Ask HN: What other low-probability high-impact events are we ignoring? | Hacker News Reader

Ask HN: What other low-probability high-impact events are we ignoring?

35 pointstc84 comments

The gulf oil spill is a canonical example of a "low-probability, high-impact event." Everyone who cared knew that this sort of thing could happen, but the risk was widely perceived as tolerable.

What other high-impact scenarios are out there that are likely to create a meaningful "event" at least once in the next 30 years? How are we currently mis-pricing the risk?

[Edit for clarity. Low-probability, in this instance, means risks that are low when taken in discrete units. Getting on an airplane is low-risk. With 14M scheduled US flight per year, though, it is almost certain that one plane will crash once in awhile. We're looking for events here that have a perceived low risk (correctly or not), and that are likely to surprise people when they actually happen. In hindsight, it will be clear to us that the event was actually likely given the extended circumstances.]

View on HN

I'm confused by the 'likely to create an event in the next 30 years' part - either it's unlikely or it's likely. There are events that are quite likely, but with a low _perception_ of risk. Oil spills happen all the time, it's just been a while since one has happened in a rich Western country. Why? Because we've already tapped almost all of our oil - most of the worst spills happened long before we were born! Now the spills happen in places like the Middle East and Nigeria, but because only poor people live there, nobody notices or cares.

Other events that were or will be likely to occur, but have a low perception of risk, include the recent financial crisis, and, looking forward a decade or two, ocean level rise flooding major cities, and a US debt default.

Some interesting events that (seem to) have a genuinely low probability, but would really change the world if they happened:

* Asteroid hit (either a big one, or a smaller one that hits just right).

* A 'supervolcano' eruption that puts us into nuclear winter

* Solar flares fry every piece of electronics on the planet

* Sudden tipping point in the Antarctic or Greenland ice sheets that raises ocean levels by a few meters over a year.

* A strong 'godlike' AI (benevolent or otherwise)

* A self-replicating nanoassembler

* Godzilla attack

I find it interesting that you would put "US debt default" in the category of things likely to happen in the next decade or two. The reason that the US is able to borrow money for practically nothing is that it has never defaulted on debt. Now, clearly there is a possibility that at some point in the future the US will default, but I don't how you would determine that is likely in the next couple decades. Remember we had a significantly higher level of debt as a percentage of GDP following World War II than we do now. We didn't default then.

Depends on your definition of default. Since the dollar is a fiat currency there is essentially no chance of the US government skipping an interest or principal payment. However, it seems highly likely that they will attempt to orchestrate some steady devaluation of the dollar to reduce the value of the debt in real terms. The high impact event would be if they mismanage the devaluation and accidentally introduce high (or hyper) inflation for some period of time before they can get things under control. Check out the history of inflation and interest rates in the 1970's to see what this might look like.

That's what everyone thought about Russia before 1998. But they chose to default on ruble denominated debt rather than hyperinflating the currency.

Hopefully the Fed is smarter than the Russians, an actual US Treasury default would be a cataclysmic event that would drive all risk premiums everywhere through the roof. I suspect that they will choose riding the inflation tiger and trying to terrify the politicians into some semblance of fiscal rectitude over seeing them just plain crap out on the debt. I also don't suspect that the Russians have anything approaching the political neutrality of the Fed anywhere in their government, nor have they ever.

Treasury rates are almost absurdly low right now, so we can clearly agree that there is very little perception of risk that the US will default. That's why it makes a great example of this phenomenon; people will look back and see all the (in retrospect) obvious signs of a coming default and wonder why it wasn't obvious now.

I would hope the structural differences between the US situation in 1945 and now would be obvious - exporter vs importer, young vs old, short term debt (the war) vs long term (SS and Medicare, plus maintaining an ongoing worldwide military presence). And we don't currently have the advantage that every possible economic competitor of ours was recently carpet bombed and utterly drained by years of total war, which certainly didn't hurt our exports.

Adding for clarity: I don't currently believe either a default or major coastal flooding is inevitable or unstoppable, I just think there is substantially more risk associated with it than is generally perceived. Ironically, the perception of little risk can help make such events more likely, because after all there is little point wasting lots of effort trying to prevent something that probably won't happen, right?

