We're Already Doomed: Existential threats for the 21st Century

[Carry2]

This was another lengthy topic that sprang up during the recent Singularity (http://www.giantitp.com/forums/showthread.php?t=261635) thread, where a few posters were basically of the opinion that GNR technologies were a moot point given the looming dangers posed by peak oil, global warming, rising populations and standards of consumption, ecological damage and political destabilisation, raising the spectre of economic stagnation, demographic collapse, or an all-out-apocalyptic nuclear exchange or climatic paradigm shift.

So, let's give this a fair shake. I guess, in order to evaluate these risks, you'd have to do a breakdown analysis on the following points-

* Projected population growth and economic/social development by region (OECD, China, India, Sub-saharan Africa, the Middle East, Latin America.)
* Total demands imposed on natural resources (food production and freshwater reserves, energy output and mining, forestry and fisheries.)
* Food and water strategies- phosophorus reclamation, hydroponics, GM crops vs. effects of soil erosion, urban expansion, temperature changes and rising sea levels.
* Energy strategies- timing of peak oil vs. current and extrapolated economic competitiveness of renewables, conservation and next-gen nuclear.
* Biosphere strategies- international accords, ecotourism and ecological monetisation, 'ark' projects vs... well, all the stuff that impacts food and water strategies.
* Geopolitical questions... which are probably of vital importance but equally probably can't be discussed here in any great depth without violating board rules. Suffice to say that none of the pressures above are likely to do world peace a special favour.

As I mentioned in the original thread, I do see at least one ray of hope here: theoretically speaking, actually hitting peak oil (or peak fossil fuels in general) would go a long way towards curbing global warming. By definition, anthropogenic CO2 emissions can't go up while oil supplies are dwindling, and as prices rise, renewable power ought to receive a lot more attention.

At any rate, that should be enough material to have all sorts of holes poked in. Proceed.

[endoperez]

Many of these are only an existential thread due to political issues, so people should be careful not to stray too close to banned topics.


Any way, did you know that there's a group of scientists already discussing this, who "[aim] to establish within the University of Cambridge a multidisciplinary research centre dedicated to the study and mitigation of [existential risks]."

http://cser.org/resources.html

The threats they list include:


progress in AI
developments in biotechnology and artificial life
nanotechnology
extreme effects of anthropogenic climate change

[Grinner]

Well, combining ecological disaster (i.e. deforestation) and increasing CO2 emissions, how would we actually decrease the amount of carbon dioxide already in the atmosphere?

Anyway, my money's on nuclear warfare.

[Carry2]

Oops. ...I forgot about deforestation being a substantial CO2 source.

But yeah, for the purposes of this thread I specifically wanted to focus on doomsday scenarios that weren't based on genetics, nanotech or AI. (And yeah, since we can't talk politics, that more-or-less limits us to climate change, nuclear winter, and malthusian catastrophe.)

I guess one other positive note is that some of the developing nations (like China and India) are in some respects more far-sighted than, say, the States, given their recent investment in stuff like thorium reactors. (Those are apparently a nice way to decommission nuclear warheads, too.)

[Eldan]

Well, combining ecological disaster (i.e. deforestation) and increasing CO2 emissions, how would we actually decrease the amount of carbon dioxide already in the atmosphere?

There are some projects, and I think even prototypes, for sequestration methods. I.e. capture CO2 from the atmosphere, then store it in things like porous, airtight rock.

[Eldonauran]

Anyway, my money's on nuclear warfare.

Yeah. I'm with you on this one. We're going to blow ourselves up long before 'climate change' becomes a major issue to human survival. :smallsigh:

[Kato]

Yeah. I'm with you on this one. We're going to blow ourselves up long before 'climate change' becomes a major issue to human survival. :smallsigh:

Aw, don't b such a pessimist. I'm sure we are smart enough to figure out that throwing nuclear bombs around is a bad idea. It has worked for fifty years now, I think there's a chance of us going another hundred years or so.

Climate change certainly won't wipe us out but I'll carefully mention I don't see the point in looking a bit after the environment instead of being all self-centered and ignoring any possibly arising risk because it might hurt our all too comfortable lives.

