How Likely is Total Climate Doom?

Nowadays there is a certain type of extreme pessimist that we might call a climate doomer. A climate doomer may believe that global warming will cause the end of human civilization, or perhaps even human extinction. A favorite blog of climate doomers is the blog Nature Bats Last. In this blog post on that site, Guy McPherson compiles an alarming set of statements and links to support the position that global warming will cause the collapse of civilization and perhaps even human extinction.

But how likely is the "total climate doom" scenario, meaning human extinction caused by climate change? Let's try to calculate the odds of it, using a simplified type of probability analysis.

Factor #1: Fossil Fuel Resource Production

Currently the amount of carbon dioxide in the atmosphere is is about 400 parts per million. How high will this level be at the end of the century? Estimates vary widely. A recent IPCC report includes the following graph, which shows possibilities ranging from about 460 to 1000. Three out of six scenarios shown on the graph predict a lower carbon dioxide level, of only about 460 to 540.

IPCC scenarios

It is very hard to predict how much carbon dioxide will be in the atmosphere at the end of the century, because the matter depends on how high the production rate will be for various types of fossil fuels (the higher that production, the greater the amount of carbon dioxide will end up in the atmosphere). This issue is much more complicated than one might think from statements such as “We have enough coal in the ground to fry the planet.” Such a statement may be as misleading as the statement that there's enough gold in the ocean's seawater to make every person a millionaire (a statement that doesn't mean much because it's too difficult to extract such a resource).

For each fossil fuel resource there is an “availability pyramid” like the pyramid shown below. Most of the resources are at the bottom of the pyramid, and such resources are much harder to extract than the easy-to-extract “low hanging fruit” at the top of the pyramid. At some position in the pyramid it becomes no longer economically viable to extract the resource, but we don't know where that point is. It is therefore very difficult to predict fossil fuel resource production in the remainder of this century. Peak Coal and Peak Oil may put a brake on such production.

There are quite a few experts who predict that the production of coal and oil will plunge later in this century, as we work our way down the coal and oil availability pyramids, and start trying to extract resources that are more and more difficult to extract. For example, David Rutledge of Cal Tech predicts that 90% of the world's coal production will occur by 2070, which means a plunge of coal production later in this century. He suggests that this will mean that carbon dioxide levels will not exceed about 500 parts per million by the end of the century.

For the sake of this simplified probability analysis, let us assume that there is a 50% chance that fossil fuel production will not decline very much because of availability and extraction difficulty reasons (which we can call Condition 1A), and a 50% chance that such production will indeed plunge in this century because of availability and extraction difficulty reasons (which we can call Condition 1B). The first of these two conditions is necessary for the worst-case-scenario of a climate doom bad enough to cause human extinction.

Factor #2: Clean Energy, Conservation and Legislative Measures

Another factor that will determine how much carbon dioxide is in the atmosphere at the end of the century is how much effort humans make to restrict their use of greenhouse gases, and prevent global warming. If we keep on with “business as usual” without doing much to fight global warming, that will make a worst case scenario more likely. But if we conserve and cooperate, build lots of clean energy, eat less meat, and follow international protocols such as successors to the Kyoto Protocol, that will make a worst case scenario less likely.

For the sake of this simplified probability analysis, let us assume that there is a 50% chance that humans will not do very much to restrict global warming through such measures (which we can call Condition 2A), and a 50% chance that humanity will get very serious about reducing global warming through such measures (which we can call Condition 2B). The first of these two conditions is necessary for the worst-case-scenario of a climate doom bad enough to cause human extinction.

If global warming gets much worse during this century, this should increase the chance of people being alarmed enough to start taking the necessary measures to fight global warming through measures such as conservation. So we should not rate the likelihood of Condition 2A as being more than 50%.

Factor #3: Climate Sensitivity

Another factor that will determine how bad global warming will get is what is called climate sensitivity. Climate sensitivity means how much the earth's temperature will go up for after a given rise in carbon dioxide in the atmosphere. Scientists debate how much the temperature will rise if the carbon dioxide in the atmosphere doubles from its current level of 400 parts per million, to become as high as 800 parts per million. A post on RealClimate.org says, “The ‘meta-uncertainty’ across the methods remains stubbornly high, with support for both relatively low numbers around 2ºC and higher ones around 4ºC, so that is likely to remain the consensus range.” The more dire projections of future global warming assume a high climate sensitivity.

