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Comment by jesperlang | Hacker News Reader

I cannot upvote this enough. We have a strict budget left for carbon emissions. It's not an exam in the future that we are currently studying for to pass. But thinking in budget terms also means talking about budgeting/rationing but I guess it needs to become really bad before we even dare to touch that...

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What happens when the budget runs out?

Shit goes south with no way to recover?

As far as I understand it, it not a binary "we are fucked" / "we are unfucked" if you are talking globally, or even large nations like the US, EU, Russia, China, etc.

It's a gradient. The more CO2, the warmer earth gets.

It's not just that. There are critical mass effects where, after a certain level, positive feedback loops will cascade to all systems. There's definitely a point where we're fucked and won't be able to unfuck ourselves.

I'm far from an expert on climate. But my understanding when I looked into these issues ~8 years ago for a class, was that massive positive feedback loop stuff was not really accepted by the mainstream of scientists.

Of course there are positive feedback components, but there are negative ones too. And stuff like clathrate gun, etc., can't be found in the IPCC reports.

The 2 degree goal is more or less arbitrary. edit: by that I mean 1.9 isn't much better than 2.1--not that 2.1 is no big deal

the point is that these effects are difficult to predict. The challenge is that a changing climate may upset ecological balances in ways that are difficult to predict and difficult to counter.

Take the indian subcontinent as a great example. That is a region of a billion people dependent entirely on the monsoon for water. The region is surrounded by deserts to the west and north. If the monsoon is disrupted due to climate change, what will happen to those billion people? It's worse still if you consider that glacial meltwater from the himalayas also feeds China's largest rivers.

On the flip side, too much rain and there is also a disaster.

This is the point - we don't know what will happen but can be certain it will be bad.

Yes and no, it's not a linear gradient, there are points on the gradient where things get exponentially worse, and everything rapidly accelerates, like a runaway diesel engine.

We can go from "Livable with adaptation" to "millions displaced from unlivable catastrophes and conditions" by hitting some of those milestones.

Perhaps that's true. But the ability to know where those points are with any degree of certainty, we are utterly in the dark about.

You're driving a car at night with no headlights, but since there's no way to be certain about what's ahead, should you: pump the gas or pump the brakes?

- No way back from spiraling climate change

- Positive feedback loops of melting ice -> lower albedo -> more energy absorbed from the sun -> more ice melts

- Unstoppable acidification of oceans and death of vasts amounts of sea life

- Disruption of thermohaline ocean currents, disrupting weather everywhere with little time for nature to adapt, leading to mass extinctions

- Areas where we currently grow most food will quickly become impossible to farm

Basically the point is that the "budget" is how much we can pump and still go back and fix.

Don't forget the feedback loops that adds even more carbon, like permafrost thawing and more frequent/extended forest fires. Even if we stop extracting and burning fossil carbon, still new carbon will be keep being added to the carbon cycle, more each year, due to global warming that seem to have the biggest temperature anomalies around the Arctic. And there are others that slow down the cycle of carbon, like carbon sinks becoming less effective or even turn into net emitters.

It is not possible to just push the brakes and expect an immediate result, the extra carbon that is in the atmosphere will continue warming the planet and the actual warming will fuel positive feedback loops that will make things even worse (and they are not limited to just melting ice).

And, of course, things will keep getting far worse as much as we delay doing something significant in this area.

Global warming is likely avoidable using geoengineering technology. But, for some reason, many don’t think a technological solution is morally appropriate. For instance, here is a concerted effort trying to permanently ban all scientific research on geoengineering [1].

Sure, no one wants to loft sulfur dioxide into the upper atmosphere, but it won’t cost much [2] and we have plenty of natural experiments demonstrating safety (volcanoes). The critical thing is that it would buy time to transition. It’s not like there isn’t a massive interest in transitioning from fossil fuels. But, will we transition fast enough to prevent irreversible runaway positive feedback loops?

[1] interestingly, the rationale for banning solar geoengineering is not the potential danger of the technology, but the (claimed) inability to govern the process. https://www.solargeoeng.org/

Alternatively, here is a view from the Editor of Science, calling for “Symmetric Precaution.” https://www.science.org/doi/10.1126/science.abm8462

[2] https://iopscience.iop.org/article/10.1088/1748-9326/aae98d/...

I agree. I think we should be discussing geoengineering. Outside of technical feasibility, I believe there are two arguments against doing geoengineering:

- It'll reduce the motivation to transition. You can imagine the current politicians and lobbies against climate change trotting out an argument along the lines of we don't need to transition because we have geoengineering. - The second argument which holds more weight I think is that it creates a time bomb. You need to continue increasing the amount of geoengineering that's happening. I believe the name for this is "termination shock": all the pent up warming happens in a much smaller time scale which could have massive unintended consequences.

"The Risk of Termination Shock From Solar Geoengineering" https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/201...

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