And now I think I'll better stay out of here because I think this thread won't see page five before something too political comes up :smallsigh:

[Eldan]

Yeah. I'm with you on this one. We're going to blow ourselves up long before 'climate change' becomes a major issue to human survival. :smallsigh:

It already is a major issue. There's already wars over water and fertile land. Just because it can still get much worse in the next few 100 years doesn't mean it isn't a problem now. We're already losing glaciers, we are getting more extreme storms and droughts, the deserts are expanding, the oceans are getting more acidic, the coral reefs are bleaching and the permafrost is melting. It's a question of scale.

[Karoht]

www.growingpower.org
Starvation and access to food is not about our ability to produce food. But, these sort of techniques certainly would make it easier to produce it, sustainably, anywhere in the world.

Combo that with
www.earthship.net
to greatly minimize the footprint and demand on traditional infrastructure.

Lots of problems solved or greatly minimized.


Yeah, economic instability leading to war is what I am expecting to kill us all.

[Sith_Happens]

I remember reading somewhere that the world population is set to stabilize at around 9 billion, due mainly to the negative relationship between living standards and birth rates.

[Lord of the Helms]

As I mentioned in the original thread, I do see at least one ray of hope here: theoretically speaking, actually hitting peak oil (or peak fossil fuels in general) would go a long way towards curbing global warming. By definition, anthropogenic CO2 emissions can't go up while oil supplies are dwindling, and as prices rise, renewable power ought to receive a lot more attention.


The problem here is that peak oil and peak fossil fuels are two different pairs of shoes. Natural gas supplies will last considerably longer than oil, and coal even longer than that; while the former isn't as bad a CO2 offender as oil, IIRC coal is actually even worse than it. And while the rising prices of fossil fuels are making renewables more and more attractive, the fact is still that so far, they are among the cheapest energy sources out there unless you were ever to internalize all external costs (in which case wind and hydro are cheaper).

That said, currently renewables, particularly wind and solar, are booming like crazy even in places where you'd least expect it (China and the Arab Gulf states of all places) so it's no all looking bad.


There are some projects, and I think even prototypes, for sequestration methods. I.e. capture CO2 from the atmosphere, then store it in things like porous, airtight rock.

"Porous" and "airtight" seem to be slightly contradictory terms :smallwink:

[kpenguin]

You know, all those threats seem rather tangible, not existential at all.

[Joran]

You know, all those threats seem rather tangible, not existential at all.

Humanity survived a bleeping Ice Age. If we can survive that, we can survive anything on the OP's list.

I'd be more scared of a rock from space, or for me here in the states, Yellowstone blowing up and blanketing the Midwest in a pile of ash.

[kpenguin]

Humanity survived a bleeping Ice Age. If we can survive that, we can survive anything on the OP's list.

I'd be more scared of a rock from space, or for me here in the states, Yellowstone blowing up and blanketing the Midwest in a pile of ash.

Yeah, but those aren't existential either. I think the rise of artificial intelligence, the realization of posthuman dreams, and the increasing non physical presence of our persons are more likely to trigger existential crises.

[Scowling Dragon]

What I hope happens, is that we get this mad max type apocalypse going where the evil overlords with control over the remaining working technology are the people with access to the renewable energy resources like the wind farms.

So it would be mad max with electric scooters.

[Avilan the Grey]

One thing is sure; all those that say that Climate Change will doom us, has not paid attention to prehistory. Climate change made us stronger. Since we first stared at the sky 200.000 years ago we have survived near extinction, ice age in siberia (that came very quickly; some say it was only 1 generation betweeen the original settled climate, and the onset of the ice age, yet we adapted), the flooding of the black sea and sudden rise of sea levels (all sea levels rised with far more than even the worst-case scenarios for the present global warming, and that was a flash flood, the rise in sea-level probably took a few weeks, at most, though the flooding of the black sea toook 30-40 years), the draught of africa that indirectly created the Kingdoms of Egypt (100 years from flooded grassland to desert! also very quick event!)... and so on and so forth.

