I think the argument is that if we stopped all our CO2 emissions right now we would comply with the 1.5 C target in 2050 but would "only" break it in 2100. Since stopping all our emissions is not even close to what's happening (actually CO2 emissions are rising right now) that's not a viable model. So we will probably need to recapture CO2 as well – or rather we will need to develop the necessary tech first.

>So we will probably need to recapture CO2 as well – or rather we will need to develop the necessary tech first.

Maybe this is a stupid question, but isn't the necessary tech "planting trees"?

The main problem with trees is they’re very slow. It would take decades after we started planting billions of trees a year before they’d have grown to the extend where they’d have captured reasonable amounts of carbon.

So, yes, it’s an option. But it’s a slow option we’d need to start implementing immediately if we wanted it bear fruit.

(We produce enough CO2 that it takes 40 billion hardwood trees growing for 40 years to sequester as much CO2 as we make in a year. We’d have to plant a lot of trees, and then not touch them for years, to affect the course of things)

If you pants trees om every bit of avaliable land, that stilll would not be enough to compensate for the emissions - we use a lot of land for farming, and are emittinghundreds of years wortg of tree-catrure per decade.

A tree captures CO2 temporarily. We would have to bury the wood to actually remove it from the atmosphere.

You are aware that "temporarily" in this context is the lifespan of a tree, right? Trees live anywhere from several decades to 20+ centuries, and their remains, once broken down, provide nutrients to the soil so more trees can grow.

Also the tree is not capturing carbon, instead emitting, half of the year if not planted in the optimal places near the equator. And it's carbon neural or negative once almost fully grown.

Hence why you need to cut them down and bury.

That's not true. Trees metabolize year round, and they literally breathe CO2.

They breath oxygen, they "feed" on CO2, once fully grown they need less food and that changes the balance

No, that is wrong. Plants emit O2, and consume CO2. This is called respiration.

Once a tree is fully grown it essentially stops capturing CO2.

Again, that is not true. Trees need CO2 for respiration. Basic biology, folks.

Basic biology should tell you that the only thing that counts for carbon capture is biomass added. Anything that the tree does that doesn't permanently add to its mass can't capture carbon permanently. Hence, once a tree stops growing, it stops capturing carbon. It still respirates because it does things that require energy, but any carbon it captures doing so is released fairly quickly again, e.g. when the leaves it produced in spring fall off and rot. Of course many trees keep growing a little even after they reach maturity, but the rate of growth is minuscule. A mature stable forest stores a large amount of carbon, but it hardly captures any more.

Well, you know what? Plants reproduce, too.

And, BTW, trees don't stop growing. They keep adding mass in their trunks. Literally the first google hit for "do trees stop growing": https://earthsky.org/earth/what-makes-a-tree-stop-growing

Edit: guess what? They even grow faster as they get older! https://www.npr.org/2014/01/16/262479807/old-trees-grow-fast...

That is a different point.

Anyway, the land we have is limited. You literally can't cover the planet in one big forest to capture the gigatons of carbon we have released. You have to do active forest management and store the carbon somewhere stable, for example as biochar.

Reducing the numbers of those pesky humans would help.

That's the one thing climate change is good at once it gets bad. I thought we wanted to avoid this?

No. The one thing we want to avoid is making the Earth into an unlivable hellscape for those who remain alive.

You can't reduce the number of humans quickly enough without a genocide.

Doesn't mean we still don't need to reduce numbers for long term sustainability.

You are mostly right, but some of that carbon does sink into the soil and get captured for much longer periods, and some of that will will sink further and likely never see the surface of the earth again unless someone digs it up.

And recapture isn’t going to be easy. We’d have to figure out how to drive the global economy off of the recapture process

If there are no significant emissions to tax, then fixing environmental damage done by past generations sounds like something for governments to pick up with public money. We also spend public money on forest management, wildlife bridges to create reasonably sized habitats, etc.

It's also a while out. We have bigger issues today than "who's gonna suck back out some CO2 once we cut emissions sufficiently". We'll get to that in due time.

For what it's worth, if you have unavoidable emissions today that you want to compensate, and want to also fund the people working on CO2 capturing technology, see https://climeworks.shop for a pay-what-you-want option. I don't really believe in planting trees (which is way cheaper per ton of CO2 it claims to absolve you of), and these machines apparently emit "only" 10kg for every 100kg of CO2 captured (90% effective sounds reasonable), and it's accounted for who claimed which share of the machine's captured volume so it sounds directly effective to me. It's just that the scale is peanuts and will remain so until public bodies and companies start to run out of emission reduction options and decide to use it - but at that point we better have this tech geared up.

It's easier to just drive the prices of CO2 certificates up. A EU CO2 certificate for 1 ton of CO2 costs 25€. If you buy it and resell it at a higher price like 100€ it's either too expensive and will never be bought or if it will be bought you will be economically harming CO2 emitting companies.

My initial thought is that funding those participating in an ineffective scheme does not strike me as the most helpful option. But I really don't know enough about it to comment on whether that is the case here, or if it might indeed make sense for me to do this. Do you know of any research (doesn't have to be published, a blog post with a good analysis is just as helpful) that looked into whether this is a good idea?