What will happen on Earth if we detonate nuclear warheads?

Week 1

Five megatons of black carbon will enter the atmosphere immediately. The black carbon absorbs heat from the sun before it can reach the Earth.

Week 2

Earth becomes too dark as black carbon blocks light from reaching Earth. Chemical reactions in the atmosphere eat away Earth's ozone layer. Ultraviolet radiation is now 80 -120% more intense than before the war.

Month 2

Earth cools down: The average surface temperature reaches -25 °C (-13 °F). Earth's falling temperature reduce the amount of rain the planet receives. Plants stop growing and their DNA begins to destabilise.

Year 2

Without plants, 2 billion people would run out of food and starve to death. Most areas are now extremely cold and inhospitable. 

Year 5

The ozone layer is now 25% thinner than it used to before the war. Cases of skin cancer are on the rise among the remaining survivors.

Year 10

The ozone layer is recovering and it's now 8% thinner. 

Year 20

Earth begins to warm up again but it's still colder than before the war. Plants begin to grow but at a super low rate (5 years count as one growth season). 

Year 30

Earth now receives more rain than 15 years ago. Plants growth begins to stabilise but it is still very slow.

Year 50

Nature begins to take over once again. Some areas are still inhospitable due to extreme radiation levels.

All of this could happen with just 100 nuclear warheads.