Societal Disruption or Collapse on a Regional or Continental scale. If it is a large nation, then world-wide economic damage lasting decades can result.
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- Basically every Film of the Book (or radio version) as well as the book of The War of the Worlds. The global scale of both the 1953 and 2005 films might raise it to a Class 1.
- Angel, indicated in the final episode's last scene and mostly shown in the comics. Los Angeles becomes a chaotic demon war zone, although it's undone in the end of "After the Fall".
Anime and Manga
- The shockwaves created by the title character in AKIRA. One takes out the center of Tokyo. Then it happens again. In the entire series, it happens 2.5 times.
- In the third arc of BioMeat, 90% of Japan's population has been eaten alive by the eponymous creatures and there are only two populated cities left. But by the end of the series, the only city left is Osaka.
- In Earth Maiden Arjuna, Japan's entire water supply is polluted by chemicals held in plastic containers dissolved by evil bacteria.
- In the manga version of Violence Jack, the Kanto area of Japan was destroyed by an earthquake that was caused by the battle between Satan and Devilman and had been separated from the mainland.
- In most arcs of Higurashi no Naku Koro ni, the Great Hinamizawa Disaster causes the entire village to be wiped off the map, with additional fallout as former residents go crazy across Japan.
- Cell in Dragon Ball Z absorbed the life force of entire towns' residents and while searching for Android 18, and blew up dozens of islands. He also wipes out an entire military fleet. Nappa does the same earlier on, and he and Vegeta also blow up part of an Earth city shortly after arriving.
- The Overdrive disaster in Rave Master destroyed what was thought to be one-tenth of the world. They later found out the world was bigger than they thought, but it still wiped a decent sized country off of the map.
- Several characters in Slayers are capable of Class 0 apocalypses. Lina Inverse routinely uses her Dragon Slave, a spell that is capable of reducing cities to rubble (she also has access to more powerful magic). Rezo the Red Priest was also able to destroy the Holy City of Sairaag with a Mega Brand spell (the most powerful use of that spell by any character).
- In Puella Magi Madoka Magica, this is what happens in the aftermath of most of Homura's timelines as a result of Walpurgis Night's rampage through Mitakihara Town before being defeated. It's implied that were Walpurgis not stopped, she would eventually score higher on this scale.
- On the Blue Night in Blue Exorcist, many high-level exorcists suddenly combust into bright blue flames. This changes the exorcist population and hierarchy significantly.
- Z in the 3rd Tenchi Muyo!! OVA series does this, firing the Chobimaru at Earth with Tenchi failing to stop it. When the timeline's reset and Noike does it again to set things right, a much stronger Tenchi is able to stop it... though he ends up "dying" again, much to his displeasure.
- Fullmetal Alchemist: the Big Bad rips out the souls of everyone in Amestris save for a handful of people in his inner sanctum. The souls are returned to the bodies in the next chapter, though.
- Gundam loves this!
- In Mobile Suit Gundam, Zeon's "Operation British" - the Colony Drop to take out Jaburo - ends up being diverted and half of the colony lands on Sydney, Australia, wiping out 16% of the colony. As well, the narration mentions that the first week of fighting saw both sides losing half their respective population.
- In Mobile Suit Gundam 0083, the Delaz Fleet performs a Colony Drop on North America, intending on wiping out its food supply. Didn't really work - they were back on their feet by the time of Zeta Gundam.
- In Mobile Suit Gundam ZZ, Neo Zeon drops a colony on Dublin, Ireland in a show of power!
- In Mobile Suit Gundam SEED Destiny, ZAFT radicals drop the ravaged remains of Junius Seven on Earth, causing the Break the World incident that ravages the planet.
- An issue of The Authority features a swarm of alien creatures that are launched at Earth. They can't fly, though, so their landing in Japan is "just blind luck".
- In The New Universe, Ken Connell accidentally obliterates Pittsburgh and everything 50 miles across trying to get rid of the Star Brand.
- In The Conversion Bureau: Not Alone, large parts of South Africa in and outside of Johannesburg have been swept clean of human civilization, the rest of the country is plummetting into fascism, and the rest of the world ends up deeply scarred by the possibility of inter-dimensional pony conquest, making it a borderline Class 1 example.
- In Everything Into Darkness, the plot is kicked off by a Class 0 being unleashed upon Iwatodai via Ikutsuki setting loose dragons on the city from a gate beneath Tartarus, and inadvertently sending most of SEES to Elibe as a side effect.