I think then your claim is that the true risk and the perception of risk are very different, not that default is necessarily likely (i.e. > 50%). If you were really confident that default was likely within 20 years, you could make an awful lot of money shorting T-bonds (or something).

You can buy credit default swaps in T-bills, so if the US defaulted you could make a nice return - if you think you can find a counterparty in the form of a large insurance company or bank who would actually survive a US default, which seems unlikely. An article in the Economist (IIRC) made the comment that these CDS's had best be denominated in Kalashnikovs and cans of spam.

The USA may have never defaulted on debt, but twice we altered repayment terms. The lesser example was in 1970 when the USA decided to delay paying interest by 10 years.

The nastier example was in 1933 when the USA devalued the US dollar against gold by 40% and unilaterally rendered null and void all contract terms where the USA had agreed to pay back debt in the borrower's choice of dollars or gold. Technically not quite a default, but it was a pretty subtle distinction for lenders who got paid back what was effectively 60 cents on the promised dollar.

The last time that the government came close to failing to pay as promised was in 1995. Under Newt Gingrich, Congress refused to do any business, it brought government to a standstill and the government was unable to make payments. Luckily the deadlock was resolved just before the government would have been forced to not make bond payments.

When it comes to the current debt, I would again not expect an outright default. But I'd expect another fudge where some owed debt does not get repaid. And the prime candidate for how that will be done is that the US government will restructure Social Security so that the government won't have to pay back bonds owed to Social Security. (Bush tried to do this, but didn't manage to push it through.)

Here is that story. In past years Social Security has brought in more money than it has paid out, and the difference was invested in government bonds. Now that the government is facing Social Security paying out more that it takes in, the government is supposed to pay those bonds back but doesn't want to. Structurally, on paper, Social Security is fine for decades to come. However that depends on the US government paying back a lot of this owed debt, which nobody in government wants to do. Hence all of the talk about Social Security being broken. And the one feature that any "fix" is guaranteed to have is that the US government won't be paying back all of the money that was "lent" to the government from Social Security funds.

Isn't the worst case global warming scenario a sea level rise of a few centimeters over the next thirty years. Flooding of major cities sounds highly unlikely.

Given that climate is regulated by several different feedback loops that we only partially understand, the worst case scenario can be much much worse than a few cm sea level rise. Note that one particular failure mode for feedback control systems involves negative feedback turning into positive feedback as you make seemingly subtle changes to system parameters. The results are, needless to say, often catastrophic.

Cosma Shalizi illustrates this problem nicely here: http://cscs.umich.edu/~crshalizi/weblog/543.html

A couple of articles to back up the African oil spill claim:

http://www.michaelmoore.com/words/latest-news/africas-oil-sp...

http://www.independent.co.uk/news/world/africa/niger-delta-b...

It very true that we operate with a "out of sight, out of mind" mentality, particularly here in the western world. Oil companies don't deal with many of the spill scenarios they create well enough simply because they aren't being held accountable. Social responsibility should be a requirement for corporations.

But do I really care? I drive a small SUV.

(answer: of course I still care!)

> I'm confused by the 'likely to create an event in the next 30 years' part - either it's unlikely or it's likely.

Let's suppose the event is an accident occurring during some industrial process. This process is going to happen very frequently over the next 30 years. While the probability of an accident during any particular instance of the process may be low, the probability of the accident happening at least once during that period may be quite high.

Some math:

p -- accident probability

n -- # of times the process happens in the period under consideration

Probability of accident happening at least once: 1 - (1 - p)^n

For example, suppose the process fails 0.01% of the time (1/10000) and happens twice a year for 30 years. Then an accident happens 1 - (0.9999)^60 ~= 0.6% of the time. If the failure rate is 1%, the probability of at least one failure jumps to 1 - (0.99)^60 ~= 45%.

I neglected to mention the assumption that failures in different executions of the process are independent.

The biggest solar flare known occurred in 1859: http://science.nasa.gov/science-news/science-at-nasa/2008/06... probably a 500 year event. It set telegraph paper on fire and would have fried any exposed electronic equipment. however anything in a Faraday cage or underground should survive.

