I won't go into detail:
In 2020(Approximately) there will be an oil crisis. Not some gulf spill but the fact that we used up carbon fuels quicker than they could replenish so we are left will little oil. Because of the populations lack of heeding to warning they didn't buy hybrid cars or fully electric cars. America, oil dependent as it is, will demand cheaper prices from the middle east despite little oil and desperation. Middle Eastern countries like Saudi Arabia, UAE, Iran, Yemen, etc. will be pressed and eventually occupied by US forces in need of oil. In the mean time, we need even more oil and we buy oil from some remaining drills in China, who isn't effected as much because of many bicycles and electric cars. China now profits from our desperation and middle eastern countries are PO'd. We have terrorist attacks weekly, China profits, America is frantic and gas is $20 a gallon.
Iran will launch multiple nuclear warheads on the US in defense of invasion in need for oil and the US will fire back with many times the amount of nukes. Iran will be destroyed and all other Nuclear bearing Middle Eastern countries will launch more nuclear missiles. Those countries are destroyed by US and it's allies.
China will now band with Russia, and North Korea to be united under a "common enemy" and China will wipe out the US and it's allies for good and China will be greatly destroyed.
Despite of China thinking all is over, it's not. Nuclear Radiation and Radiated clouds will block out the sun and the world's food sources will die. Also, along with that, no more CO2 or water vapor is retaining heat so the Earth gets very very cold. Humans die off along with most other animals. Most of the ocean freezes over but seals, fish, and polar bears are lucky. Humans could not adapt in time for the large change.
Was that good enough?