For the sake of this simplified probability analysis, let us assume that there is a 50% chance that climate sensitivity is high (which we can call Condition 3A), and a 50% chance that climate sensitivity is relatively low (which we can call Condition 3B). The first of these two conditions is necessary for the worst-case-scenario of a climate doom bad enough to cause human extinction.

Factor #4: Amplifying Feedback Mechanisms

If conditions 1A, 2A, and 3A mentioned above all occur, this will be enough to cause horrifying trouble for the human race, resulting in the ruin of many coastal cities, the loss of countless species, a huge increase in wildfires, and a huge increase in desertification. But by themselves those conditions would not be enough to cause human extinction. The human race could always abandon all areas around the middle of our planet, and move entirely to regions such as Canada and Russia (or, if things got really hot, to the continent of Antarctica after its ice melted). In order for you to have human extinction by global warming, you would also need to have feedback mechanisms that amplify global warming once its gets going very strong.

Pessimists have raised concern that such amplifying feedback mechanisms may exist. One of the most frightening possibilities is the melting of methane hydrates, natural sources of methane that exist in places such as Siberia and Antarctica. Methane is a greenhouse gas 20 times more potent than carbon dioxide. So if man-made global warming starts melting frozen methane hydrates, that might cause the release of more and more methane into the atmosphere. That in turn could cause more and more methane hydrates to melt. It could possibly be a deadly feedback mechanism that could amplify global warming.

Experts disagree over how much we should be worried about the possibility of such feedback mechanisms. Some say it's a huge concern, while other say the risk is small.

For the sake of this simplified probability analysis, let us assume that there is a 50% chance that planetary feedback mechanisms will one day start amplifying global warming (which we can call Condition 4A), and a 50% chance that such feedback mechanisms will not be a very big factor (which we can call Condition 4B). The first of these two conditions is necessary for the worst-case-scenario of a climate apocalypse bad enough to cause human extinction.

Factor #5: Geoengineering

There is one last factor we must consider: the possibility of geoengineering. When people use the term geoengineering when talking about global warming, they are talking about man-made measures designed to directly reduce the effects of global warming. Various techniques have been proposed. One technique would place on the oceans many specially designed ships that would create mist out of sea water, a salty mist that would rise in the atmosphere and increase the amount of sunlight reflected by the atmosphere (thereby lowering temperatures).

Opinions vary over whether geoengineering techniques would work to effectively fight global warming. For the sake of this simplified probability analysis, let us assume that there is a 50% chance that geoengineering techniques would not effectively reduce global warming (which we can call Condition 5A), and a 50% chance that such techniques would be effective (which we can call Condition 5B). The first of these two conditions is necessary for the worst-case-scenario of a climate apocalypse bad enough to cause human extinction. No such climate doom would occur if we had an effective way to prevent it with geoengineering.

So What is the Chance of Total Climate Doom?

So given all these considerations, what is the chance of global warming causing the extinction of the entire human species? In each of the five issues I have discussed, there is a particular condition that must occur in order for total climate doom to happen. Let us assume that the probability of each of these conditions is independent of all of the others. If that is true, then to calculate the combined probability of each condition occurring we multiply together the individual probabilities. This gives us the following formula:

Probability of total climate doom =
probability of Condition 1A (undiminished fossil fuel resource production) multiplied by
probability of Condition 2A (“business as usual” without huge efforts at conservation and clean energy) multiplied by
probability of Condition 3A (high climate sensitivity) multiplied by
probability of Condition 4A (amplifying feedback mechanisms) multiplied by
probability of Condition 5A (no effective geoengineering)

Substituting the probabilities I have listed, this gives us a probability of total climate doom equal to 50% multiplied by 50% multiplied by 50% multiplied by 50% multiplied by 50%. So according to this simplified analysis, the probability of total climate doom (meaning complete human extinction because of global warming) is roughly 1 chance in 32, or about 3 percent.

It would seem, therefore, that the chance of complete human extinction by global warming is quite low, but still large enough to be worth worrying about.