One possibility which seems very much overlooked is that of a catastrophic ecosystem crash. The recent bee die-off gives a hint of the kinds of things that are possible. Another possible catastrophe is a plague or parasite that is resistant to all of our methods of disease control. It could attack either us, or our crops. Our disrespect for complex ecosystems which we still barely understand is the most egregious example of short-term thinking, to my mind.

Are 'they' still saying that all fish could go extinct fairly soon, too? Or at least all tuna?

Like the bee example, it just seems like something I dismiss because I can't imagine it actually happening.

reference: http://www.cbsnews.com/stories/2006/11/02/health/webmd/main2...

A major loss of shellfish is much more likely.

The cause is that CO2 in the atmosphere becomes carbonic acid after it dissolves in water, and if the ph of the seas changes even a little bit, then calcium carbonate shells (which is what everything from clam shells to coral is made out of) becomes unstable and starts to dissolve.

According to the best current projections this is now hard to stop given current CO2 levels, and a major die-off is likely around the middle of this century.

The effects of this on global ecosystems are hard to estimate, but will definitely be large.

By "ecosystem crash", what we really mean here is "an environment in which nobody will want to live". I am not at all skeptical towards various warnings about the environment, but we do have to acknowledge that the Earth has supported life for long before we ever came around, and will continue to support life long after we're gone.

And, humans are resourceful. It's likely that, even in the worst of scenarios, at least some humans will find a way to survive -- even if it's subsistence living.

The question is, would it be an environment that we would want to live in?

I think that's an important distinction that might help sort out some of the ecological "debates".

At subsistence levels, it is not unlikely that all but the most basic human learning would be lost to active memory in a generation or two. While the species will persist, the ability to live as flailing gods will not.

I wonder, how do we preserve our science across such gaps in ability to sustain it. Should we even bother?

I'm sorry but there's been several occasions in human history where civilization has fully collapsed (region specific) and lost the written word (namely proto-greece) but fully recovered with no outside influence.

If something doesn't spell our doom either in the short term or in the moderately-short term then we will quickly recover from where we left off. A generation or two of subsistence living will not entirely wipe out human civilization. No one is going to have to reinvent the wheel, because we've got so many present in our civilization that they could easily be scavenged for hundreds of years before the quantity became depleted and it would likely take a good thousand years before someone couldn't find an 'original wheel' to at least take inspiration from. Aluminium alloy wheels have such high proportions of aluminium in them that even the exceptionally slow oxidization (I work in siding and I can tell you that 20 year old aluminium siding barely has marks on it and it's paper thick, a few pounds would take millennia to degrade but would likely still be clearly recognizable).

If we're really concerned about our longevity I'd suggest manufacturing information arcs that can teach the major language of the geographical area allowing people 100 years down the road to access the knowledge stored when civilization recovers. It would have to be built for longevity and nothing else (IE it can't easily be recovered for materials by scavengers or used to draw power). Essentially you'd want a very long life RTG to power a multiple redundancy computer system and basically load encyclopaedias and patent databases and an archive of literature, magazines and journals.

To be sure, though I think that the no outside influence restriction is a bit contrary to the archeological record. Though I didn't make it clear, what concerns me are not the coarse technologies of life--wheels and pottery and what not--but more fine, non-obvious innovations. Consider concrete: with the dissolution of the Roman political structure the secrets of concrete were lost. It took 13 centuries, until the 1750s, to rediscover its formula. During that time, public works were greatly retarded. Indeed, the Anglo-Saxon (whose buildings rarely had windows for stability purposes) culture produced a rather famous poem we now call The Ruins in which Roman ruins are attributed to the works of giants.

What concerns me is not the transmitting of basic machines across the simplification of a society, to use Joseph Tainter's jargon, but, rather, difficult, contextual knowledge. Our knowledge of Mathematics, for example, was preserved by luck: the Byzantine Empire harbored enough learned individuals and archivists until such a time as the Crusades swept through. All of my work simply assumes an industrial, technological civilization with advanced computational capacity. Any textbooks I might produce in the future will have the implicit assumption of contemporary operating systems, compilers and hardware. If, through sheer chance, any of my potential works survived across a collapse they would be useless without further context. I imagine that the same holds true for advanced works of physics, especially that which requires hugely complex experimental devices.