[Kato]

One thing is sure; all those that say that Climate Change will doom us, has not paid attention to prehistory. Climate change made us stronger.

Yeah, putting aside the few hundred thousand that probably died because of that, the rest sure got stronger. If you take it from that perspective...

[Scowling Dragon]

What it might do though, is destroy our current awesome worldwide interconnected civilization which is what everybody is worried about.

If it happens I hope we at least have a method of preserving all our knowledge.

[Avilan the Grey]

Yeah, putting aside the few hundred thousand that probably died because of that, the rest sure got stronger. If you take it from that perspective...

Exactly. WE as a SPECIES. Not WE, personally. Seriously. I am not a social darwinist, but when discussing things like this, this is the level you need to be on. Humanity will prevail; even a nuclear war.


What it might do though, is destroy our current awesome worldwide interconnected civilization which is what everybody is worried about.

If it happens I hope we at least have a method of preserving all our knowledge.

To a point. We might lose Minecraft and Internet Pr0n, but remember that even stone age people, during an iceage, traded with eachother over distances of hundreds of miles.

[Kato]

Exactly. WE as a SPECIES. Not WE, personally. Seriously. I am not a social darwinist, but when discussing things like this, this is the level you need to be on. Humanity will prevail; even a nuclear war.

Sorry if I misunderstood but it seemed like you were saying we shouldn't care about climate change because not all of humanity would die. (And I will stop here because politics and stuff)



@Dragon: I really think loss of knowledge is... well, people don't get stupid all of a sudden. More advanced people will have a better chance to survive (except when it comes to a nuclear war when the less "imporant" regions will be the least affected ones) and even though we might lose a bit of knowledge complete destruction of civilization short of mass extinction is mostly a problem for sci-fi writers.
And if humanity for some reason really stops existing entirely... what do we care about preserving our knowledge?

[Avilan the Grey]

Sorry if I misunderstood but it seemed like you were saying we shouldn't care about climate change because not all of humanity would die. (And I will stop here because politics and stuff)

Nono, I only mean that the doomsayers that claim that if we don't do something humanity will DIEEEE are wrong.

[Grinner]

Nono, I only mean that the doomsayers that claim that if we don't do something humanity will DIEEEE are wrong.

I agree. It's silly to say that we'll die due to climate change.

We won't die. Everything else will. :smallwink:

[Bulldog Psion]

Nono, I only mean that the doomsayers that claim that if we don't do something humanity will DIEEEE are wrong.

Still, I'd personally prefer not to plumb the deep end of the pool and find out, y'know? :smallwink:

[Ravens_cry]

I don't doubt humanity will survive. We do that. Given our severe lack of genetic diversity, it is likely at at least one point we faced an event that nearly lead to our extinction.
Humanity (http://io9.com/5501565/extinction-events-that-almost-wiped-out-humans) was once an endangered species.
No, the question is what else will.:smalleek:

[Avilan the Grey]

Still, I'd personally prefer not to plumb the deep end of the pool and find out, y'know? :smallwink:

But I don't care about raised sea levels, I live on a hill! :smallwink::smalltongue:

[tbok1992]

I don't doubt humanity will survive. We do that. Given our severe lack of genetic diversity, it is likely at at least one point we faced an event that nearly lead to our extinction.
Humanity (http://io9.com/5501565/extinction-events-that-almost-wiped-out-humans) was once an endangered species.
No, the question is what else will.:smalleek:

Yeah, that's what I'm concerned about. I don't want my children to look in a book filled with all these beautiful extinct creatures and have to ask me "Why did they all die?" . And I really don't want to answer "Because corporate America was too greedy and too lazy to change their ways to let them live, and we were so apathetic we let them kill them all with nary a peep of protest."