But this does not mean that we can be complacent, or that we should lessen efforts to fight global warming. For one thing, a 3 percent risk must be considered a very substantial risk when one is talking about something such as total human extinction. For another thing, there is a possibility not quite as catastrophic as total climate doom, a possibility that we might call decimation by global warming. As decimation means literally to destroy a tenth, we may define decimation by global warming as the possibility that something like a tenth of the human species will be wiped out by global warming. That possibility is a lot more likely than total climate doom, and might require only three or four of the five conditions necessary for total climate doom. The math would get a little complicated as to how to calculate such a likelihood, but I think the chance is significantly higher than 3 percent. Such an outcome would be far worse than any world war the world has seen, and its avoidance is something all of us have a moral duty to prevent.

Speaking in purely practical terms, I think that to argue for “total climate doom” is perhaps not very helpful in the fight against global warming. If you persuade a man that global warming will cause great trouble for mankind, many deaths, and a risk of extinction, that person may well change his actions to help fight the problem. But if you persuade a man that the whole human race is going to become extinct from global warming, then the person may just tend to think that action is futile, and that it makes no difference how he acts.

If Mankind Were To Perish, What Would Be Its Epitaph?

An epitaph is a short statement (often only a single sentence) honoring someone who has died, or summarizing his life. An epitaph is often written on a tombstone. Some classic epitaphs include the following:

Here lies dear old Fred
A great big rock fell on his head.

Here lies Lester Moore,
Four slugs from a 44
No Les, no More

Here lies the body
of Jonathan Blake
Stepped on the gas
Instead of the brake.

The death of an individual is sad to contemplate, but there is a possibility vastly sadder to ponder: the possibility of the entire human race becoming extinct. If that were to happen, perhaps someone or something might erect a memorial for the extinct human race. In such a gloomy case, what epitaph might be written for the human species?

The following would work pretty well as an all-purpose epitaph for the human species, no matter how we might become extinct:

But what about specific extinction scenarios? One possibility is that we might invent super-intelligent machines which learn how to make copies of themselves. The number of super-intelligent robots might grow larger and larger, and the number of humans might grow smaller. The new super-brainy robots might take over entirely. The new robotic species might keep us humans around for a while, but they might eventually decide: the only intelligent beings that should exist on this planet are super-intelligent beings. Then they might get rid of us fleshy humans entirely. In such a case they might erect a memorial for the vanished human race, and it might look like this:

Still another possibility is that the human race may become extinct because of a gradually deteriorating environment. Rather than cutting back our wasteful ways that put the planet in peril, we may continue spending more and more, shopping more and more, eating more and more, and driving more and more. This may cause global warming to get worse and worse. The result might be runaway global warming, as various feedback loops kick in, which cause global warming to accelerate more and more (such as the melting of methane deposits in Siberia and Antarctica). Temperatures may rise so high that the human race perishes. In such a case the following might be a suitable epitaph for mankind:

Another possibility is that the mankind may destroy itself in a war. There need not be any fancy technological breakthroughs for this to be a possibility, because the USA and Russia still have many thousands of nuclear weapons. One day they might be used, in a deliberate attack, or a war that escalates from a small-scale use of nuclear weapons due to an accidental launch or a limited launch by a madman. Or the human race might perish in some new type of war, such as a biological war using genetically engineered germs. In such a case, the following might be used as an epitaph for our species:

But let us hope that none of these gloomy epitaphs ever get written. Let us hope that instead someone one day writes a book that tells the story of the first million years of human civilization, a book that might look like this:

Bouncing Black Holes May Cause the Sun to Suddenly Vanish

The sun has been shining for billions of years, and scientists say that in all probability it will continue shining brightly for billions of additional years. We assume that there is 100% probability that the sun will continue to shine throughout our lifetimes. But surprisingly enough, there is a very small chance that the sun will suddenly disappear at any time -- perhaps a thousand years from now, perhaps ten years from now, or perhaps even tomorrow.

The sun might vanish at any time because there is a very small chance that a particular theory I will now describe is true. If this theory is true, the sun might instantly disappear at any time.

The theory I mention is a theory involving black hole collapses. To explain that theory, I must first discuss why scientists think that black holes are formed. Scientists say that black holes are formed when very massive stars begin to collapse, with the collapse being caused by the enormous gravity of the star. A star that is more than five times more massive than the sun has a tremendous gravity many times higher than the gravity of our planet. But such a star emits lots of energy through thermonuclear fusion, and that causes an outward force that balances the inward force caused by the star's gravity.