- 28 Days Later, which sees the complete destruction of Great Britain by a mutant virus — in fact, it's implied that Britain was deliberately quarantined (and lied to about the extent of the disaster) because it's an island and at least The Virus could be contained there.
- The sequel, 28 Weeks Later, shows the reestablishment of a small community of merely 15,000 people in London and its destruction.
- During the credits, the infected are shown escaping into Paris, suggesting that we may have moved into a Class 1. Or at least a much larger scale Class 0 (The whole of Europe).
- Armageddon. While a direct hit of the asteroid would be Class 6 or X, the smaller chunks that reached Earth beforehand wiped out a couple of cities.
- Batman (1989) comes within days, perhaps even just hours of a Class 0. The Joker's televised Brand X stunt had an entire major city too terrified to clean their bodies, or their clothes, or the buildings... An entire city yanked back to The Dung Ages. Fleas, ticks, lice... Eventually people would start dying of things besides the poison, which would have led to total panic. One good riot under those conditions would kill everyone in the city as Joker contaminated damn near everything needed to treat wounds on that scale. After a few days without maintenance, restoring water and power would be a multi-million dollar effort. A few weeks after that, all the bodies will have been devoured by vermin, resulting in a population explosion that would sweep the Eastern Seaboard, possibly repeating the process. Batman broke the Joker's "poison code" just in time to prevent millions (perhaps even hundreds of millions) of deaths. The original script was more clear about this, but the execs nixed a montage of filthy people fleeing Gotham.
- Cloverfield. May range up close to a Class 1, seeing as how the monster is still alive at the end, and while it might not keep rampaging, it sure as heck doesn't seem like anyone can stop it. Word of God, however, has stated that the big nasty bit it.
- The Day After Tomorrow sends America and Europe into a deep freeze including mile-high glaciers. By the time they understand the gravity of the situation, Canada and Alaska are already essentially doomed. Fortunately, everyone else in the US is able to move to Mexico. The British, on the other hand, are left to perish with dignity, while Australia suffers largest typhoons ever recorded.
- Deep Impact, which only saw the East Coast destroyed by a massive tidal wave; it also mentions Europe and Western Africa being destroyed, and a view from space shows the Caribbean islands having more than a little problem on their hands.
- Many of the Godzilla films.
- In the early-1970's Japanese movie Nippon Chimbotsu (Japan Sinks), which was remade in 2006, the entire Japanese archipelago is destroyed, Atlantis-style, by a series of massive earthquakes, tidal waves and volcanic eruptions triggered by shifts in the tectonic plates on which the islands rest. The survivors are evacuated literally worldwide.
- Shaun of the Dead has an unknown number of people zombified, but few enough the UK manages to get back up on its feet and uses the zombies as cheap labor in retail chains as well as unwitting participants in game and talk shows. Think zombies in 'Wipe Out'.
- The 2008 remake of The Day the Earth Stood Still (2008) has Gort in the form of a grey goo take out roughly a third of the US. Klaatu stops it with a pulse, presumably wiping out at least tens of thousands more relying on electricity. If the pulse is permanent, then it may be a Class 2.
- The 1973 adventure film Sannikov Land is set on an island warmed by a volcano. When the volcano goes to sleep, the island becomes as frozen as the rest of the Arctic, and everyone on it will die.
- At the end of Cabin Fever, a Class 0 appears to have been narrowly averted, as the posse shows up to clean up after our intrepid heroes succumb to a flesh-eating virus. This lasts until we see the body of the first guy seen with the virus lying bleeding in a river, which is then harvested for bottled water, implying a true Class 0 or 1 somewhere down the line.
- In Doomsday a deadly plague, known as the "Reaper Virus," has broken out in Great Britain, killing hundreds of thousands in its wake.
- Lex Luthor's ultimate plan in the Superman movie is to trigger a Class 0 by sinking California and driving up real estate prices.
- The Third World War might be a Class 0, as Birmingham and Minsk are destroyed by nuclear weapons.
- The cometary impact at the end of Newton's Cannon did this to a major chunk of Europe.
- From Motel of the Mysteries, the complete burial of North America in accumulated junk mail would rank near the top of the Class 0 category. Technically it ought to be a Class 1, if the rest of the planet was set back so far that they forgot what a "motel" (or, worse, a toilet!) is; because the whole book's just one long Running Gag, however, let's avoid living out Contrived Stupidity Tropes, and evaluate it by the direct physical effects of this lame-o disaster.