[Kato]

I don't doubt humanity will survive. We do that. Given our severe lack of genetic diversity, it is likely at at least one point we faced an event that nearly lead to our extinction.
Humanity (http://io9.com/5501565/extinction-events-that-almost-wiped-out-humans) was once an endangered species.
No, the question is what else will.:smalleek:
Meh, there are always events of great extinction in certain regions or for certain species for one reason or another. Wasn't there some speculation that last bottleneck could have just been the fact that just a small amount of people left Africa and spread over the world, while the rest stuck behind? Then it's really to be seen from a different angle...
I don't quite get your last eek. Worried something dangerous might survive or nothing? I think we are able to drag along anything we need to survive. Selfish, yeah, but it's not like we will be the last thing standing on earth, unless we want to make it so. And we are not that stupid (yet)


But I don't care about raised sea levels, I live on a hill! :smallwink::smalltongue:
Hey, soon I'll live in a coastal city, yay! And if it gets worse I can always move further up :smalltongue:

[Lamech]

That said, currently renewables, particularly wind and solar, are booming like crazy even in places where you'd least expect it (China and the Arab Gulf states of all places) so it's no all looking bad.


I'm not remotely surprised at them booming in the Arab gulf. You know what wind needs? An area where the wind can blow free without crap getting in the way. Like a giant flat desert. You know what solar needs? A lot of land that no one else is using, no rain/snow clouds, and direct sunlight. Like a desert.

You also need funding for it. Which comes from oil.

[Joran]

Yeah, but those aren't existential either. I think the rise of artificial intelligence, the realization of posthuman dreams, and the increasing non physical presence of our persons are more likely to trigger existential crises.

A big enough rock and we and all life on Earth is toast.

Unless of course, you mean existential crisis, in which we try to find meaning in a meaningless world? I'm right there buddy.

[kpenguin]

Unless of course, you mean existential crisis, in which we try to find meaning in a meaningless world? I'm right there buddy.

Crises is the plural of crisis, bro :smalltongue:

I'm just saying that for a thread about existential threats, none of those threats seem very existential.

[Joran]

Crises is the plural of crisis, bro :smalltongue:

I'm just saying that for a thread about existential threats, none of those threats seem very existential.

Agreed. Humans are persistent little buggers, or at least I hope we are.

[HandofShadows]

Agreed. Humans are persistent little buggers, or at least I hope we are.

Yeah, humanity is persistant. But the thing that made us so successfull is that we can be utter bastards. Not only to other species, but to our own species.

[Scowling Dragon]

I thought it was because

"Hey nature? You know how made this amazing net of cycles and stuff? Well we will mess it up for our own pleasure!"

[Leliel]

Yeah, humanity is persistant. But the thing that made us so successfull is that we can be utter bastards. Not only to other species, but to our own species.

Such as claiming all humans are utter bastards, as if that's unique on Earth.

Honestly, the only life that isn't are domestic animals, and they can be provoked. And I'm including plants.

I really, really hate this kind of wrist-wringing emo anti-favoritism, which is probably an existential crisis unto itself. Apathy is one of the most insidious and subtle dangers in the universe.

Scowling Dragon has it right-we're the magnificent bastards of the world, as opposed to all other species' run-of-the-mill self-defeating jerkassery. We will survive if the magnificence outshines the bastard.

EDIT: And even then, we'll probably have a chance to grow around the problem. Sapience is only slightly less good of a survival strategy than, say, being a cockroach.

[HandofShadows]

Such as claiming all humans are utter bastards, as if that's unique on Earth.

Honestly, the only life that isn't are domestic animals, and they can be provoked. And I'm including plants.

There is a huge difference between what animals do and what man does. Animals don't wipe out entire species wholesale. Animals don't go and try to wipe out their fellow species because they look a little different. Animals main goal is to surive to create another generation. Humanity often destroys for VERY short term gain that has nothing to do with surival.




I really, really hate this kind of wrist-wringing emo anti-favoritism, which is probably an existential crisis unto itself. Apathy is one of the most insidious and subtle dangers in the universe.

You call it apathy, but it's not. Apathy means that you don't care, and that is clearly not the case. I have studied a great deal of history so I know what humanity can do. The real danger is people that try to hide from what humanity is, has done and can do for both good and ill. For unless you recognize your faults, can you hope to overcome them.

