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turchin comments on Levels of global catastrophes: from mild to extinction - Less Wrong

3 Post author: turchin 27 December 2015 05:26PM

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Comment author: turchin 27 December 2015 09:54:50PM 1 point [-]

Because it is "runaway" )). This means that temperature would rise really high like on Venus. Some scientists think that this is possible because methane and water vapor are also greenhouse gases, and quick release of methane from arctic floor may be the start of this process. See more here: http://arctic-news.blogspot.ru/

Comment author: CellBioGuy 29 December 2015 06:07:46AM *  3 points [-]

Arctic news is generally not credible, using incredibly stupid polynomial fits to observed methane levels at single surface stations to infer absurd and impossible levels in the near future and generally hyping all the positive feedbacks they can find an inkling of in the literature and ignoring every known negative feedback.

As well as the fact that the Earth has been through massive atmosphere excursions in the past from much higher greenhouse condition starting points, like the Paleocene Eocene Thermal maximum or the Permian event, without ever leaving the bounds of long-term homeostasis. The next half milion years stand to be VERY interesting for the biosphere, but this has happened before no matter what scale we push things to.

Comment author: turchin 29 December 2015 10:46:10AM *  1 point [-]

While I don't agree with everything arctic news say and I see that they overhype some recent small changes in methane concentration, I heard the idea of runaway global warming before. I also think that artificial runaway global warming is possible if nukes will be used to destabilize methane of ocean floor. While answering previous comment I was surprised to find in wiki that if median earth temperature once rise to 47C, than water vapor greenhouse effect will push it until new stable state at 900 C. I still think that we should be more afraid of small probability (I estimate it in 1 per cent) of runaway global warming than of high probability conventional global warming (2-4 C).

The main thing about it is, in my opinion, connected with your notion in the second period in your post that we don't observe past runaway global warming. (Except small scale one like 55 mln. years ago.) One of the reason for that may be observation selection: there is no life on all planets with runaway global warming (Venus).

But more serious consequence of it may be that runaway global warming is long overdue and our atmosphere is in metastable condition where small influence may flip-flop it. I wrote an article about in before "Why anthropic principle stopped to defend us"? https://www.scribd.com/doc/8729933/Why-anthropic-principle-stopped-to-defend-us-Observation-selection-and-fragility-of-our-environment (It needs to be rewritten).

Comment author: CellBioGuy 30 December 2015 09:50:46PM *  0 points [-]

Points taken. Still, the PETM was as recent as 50 million years ago, when the sun was on the order of 99.5% as bright as it is now and the base state from which the temperature and atmospheric carbon rose (as quickly as we have measurements able to say - as in, it took less than 15k years and they cant be more specific than that and there's evidence that at least some places warmed ifaster) was one in which there were fewer eroding mountain belts to suck up carbon and more subduction zones to produce it and a geological equilibrium CO2 concentration on the order of 3-4x that of today with an average global temperature of about 8 C warmer than today, before the pulse even happened. I find it unlikely the solar and geochemical situation has changed considerably over that ultimately not terribly long timeframe,

Comment author: turchin 31 December 2015 12:01:55AM 0 points [-]

I have read somewhere that the main difference is that now we have 10 times more accumulated methane in the form of methane hydrates on ocean floor and permafrost. Methane is strong green house gas, like 100 times stronger than CO2. But as it lives only 6 years in atmosphere, the main difference would be not its amount, but the speed which which it could be realised from permafrost. This depends of speed of CO2 accumulation (which is now very high, while the total level is still low). The last thought is mine conclusion from what I read.

Geochemical situation also changed as we had several ice ages which are very good for methane hydrates accumulation and also because geography of Arctic ocean changed.

Anyway, I think that we runaway global warming may be easily prevented by artificial nuclear winter or some cloud seeding, if situation will be urgent. But AI situation is more complex.

Comment author: ChristianKl 27 December 2015 10:00:44PM 0 points [-]

Could you point me to an article that specifies that this would actually race temperatures to Venus levels?

Comment author: turchin 27 December 2015 10:15:45PM 0 points [-]

This wiki article have many links: https://en.wikipedia.org/wiki/Runaway_climate_change But I would like to clarify my position: I am not a climatologist and can't independently evaluate these claims on math level, but I understand their logic and think that while runaway climate change is low probability event, we should do more to prevent it. The interesting point is similarity between two communities. The community of people who think that self-improving AI is possible and is x-risk and community of people who think that runaway warming is possible and is x-risks. The most interesting thing is that both communities choose to ignore each other. But the mechanism of risk (positive feedback) and timeframe (2030) is almost the same.

Comment author: ChristianKl 27 December 2015 10:27:55PM *  1 point [-]

That article says:

Global warming of that magnitude would make most of the planet uninhabitable by humans.

That would be really bad but it's not the same as total extinction.

timeframe (2030)

I don't think that's the timeframe of the LW community as shown by our census.

Comment author: turchin 27 December 2015 10:43:33PM *  0 points [-]

timeframe (2030)

I checked the timeframe in Arctic-news.com. They said that things will become serious after 2030, but extinction will happen around 2060. It is shown on last graph in http://arctic-news.blogspot.ru/p/the-mechanism.html As I remember the LW census, it put AI on 2060? Could you remind me exact data?

Comment author: ChristianKl 28 December 2015 12:05:42AM *  1 point [-]

As I remember the LW census, it put AI on 2060? Could you remind me exact data?

(in the form mean + stdev (1st quartile, 2nd quartile, 3rd quartile) [n = number responding]))
From 2013:
Singularity year: 1.67E +11 + 4.089E+12 (2060, 2090, 2150) [n = 1195]
From 2014:
Singularity: 2143.44 + 356.643 (2060, 2090, 2150) [1177]

Comment author: turchin 27 December 2015 10:37:49PM 0 points [-]

I fail to see the difference. Of course, if we take into account possible space colonies it will not be extinction... Also the article speaks about "which refers specifically to climate changes that cause a planetary body's water to boil off". I don't think it is survivable.

Also runaway global warming is (relatively) easy to prevent by the means of geo-engineering.

Comment author: ChristianKl 27 December 2015 10:57:16PM 0 points [-]

Most of the planet being uninhabitable means that there are still part of it that are habitable.

Comment author: turchin 27 December 2015 11:25:45PM 1 point [-]

May be it will be highest mountains after 7000 meters, which will turn from - 50 to +30 C. Wiki said that threshold for water runway warming is 47 C (at 10 per cent high solar luminosity) and if it reached, the temperature will reach 900 C in new stable state. https://en.wikipedia.org/wiki/Future_of_the_Earth#Loss_of_oceans It means that very hot earth where small highlands will still be habitable - is still in unstable condition and could have much higher global warming.