- The Silmarillion has the destruction of Númenor by Eru. Morgoth's triumph just before the end of the First Age may also count, and the destruction of Beleriand in the War of Wrath definitely does.
- Alas, Babylon is somewhere between Class 0 and Class 1, in that the US and USSR engaged in large scale nuclear war that decimated their respective populations, but left the third world more or less intact. The majority of the US is knocked back to 19th century technology, and using wheat for something as trivial as making alcohol would get you lynched.
- The disaster preceding the events in Margaret Atwood's The Handmaid's Tale is a Class 0 or a Class 1, leading to a dystopia in the United States, but there are hints the rest of the world isn't as dramatically affected.
- Sergey Lukyanenko's Линия Грёз, as set in the Master of Orion universe, features several varieties of planet-scale destruction. As most races in the conflict span over multiple systems, those attacks are Class 0. This might of course instantly move up to class 5 or 6 if the species in question has been reduced to inhabiting only one planet (usually their native one) or the attacks are directed against all planets inhabited by the fraction simultaneously. Luk'yanenko avoids the topic of pre-space age species; in the games it's possible to find native sentient life on generally life-friendly planets. Wiping those aborigines out is discouraged, though, as they turn into an agricultural boon for the race to settle on the planet. Examples of destruction:
- Massive biological weapon bombardments employed by the human Empire during the last great interspecies war on Bul-Rathi planets.
- Human free hunters carry a small antimatter payload, which they are supposed to drop if they happen to get close enough to any hostile inhabited planet.
- The human Empire goes for planet-wide meson bombardment on planets that are about to be conquered by an alien race and indefensible at the current tactical situation. Several decades later a refugee remarks that there is hope for her homeworld - the oceans are about to stop boiling.
- A large bomber spaceship is sacrificed during an orbital battle above a planet for tactical reasons. As the battle itself ends, the ship is damaged beyond salvaging and is left to drop to the surface without disarming the payload. This results in boiling the oceans, melting the crust to glass-like results and irradiating the entire planet. The scattered and partly exploded bombs embedded in the glassed crust make the planet completely uninhabitable.
- Sergey Lukyanenko's Веллесберг / Лорд с планеты Земля shared universe features a quark fission bomb which slowly turns a planet into fine dust. While the planet in question is Earth, humanity has already settled all over the galaxy, using time travel to found colonies in the past, placing this example here in Class 0.
- In John Birmingham's Without Warning, a strange energy bubble spreads over North America, annihilating all life on the continent save for Alaska a small portion of the Pacific Northwest and about the southern third of Mexico. Another Class 0 happens later when Israel is forced to use its nuclear arsenal to fend off an Arab invasion.
- Time Scout's backstory includes a mysterious The Accident, somehow involving a space station, that devastated the globe's coastal communities and caused random Time Portals to open up.
- William R. Forstchen's One Second After has the US hit by a massive EMP resulting in a collapse of society and, in the end a Disunited States Of America. Iran and North Korea are nuked in retaliation although it's implied that they may not have done it.
- Subverted in Septimus Heap, as the Darke Domaine that overruns the Castle in Darke eventually is contained with few victims.
- In John Barnes Mother of Storms there is a background incident caled "The Flash" that happened ten years previous to the beginning of the book that refers to a terrorist nuking of Washington DC.
- The eponymous disaster in Harry Turtledove's Supervolcano Eruption which wipes out large chunks of Wyoming, Idaho and Montana as well as smaller pieces of Utah and Colorado. However it's stated that the aftereffects have the potential to become at least a Class 1. There is also a nuclear exchange between Israel and Iran that further complicates matters.
- Adron's Disaster, from the Dragaera series, reduced the Empire's capital city to a miles-wide sea of raw chaos, and kicked off a continent-disrupting Interregnum whose impact on society is still being felt.
- A background event of David Brin's Existence is Awfulday which was the setting off of a couple of "dirty bombs" in Washington DC.
- Under the Dome by Stephen King is a very small example of this as only one small town in Maine is affected.
- In The Passage and it's sequels the vampire plague only affected North America. A quarantine kept it from spreading further.
- At the end of Ciaphas Cain: Caves of Ice, the Valhallans detonate an impromptu fuel-air bomb composed of several million liters of refined promethium poured into mine shafts, with the intent of destroying a Necron tomb. This results in a gigaton-range blast that buffets their orbiting troopship. Meets the minimum requirements by dint of obliterating the only civilization on the planet (the refinery).