Euclid held up well enough as his works were self-contained. What modern works can say the same?

This does not seem like a real threat in the the same way as the things the asker is talking about (i.e. things that are unlikely to happen at any given moment, but not at all unlikely on a realistic scale). Global ecosystem crashes seem to be once-in-millennia events. And our "disrespect for complex ecosystems" is about as likely to avert a looming global crash as it is to trigger one that wouldn't have happened, given that our impact on the matter is an unknown factor.

our "disrespect for complex ecosystems" is about as likely to avert a looming global crash as it is to trigger one that wouldn't have happened, given that our impact on the matter is an unknown factor.

???

This is supposed to be comforting, how? Try this paraphrase: we're twiddling the knobs on the ecosystem, we know we're likely to make big changes, but we're not sure what. Would you like operators of a nuclear plant to follow this behavior?

As far as I can tell, we do not know that "our disrespect for complex ecosystems we barely understand" is likely to make big changes to the global ecosystem. That's almost required by the "we barely understand" part — the effect we have is unpredictable both in scale and gravity.

It's more like, if you found yourself in a universe full of potentially dangerous forces that you don't understand, would you try to harness them or just hide from them? So far, the human race has traditionally gone with the former. Some of the things we've done have had great positive effects. Some have been catastrophic. Most have been relatively inconsequential. The result is never clear beforehand — that's the whole idea behind experimentation and the scientific method. Otherwise you're left with fearmongering and superstition.

As far as I can tell, we do not know that "our disrespect for complex ecosystems we barely understand" is likely to make big changes to the global ecosystem...Some of the things we've done have had great positive effects. Some have been catastrophic. Most have been relatively inconsequential.

Inconsequential? Then you haven't been paying attention to history. We've had freakin huge impacts on our ecosystem throughout our history, even predating recorded history. The disappearance of huge tracts of North American forest. The same for British and European forests. The Colorado River dwindling into nothing. Virtual eradication of Bison. Eradication of the Passenger pigeon. Aborigines causing the unintentional desertification of much of Australia. The current desertification of Africa. Virtual disappearance of Salmon from the North American west coast. None of these have been inconsequential. Some have caused tremendous benefits to people, but all have had significant negative impact.

The result is never clear beforehand — that's the whole idea behind experimentation and the scientific method. Otherwise you're left with fearmongering and superstition.

Many scientists refrain from experimenting on their own bodies. This has nothing to do with "fearmongering and superstition." When scientists do experiment on themselves, they are generally certain that it won't have permanent consequences. Again, nothing to do with "fearmongering and superstition." You categorically state that we won't know what happens.

I didn't say everything we did was inconsequential. I said some things were good, some things were bad and others were inconsequential. Unless you're saying that those events named amount to everything any human has ever done, it seems like you're agreeing with me in a very hostile manner.

And nobody's talking about doing experimentation on their own body here, so I don't see how that's relevant, unless you're saying that all uncertain actions (experimenting with electricity, nuclear power, etc.) are like experimenting with your body and should not be done.

The analogy is: Body = Ecosystem.

We're doing significant things to ecosystems. The magnitude of what we do gets larger as our technological capabilities in crease. We're still not close to understanding ecosystems well enough to ensure we won't do anything bad.

The last record-breaking accidental oil spill in the Gulf of Mexico was the Ixtoc I, in 1979. I should also note that the Atlantic Empress spill, also in 1979, and the Amoco Cadiz, the previous year, had a combined spillage equal to the Ixtoc I.

The record-breaking deliberate oil spill happened during the Gulf War, in 1991.

In the past thirty-five years, there have been ten oil spills in which over a million barrels of crude were released. I don’t see how you can classify this kind of thing as “low-probability”, in the same category as asteroid strikes.

http://en.wikipedia.org/wiki/Oil_spills#Largest_oil_spills

> The gulf oil spill is a canonical example of a "low-probability, high-impact event."

