We need carbon removal in addition to deep emissions reductions to get to net-zero. But as we show in a new study the durability of removals is key to ensure net-zero actually stabilizes global temperatures and meets our climate goals: www.nature.com/artic... - ThreadSky

hausfath.bsky.social • 133 days ago

We need carbon removal in addition to deep emissions reductions to get to net-zero. But as we show in a new study the durability of removals is key to ensure net-zero actually stabilizes global temperatures and meets our climate goals: https://www.nature.com/articles/s43247-024-01808-7

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docstymie.bsky.social•133 days ago

It feels very much like some will use these arguments to not pursue nature-based solutions and while we wait for “permanent” solutions to become feasible, we will just fall further behind. Sigh.

hausfath.bsky.social•133 days ago

We need to value temporary removals for their climate benefits and spend more on restoring ecosystems. But I think building a system today that allows folks to claim to neutralize their fossil fuel emissions by planting trees is deeply problematic.

docstymie.bsky.social•133 days ago

"But I think building a system today that allows folks to claim to neutralize their fossil fuel emissions by planting trees is deeply problematic."

I completely agree with this.

hausfath.bsky.social•133 days ago

That being said, if you could create a credible regulatory system that prices in liability for reversals so that temporary removals could be "horizontally stacked" or transition into more permanent solutions over time that would work.

docstymie.bsky.social•133 days ago

This is what I liked about the Nori blended ton approach to tying soil carbon removals to permanent removals in a short time frames. We need more thinking like that.

hausfath.bsky.social•133 days ago

I helped advise Nori on developing that approach. Its a shame it didn't get more uptake by the market.

docstymie.bsky.social•133 days ago

I remember that now. It’s such a great idea! I’m still sad at what happened to them and my friends there.

hausfath.bsky.social•133 days ago

You just need to also deal with issues like back-end durability accurately (which most projects do not do today!): https://www.theclimatebrink.com/p/forest-carbons-back-end-durability

hausfath.bsky.social•133 days ago

Looks like the y-axis of the graph were mislabeled, here is the correct version (note that all the figures in the paper itself are accurate 😉)

hausfath.bsky.social•133 days ago

In the study, published today in Nature Communications, we simulate the climate impact of 6 GtCO2 of residual CO2 emissions at the point of net-zero (the typical value in scenarios examined in the recent IPCC report) under different durability assumptions.

hausfath.bsky.social•133 days ago

If CDR only has a durability of 100 years (e.g. much of the CDR market today), it would result in 1.1C more warming by 2500 in a scenario that otherwise stabilizes warming below 2C. CDR with a >1000-year durability is required to stabilize global temperatures.

hausfath.bsky.social•133 days ago

Sorry, this number should be 0.8C (damn typos!). 1.1C is for immediate re-release with no storage.

danolner.bsky.social•133 days ago

Aah. Do we *have* any 1000+ year carbon storage methods...? (Couldn't find any from a quick scan of the paper, tho it does point out shorter-term CDR can still be helpful.)

hausfath.bsky.social•133 days ago

DAC, BECCS, Bio-Oil Injection, Enhanced Weathering, Ocean Alkalinity Enhancement, and Direct Ocean Removal all have 1000-year+ durability, among others:

hausfath.bsky.social•133 days ago

Our new paper provides further evidence that credible net-zero commitments require a like-for-like approach: https://www.annualreviews.org/content/journals/10.1146/annurev-environ-112320-105050.

Given 100,000-year+ atmospheric lifetime fossil CO2, it can only be credibly neutralized by permanent carbon removal.

hausfath.bsky.social•133 days ago

That said, less durable solutions still have a role to play. Temporary removals such as afforestation/reforestation can counterbalance land use emissions, and temporary reductions of warming have real value in minimizing peak temperatures.

tfinch.bsky.social•133 days ago

Is afforestation less durable because trees die, or because you can't guarantee that forests will still exist 1000 years from now? If afforestation boosts the long-term average terrestrial carbon store, doesn't that provide a long-term carbon store even if the individual C atoms come and go?

rustneversleeps.bsky.social•133 days ago

As I understand it, this paper discusses CDR for residual CO₂ emissions.

To the extent those emissions derive from fossil carbon, for durable net-zero we'll need carbon removals from the (now) active carbon cycle and return to geologic carbon storage.