But when the star nears the end of its lifetime and runs out of hydrogen and usable helium to burn as nuclear fuel, then there is no longer any outward force to counteract the force of gravity. The star's enormous gravity causes the star to suddenly shrink in size. Gravity crushes the mass of the star in a mighty collapse. Scientists think this causes a supernova explosion, along with the formation of a black hole. Much of the star's mass is blasted off into space, but the remaining mass then collapses into a state of infinite density called a black hole.

What happens to all that matter once this black hole forms? This is a matter for speculation; no one knows for sure. There are many exotic speculations. One speculation advanced by more than one scientist is that when black holes are formed, they create a spacetime wormhole. The idea is that the matter lost in a black hole travels through a wormhole, and then suddenly appears elsewhere in the universe. Such a sudden appearance has been called a white hole. Of course, this idea is pure speculation, and there is no evidence for white holes. But let us consider what the consequences might be if white holes were to be created from the creation of a black hole.

If a white hole were to be created, one possibility is that we might suddenly see a gushing of matter coming out from some point in space, perhaps some point in interstellar space. But we've never observed anything like that happening. So let's consider another possibility.

Another possibility is that once a white hole is created from a black hole, the white hole then immediately collapses to become a black hole again. This would make sense from a gravitational standpoint. Imagine if a star of 10 solar masses were to collapse, causing 7 solar masses to collapse into a black hole. That might cause the appearance of a white hole elsewhere in the universe. But an instant after that white hole appeared, you would then have 7 solar masses suddenly existing in some small area. Gravity would then probably cause all that matter to collapse in a process similar to the process that produced the original black hole.

We are led, then, to a fascinating possibility – the possibility of “ever-bouncing” black holes. The creation of a black hole might be the beginning of a process that works like this:

1. A super-massive star collapses to become a black hole.
   
2. The black-hole creates a spacetime wormhole, which causes the appearance of a white hole somewhere else in the universe, as the mass from the star collapse reappears elsewhere.
   
3. The matter coming from that white hole is so dense and concentrated that it very soon collapses to become another black hole.
   
4. That black-hole creates a spacetime wormhole, which causes the appearance of a white hole somewhere else in the universe.
   
5. These steps keep repeating over and over again endlessly, ad infinitum, forever and ever.
   

Theory of ever-bouncing black holes

Because many black holes have been created in the history of the universe, if this “ever-bouncing” black hole theory is true, then white holes could be appearing at various points in the universe millions of times every second. 

At this point the reader may well be thinking: well, that's a fascinating idea, but it is no reason for thinking that the sun may suddenly vanish – because the sun is not a supermassive star of the type that becomes a black hole.

It is true that the sun will never become a black hole purely because of its own gravity. But if this wild theory of “ever-bouncing” black holes is correct, then the sun still might be in danger. This is because when a white hole appears from the creation of a black hole, the white hole could randomly appear within the volume of the sun.

If we assume that a white hole appears at a random position in space, it is overwhelmingly likely that the white hole would appear in interstellar space, the space between stars. But there is a very small but nonzero chance that the white hole could appear in the worst possible place – right in the very volume of space that the sun occupies. Who knows, there could be some strange relativistic reason why a white hole is more likely to appear where there is already matter, perhaps something along the lines of matter being attracted to matter.

If such a white hole were to suddenly appear within the volume of the sun, it would be as if the sun were to suddenly acquire a mass many times greater. Most of that mass would be material that could not be used for nuclear fusion. So rather than suddenly becoming much brighter, the sun would suddenly be like a super-massive star at the end of its lifetime, about to collapse into the super-density of a black hole. Shortly thereafter, the sun would presumably collapse to become a black hole. There might or might not be the flash of a supernova explosion. Then the sun would vanish.

Imagine what it would like for you if this were to happen. You might go to work one day at the office. Then in the middle of the day, people would suddenly start shouting, as they noticed that it was inexplicably dark outside. Some people would say: “Wow, I didn't know there was a total eclipse today.” People would wait for the supposed eclipse to end. But the sunlight would never return.