I think that what's going on is awareness.

There was a much larger deep-water spill in Mexico in 1979. There have been huge on-shore spills, some that ran into the sea. There have been huge tanker spills. And so on.

The difference is that this one is off the US coast, we have on-scene video, and folks who claimed to be uber-competent have, arguably, dropped the ball.

Yes, they've probably gotten more blame than they deserved, but they've also tried to exploit this incident for political gain, so ....

Oil spills aren't really that low probability when you don't follow any of the safety procedures and you use broken equipment.

And rare events always seem like they could obviously happen in retrospect.

http://www.fastcompany.com/1658137/infographic-of-the-day-bp...

With such a flagrant history of safety violations, I'm surprised it didn't happen sooner.

Most of you aren't trying hard enough to come up with things we'll PROBABLY live to see:

1. California earthquake

2. global economic depression

3. war involving developed countries(N Korea vs S Korea, India vs Pakistan, Iran vs Israel, China vs Taiwan, etc)

4. 2 leading into 3(maybe)

5. pandemic

6. The Next Big Thing(biotech? nanotech?)

7. car accident resulting in serious injuries involving yourself or a loved one

8. serious illness involving yourself or a loved one

Let me add a scary possibility, the use of a nuclear bomb on a major city.

It is worth noting that India and Pakistan have fought several recent wars, and are now both nuclear armed. Worse yet, everyone's wargame simulations have concluded that their next war WILL go nuclear. As one friend of mine (whose father is high up in India's air force) put it, "The only real question is whether the bomb that Pakistan drops on New Delhi works."

To be specific, the likely scenario is that they go to war, Pakistan, lacking reserves, knows it has to win fast. Pakistan throws everything into the battle front, India breaks through somewhere, and Pakistan, with nothing to stop India's breakthrough, drops a nuke on Indian troops in Pakistani territory. (There is a perverse logic to having all of the civilian casualties be your own.) India, having just lost major numbers of troops, has little choice but to escalate to nuclear war against Pakistani military targets. Pakistan, with a more limited supply of nukes, has only one way to escalate. And New Delhi is the easiest to reach major city.

There is speculation that the last military coup in Pakistan happened in part because the Pakistani army was scared that Pakistan was escalating into another war with India, and it was the easiest way to force the situation to de-escalate.

Earthquake along the New Madrid fault. Almost nothing in the midwest is built with earth quakes in mind.

New York's construction is even more vulnerable, and there are a lot of fault lines there.

Another very real possibility is that the Cascadia zone could have a megathrust earthquake. This would be a 9.0 hitting cities like Seattle, Victoria and Vancouver that are completely not prepared for it. The last one in 1700 gave Japan a really nice tsunami as well.

That could also potentially trigger the lahar that is waiting on Mt Rainier. Which brings to mind all of the volcanos listed at http://en.wikipedia.org/wiki/Decade_Volcano - the eruption of any of which would qualify as low probability high impact event.

A nuclear event would fit that and could certainly happen in the next 20 years --

- Israel bombing all suspected Iranian nuclear facilities. Iran retaliating with a nuke.

- Low level or dirty bomb by any number of terrorists groups in the world. India/Pakistan is a pressure cooker right now. Could happen in Europe, the Mid-East or America.

An airliner crashing into a building that houses a major intercontinental cable landing, an e911 datacenter, and a dns root node. Beleive it or not there are several such in the world.

I find it hard to believe this is true! Maps or GPS coordinates, or it didn't happen!

A major global pandemic seems like a plausible scenario. We've had a few (semi..) close calls with SARS and swine flu but have been lucky that they haven't mutated to be airborne and infectous from human to human.

You don't have to go further back than the 1918 global flu pandemic to see an example of what a global pandemic can do. 3% of the global population died.

You may think that we have better vaccines and better systems in place now than we did 100 years ago, but you'd be largely mistaken[1]. A vaccine takes so long to develop and produce that when it's ready for the market millions of people will already have died. Pandemics spread quickly. Adding to the problem is that the world is so connected and people so mobile that once the virus is out it could easily spread across the globe in a matter of days. One infected stewardess in Heathrow airport wil lmake sure of that.