[endoperez]

There is a huge difference between what animals do and what man does. Animals don't wipe out entire species wholesale. Animals don't go and try to wipe out their fellow species because they look a little different. Animals main goal is to surive to create another generation. Humanity often destroys for VERY short term gain that has nothing to do with surival.

If animals don't wipe out entire species, what do you think caused the deaths of all those species that disappeared before humans appeared? It wasn't all meteors.

[SoC175]

Yeah, putting aside the few hundred thousand that probably died because of that, the rest sure got stronger. If you take it from that perspective...But isn't that the only perspective that matters in the end? As individuals we're all unimportant and doomed to die within a century anyway. I take existential threads to mean threats to mankind's existence.

Thus if on of this thread wipes out 6,8 billion humans, but the rest survives and eventually resettles earth, it wasn't an existential threat.


Really, I can imagine mankind surviving in some bunkers subsisting on algae slime long after every other mammal we know today is long extinct. Even if we're not 7 billion anymore then, we're still around

Animals don't go and try to wipe out their fellow species because they look a little different.Well, Chimps (http://www.reuters.com/article/2010/06/21/us-chimps-war-idUSTRE65K48G20100621) wage war (http://arstechnica.com/science/2010/06/the-killing-fields-chimpanzees-wage-war-for-new-territory/)

[Scowling Dragon]

Yeah! And nature just loves to get together and sing Kumbayah.

Animals are brutal, cruel and often just simply predatory. An animal, if given the power will not stop and think if its causing the extinction of a species. It just will.

Thats whats natural selection is all about. Survival of the strongest. The weak all die.

[Kato]

But isn't that the only perspective that matters in the end? As individuals we're all unimportant and doomed to die within a century anyway. I take existential threads to mean threats to mankind's existence.

I was just commenting on the implication we shouldn't care about climate change because not all of humanity would die from it (which was not what the poster meant anyways but I still felt I should mention it)


And regarding the "humans are bastards" posts...
MAN!!! (http://www.youtube.com/watch?v=sTg5Ldqm8ME)

[Leliel]

There is a huge difference between what animals do and what man does. Animals don't wipe out entire species wholesale. Animals don't go and try to wipe out their fellow species because they look a little different. Animals main goal is to surive to create another generation. Humanity often destroys for VERY short term gain that has nothing to do with surival.

Oh, please.

Humanity as a mass-extinction factor is simply due to our position as apex predator of everything. As mentioned, animals are just as reckless, if not more so, and yes, they do wipe out possible threats to their territory with extreme prejudice (the core motive for human prejudice is fear). And...romantic culture in general. Your point is invalid.

We just happen to be holding all the cards, and have only recently begun to realize that the game we're playing is a cooperative one.

All too often the "humans are bastards" meme is a prelude to "so we won't bother doing anything about it". That's a source of true recklessness right there.

[Scowling Dragon]

I kinda agree. There is this sort of "giving up before we even begin" factor to this type of thought.

[Sith_Happens]

Scowling Dragon has it right-we're the magnificent bastards of the world, as opposed to all other species' run-of-the-mill self-defeating jerkassery. We will survive if the magnificence outshines the bastard.

Wow, that is one of the best quotes I've seen in a while.

[tbok1992]

Oh, please.

Humanity as a mass-extinction factor is simply due to our position as apex predator of everything. As mentioned, animals are just as reckless, if not more so, and yes, they do wipe out possible threats to their territory with extreme prejudice (the core motive for human prejudice is fear). And...romantic culture in general. Your point is invalid.

We just happen to be holding all the cards, and have only recently begun to realize that the game we're playing is a cooperative one.

All too often the "humans are bastards" meme is a prelude to "so we won't bother doing anything about it". That's a source of true recklessness right there.

Agreed. To put it more succinctly, humans are both the most prolific and powerful invasive species and the only one with the intelligence to actually curb their depreditations on the environment.

[Bulldog Psion]

Well, there's one of the existential threats for you -- the naysaying against ourselves which causes apathetic abandonment of action.

Our kind needs a new, energizing philosophy that recognizes the darkness within us and the need to combat it, but also encourages our nearly boundless potential. A positivism founded both on emphasizing our ability to control ourselves if we choose to do so, and the need to do so, while recognizing our creativity and driving us forward to higher accomplishments.