See: https://www.annualreviews.org/content/journals/10.1146/annurev-environ-112320-105050

hausfath.bsky.social•133 days ago

But the science is clear: if we want to stabilize global temperatures, only permanent removals (>1,000 years) can credibly neutralize ongoing emissions from fossil fuels, and it is important that our net-zero systems reflect this physical reality.

pnrjulius.bsky.social•133 days ago

Couldn't short-term CO2 removal still be part of the strategy though? Something to buy us time until we find something better?

hausfath.bsky.social•133 days ago

For more details, see my write-up of the new paper over at The Climate Brink: https://www.theclimatebrink.com/p/durability-of-carbon-dioxide-removal

thijshuijskes.bsky.social•131 days ago

I like this remark. Haven't heard this before as an argument.

geonv.bsky.social•133 days ago

If the market is letting folks sell carbon storage credits with durabilities of 100 years or less, can I sell storage credits for having a kid? Buying a baby tortoise? Refraining from fishing for Greenland sharks?

thijshuijskes.bsky.social•132 days ago

Hi Zeke, for clarity, are you simulating that all CO2 stored by CDR will be released after/within a 100 or a 1000 years? Thanks

hausfath.bsky.social•132 days ago

We explore three different definitions of storage (as discussed in the supplimentary materials). The main paper shows an exponential decay function with a mean residence time of 100 or 1000 years:

thijshuijskes.bsky.social•131 days ago

Hi Zeke, thanks for the answer. I haven't studied the paper in detail (but have downloaded it...), looks like very interesting work.

I have had a glance at the equation for re-release of emissions. I am no expert in bio type of CDR. However, I am an expert in geological sequestration... (1/n)

thijshuijskes.bsky.social•131 days ago

and this mechanism seems quite harsh for geological storage. I saw that for a constant 6 Gt/y storage rate, for the 100yr and 1000yr scenario respectively ~22% and 2.5% (of the cumulative stored mass) has been re-emitted after 50 years of storage. (2/n)

thijshuijskes.bsky.social•131 days ago

Even if all storages would have broken and/or undecommissioned wells, this seems like a (very) unrealistic number.

For a storage license (following the suggestions in IPCC SR-5), it needs to be shown that it is very likely that a storage has not leaked >1% after 1000 yrs. (3/n)

bxe123.bsky.social•132 days ago

We need the solar-powered snowmaker™️

asknoswiss.bsky.social•133 days ago

I thought this was stupid 15years ago, why not just stop emitting Carbon. Turns out not even a pandemic really stops people from doing that…
We are doomed

tominyman.bsky.social•133 days ago

Durability and permanence yes agree, but we should also double or even multiply by 5 the amount of biomass, plankton, animals, trees, bushes, in the world. Too high focus on 1000 yr permanence is actually denialism killing restoration and rewilding.

thijsheus.bsky.social•133 days ago

Is it fair to say that 100 year CDR is just kicking a can down the road? Because I'm not against doing that and betting we have more advanced tech by then to kick that can yet again, and possibly further.

Anything that gets us to 2050 is good in my book.

thinkling.bsky.social•133 days ago

Alternately, why does it not work to keep doing 100-year CDR permanently? Assuming we end up with plentiful green energy (big assumption but is essentially part of net zero already?), that doesn’t seem as hard/expensive?

hausfath.bsky.social•133 days ago

If you can design a fool-proof liability system to persist over a millennia it would be fine. But in our uncertain world there is something to be said for functional stability after an intervention 😉

thinkling.bsky.social•133 days ago

At vaguely comparable cost, longer storage is preferred, sure. But this thread sounds to me like saying “we absolutely must have permanent storage”, which is not clear to me. If society collapses to the point that we become unable to keep up the CDR, wouldn’t further CO2 emissions collapse as well?

thijsheus.bsky.social•133 days ago

Yeah, agree, go for as long as you can. I just don't want perfect to become the enemy of the good, and/or doomsayers abusing nice papers to claim that all mitigation strategies are hopeless.

umsonst.bsky.social•133 days ago

Around 2030-2035 we will fight for our very survival - too many feedbacks now coming into motion which are synchronizing - system goes now non-linear, signs pop now up everywhere in the Earth system...

drlarsbergmann.bsky.social•133 days ago

Scaling carbon removal technologies up to a dimension that would make any sense at all is a huge challenge.

Simultaneously ensuring the durability of that removal adds another very big technology challenge.

NetZero is far away.

jbond23.bsky.social•133 days ago

I can't get past the scale problem.

13GtC/Yr turned into 40GtCO2/yr until the 1TtC of accessible fossil carbon is all gone. A temperature rise of >5C. 200k years before CO2 and temperatures drop back again.

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