[1] I'm no expert on biotech so please correct me if I'm mistaken.

Government regulators tend to choke off vaccine development, but those policies would change in a hurry during a dangerous pandemic.

Of greater importance is a disease that there is a vaccine for but which the U.S. government is actively suppressing: smallpox. DNA synthesizers are already at the point where anybody who wants to can resurrect smallpox. It is only a matter of time before that scourge is set loose. The results will be ghastly.

Funny, last night I watched a West Wing episode where they mention the possibility of a smallpox outbreak. Is it still true that there are just a handful of smallpox vaccines on hand in the US?

Vaccines don't have a shelf life of forever, and storing components to defeat a disease that no longer exists beyond a few petri dishes in a military lab isn't really efficient.

Odds are there is barely any.

There is not remotely enough vaccine to handle a smallpox attack.

EDIT: Apparently the U.S. has rather a lot stockpiled, but good luck getting any in advance of the end of the world.

> swine flu but have been lucky that they haven't mutated to be airborne and infectous from human to human

As far as I can remember, most of the flu last year was of the swine variety and was spreading human to human. We were lucky it wasn't so deadly as it might have been. It spread far and wide though.

In terms of mispriced expectations, it's unprecedented for 1/3 of the world population (<2bn people - India & China) to smoothly transition from 3rd/2nd to 1st world economies without massive internal 'social unrest' (&/or war). Yet that is what we appear to expect... Hope it's the first time.

Climate is what we expect; weather is what we get.

Most low-probability, high-impact events are un-predictable by definition. Only in hindsight do they appear obvious. This has to do with many factors such as the narrative fallacy and confirmation bias, which Taleb describes as the Black Swan.

That being said, here a few high-impact (moderately low probability) events that could be on the horizon.

* Northern California Earthquake * Israel v Iran Nuclear Conflict that triggers WW3 * Singularity

At the risk of sounding crazy, I'll say fascism in a Western country.

Sadly, that is not crazy. Remember it was not that long ago in historical terms that fascism did hold a Western country.

Even now, while it is unlikely, it is very possible for it to happen. It is even possible for it to happen through the democratic process (in fact, that may be more likely with the current makeup of the West). People tend to turn to absolutes when they become desperate and it is quite forseeable that some combination of economic, military, political, or natural disasters will make some country so desperate they will once again try anything.

To call that realistically possible, you'd have to believe that World War II and the invention of nuclear weapons didn't fundamentally change the Western world (I think they did. World War II because we saw the results of fascism going unchecked in a major power. Nuclear weapons because realistically another world war would be close to Armageddon)

It Can't Happen Here

http://en.wikipedia.org/wiki/It_Cant_Happen_Here

Edit: corrected link, sorry.

Edit 2: Or...not. Apparently I can't have a URL with an apostrophe.

Here you go: http://en.wikipedia.org/wiki/It_Can%27t_Happen_Here

How low-probability is an event if it's likely to happen in the next 30 years?

Isn't that kind of like asking "What's an unlikely event that's likely to happen"?

I suppose by "low-probability", tc means "unlikely to happen at any particular time, in any particular place".

Think serious car accidents: unlikely enough that most people never have one, yet many thousands happen each year. The effects can be devastating to the people involved, but everyone keeps telling themselves that "it won't happen to me", and many people forego actions that would decrease or mitigate their risk, or even engage in actions that increas it substantially.

This is the problem with the whole concept of risk: because your chances of suffering a car accident are actually relatively high when compared with all sorts of other risks.

On a scale of things unlikely enough that most people never have one a car accident is pretty near the bottom.

I'm suprised that no-one's suggested aliens arriving, an event which can arguably be getting more and more likely as time goes on.

The trick to that statement being that we don't know where the baseline is...at .00001% likeliness this year, an exponential increase of 1.0001x every year isn't particularly likely.

There are many in the same vein that would have similar impact on society.

Aliens arriving, being discovered, or merely communicating with us, there are so many possibilities, many of them with the potential for being as disruptive to human civilization on Earth as an asteroid impact. The mind boggles at the possibilities.

