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Comment by bjourne | Hacker News Reader

The math doesn't work out. Since the beginning of the Industrial revolution humankind has emitted about 550 GtC (gigatons of carbon) into the atmosphere. All plant life on earth contains about 450 GtC. Assuming all of it is forests (which isn't the case, a lot of it is algae, plankton and weeds) and assuming 100% capture rate (which also isn't the case due to forest fires, rotting and reduced albedo), earth's tree cover would more than double to capture all carbon emitted so far.

Clearly, that is not realistic. A more realistic (but still implausibly ambitious) goal would be increasing the earth's forests by 10%, storing 45 GtC for us. Well, it is better than nothing but at the current (increasing!) rate of 10 GtC emissions added per year that nets us another 4.5 years.

https://www.vox.com/science-and-health/2018/5/29/17386112/al... https://www.co2.earth/global-co2-emissions

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I've come to terms with the fact that nothing is going to stop anthropogenic climate change and we'll just have to adapt to it. It's not a technical problem but a political game-theoretic problem.

Major CO2 cuts would require a global all-cooperate (in a game theory sense) scenario and that's unlikely given that the payoff is very high for defecting. This is because global cuts in fossil fuel use would make fossil fuels incredibly cheap, increasing the economic advantage for nations that use them. This is going to be hugely appealing to developing nations with large populations. We already see this with China and India and pretty soon you're going to see it in Africa.

The only way I can see CO2 emission growth halting or reversing is a huge breakthrough in energy generation that results in something dramatically cheaper and easier to deploy and scale than fossil fuel. It would take Mr. Fusion (Back to the Future reference), solar and batteries that are just absolutely dirt cheap, or something equivalently awesome. I don't see anything like this arriving before CO2 hits 800-1000ppm.

We are pretty adaptable. A bio professor of mine was fond of saying that humans are like cockroaches and that this was a compliment coming from a biologist. We should be preparing to move Miami.

> that's unlikely given that the payoff is very high for defecting.

Trade policy (e.g. through the WTO) can be designed in a way that allows countries to internalise the damage caused by greenhouse gas emissions by imposing higher tariffs on countries that do not cooperate.

But you still need everyone else to cooperate. And in a multipolar world (or at least a world with some viable political blocs outside of the US led order) that will be difficult to say the least.

What makes you think the US is not the defector?

Most of the world is defecting at the moment. Few are truly serious about cutting emissions dramatically.

The US is relatively high (but by no means the highest) in per capita CO2 while China is the #1 emitter in total and also per dollar GDP (last I checked). The per dollar GDP number would make China the largest emitter in terms of carbon intensity of its economic activity.

I’m too tired to respond in detail but this underestimates the scale of the problem. There is no “adapting” to the scenario if we don’t stop kicking out CO2. We’re talking billions dead and most large species extinct, over the course of decades at most, depending on how quickly the planet flips from one steady state to the next.

Sea level rise would be no problem. Storms would be no problem. But it's hard to imagine how we could possibly adapt to the worst case scenario, which would be if runaway feedbacks triggered conditions similar to early mass extinctions...

This old article from ScientificAmerican still keeps me up at night.

http://burro.case.edu/Academics/USNA229/impactfromthedeep.pd...

Exactly this.

It scares the life out of me that even on HN, a community of generally scientifically-engaged people, the scale of the problem is often not understood.

We are literally looking at the end of civilisation as currently constituted, and billions dead, and we are not doing anything close to enough.

You're ignoring the gun about to go off: https://en.wikipedia.org/wiki/Clathrate_gun_hypothesis

We already see ocean acidification and warming - if that triggers the release of methane deposits stored under the ocean, that's a potential extinction-level event (or at least a civilization reset back to the stone ages).

I don't disagree that there are huge risks. I just don't think anyone is taking those potential massive risks seriously, and that includes a substantial number of environmentalists and the leaders of most of the world.

Another thing that might cause change to actually happen is if we're "lucky" enough to get a "minor" catastrophe that totally changes global opinion but isn't anywhere near as massive as the stuff you're talking about.

Considerable academic studies and literature on this subject exists. Recent capture rate from current global forestation is estimated to be approximately 2.5 GtC/year. Current global carbon stock of forests is estimated to about 861 GtC [1] ( virtually twice that hastily sourced figure for total plant life even without those assumptions about algae etc )

Sequestration of current forests, despite the fact they are currently being depleted rather than maintained or increased is estimated by studies to be equal to about 5% of current overall anthropogenic emissions. [2]

For in-depth advice see Chapter 11 of IPCC AR5 [3]

" Reducing emissions from deforestation; reducing emissions from forest degradation; conservation of forest carbon stocks; sustainable management of forests; and enhancement of forest carbon stocks (REDD) consists of forest-related activities implemented voluntarily by developing countries that may, in isolation or jointly lead to significant climate change mitigation. REDD was introduced in the agenda of the UNFCCC in 2005, and has since evolved to an improved understanding of the potential positive and negative impacts, methodological issues, safeguards, and financial aspects associated with REDD implementation. "

[1] https://www.globalcarbonproject.org/global/pdf/pep/Pan.etal....

[2] https://forestsnews.cifor.org/12135/clocking-the-worlds-fore...

[3] https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5...

Did you take into account that trees have died since the start of the industrial revolution, taking their carbon with them, and that new trees grew and are sequestering more carbon? I.e. if there were 200 GtC of trees and the average tree lived 100 years that is 400 GtC sequesters in 200 years. (I don't know exact figures.)

That's not the case. When a tree dies it will be broken down by microbes, animals, fungi, etc and as that happens, all of the co2 it sequestered will be released back into the atmosphere.

The only time this was not true was during the carboniferous period.. before those microbes existed.. that's how we got coal. But that will never happen again.

I can't tell if I'm missing something or if this number is missing, but how much of that 550 GtC has actually stayed in the atmosphere until now?

I don't have the figures, but I believe most of that went in to the oceans, causing other problems there.

> earth's tree cover would more than double to capture all carbon emitted so far.

> Clearly, that is not realistic.

It's perfectly realistic in terms of what the trees can do; it's happened before.

The question is whether we want to cede so much space to trees, which I agree that we don't.

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