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Dr Tom Harris @drtomharris.bsky.social · 26m

I'm actually preparing an article on AI emissions at the moment, more soon...

Dr Tom Harris @drtomharris.bsky.social · 3h

Thanks. I'm not actually aware of any issues with Substack. I started using it because other people I respect use it. I've not had any problems.

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Dr Tom Harris @drtomharris.bsky.social · 3h

I understand the concerns around AI, but its emissions in generating graphics is actually small, much smaller than GenAI. That's due to its diffusion approach on small models.
I use it because I don't have a budget for original artwork and don't like to steal from the web. I believe it has impact.

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Dr Tom Harris @drtomharris.bsky.social · 5h

I would guess it's underestimating the reduction. The IPCC report shows the amount of ocean sequestration going up as emissions rise, and I think it's linear. This may reduce that expectation though.

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Dr Tom Harris @drtomharris.bsky.social · 5h

The results show a need for better monitoring of these tipping elements and for increased efforts to stop greenhouse gas emissions and land-use change.

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Dr Tom Harris @drtomharris.bsky.social · 5h

It presents observation-based evidence that the stability of these four tipping elements has declined in recent decades, suggesting that they have moved towards their critical thresholds, which may be crossed in the near future through unmitigated global warming.

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Dr Tom Harris @drtomharris.bsky.social · 5h

The paper reviews four such interconnected systems, the Greenland ice sheet (GrIS), the Atlantic Meridional Overturning Circulation (AMOC), the Amazon rainforest and the South American Monsoon system (SAM).

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Dr Tom Harris @drtomharris.bsky.social · 5h

A new review study examines four of the most dangerous climate tipping elements, confirming that they are destabilising. Risks are increasing that they will flip and not just in isolation.

drtomharris.substack.com/p/are-we-hea...

#tippingpoint #climatechange #feedback #greenland #AMOC #Amazon

Are we heading for cascading tipping points?

A new review study examines four of the most dangerous climate tipping elements, confirming that they are destabilising. Risks are increasing that they will flip and not just in isolation.

drtomharris.substack.com

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Dr Tom Harris @drtomharris.bsky.social · 1d

The mechanism surpassed heating in the past due to less CO2 rich water reaching the surface, but now the same mechanism will hinder sequestration.

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Dr Tom Harris @drtomharris.bsky.social · 1d

The oceans sequester about 25% of our carbon dioxide emissions, but the results of this study suggest future weakening of the Southern Ocean’s capacity leading to faster atmospheric build up and further future warming.

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Dr Tom Harris @drtomharris.bsky.social · 1d

The work is relevant to todays situation as once again ocean stratification is increasing, but this time due to increasing heat input due to our greenhouse gas emissions. This is being manifested in the dramatic increase and intensity of marine heatwaves.

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Dr Tom Harris @drtomharris.bsky.social · 1d

The data matches the other proxy records very well and confirms that the stratification was stronger, inhibiting mixing during the earlier cooler periods, than in the later warmer ones. This lower upwelling effectively kept CO2 levels lower by as much as 36ppm, explaining the lukewarm climates.

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Dr Tom Harris @drtomharris.bsky.social · 1d

The new study used a novel technique of 2D laser ablation on samples dredged from the Southern Ocean to produce a detailed and well dated record of lead deposits which are influenced by the degree of mixing between different layers of the ocean.

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Dr Tom Harris @drtomharris.bsky.social · 1d

Prior to 430 ka, a period called the Mid-Brunhes Event, the interglacial periods were lukewarm compared to the events since, including the Holocene. CO2 levels were 30-40ppm lower than the later events. This kept the periods cooler and allowed greater Antarctic sea ice and a colder Southern Ocean.

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Dr Tom Harris @drtomharris.bsky.social · 1d

Stratification in the oceans controls the mixing of different layers of water, inhibiting upwelling and deep water formation. These two water column movements regulate the carbon storage of the oceans by releasing old carbon from the deep and absorbing and sequestering new carbon from the surface.