People would gradually realize that the sun was gone forever. There would then be a desperate struggle, as everyone tried to gather up food, clothing, and generators that might allow them to survive as long as possible in the cold. It would soon become colder than the North Pole. Crops would stop growing. Remnants of the human race would probably be able to survive for a few months longer until the food and fuel ran out. A few lucky ones might even be able to survive for a few years.

Of course, the chance of this happening is extremely remote, but it is interesting to realize that there are theoretical reasons why the sun might suddenly vanish at any time. I don't know what effect such speculation has on you, but I, for one, am going to take serious measures to protect myself from this theoretical cosmic menace.

I am going to go out right now and buy myself a nice pair of wool mittens.

7 Ways a Future Hitler Could Ruin the World

On March 19, 1945, Adolf Hitler may have sensed that all was lost. On that day he issued the so-called Nero Decree, which almost seemed to have been designed to burn up Germany in a fiery apocalypse of destruction. Perhaps he thought: if I have to go, as many of my countrymen as possible are going with me. His order dictated that “all military transport and communication facilities, industrial establishments and supply depots, as well as anything else of value within Reich territory, which could in any way be used by the enemy immediately or within the foreseeable future for the prosecution of the war, will be destroyed.” That's almost an order to blow up or burn everything in his country. Thankfully Albert Speer (one of Hitler's subordinates) disregarded the order.

If Hitler could have issued an order like that, perhaps some future dictator will give a similar order. But such a dictator might not just want to blow up his country – perhaps he might want to ruin the whole world. Faced with a prospect of death or the loss of a war or the collapse of his regime, the dictator may think to himself: if I have to die, everybody else is going with me. Or perhaps the dictator might have a religious motivation. He might think he is God's agent in bringing about the Last Days or End of the World predicted by some prophet or religious book.

But how might such a dictator bring about worldwide ruin in a final orgy of global destruction? Below are some of the ways.

The Wish of an Evil Dictator

Method 1: Start a Nuclear War

A diabolical dictator armed with a nuclear bomb could probably do more than just blow up a single city. He might also be able to start a full-scale nuclear war in which hundreds of nuclear missiles get released. The dictator might spread some disinformation designed to make one superpower suspicious about an attack from a second superpower. The dictator might then smuggle in a nuclear weapon into a major city of the first superpower, and explode it. This might result in a retaliatory attack by the first superpower against the second superpower, which could escalate into a full-scale nuclear war.

For example, the dictator might spread rumors or misinformation that Russia is going to attack the United States. The dictator might then blow up a nuclear bomb in the United States. The dictator could then say: “You see? We warned you they were plotting against you.” The US might then launch two retaliatory missiles against Russia, which might then retaliate by launching 4 missiles at the US, which might trigger the US to launch 8 missiles against Russia, and so forth. The resulting nuclear exchanges might trigger a nuclear winter which kills almost everyone worldwide.

This is a frightening thought: one nuclear bomb leveraged to cause a war that kills almost everyone.

Method 2: An EMP Attack

A diabolical dictator armed with only a few nuclear missiles might be able to wipe out half of the world's electrical and computer systems. To wipe out much of the electrical system of the United States, it would be necessary merely to blow up a nuclear bomb in the upper atmosphere, in the middle of the country. The resulting Compton Effect would cause an electromagnetic pulse effect that would wipe out electricity, telephones and computers all over the country. If the dictator had four nuclear missiles, he might be able to wipe out half of the world's electricity and computer systems, by blowing up one nuclear bomb in the upper atmosphere above the middle of the United States, another in the upper atmosphere above the middle of Europe, another in the upper atmosphere above the middle of China, and another in the upper atmosphere above the middle of Russia.

Method 3: A Biological Apocalypse

By funding a few biological warfare laboratories, an evil dictator might be able to prepare a plague that could wipe out 50% or more of humanity. The laboratories might make genetic modifications of an existing bacteria or virus, modifications that might vastly increase the lethality of the germs. A recent scientific paper described a way in which a common flu virus might be modified to make it vastly more lethal.

Once his labs had developed such a super-bug, the dictator could arrange for the germ to be spread to each continent in the world. If the disease caused by the germ had an incubation period of several weeks, the disease might spread all over the world before biologists recognized the threat. By then it might be too late.

