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Assuming current technology, is there any catastrophic event from space/earth that humanity are able to see/detect/calculated it coming. (Would prefer a space event but earth ones are welcomed)

This event should be able to wipe out at least 90% of living things.

  1. We are able to detect this event 1 year before it strikes

OR

  1. We are able to detect this event 5 year before it strikes
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So, I assume you would like to exclude the good old super- meteorite? – Confused Merlin Jan 22 at 6:30
    
I claim, any meteroite, which we would not be able to fend off in some way, would be so large, it would destroy the entire earth. How about a massive solar flare, burning off our atmosphere? – Sempie Jan 22 at 6:40
    
@ConfusedMerlin i am afraid humans will be disappointed if such a overused cliche is actually happening <.< – Mono Jan 22 at 6:42
    
@Sempie I believe solar flare happen too quickly for us to even issue any warning – Mono Jan 22 at 6:43
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How about a massive meteroite (size of moon or larger) on its way to the earth. Mankind is able to distract the meteroite, but it hits the venus. As a outcome, chunks and dust, which where venus and meteroit before, are now on the search of a stable orbit around the sun. This blocks (partiell, periodically) sunlight and changes weather dramatically. The exact weather change is not forecastable, so you could actually do what you want in your story. – Sempie Jan 22 at 7:00
up vote 15 down vote accepted

if we go for the less classic solutions (meteorites, comets, asteroids and so on) there isn't much we can actually predict. Stuff coming from the sun usually comes without warning and it takes very little (compared to astronomic times) to reach earth. Other things are:

1) not very visible until it's too late (Aliens? )

2) Visible enough that we can know it in advance (Comets or even incoming planets)

3) Too sudden (Solar Flares)

4) The information of the event comes with the event itself (Gamma Ray Bursts, which travel at the speed of light so you get a visual of the event at the same time of the damage being done)

An idea could be a Rogue Black Hole (yes, they are a thing): a black hole wandering around the universe and ends up in our solar system.
Since the black hole is not "eating" anything at the moment it's undetectable (It should be emitting Hawking Radiation though, but i don't think it's that much detectable, it should be very faint actually).

All of a sudden it gets close to Neptune with catastrophic results, and everyone is aware of that black hole now.
The black hole has now matter swirling around it (an accretion disk) and it would be very bright because of the heat emanated by the disk, probably it could even be seen with naked eye (it mostly depends on the disk size at this point. But we can safely assume it'd be easily visible at a certain point)

Now we have 2 scenarios, depending on the black hole size:

  1. The black hole is very tiny and almost at the end of its life (we're talking the same order of magnitude of atoms, if not tinier. A black hole of $1*10^{-9}$ nanometers, way less than an hydrogen atom which is 0.053 nanometers, will have a 673468.0 metric tons mass and a lifespan of 813 years)

  2. The black hole is big enough to influence other celestial bodies (a coin sized black hole will have roughly the same mass of the earth, so i think that'd be enough)

In the 1st case the black hole won't have a long life span but it can have a direct effect on the earth by evaporating next to it, emanating a lot of radiation. So our scientists might calculate that in a few years the black hole that perturbed Neptune will get close to the earth and end its life close to it exploding with terrible force, emanating gamma rays which will kill most of the life on earth

The 2nd case is more catastrophic. The black hole can't reach the earth or it will completely destroy it.
The best course of action for a not-so-catastrophic catastrophe would be if it hit mars and then the debris would hit the earth or if it passed so close to the earth to perturb its orbit causing earthquakes and possibly a new ice age, or even move the earth closer to the sun (and/or tilt its axis) and make it hotter. In any case this will do a lot of damage to the current life on earth

This video might give you an idea on how catastrophic a coin sized black hole is (and also how a very tiny black hole might "affect" life on earth on evaporation): https://www.youtube.com/watch?v=8nHBGFKLHZQ

I haven't said anything about the black hole's speed but that can be arbitrarily set to suit your needs (depending on how much "sciency" you want to go, you might need to do some calculations). Just remember that you need to make it go quite fast to not be caught by the sun's or other planets gravitational field, becoming part of the solar system and ending up in a stable orbit before unleashing its wrath on the earth

Also remember: Black holes do not suck things! they have a huge gravity pull but no bigger than the thing they formed from. If the sun would instantly turn into a black hole, planets would still have the same orbit (well, we would die because of no more heat but that's not important). The only difference would be in the area which was previously occupied by the sun, that's the point where a black hole's curvature of space time (which is its "gravity") does the weird things. This is just to say that what i wrote is kinda plausible with today's knowledge of black holes.