There are a lot of such events looming in the improbable horizon. Each would be viewed as a total surprise when in fact it's known that there is a nonzero (but small) probability of the event occurring:

- a moderately sized meteorite strikes a major city.

- the capital requirements set after the recent financial crisis might turn out to be horribly inadequate if just the right series of coincidences occurs.

- The US could have significant post-election riots, etc.

- With a slight increase in trauma injuries, all ERs and available hospital beds and skilled professionals could be quickly used up within a 1000 mile radius of an event. Many would die in transit, etc. Think back to the superdome.

- A significantly noteworthy event could easily overwhelm mobile phone network capacity in any major city making communication nearly impossible, this would be made worse due to the panic that it inspired.

- An unsophisticated terrorist group could bring mass transit in the top 5 major US cities to a standstill for a budget of less than $10K. (simply by igniting backpacks full of regular gasoline in buses, subways in some sort of unison). This would probably provoke martial law.

- The US could elect a Hitler-esque strongman. Both Bush and Obama are shades of this sort of leader in their own way. That anyone (especially the media) took McCain's candidacy seriously is evidence of this.

- Mexico could become a failed state, putting pressure on the US, and sending the US toward a nationalistic strongman leader type.

How about a major earthquake along the San Andreas fault in southern California? We've had a couple little shakes this week. There isn't much we can do to prevent it from occurring -- we can only reduce the impact. Build strong and keep emergency supplies on hand.

I'm upvoting this because (a) I know that a huge percentage of you live directly on top of the San Andreas fault; (b) I've seen the upcoming earthquake mentioned a few times on this thread, but always in a list with things like "the Singularity".

For god's sake. The difference between a major Northern California earthquake and the effing Singularity is that one of these has happened in the last century and is guaranteed to happen again.

Lay in an emergency supply of drinking water and strap your heavy shelves to the wall.

Contrary to the majority of predictions here, this would be a positive change: We should all at one point or another, hopefully not too far into the future, realize we've been led tragically astray in terms of our nutritional health by well meaning but unfortunately ill informed government officials and doctors. The current common wisdom will likely reverse and take with it many of the diseases of civilization: diabetes, coronary heart disease, obesity, maybe even cancer. That out of the way, current debates about socialized medicine and escalating insurance costs would turn into bad memories and we'll think "how could we have been so ignorant?" We'll live better, healthier, cheaper and maybe even longer. Local economies will revitalize, the environment will benefit, and it'll be "easy". Of course, current dogma will fight tooth and nail, proclaiming the new path leads to disaster, but disaster is what we have now, and it'll be soundly defeated. Nostrademus has spoken… :)

I'm surprised nobody has mentioned anything to do with the structure of the internet. Suppose someone takes out all of the root DNS servers or the bgp system breaks down, or something similar. Even though there might not be any loss of life, this could cause tremendous amount of damage in other areas.

I've heard seismologists describe the San Andreas fault in California as "10 months pregnant".

There's a good chance there will be a massive earthquake on it in the next 30 years.

Everyone who cared knew that this sort of thing could happen, but the risk was widely perceived as tolerable.

There are billions of things that could happen, that might happen or that will eventually happen given enough time. We should reasonably ignore those or it starts to get silly :)

I think what you are really talking about are "Elephant in the Room" problems. Things which shouldn't happen, or are low probability, but end up being caused by bad management or human error.

If someone had asked this question 6 months ago would anyone have brought up deepwater oil drilling? I somehow doubt it. Finding these scenarios is difficult, if not impossible, because they rely on things that don't get reported till it has happened.

Solar flares. Magnetic pole reversal. The Yellowstone caldera going boom again.

I think what's brewing on the Korean Peninsula is a great example of a potential low-probability, high-impact event. Things are heating up further and further, and the potential outcome could be devastating.

My vote is for the Yellowstone Supervolcano. If you take a look at the image showing potential range of the ash cloud, you can see it might cause a few problems if it were to blow. Maybe not a next-thirty-years type of event, but still an interesting possibility with potential for tremendous casualties, and very little that can be done in the way of prevention.

http://www.earthmountainview.com/yellowstone/yellowstone.htm

THE BIBLE CODE PREDICTS THAT YELLOWSTONE WILL BLOW MARCH 31 OR APRIL 1, 2004

W T F?!

