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timtyler comments on You're Entitled to Arguments, But Not (That Particular) Proof - Less Wrong
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Yeah but this really isn't a difficult calculation. Yeah, you might green a desert or two to make up for some of the farm land that gets ruined but you'll have no infrastructure set up to take advantage of it. It will cost you hundreds of billions of dollars while people starve. Human civilization has adapted to the planet in a particular way and there will always be high costs associated with rapid change to the planet that humans can't easily adjust to. If we had built our cities knowing that the climate was going to change rapidly that would be one thing, the costs would be minimized.
Also, I think we can hold off worrying about the next glacial period until we're considerably more than 12,000 years in to it.
Greenland and Antarctica have enormous inertia. Ice takes a long time to melt - and antarctic ice is an average of 2 kilometres thick - it will probably take tens of thousands of years to melt it. So change is unlikely to be particularly rapid.
I am not advocating particulaly rapid change. Extended change may well be even more inconvenient, of course. It is quite possible that we should try and get climate change over with as soon as possible - to avoid lengthy disruptive changes.
A warmer planet will have more and better farming opportunities, and will sustainably support more people. It is the arid ice-age climate with its deserts and permafrost that is hostile to living systems. Today we have to construct greenhouses artificially to grow plants for food. If we can just end this horrifying ice ige, the whole planet will become our greenhouse.
There is no good reason to think that. The last few interglaicials were only around 10,000 years long. The end of this one may well be overdue.
You're talking about things that a civilization considerably more advanced than ours should strongly consider. But we don't even know how to heat the planet without nasty externalities. Right now human civilization is in the "don't fuck it up" stage. You don't go messing with the climate until you know what you're doing or you have to take the chance just to survive.
No. The important thing is to get away from the cliff edge that represents reglaciation. That is the catastrophe which we most urgently need to avoid. Staying near to the edge of the "reglaciation" cliff is a really bad option for humanity and the rest of the planet. That way, potentially billions may die in a reglaciation catastrophe. Safety considerations are one of the main reasons for wanting to further warm the planet up.
We should not hang around on the edge of the "reglaciation" cliff, waiting for technology to develop. Nor should we engage in ridiculous schemes intended to cool the planet down. We should just walk away from the cliff - and probably go as quickly as conveniently possible before the ground crumbles beneath our feet. The longer we dilly-dally around, the bigger our chances of going over the edge.
This does not seem very complicated to me. Reglaciation looms as a clear and present danger. We must do our very best to go in the opposite direction. We can debate how fast we can safely run, how far away is a safe distance, etc - but run we absoultely must.
The Milankovic forcing is small. Even in the unforced case we would probably miss the next trigger and have 50 Ka of peace and quiet. Now we're well past the threshhold. Find something else to worry about, please, like ocean acidification, coastal flooding, rapid regional climate shifts, and ecosystem disruption for instance.
You are assuming that Milankovitch cycles are the cause of the problem?
That is debated - due to things like:
http://en.wikipedia.org/wiki/100,000-year_problem
...and the list here:
http://en.wikipedia.org/wiki/Milankovitch_cycles#Problems
See also some of the alternative hypotheses:
"Sun's fickle heart may leave us cold"
...and...
"A New Theory of Glacial Cycles"
Unreferenced claims that "we are well past the threshold" don't count as particularly useful evidence.
I recommend you back up such material if you want to continue this discussion.
If it becomes an imminent threat, reglaciation may be easier to avert than warming. Right now, we know more about how to heat the planet than how to cool it off.
Reglaciation is an imminent threat - and we don't know if we would be able to stop it.
A lot of the misguided research on mitigating global warming has investigated how to cool the planet down. I know of no research effort on a similar scale devoted to heating the planet up. So, I am not clear about where the idea that we know more about how to heat the planet than we do about how to cool it is coming from.
Well, it's fairly well-known that putting a lot of greenhouse gases will warm up the planet. ;)
Sure - and there's also black carbon:
http://www.time.com/time/health/article/0,8599,1938379,00.html
...and planting trees in the north:
http://www.scientificamerican.com/article.cfm?id=tropical-forests-cool-earth
Hopefully in due course we will have fusion and mirrors in space on our side as well.
I don't think anyone knows if a concerted effort could prevent reglaciation, though. If anyone wants to make the case that we should downplay the risk of reglaciation because we could avert it, I would say: prove it. This looks potentially extremely dangerous to the planet to me: show me that it is not.
Until we are much more confident in our climate control abilities, I think a safe distance is prudent. IMO, that involves at least melting Greenland.
The planet? The planet is used to glaciers. It's the humans who may not like them.
I mostly mean the planet's lifeforms. Few living things like ice crystals. They typically rupture cell walls - causing rapid death.
That was what we thought ten years ago. There has been considerable and surprising progress on ice sheet dynamics. Basically, ice sheets do not melt from the top. They crack, fail mechanically, and slip into the sea. This is especially true of those whose base is below sea level, specifically the West Antarctic Ice sheet (WAIS).
14 Ka ago sea level rose by several meters per century for several centuries. The mechanism was the partial failure of the WAIS. There's still some left.
Don't get me wrong; this will not happen next week, and there will be no resulting tsunami. But a meter of sea level rise in this century is likely, two is plausible, and four isn't totally excluded.
You seem fond of don't-worry arguments. This makes you an instance of Eliezer's point.
You sound as though you are arguing with something in my post - but it is not clear what - since you don't really present much of a counter-argument. Greenland and Antarctica really do have enormous thermal inertia. Ice really does take a long time to melt - and Antarctic ice really is an average of 2 kilometres thick.
You are arguing with the "it will probably take tens of thousands of years to melt it"? Consider that a ballpark figure. Currently the Antarctic ice sheet is getting thicker and thicker - and it is -37 degrees C down around the pole. So: it is not going anywhere anytime soon.
Perhaps paranoia has its place - but I think it is best recognised as such.
Those who make calls to action often distort the picture - to make their cause seem more urgent.
So: such causes become surrounded with distortions and misinformation designed to manipulate others.
We don't need to melt them to raise the sea level. All that ice floating around does just as well.
We have had around 1.7 mm per year for the 20th century.
That seems pretty slow to me.
It is true that the record - at the peak of the last glacial retreat - was some 65mm / year - but there was a lot more ice all over Russia and Canada back then - and we are unlikely to see anything like that with today's much-smaller ice caps.