More on Black Holes lifespan:
https://www.quora.com/How-long-does-a-black-hole-last

Black Hole features calculator:
http://xaonon.dyndns.org/hawking/

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a black hole planemo would be easily detected well before it formed an accretion disk, just from its influence on the orbits of other planets and KBOs – quintopia Jan 22 at 20:59
    
That depends on how big the black hole is and how it reaches the solar system. If it comes from below or above the solar system's plane it most likely won't find anything on its path – valepu Jan 23 at 0:19
    
I'd love to see a calculation on how far away an Earth mass moving at Earth speeds perpendicular to the ecliptic would have to be to have a visible effect on the orbit of, say, Jupiter. I don't know enough about the sensitivities of modern equipment to do it myself. – quintopia Jan 23 at 1:14
    
Actually me too, but let me remember you that just these days they are talking about a possible 9th planet 10x the earth's mass at 20x neptune's orbit because of some kuiper's belt objects orbits, but they can't be 100% sure. This is how difficult is to find bodies that don't emit light. On steam there's a game called "Universe Sandbox^2" which let's you simulate solar systems, might be fun to try. – valepu Jan 23 at 10:11
    
i found this question on astronomy SE which might be interesting (although it's about a stellar mass black hole) astronomy.stackexchange.com/questions/12296/… – valepu Feb 12 at 14:24

Ruling out the classic meteorite, an interesting option can be a big and opaque cloud that cross the solar system between sun and earth blocking the sun for some decades, let say a century, and thus fast driving earth to a ice age.

While we can discover the cloud 5 years beforehand, we cannot prepare to an ice age so fast and moreover, with no light (or 80-90% less) all life on earth are basically doomed, except, perhaps, some niche where some extremophiles can survive.

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I know this question calls for some amount of pseudo-science, but earth orbits the sun. Meaning the cloud would have to be big enough to completely wrap around the sun. That or the cloud could orbit the earth. Maybe gets pulled in by earth's gravity over time. – Prinsig Jan 22 at 13:36
    
Our solar system (and sun) is not so big, relatively speaking. The the sun diameter is about 1.4 million Km while 1 AU is about150 million Km. One of the smallest known nebulae (NGC 7027) is 946.066 million Km by 1.892.132 million Km, so a cloud smaller than 1 AU is not so massive. But I agree that the cloud must have the correct trajectory... – Gianluca Jan 22 at 14:19

The problem with global warming.

The scientists assume that Venus or Mars looked similar to Earth, and they also assume that it is the global warming that turned them into hell.

The temperature on Earth rises slowly, and nobody knows when is the critical point of no return, but it is going to come. In such scenario, no living organism would survive.

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While I agree that global warming is a little more complex of an issue than simply "humans did it", I also think you're oversimplifying. Way, way, way oversimplifying. – AndreiROM Jan 22 at 20:07
    
In particular, Mars' problems would not be described as "global warming". Mars lost its atmosphere due to insufficient gravity and a lack of a magnetic field to protect it from solar wind. And Venus started out like the Earth was then, not now. It remains more like the Earth used to be than the Earth does. For example, it contains significant sulfur in its atmosphere. – Brythan Jan 22 at 21:52
    
Runaway global warming would not be anything like fast enough. The oceans are a massive heat sink. But in the long term (500 million years or so) it will happen. As the sun gets hotter first all ice will melt and then global cloud cover will increase to stabilise surface temperatures. When cloud cover reaches 100% its all over for life. The oceans will boil mere thousands of years later. – nigel222 Jan 23 at 11:11

Humanity can calculate that World War III is coming in advance. If the war goes all the way to the nukes for any reason, such as a group of extremists that hid themselves within the ranks of both sides turns them on, they can wipe out most of the living things overnight and then the fallout will do the rest, killing out things for the next few decades.