- The Years of Rice and Salt. The Black Death was 90+ % fatal between the Volga and the Atlantic, depopulating Europe in the 1300s. The book covers the next 6 centuries of how the other civilizations go on without Western civilization's interventions and contributions.
- In Ben "Yahtzee" Croshaw's Jam, a regional Class 5 happens to Australia as the eponymous substance is accidentally unleashed upon the continent, and swallows every organic being that isn't above ground level.
- In Robert Ferrigno's Assassin Trilogy New York and Washington DC have been nuked by terrorists fifteen years before the first book as well as Mecca being radiated by a dirty bomb. When it's revealed that elements of Israel's government were behind this Israel is destroyed in the backlash and a civil war results in a Disunited States Of America.
- In an alternate timeline in Doctor Who's "Turn Left" where the Doctor dies in the early 21st century, a nuclear storm drive ship called Titanic hits London, wiping out the entire city and locking out any immigration to and from the UK. The ship itself easily had the potential to be on the scale of Class 5 or 6, so it's assumed that the disaster was actually mostly averted. Later, over 50 million Americans are forcibly turned into creatures made of fat called Adipose, killing the humans they were made from.
- In two unrelated bad futures of Heroes, a man with nuclear-based superpowers destroys an entire city (New York City and Costa Verde, California, respectively). Another future shows Tokyo being destroyed in a flash of light.
- In Torchwood, the opening of the rift summoned a massive beast named Abaddon whose shadow killed off hundreds, if not thousands of people before Jack stopped it.
- In Red Dwarf, due to a volcanic eruption, most of Fiji is now several feet underwater.
- Buffy the Vampire Slayer's destruction of Sunnydale when it's sucked into a crater.
( While the world of Revolution
is Class 1 verging on Class 2 at the end of the first season there is a Class 0 when Philadelphia and Atlanta are nuked by the Patriots
- Damien Richter's activities and a brief orbital bombardment with hypervelocity mass drivers destroyed much of the capital planet of Avalon in Tech Infantry. And the first Bug Invasion wipes out Rio de Janeiro and the surrounding area of Brazil two centuries before that.
- The main weapon batteries of any Warhammer 40,000 cruiser can, in the words of Ciaphas Cain, note , "level continents." 40K doesn't even need weapons to accomplish this - the debris from a naval engagement can cause catastrophic damage all on its own. Think about it, the average cruiser in that setting is several kilometers long, several hundred meters wide and tall, and weighs in at millions upon millions of tons of armoured hull. If one of these ships breaks up in orbit, even the fragments will be million-ton steel meteors, and if it goes down in one piece, the planet below gets nailed by a meteorite like a large mountain! And that's not even mentioning the even larger heavy cruisers, battlecruisers, grand cruisers and vastly larger battleships.
- The city of Mordheim was struck by a comet made of Wyrdstone. Most of those who weren't killed were driven mad or mutated. What was left of the city was looted by human and non-humans who warred amongst each other in the lawless streets for the best spoils.
- Killing off darklords in the Ravenloft setting has been known to cause entire domains to disappear, their native populations included.
- Final Fantasy VII, with the destruction of Midgar at the end of the game. The ambiguous ending left some gamers thinking that a Class 3 scenario occurred, but Final Fantasy VII: Advent Children corrected this.
- However, what Sephiroth planned was of Class 5.
- Jenova's landing 2000 years ago was a Class2 to the Ancients/Cetra.
- The backstory of Final Fantasy Tactics indicates that at some point after Final Fantasy XII, a huge catastrophe hit Ivalice and destroyed the entire political structure, several races (like Moogles), and most of the advanced technology, like Airships. Its never said if it also hit the rest of the unnamed world where Ivalice is located, so this may actually be a Class 2.
- The Catastrophe in Snatcher rendered most of Eurasia uninhabitable, prompting mass immigration to new islands built in Japan.
- The Zone in S.T.A.L.K.E.R.: Shadow of Chernobyl
- Interestingly, while civilization inside the Zone is pretty much gone, the rest of the world is actually better off. The chance to observe the laws of physics and biology change first-hand has resulted in the creation of several advances in metallurgy and antibiotics, and nobody lived in the Zone beforehand who wasn't trying to perfect mind control anyway.
- Though this may become a higher class, as it is suggested the Zone is expanding, and it has been established that the Zone is independent, and if the Zone expands...well, a world full of Bloodsuckers won't be so much fun.
