Um, I would say for population growth, it would be so many people that everyone would only get assigned a certain unit of space to live and move around in as well as something like a one child law.

For WMDs it would be a nuclear fallout that would force people to relocate underground, never to see the sun again.

The environment is an easy one. No trees, increase of global warming and the melting of the polar ice caps, which would end up flooding a whole bunch of land and making it even harder to manage our population.

The terrorism is already sort of self explanatory, just what the terrorists are doing now times a million I guess.

For WMDs it would be a nuclear fallout that would force people to relocate underground, never to see the sun again.

@bleachedsnow Can you think of an example for that? Like, Country A attacks Country B, Country B has allies as Country C, D, and E, etc

@Gargron

Well there's a ton of countries that have nuclear weapons now. Russia, US, North Korea, China, India... Maybe not a ton but it's getting there. I heard Iran or Israel is making them too.

Digging to the Earth's core and unleashing Hell, which takes over the world and kill us all. It will truly be a hell on Earth.

My answer

Oh people, you just can't do anything scientifically.

Another one, apparently there's a fungi that feeds on plastic. The plan is to put this into our landfills so it'll feed on our wastes.

End of the world: the fungus will grow too large and spread faster than we can contain it, it advances on our world and eats us alive.

Well...I believe a possible epidemic could appear,or something... probably starting in a less developed country or a supervirus exposed to the world. And it moves around the world to fast to make a cure/vaccine.

OR a possible zombie outbreak. Well, now that they found that zombie gene in gypsy moths, i believe its highly possible that someone stupid will modify the gene saying 'oh we made a zombie gene for the whole human population' and thus zombie apocalypse...

or the divide between the rich and the poor gets worse and we all fight in a very long civil war (rich vs poor)/ the collapse of counties.

or we all get censored by more SOPA/ACTA/PIPAs and are controlled by a one world government of doom and destruction. We live life blissfully unaware of everything that is going on as people die around us...or something like 1984/Fahrenheit 451

@Viral +100,000,000

zombies?.. lol..

seriously.. it will all be the same as now if we're talking about the near future.. maybe a little deviance somewhere.. but yeah.. more or less the same as now..

but if, by chance, some revolution [specifically: advanced nanotechnology] takes place, then it's another story..

nuclear weapon becomes an ancient thing and terrorists would divert to nanotechnology for their plans..

example? Those little bugs that eat everything from the G.I. Joe Movie..

Over-population. Too many people, not enough food being produced to keep the wealthy nation's fatties full. Most people die from starvation.

Then the government will be like no moar babies, and the hippies will be like oh hell no man, we hella like having kids. Then there's the Freedom of Sex War and the hippies will take over a base somehow, then launch a nuke at a country capital saying, "Like, take this man." Then the other countries will see that there is a nuke and will be like "lol nuke time, Fallout this shit bitches" and the world will be like boom and kabewm. Lastly, the surviving humans will start sexing up the animals and produce human hybrid birds, sheep, cows, monkeys, fish.

Yep.

We discover new energy and use it on a rocket ship, but the instability of the fuel causes the rocket to to propel in reverse causing it to rip through the planet and create a giant hole. The loss of gravitational pull will then leave the rest of the planet dismemberred and floating away from each other.

This is like the best thread ever.

The worse case scenario is the current state left untouched.

For mass destruction weapons:

The world is blown the fuck up due to nukes and H-bombs and the like. Or rather, the entire earth becomes barren due to radiation and no plants can grow and everyone dies. ;-;

Oh @Gargron ever heard of other sites besides CL?

On a more serious note: http://www.cracked.com/search/search.php?sa=search&q=world+end

http://www.cracked.com/article_16583_the-5-scientific-experiments-most-likely-to-end-world.html

http://www.cracked.com/article_18387_5-ways-world-could-end-youd-never-see-coming.html

http://www.cracked.com/article_15643_5-scientific-reasons-zombie-apocalypse-could-actually-happen.html

hope you found something worth your while.

Over population- The human populous reaches a certain number, causing a counter to be set off, causing the moon to suddenly shift and start descending towards us, giving us a limited amount of time to stop it. Then we have to deal with aliens and badass galaxy fights before finally turning into pixie dust at the alter.

THe Beiber fever will kill us all

ok lets get serious, The Rapture, If the bible is true, and people disapear, what will be of us? Millions of people disapear(probably by emp that takes down all aircraft) and you might be the one who is left on earth. Governments fall, Anarchy rains, The fight for survival is on. Food is now scarce, and coffee is no longer shipped, electronics might be usless.

fill in the rest this would be an awsm movie

well theirs the mass panic/hysteria that can happen from 2012 that will lead to mass suicide witch will lead to looters then killing then to anarchy (get your cook books ready) and so on and so forth but also there a chance that the earths magnetosphere will flip and cause a EMP effect that will turn every electric device off killing a few thousands and aging with the mass panic/hysteria and then with no power other stuff can happen [make up for space] but also the EMP can cause a data loss which means no internet and bank credits

SOPA, ACTA and PIPA being passed

Over population, the worlds resources would be extremely limited and humans would kill the world slowly.