Lack of such a powerful and energizing vision -- since we only have a mix of tired, worn-out ideas and a bunch of tut-tutting negativism as the main choices at the moment -- is one of the existential threats for the 21st century. IMO, of course. :smallwink:

[Carry2]

I kinda agree. There is this sort of "giving up before we even begin" factor to this type of thought.
Hmm. I suppose the thread title may have been a little pessimistic.

[The LOBster]

Well, Chimps (http://www.reuters.com/article/2010/06/21/us-chimps-war-idUSTRE65K48G20100621) wage war (http://arstechnica.com/science/2010/06/the-killing-fields-chimpanzees-wage-war-for-new-territory/)

And dolphins - you know, the same dolphins who used to be Always Lawful Good - are really more of an Often Chaotic Evil race in real life. Damn things are as depraved as PF Ogres and a good deal smarter :smalleek:

[willpell]

And dolphins - you know, the same dolphins who used to be Always Lawful Good - are really more of an Often Chaotic Evil race in real life. Damn things are as depraved as PF Ogres and a good deal smarter :smalleek:

Tangenting I know, but I ignore the subtext in D&D that certain animals tend toward an alignment. In my book, pretty much all animals appear in all the Outer Planes as appropriate variations; some of the "classics" are more common than their opposites, but both exist. So a Celestial Lion is noble and regal, but so is a Celestial Hyena, although they're less common. A Fiendish Hyena is filthy, craven and treacherous, but a Fiendish Lion (again, less common) is the same way. In cases where humanity assigns imaginary characteristics to animals, therefore, the myth is both upheld and inverted.

[TheWombatOfDoom]

Tangenting I know, but I ignore the subtext in D&D that certain animals tend toward an alignment. In my book, pretty much all animals appear in all the Outer Planes as appropriate variations; some of the "classics" are more common than their opposites, but both exist. So a Celestial Lion is noble and regal, but so is a Celestial Hyena, although they're less common. A Fiendish Hyena is filthy, craven and treacherous, but a Fiendish Lion (again, less common) is the same way. In cases where humanity assigns imaginary characteristics to animals, therefore, the myth is both upheld and inverted.

Celestial Lion - Mufasa. Fiendish Lion - Scar. :smallbiggrin:

[Kato]

Tangenting I know, but I ignore the subtext in D&D that certain animals tend toward an alignment. In my book, pretty much all animals appear in all the Outer Planes as appropriate variations; some of the "classics" are more common than their opposites, but both exist. So a Celestial Lion is noble and regal, but so is a Celestial Hyena, although they're less common. A Fiendish Hyena is filthy, craven and treacherous, but a Fiendish Lion (again, less common) is the same way. In cases where humanity assigns imaginary characteristics to animals, therefore, the myth is both upheld and inverted.

Except cats. All cats are always chaotic evil, even if they sometimes pretend to be good it's only to further their selfish ends.
(And, of course, all dogs go to heaven (LG))

[DigoDragon]

While we're perfectly capable of destroying ourselves, I have faith that when we call ourselves out on it, we'll stop and talk things over before we wipe our existance off the planet. Talks won't be easy, but I think we can compromise as a single species.

My bet is that what will come closest to seriously destroying us is a rogue asteroid that avoids our detection.

[Wardog]

So, let's give this a fair shake. I guess, in order to evaluate these risks, you'd have to do a breakdown analysis on the following points-

* Projected population growth and economic/social development by region (OECD, China, India, Sub-saharan Africa, the Middle East, Latin America.)
* Total demands imposed on natural resources (food production and freshwater reserves, energy output and mining, forestry and fisheries.)
* Food and water strategies- phosophorus reclamation, hydroponics, GM crops vs. effects of soil erosion, urban expansion, temperature changes and rising sea levels.
* Energy strategies- timing of peak oil vs. current and extrapolated economic competitiveness of renewables, conservation and next-gen nuclear.
* Biosphere strategies- international accords, ecotourism and ecological monetisation, 'ark' projects vs... well, all the stuff that impacts food and water strategies.
* Geopolitical questions... which are probably of vital importance but equally probably can't be discussed here in any great depth without violating board rules. Suffice to say that none of the pressures above are likely to do world peace a special favour.