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Dr Tom Harris @drtomharris.bsky.social · 1d

A new paleoclimate study links stronger ocean stratification to past ‘lukewarm’ interglacials, but points to lower ocean carbon sequestration in the future.
www.nature.com/articles/s41...

#climatechange #oceans #stratification #sequestration #paleoclimate #interglacial

Enhanced deep Southern Ocean stratification during the lukewarm interglacials - Nature Communications

Lead (Pb) isotopes from a ferromanganese crust reveal that during lukewarm interglacials before the Mid-Brunhes Event, stronger deep Southern Ocean stratification limited CO2 release, helping keep atmospheric CO2 levels lower.

www.nature.com

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Reposted by Dr Tom Harris

Prof. Stefan Rahmstorf @rahmstorf.bsky.social · 1d

“Bivalve records are really amazing. They are like the tree rings of the sea. They offer a continuous, annually resolved record of ocean conditions.”
New study finds #AMOC destabilization since 1950 "suggesting that the region is moving toward a tipping point."🌊
insideclimatenews.org/news/0310202...

New Study Shows Disruption of Ocean Currents That Stabilize the Global Climate - Inside Climate News

Clam shell growth rings contain clues about the looming potential for a tipping point into climate collapse.

insideclimatenews.org

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Reposted by Dr Tom Harris

Prof. Anders Levermann, PhD @alevermann.bsky.social · 3d

insideclimatenews.org/news/0310202...

New Study Shows Disruption of Ocean Currents That Stabilize the Global Climate - Inside Climate News

Clam shell growth rings contain clues about the looming potential for a tipping point into climate collapse.

insideclimatenews.org

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Dr Tom Harris @drtomharris.bsky.social · 5d

Greater sea ice loss in the coming decades is linked to larger reductions of clouds, stronger surface warming, and enhanced ocean heat uptake.
The baseline state of sea ice and deep ocean temp in models effectively preconditions the level of warming, cloud feedback, and heat uptake in the future.

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Dr Tom Harris @drtomharris.bsky.social · 5d

This relationship isn't merely correlative: it is mechanistically explained through ocean-atmosphere feedback. Higher sea ice extent enhances cloud cover, which has a cooling effect overall by reducing incoming solar radiation.

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Dr Tom Harris @drtomharris.bsky.social · 5d

These initial conditions then amplify warming responses under greenhouse gas forcing, meaning they lead to a more severe and accelerated warming effect than what was previously estimated. Essentially, the climate system's starting point makes it more sensitive to the impact of greenhouse gases.

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Dr Tom Harris @drtomharris.bsky.social · 5d

The study found that the extent of Antarctic summer sea ice is a crucial indicator of the Southern Hemisphere's climate. Models that start with a higher, more accurate representation simulate colder surface waters, colder deep ocean temperatures, and thicker cloud cover in the mid-latitudes.

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Dr Tom Harris @drtomharris.bsky.social · 5d

They also find that projected cloud feedback is 19-31% stronger which has a big effect on climate sensitivity, potentially explaining some of the gap between low sensitivity models and high sensitivity observations. This leads to up to 7% faster global warming.

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Dr Tom Harris @drtomharris.bsky.social · 5d

The work is based on the starting point of Antarctic sea ice in models. Using observational constraints, they find that ocean heat uptake and the resulting thermal expansion caused sea level rise will be up to 14% higher than the average CMIP6 projections.

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Dr Tom Harris @drtomharris.bsky.social · 5d

A new study provides a critical and previously underestimated connection between Antarctic sea ice, cloud cover, and global warming. The work reduces uncertainty in models based on observations over the last four decades.
esd.copernicus.org/articles/16/...
#seaice #antarctica #climatechange #clouds

Increased future ocean heat uptake constrained by Antarctic sea ice extent

Abstract. The ocean takes up over 90 % of the excess heat stored in the Earth system as a result of anthropogenic climate change, which has led to sea level rise and an intensification of marine extre...

esd.copernicus.org

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