Comment by mcv | Hacker News Reader

Comment by mcv | Hacker News Reader

The title is very misleading. There is no hard deadline to save ourselves from climate change, or if there is, we already passed it. We're currently at the point were every year we continue doing nothing, means it takes multiple years (decades? centuries?) to recover from the accumulated effects.

Permanent ice is already melting, climate is already changing. Even if we completely stop emitting CO2 right now (which we can't), there would still be too much CO2 in the atmosphere for some time, leading to further heating and longer melting. Even if we were to remove all excess CO2 from the atmosphere right now (which we obviously can't), Earth would still be too warm and icecaps would continue to melt while global temperatures would slowly revert to normal.

We're doing none of those things; we're still arguing over whether we should do anything at all. Our inaction over the past couple of decades on this issue is going to have repercussions for the next centuries.

The issue right now is: how bad do we want things to get? We can't stop it anymore, but we may be able to mitigate it. I really really hope we can prevent the Eastern Antarctic icecap from melting, because that would truly be a disaster. When that melts, most major population centers will have to be evacuated.

> global temperatures would slowly revert to normal

I share your concern regarding the gravity of the situation, and that a whole battery of efforts need to be made in order to mitigate the effects of current global warming. But I wish intelligent people would refrain from supporting the notion that there is any kind of "normal" regarding the climate. There is no such thing.

We have enjoyed a climate favorable to humans (in many places) in the last 8000 years or so, which has really been an anomaly in terms of the geological record. And the notion that we can manipulate the climate forever so that cities can stay put where they happened to be built at some point has to go. It is not sustainable.

> But I wish intelligent people would refrain from supporting the notion that there is any kind of "normal" regarding the climate. There is no such thing.

While I agree that that is true for a sufficiently long timescale, the rate of change that we force on the world right now does make it look like we're changing the normal.

I believe if we refrain to refer to it as "normal" and use "the current balance" it would be more precise.

And yup, we are changing that fast, not as fast as a supervolcano of the past or an asteroid impact but not so many orders of magnitude away from it, even more considering geological scales.

That is a fair point. It's unavoidable in a discussion about these issues that things get simplified, or nobody will understand it anymore. I try to be more nuanced than most, but I think it's impossible for anyone to fully grasp the total complexity of the situation.

It's undeniable that the past 8000 years have been pretty good to us, and that's not going to last forever, but the impact we're currently having on the planet is much faster, and very likely to be larger and more dramatic than the end of the last ice age.

>Even if we completely stop emitting CO2 right now (which we can't), there would still be too much CO2 in the atmosphere for some time, leading to further heating and longer melting

Do you have any data on this? If you look at how quickly things cool off at night, Earth's biosphere reaches steady-state thermal equilibrium over the course of a few days. Your claim is essentially that we've already set off an albedo forcing function that we can't stop, and which is also stronger than existing negative feedback loops. Seems unlikely to me.

Well, the CO2 in our atmosphere is too high, and it's been built up over the course of more than a century. It won't immediately drop back to normal levels even if we did somehow manage to stop producing any CO2 at all.

At night the temperature drops not due to a lack of CO2, but due to a lack of sunlight. If we were to be able to partially block the sun, or reflect significantly more sunlight back into space, we would indeed be able to lose heat more more quickly, but that would require engineering on a scale we've never done before.

So sure, paint the entire Earth white, but how? Or build a giant solar screen in space, but again: how? Besides, blocking sunlight will also have many negative repercussions.

http://www.niac.usra.edu/files/library/meetings/fellows/mar0...

I do remember a paper from Pr. Jem Bendell, from the Institute of Leadership and Sustainability, who did a nice litterature review on the subject:

www.lifeworth.com/deepadaptation.pdf

https://climate.nasa.gov/ has lots of data.

"Even if we stopped emitting greenhouse gases today, global warming would continue to happen for at least several more decades, if not centuries. That’s because it takes a while for the planet (for example, the oceans) to respond, and because carbon dioxide – the predominant heat-trapping gas – lingers in the atmosphere for hundreds of years."[0]

[0] https://climate.nasa.gov/faq/16/is-it-too-late-to-prevent-cl...

Interesting, thanks. The mechanisms that cause such a delayed temperature response are still opaque though, figure I gotta read more in-depth technical stuff to really understand.

The delayed response is because the temperature rise isn't merely caused by the carbon we've emitted this year, but by all the carbon that has been accumulating in the atmosphere over the past 100 years. Carbon isn't instantly removed from the atmosphere when we stop burning it, so it's going to stay around for a long time. Plants absorb it, but we've been burning more carbon than plants can absorb for a long time.

And for all the time that there's more CO2 in the atmosphere, the atmosphere will continue to trap more heat from the sun, and temperatures will continue to rise.

And that's just CO2. Plants cannot readily absorb methane for example, where you have to rely only on physical processes or our own ingenuity.

So warming is global and when there is night at one place, then that is because there is daytime somewhere else.

Yes, if you can just shut off the sun for some time, we can definitely easily overcome global warming... ...

You didn't make an effort to charitably interpret my question. My question is essentially about whether transient response to changes in albedo occur primarily over the course of days or primarily over the course of years.

Albedo is important, being snide is not.

The impact of albedo on this process can go either way. On the one hand, melting ice caps and higher temperatures can mean less ground covered in ice and snow, therefore lower albedo and temperature will rise even faster.

But warmer seas can also mean more evaporation, more precipitation and therefore more snow, higher albedo and a brake on rising temperatures, possibly even a new ice age. (It gets mentioned sometimes; an ice age is ironically a potential result of global warming.)

But it seems to me that effect will mostly be limited to higher latitudes. There's not a lot of snow around the equator, which receives the most sunlight.

But if we could somehow increase the Earth's albedo on a large scale, then that would absolutely have an impact.

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