- Killing Floor's mutant outbreak is effectively limited to Great Britain, which seems lucky as the only survivors are either former military or Crazy-Prepared.
- In Guild Wars, this has happened on several occasions.
- The earliest known event was the Scarab Plague which struck the isle of Istan. It was centuries before the isle was fully repopulated.
- Perhaps the most devastating followed some time after when the god Abaddon was banished into the Realm of Torment. As a result of that, the Crystal Sea was devastated, half becoming a vast desert and the other turning into a hostile wastes of sulfurous sands.
- The Jade Wind in Cantha, caused by the traitor Shiro, devastated the continent turning a sea to jade and forest to stone.
- While the previous events were backstory, the first game, Prophecies, starts with the Searing. Summoned by the Charr, burning crystals rained down on the human kingdom of Ascalon, killing much of the population and leaving the survivors locked in a struggle for survival in a barren wasteland.
- Humanity eventually lost Ascalon as a result of the Searing; it was claimed by the Charr. More than two centuries later the land is still recovering.
- Shortly after the Searing, Charr forces marched into the nearby human kingdom of Orr. A desperate attempt to drive them back caused the Cataclysm, a magical catastrophe that killed everything within the kingdom and sank the island beneath the sea. Many of the slain arose afterward as undead.
- In the backstory of the sequel, the Cataclysm will be reversed, causing another Class 0 event. The return of Orr to the surface will cause massive tidal waves, destroying the coastal cities of Kryta and drowning the Battle Isles.
- In Left 4 Dead and Left 4 Dead 2, the entire East Coast United States, from New York to Louisiana, has been lost to the rapidly spreading mutated rabies virus, turning people into bloodthirsty animals who's extreme pent up rage and severe loss of mental functions leave them in a zombie like state. So far, the Civil Emergency Defense Agency has been useless to stop the spread, leaving the US Military to take over with a more violent and potentially genocidal approach (includes slaughtering entire groups of citizens because one or two might be infected).
- In the Resident Evil series, almost all of Raccoon City had become zombified, so the US government sent a nuclear bomb to contain the outbreak.
- Tales of Monkey Island: The entire Gulf of Melange in Chapter 5, right between this class and Class 1, and bordering on Class 3A. And it seems that the Caribbean just isn't pretty much the same since LeChuck regained his voodoo powers and killed Guybrush.
- In Dangan Ronpa, the outside world (according to the Big Bad, who isn't the most truthful person) is shown to be in ruins, with giant Monokumas destroying buildings and the citizens wearing Monokuma masks and smashing cars and shops like skinheads — all thanks to the Worst, Most Despair-Inducing Moment in the History of Mankind.
- The Big Bad of MOTHER 3 aims to cause this to the Nowhere Islands by awakening the massive dragon sleeping beneath them. Though he's stopped, the destruction ends up happening anyways, because the dragon's help was needed by the heroes. Whether or not anyone actually survived is left up to the player. Also technically counts as global destruction, as said islands are the only part of the world that's habitable anymore.
- In Chirault the mages level a city by accidentally touching their Reality Changing Miniature. Oops.
- In FreakAngels at first it's assumed that the flooding was global but is later revealed that only Britain was affected
- In The Order of the Stick, Azure City gets assaulted, partly destroyed and ultimately dominated by mainly Redcloack and Xykon. Whether the place will ever be returned to its original state is yet to be seen. However, most probably not, since there is a new nation there now and destroying it to bring back the old inhabitants would be this trope too, and the refugees have found a new place to live.
- In the series Generator Rex, millions die worldwide after The Nanite Event. And thanks to the nature of the nanites, it could escalate all the way up to a Class 4 - maybe even Class 6 - at any moment.
- One happened offscreen and in the past in the original My Little Pony. The kingdom of Grundleland was wiped out the last time the Smooze was unleashed, leaving only a tiny handful of survivors.
- The Spanish Flu epidemic of 1918.
- Wasn't exactly regional though, as it spread around the world including the Arctic. In addition to the death rate, the infection rate crippled communities.
- But it didn't cripple the entire world, nor was human civilization knocked a century back.
- Several cholera outbreaks over the course of history, including the one currently spreading through Zimbabwe, and more recently, Haiti as well. Cholera, smallpox, and other European diseases that wiped out nearly the entire Native American population.
- Arguably, the 2004 tsunami.