Method 4: An Asteroid Apocalypse

If an evil dictator had a space program, he could announce a plan to capture an asteroid and bring it back to near planet Earth. This could be described as a noble technological breakthrough, to help begin asteroid mining to reduce metal shortages in the future. But the dictator might have something different in mind. His actual plan might be to send the asteroid crashing into our planet, causing a devastating apocalypse. We might never know what hit us until it was too late. Looking up in the sky and seeing a new star, we might say, “Oh, isn't that nice; it's that asteroid they've dragged over here so they can mine it.” A few hours later we might be buried in dust.

Method 5: Doom from the Moon

If an evil dictator had a space program, he might also announce that he was establishing a lunar colony. Once a lunar colony had been established, the dictator could create a mass driver, which is kind of a huge electromagnetic catapult capable of launching lunar boulders out from the moon. Such a machine (possible because of the low gravity and airlessness of the moon) would actually be a devastating offensive weapon. The boulders could be launched toward our planet, and could strike it with incredible kinetic energy. A relatively small boulder could then strike our planet with as much force as a gigantic bomb. A dictator willing to send thousands of such projectiles might wipe out every major city on our planet.

Method 6: Oceanic Apocalypse

Many people are very worried about the current health of the world's oceans. Global warming is causing ocean acidification that is very troubling. An evil dictator wishing to cause an apocalypse might figure: if the ocean is the world's Achilles heel, then let me leverage that. The dictator could release a genetically engineered microbe that might lead to runaway ocean acidification, or runaway proliferation of a single microbe in the ocean's waters. The resulting ecological disaster might ruin the planet's suitability for human life.

Method 7: Air Pollution Apocalypse

Scientists recently announced the discovery of a gas called perfluorotributylamine (PFTBA), which is 7000 times worse than carbon dioxide in its global warming effects. The gas has been produced by certain industrial manufacturing processes for decades. If an evil dictator wanted to cause a global disaster, he might create a factory specifically designed to manufacture this gas and release it into the atmosphere. The factory might deliberately produce the gas for years, producing greatly accelerated global warming. The dictator might then sit back and watch the world's cities be drowned by rising seas.

A Global Government Needed?

In short, we have seen that a single mad dictator with a nation at his disposal might have a frightening variety of ways to ruin the world. This may be one argument in a favor of a global government. As soon as we get a global government, we will no longer have to worry about the whole world being ruined by one madman with a whole nation available to fulfill his heinous whims.

Flavors of Doom: 11 Variations on the Apocalypse

The End of the World has long been an object of human fascination. I will now delineate 11 different ways in which the world as we know it may end. I will give each of these ways a name that is a variation on the word “apocalypse.”

Rockpocalypse: The Stony End

Asteroids are giant space rocks that travel around the solar system in various orbits. Most exist in a belt between Mars and Jupiter, but there is a class called the Near Earth Asteroids which sometimes come close to the Earth. In fact, only a few days ago a 2-mile asteroid whizzed by our planet at the relatively close distance of 3.5 million miles. If an asteroid of about 20 kilometers were to strike the Earth, it could wipe out all human life. It is believed that an asteroid collision wiped out the dinosaurs. But thankfully the chance of a large asteroid striking within the next 100 years is very low.

Methpocalypse: Gassed to Death

We can use the term Methpocalypse for a fatal acceleration of global warming caused by the release of methane gas stored in the ices of the Arctic and the tundra of Siberia. This is an all too real possibility. Methane is sixty times more powerful than carbon dioxide as a cause of global warming, although methane in the atmosphere only lasts for about ten years. There is a huge amount of frozen methane stored in the tundra of Siberia, and there is also gigantic amounts of methane frozen in the Arctic. If regular global warming causes this frozen methane to be released into the atmosphere, we could see global warming start to accelerate out of control. An additional rise in the Earth's temperature might cause even more methane to be released, which would cause more global warming. This vicious feedback loop might end up making our planet uninhabitable for humans.

Nukepocalypse: Ending it All 1950's Style

We can use the term Nukepocalypse for an end-of-the-world scenario that has been well-known for more than 60 years: the destruction of mankind caused by a global nuclear war. The risk of such a war was known to almost everyone in the 1950's and 1960's, but now the danger seems to have faded from the public's consciousness. Unfortunately, the danger of such a war doesn't end when we stop thinking about it. The danger ends when we get rid of all the nuclear weapons. While the number of nuclear weapons had declined sharply, there are still enough nuclear missiles around to cause the extinction of mankind.

