdisciplinary approach, harnessing the breadth of expertise across St Andrews

news.st-andrews.ac.uk/archive/the-...

Nice one John - see also additional notes in thread below: bsky.app/profile/mudw...

Scientists slam Trump administration climate report as a ‘farce’ full of misinformation Experts say the report being used to justify the mass rollback of climate regulations has many claims based on long-debunked research

ICYM - Scientists slam Trump administration climate report as a ‘farce’ full of misinformation

- Experts say the report being used to justify the mass rollback of climate regulations has many claims based on long-debunked research

#climatecrisis
www.theguardian.com/us-news/2025...

Graph showing extinction rate over the past 300 million years and current pH reconstructions. Mass extinctions are consistently associated with ocean acidification.

More relevant for fossil fuel CO2 are rapid external carbon additions from large igneous provinces and the organic material they often burn up - consistently linked to mass extinction in the geological record www.nature.com/articles/s41...

The Geological Record of Ocean Acidification As human activity continues to pump nearly 50-fold more CO2 into the atmosphere than any existing natural sources, the oceans absorb it. Over time, this vast quantity of excess oceanic CO2 is expected...

These sorts of relatively slow reshufflings of carbon around the ocean also aren’t a relevant analogue for very rapid addition of carbon from an external source: in former case saturation state changes are muted, while with FF addition saturation state drops sharply www.science.org/doi/10.1126/...

CO2 storage and release in the deep Southern Ocean on millennial to centennial timescales - Nature Analysis of deep-sea coral boron isotope data, as a proxy for pH and thus CO2 chemistry, provides evidence of CO2 storage in the deep Southern Ocean during the last ice age, and its rapid release on m...

It’s a pretty basic misrepresentation- they use our paper to suggest ice age ocean was more acidic, but we show this was only true for deep Southern Ocean, while upper ocean (much more relevant for OA-sensitive ecosystems) had higher pH! www.nature.com/articles/s41...

DOE climate report response form We are collecting names to assemble a writing team to respond to the DOE climate working group report. If you'd like to contribute, enter your info below. At this point, there is no guarantee what we'll do (if anything), but we want to keep our options open by collecting names. If you have any further questions, feel free to email me. We are primarily looking for Ph.D. scientists at universities or government labs in appropriate fields. I realize that this will exclude some qualified people and I apologize, but we felt this was necessary for a variety of reasons.

🚨 If you're interested in working on a coordinated response to the DOE climate report, please enter your info on this google form 🚨

Please RT this so as many people see it as possible.

forms.gle/BL9xUAfRxA...

‘A Serious Misuse of My Research’: Climate Scientists Say New Trump Energy Report Botches Their Work “Our work has no relevance,” an astrobiologist whose research was cited in the administration’s climate change report said.

🚨 At least 10 scientists, all cited in the Trump admin's new climate change report, told me that the report completely mischaracterizes their research.

I also found five citations with significant errors, and a paragraph missing an important citation.

I've been taking some time to dive into the US EPA's Proposal to revoke the Endangerment Finding related to Greenhouse Gases.

epa.gov/system/files...

They put forth multiple lines of argument about why the current administration believes this should happen.

🧵

Add me to the list! Rae 2018 misrepresented on page 7: we show deep ocean pH rose out of the ice - but surface ocean pH (the more relevant property for the vast majority of marine life) fell!

Please see thread below on catastrophic impact of geological pH change: bsky.app/profile/mudw...

Motherfucking wind farms…

Fascinating paper 👇 not only providing evidence for ocean acidification in the end-Triassic mass extinction, but also wider discussion of the role of reverse weathering in prolonging the effects, and how this changed with the evolution of open ocean calcifying organisms. ⚒️🧪

4.6 Billion Years On, the Sun Is Having a Moment In the past two years, without much notice, solar power has begun to truly transform the world’s energy system.

Finally for anyone needing a boost on climate progress in light of record temperatures and an acidifying ocean, please check out this wonderful article by @billmckibben.bsky.social - the challenge is huge, but so is our progress www.newyorker.com/news/annals-... 🧪💡🔌⚡️☀️

Not dumb at all - today the open ocean has lots of tiny planktonic carbonate shells that coat the seafloor when they die. This acts as an anti-acid: CO2 addition is part neutralised by dissolving those shells. But they weren’t around yet in the Triassic/Jurassic.

HUGE kudos to fantastic former @earthscista.bsky.social PhD student @mollytrudgill.bsky.social for leading this work, @carbonatefan.bsky.social for ushering us in to the rock record and being generally the best, and an amazing team including several @uniofstandrews.bsky.social BSc/MSc co-authors

These data demonstrate that ocean acidification is associated with all of the major mass extinctions where we currently have pH reconstructions. The TJ pH drop is similar to possible scenarios in 2100 unless fossil fuel emissions are rapidly reduced. 🐚🌊📉.

Modelled saturation state decline. Saturation state decline modelled in cGENIE for different carbon sources and different sizes of negative carbon isotope excursion for runs with a75 kyr onset duration. With the same carbon source as the main CIE (>−12‰), we interpolate an emission rate of >500 GtC/kyr associated with the initial CIE (~5‰) and thus a >6 drop in calcite saturation state in an ocean without pelagic calcifiers.

Faster carbon input at the extinction (indicated by its more rapid carbon isotope excursion) would have led to more pronounced acidification impacts, in particular due to the lack of a deep sea carbonate buffer (read oceanic anti-acid) - indeed this may partly explain this era's major extinctions

Oxygen, carbon, and boron isotope data, showing warming, carbon input, and acidification

Our new boron data cover the "Main" carbon isotope excursion, just after the end-Triassic extinction event. Comparing the carbon and boron isotopes allows us to fingerprint a volcanic carbon source from the Central Atlantic Magmatic Province as the Atlantic opened up.

Journal title in Nature Communications

🚨New paper just out on environmental upset at the Triassic-Jurassic boundary🚨

Using boron isotopes in fossil oysters, we find a major pulse of ocean acidification and CO2 rise, driving global warming and delaying ecosystem recovery following the end-Triassic mass extinction
rdcu.be/ev6XV

🧪🌊⚒️🐚🧵

A graph showing atmospheric CO2 reconstructions over the Palaeozoic, between around 500 and 250 million years ago. Our new data show low CO2 between 340 and 295 Ma, followed by rapid CO2 rise at the start of the Permian

This work helps better constrain a good chunk of the geological history of CO2 - but plenty more time intervals to come!

Palaeo-artistic rendering based on findings of this study and previously published literature. A relatively rapid rise in atmospheric CO2 approximately 294 Ma released the Earth from its penultimate icehouse (left) and transitioned the world to a warmer and drier climate of the Early Permian (right).

Kudos to @uniofstandrews.bsky.social research fellow Hana Jurikova for leading this massive collaborative project, Ross Whiteford for developing novel calculation methods, and brilliant collaborators who contributed all sorts of samples and expertise - plus amazing geological artwork