If by "existential threat" you mean something likely to cause the total extinction of the human species, I don't think any of those would do it. I'm not sure even a supervolcano would do it. You would probably need something like a massive (dinosaur-killer) meteorite strike, or some sort of massive cosmic energy blast.

If, on the other hand, you mean "collapse of society/the developed world, to a state we probably won't get up from for hundreds of years, if at all", then my (no expert) opinion would be:

Nuclear war: probably not, at least at that scale. It would require people to consciously do something stupid, which everyone has an incentive not to do, and which we have been able to avoid for a a couple of generations at least. And we've set off enough nuclear bombs in the past to know that a few aren't world ending (unless they land on you).

Global warming: a more serious risk, IMO, as we are already doing the things that cause it, and it's going to take a conscious effort to stop it. How bad it would actually be I don't know - it depends on how the world actually works (which hasn't been completely worked out yet), and on how far we push it before doing someting about it (and whether the results of global warming exasperate or limit our ability to make things worse).

(To reiterate: we would have to change our current behaviour to cause a nuclear war; but we would have to change our current behaviour to avoid global warming).

Peak oil: I don't really know much about this issue, but I doubt it would be an existential threat. We already have alternatives to oil - they just aren't as effective/well developed. It could mess up the economy and make life suck for a lot of people (even more than now), but unless it hits so hard and so fast (and triggers some other major problem, e.g. nuclear war), I don't think it would cause a complete collapse of society.

Ditto for excessive population growth - it would make things unpleasent for people who are comfortably off, and even worse for people who are already baddly off, but I don't think it would bring down civilization.

One you didn't mention was a major, global pandemic. Which (I think) is a real risk, but I don't think it would be an existential threat. We survived Spanish Flu without society collapsing, and even the Black Death didn't do that, although it did lead to a lot of social upheavel.

Grey Goo, robot takeovers, etc, are too dependent on technologies that don't exist yet (and may never exist) to be a plausible threat (at least on the time scales that the others will come on).



So to recap:
Global warming is (IMO) the biggest problem, as it is starting to bite, will aggrevate the risk and damage of the other dangers, and will require big changes to avoid (changes that run into "prisoners' dilemma" type issues, where in the short term, those who make them will be disadvantaged/worse off compared to those that don't).

Peak oil, resource shortages in general, overpopulation, and epidemics are likely to occur, and will make things a lot worse for everyone, but are unlikely to cause the actual collapse of society.

(All-out) nuclear war could probably do that, but is unlikely to occur.

Actual human extinction would depend on cosmic events that are unlikely to occur, and which we probably couldn't do anything about anyway.

[hamishspence]

Getting hit by a very large comet might be pretty catastrophic- Hale-Bopp, for example, was huge- but never came near.

A sufficiently advanced space program might be able to do something about that.

[Scowling Dragon]

Aren't we already dealing with one right this second?

[hamishspence]

Source? I haven't read anything about people moving a currently hazardous comet out of its normal path.

[Scowling Dragon]

Crap. Can't find the source. But there defiantly was something about an asteroid with a 1/300,000 chance of hitting the planet. It was deemed too risky and some people are dealing with it.

[hamishspence]

Thing is, asteroids are easier to work with. With "unacceptably high chance of hitting the Earth 20 years from now" you can spend the next 20 years pushing it.

You can't do that with a comet- you need something that will handle the problem in a matter of months.

[Sith_Happens]

You can't do that with a comet- you need something that will handle the problem in a matter of months.

What makes it somehow harder to determine whether a comet would hit than an asteroid?

[hamishspence]

It's that (as it currently stands) you can't see an incoming long-period comet until it's already fairly close- a year or so away. Sometimes less.

There are a lot of comets out there- with orbits that are completely unknown, until the comet becomes detectable on its way in.
http://en.wikipedia.org/wiki/Asteroid_deflection_strategies