Roguepocalypse: Doom From an Orphan Wanderer

We can use the term Roguepocalypse (pronounced rohg-pock-a-lips) for the destruction of the Earth that could be caused if a rogue planet were to enter our solar system. A rogue planet is a planet that is flying around through space, after being ejected from its solar system after some unusual event (such as the collision of two planets). The closest rogue planet to Earth is CFBDSIR 2149-0403, about 100 light years away. If one of these rogue planets were to enter our solar system, it could spell the end for mankind even if the rogue planet did not collide with our planet. The gravity from the rogue planet could pull Earth out of its normal orbit, causing our planet to be farther away from the sun or closer to the sun. If Earth became closer to the sun, the temperature could become too hot for human life. If Earth became farther from the sun, the temperature could be too cold for human life. Thankfully the distance between stars is so great that the chance of our planet being affected by a rogue planet is very, very low.

Bugpocalypse: Extinction by Epidemic

We can use the term Bugpocalypse for the possibility that a new virus or bacteria might wipe out mankind. (In this case bug is used as in “I caught a bug, maybe a virus or bacteria.”) The chance of this happening naturally is very low. But advances in artificial life and genetic engineering might make it possible for some country working on biological warfare to make some artificial plague capable of wiping us all out. Some plague like smallpox but much worse might one day arise in a bio warfare lab. If a country ever developed such a deadly germ, it might accidentally be unleashed on the world, or it might be used in anger or retaliation.

Nanpocalypse: Extinction by Grey Goo

We can use the term Nanpocalypse for the possibility that runaway self-reproducing nanobots might ruin the world. Silly as this may sound, it has been a topic of serious discussion by experts in the emerging technology known as nanotechnology. The fear is that if we were ever to develop tiny self-reproducing robots known as nanobots, they might start breeding out of control, and end up processing all of man's works into a kind of waste matter called “grey goo.”

Robopocalypse: Our Machines Replace Us

The term Robopocalypse has already been used by the novelist Daniel H. Wilson for the title of a science fiction novel. We can use it more generally as a term for the scenario in which man develops intelligent robots, and the robots then decide to do away with us. They might do that after they get tired of having us restrict them, or they might think that electronic intelligence is naturally superior to biological intelligence.

Starpocalypse: Doom from Light Years Away

We can use the term Starpocalypse for any scenario in which a distant star causes our extinction. One way in which this could happen is a nearby supernova explosion. If a star within 100 light years of our planet were to explode in a supernova (the most violent type of stellar explosion), our planet might get zapped by a lethal dose of cosmic radiation. Gamma rays from the supernova could cause our planet to lose its ozone layer, which would expose Earth to lethal cosmic and solar radiation. But astronomers know that only certain types of stars (particularly giant stars) undergo supernova explosions. Based on the types of stars within 100 light years of our planet, there doesn't seem to be much of a risk of this particular type of catastrophic event.

Volpocalypse: Death by Lava and Dust

Underneath Yellowstone National Park in the United States is a gigantic volcanic structure that supposedly erupts once every million years or so. If Yellowstone were to undergo a full scale eruption, it might send up into the atmosphere enough ash and dust to cause a “nuclear winter” that would block sunlight for a year or more, destroying agricultural production. That might cause most of the world's population to starve to death, although it would probably not lead to man's extinction.

ETpocalypse: The Aliens Get Us

ETpocalypse (pronounced "ee-tee-pock-a-lips") is the scenario that extraterrestrials arrive from another planet, and decide they want our planet all to themselves. They then wipe man out completely. Presumably this would be easy to do if some other civilization was thousands or millions of years more advanced than we are.

Sunpocalypse: When the Sun Dies

Finally we discuss a type of apocalypse that we know will pose the end of human life on Earth (if it still exists when this event occurs). About five billion years in the future, the sun will have used up all of the hydrogen that it currently uses to produce light and heat through thermonuclear fusion. At that time the sun will flare up to become what is known as a red giant. The diameter of the sun will become much greater, and the temperature of Earth will rise to more than 150 degrees. The oceans will all evaporate, and all life on our planet will presumably perish. If there are any humans or human descendants alive at this time, they will survive only by migrating to some other solar system (or perhaps migrating to a colony on the outer edges of our solar system).