- This occurred in the (formerly Belgian) Congo during the 1960s. The country's infrastructure was destroyed in a series of wars and its mineral wealth was stripped by a succession of dictators. There are still manned railway stations in one town that have not seen a train in decades. Land travel is virtually impossible along the Congo river due to fact that parts of the route are either inhabited by Ax-Crazy marauders or completely overgrown.
- The Chernobyl Disaster, which displaced a good chunk of the Ukrainian population overnight.
- The two atomic bombs that were dropped in World War II, though this actually comes in second to the other bombing campaigns over Japan during WWII; the firebombing of Tokyo alone killed about as many as the atomic bombing of Hiroshima did. Firebombing operations happened far, far more often than atomic bombings, obviously. Then add in mass occasions of conventional bombing operations, and US aircraft shooting down poorly trained Japanese pilots in droves by that time period, and...well, Japan lost a massive amount of people.
- The level of destruction in Europe (especially Germany) and Japan even without the Atomic Bombs is probably a Class 0 in and of itself.
- One fellow's great uncle was a colonel in the U. S. Army who participated in the occupation of Germany. His letters about the conditions in Germany read like something out of Mad Max.
- And what happened to Germany was nothing compared to what the Wehrmacht did to Warsaw - as of 2013, they still haven't finished rebuilding parts of the city, and the 400,000 manuscripts and three million other books and maps burnt by the Nazis can never be recovered.
- Sadly, it seems like the recent earthquake that leveled Haiti could be this, as the recent cholera outbreak has compounded the problem and Hurricane Tomas could make it even worse.
- As yet, the tally for Japan's quake and tsunami isn't as high, but rising. Even with fewer deaths, the devastation and possible radiation hazards have emptied out areas that were quite well-populated.
- Hurricane Katrina, which demolished much of the Gulf Coast of the U.S., and the damage is still being felt in the economy; the death toll, however, is more like a 0.0001.
- As a point of comparison, Katrina pretty much flattened an area the size of the UK, and knocked out power to an additional area about the size of France & the Benelux countries combined.
- Eastern Europe suffered a fate between this and a Class 1 in the two world wars.
- The Mongol invasions. In Russia for example, half the population was killed, while estimates range up to 90% of Iran's population being destroyed by the Mongols and subsequent famines.
- The 2011 Tohoku Earthquake and Tsunami in Japan. The entire Sendai Region leveled as well as a nuclear incident in Fukushima's Fukushima I power plant.
- Although the only death from the Fukushima "incident" was caused by falling debris.
- The decline of Mayan civilization during the 8th and 9th centuries probably count as this.
- Though some archeologists believe that the decline of the Maya happened quietly over several generations being compelled to move away from the cities, or to never marry and have children, for economic reasons, rather than a single dramatic event.
- During World War I, pretty much an entire generation of men across Europe died, or were badly injured.
- The 'deficit' in young men was thought to be about 9 million.
- Russian and Chinese Civil Wars. Period.
- The population of Easter Island was nearly wiped after they destroyed the local flora to build those statues.
- It's predicted that thanks to Global Warming, the islands composing Kiribati will wind up totally flooded. The government is trying to convince Australia and New Zealand to accept the entire population as refugees. Other island nations such as Tuvalu and the Maldives may eventually suffer the same fate as well.
- That is the best case scenario. Worst case scenario: entire coastal cities like New York City, London, Shanghai, and Miami, as with entire agricultural regions like Bangladesh and the Nile Delta. Ironically enough, because of their wealth the ones polluting the most will suffer the least.
- Indeed, global warming and it's various side effects could cause anywhere between a Class 0 to a Class 5 or 6, depending on how long it takes before humanity begins severely cutting down on carbon emissions or does some sort of geo-engineering. If action is done relatively soon (unlikely but possible) it could be kept to a low-end Class 0, if no major action is done soon it will be a Class 0, and the longer it takes, although it's unlikely it would get above 1 or 2 unless humanity is even stupider than it is now.
- On the end of the temperature spectrum, any future ice age (the next is due as early as 10,000 years or so) may cause glaciers to cover the entire Northern Hemisphere, rendering it uninhabitable because of the ice.
- At least 3 are known to have happened in antiquity: 2250 BC saw the fall of the Sumerians and the Egyptian Old Kingdom, another around 1200 BC saw the Hittites, Babylonians, Assyrians, Cretans, the Myceneans and the Indus Valley all collapse, and Egypt just barely hang on. A third was the slow-motion collapse of the Western Roman Empire from AD 300-600.
- Between the Great Famine and the Black Death, the 14th century was this to Europe.