We can, more or less, detect the possibility of it happening before the war even starts. If we go for the real world example, then I should say that I am already getting vibes that a new global war is coming and it might bring nukes with it, or maybe even weapons that are more horrible.

When it comes to space, we can only detect a disaster beforehand if it moves slower than the speed of light. For example, as luck would have it, one of the Voyager probes might detect an asteroid coming towards Solar system and the scientists can calculate that it is on a collision course with Earth in five years.

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Can we? Are you sure it hasn't already started? – Separatrix Jan 22 at 12:27
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@user16295 If you are talking about WW the Third, then it's not started "yet", as most countries aren't mobilizing. Right now it's more like Cold War II, as the main countries such as USA, rUSsiA and a few major middle-eastern players are still resorting to using proxy forces to fight for them or on a different soil. – Nikita Akopjans Jan 22 at 12:40
    
The first truly global war was the Seven Year's War. If you count from there, the next global war should be WW VI (Seven Year's War, Napoleonic Wars, WWI, WWII, the Cold War). Since global wars seem to be started by nations trying to upset the existing global order, WW VI will probably involve the so called BRIC (Brazil, Russia, India, China) powers. – Thucydides Jan 22 at 15:21

From the setup for Arthur C Clarke's The Songs of Distant Earth:

Scientists in the 1960s discover that the neutrino emissions from the Sun – a result of the nuclear reactions that fuel the star – are far diminished from expected levels. At a secret session of the International Astronomical Union it is confirmed that the problem is not with the scientific equipment: the Sun is calculated to become a nova around the year AD 3600.

Easily adaptable to your desired shorter timescale.

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How about the solar system enters a galactic high density dust cloud. The reduction in radiation would invoke a severe ice-age but, apart from spectacular dawns and dusks, not much else. Would that work?

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I seriously doubt the plausibility of one of these "galactic high-density dust clouds" being simultaneously thick enough to obstruct the sun and thin enough to not have collapsed into a star or brown dwarf. – lirtosiast Jan 23 at 1:56

There's a 3% probability that the whole solar system breaks down. But for an unlucky butterfly effect, the disintegration of Phoebes (Mars' satellite) caused this probability to become a fact. Earth's orbit around the sun is being pushed further and further, causing the planet's climate to veer slowly into a perpetual Ice Age. Luckily enough, the Earth's new orbit allows for some fortunate species to survive. Including a bunch of human beings.

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I don't quite understand what you're saying, or how these events could cause one another. – HDE 226868 Jan 23 at 1:02
    
Good answer. Earth's solar orbit is mathematically chaotic. However observations and mathematics tell us that it is stable for the next hundred million years or so. Unless there is an as yet undiscovered gravitational perturbation to the solar system. And it would have to be dramatic to eject the earth from the solar system within five years. Five centuries upwards more believably. – nigel222 Jan 23 at 8:58

I'm thinking biology rather than astrophysics. The Tasmanian devil is facing extinction because of an infectious cancer-inducing virus. Could that happen to humanity?

It would have to be extremely infectious and very fast spreading so medical science does not beat it. Something like a flu pandemic. It would initially not cause any life threatening symptoms, so the CDC and similar agencies would not be very alarmed. By the time a global epidemic of highly aggressive cancer was noticed it would be too late. Almost everyone would have been infected.

Nature might spring something like this on us but prob ably only once in a billion years. But we might do it to ourselves. Research by some crazy scientists working for an equally crazy government with the aim of creating a doomsday weapon. They don't realize their latest brew is a success because their lab is destroyed by a natural disaster or insurrection the next day. Or their insane leader decides that because he is dying then everyone else must go with him.

By the way, if 90% deadly in one year is sufficient for your plot then all you need is nature, in the form of a particularly virulent pandemic flu that makes the Spanish flu look like a dress rehearsal. Or some other virus mutating across the species barrier in one unusually successful mutation. It could happen.

The human species went through a genetic bottleneck about 80,000 years ago and has less genetic diversity than most other species. We may be spectacularly vulnerable to a particular new mutation of an old virus. Like smallpox in the Americas, but global.

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