You mean you didn't pull the latest version of the bible code from github?

Here's a happy one, for a change: the Focus Fusion guys actually succeed, and we get radically cheaper electricity that can be mass-produced in a big way. This would change everything. Aluminum would become a lot cheaper with cheap energy for refining it. The various water shortages in coastal areas would be easier to deal with, thanks to cheaper energy for desalination. We could replace gasoline with carbon-neutral synthetic fuels. I'm probably still thinking way too small here.

Large Hadron Collider having an accident or creating a black hole.

Running out of oil, which will in turn start a whole host of problems.

Some genetic disease like the plague, wiping out most of the civilization.

An experiment on next level weapons that make nukes look like firecrackers, going out of control.

Sun going nova for no apparent reason.

America becoming a "christian nation" with science/technology being outlawed.

Someone hacking the pentagon or whatever, and detonating all the nukes at the same time.

Skynet becomes self-aware(AI/robots taking over) - will probably happen like the irobot movie.

aliens

>Running out of oil, which will in turn start a whole host of problems.

It starts getting scary when oil production vs demand becomes disproportionate. Aka, peak oil.

>Someone hacking the pentagon or whatever, and detonating all the nukes at the same time.

I recently watched Hackers Wanted and one of the interesting things the movie pointed out was that when terrorists start becoming hacker savvy, a new war front will be introduced into the world.

Evil cats: http://www.exitmundi.nl/meow.htm ?

I am posting this as an example of a "risk that is widely perceived as tolerable." Is it high risk? I think so, judging by all the other examples of non-native animals destroying parts of ecosystems.

It is hard to predict how things like this extrapolate. But that is how it is -- we are more likely to observe consequences and infer the origins, and extinction around the world is a pretty big one. The evil cats scenario is just one from that article.

A snippet: In the street where I live, there are more cats than people!

And that is a problem. All those cats catch lots of birds and mice and rats and butterflies. Biologically speaking, cats are eating a huge hole in the food chain. No, seriously! According to several alarming reports, this is exactly what is happening in countries like the United Kingdom, Sweden and my own country, Holland. Bird species are vanishing, mouse subspecies are going extinct. All because of Molly, and Lizzy, and the other many billions of domestic cats that inhabit the planet today.

Okay, this an instance where I would like the downvoters to explain the downvoting.

The submitter asked for "low-probability, high-impact" events. Cats destroying local ecosystems is a low-probability, high-impact event and perceived as tolerable. We've seen situations where non-native animals have messed up ecosystems, and there are a lot of cats in the world hunting lower on-the-food-chain prey.

Is the word "cat" taboo on HN or something?

An article on feral cats and dogs:http://www.bc.edu/schools/cas/envstudies/research/feral.html

Sigh Nobody will probably see this. I guess I'll just go upvote a couple of people to make up for it.

Why do you believe this was a low-probability event? My impression is that important safety measures were neglected, and this laxity played a key role in the failure.

A better question might be "Where else has avarice gotten the better of known sensible precautions?" I hear there are clear risks in the Commercial Real Estate market, similar to the problems which led to the residential housing crisis. Then there is the fact there has been essentially no meaningful regulatory reform of the financial system as a whole (in fact, there has been encouragement of the same bad behavior.)

As I understand it, they still haven't fixed the levies around New Orleans.

Fault in a nuclear power plant?

A lot lower-impact than people generally think. Those things are safe nowadays.

The 'Singularity' (in the sense of a super-human intelligence, for example either augmented human or purely machine) comes into being and, basically, gets to exert influence over humanity's future.

Singularity's a fun one, because its got more vectors than just Moore's law. Or, anyway, Moore's law is being played out in a lot more vectors than just IT.

Drastic life extension would count, as would 'a mature nanotech', matter edition on any scale,

Asteroids?

Washington, D.C. being taken over by a competent, efficient government.

Reply on news.ycombinator.com