What If an asteroid is hurtling towards Earth and we have 100 years until impact?

What can we do that is theoretically possible for us to survive? Here is what will happen most probably:

Years 0 to 20 (1960 to 1980)

1. The scientific community first detects the Asteroid, starts tracking it and predicts if its gonna hit Earth or not.

Years 20 to 40 (1980 to 2000)

1. Majority of the scientific community from across all nations conclude the Asteroid is about to hit Earth around 2060 and destroy everything. Total Annihilation.
2. Many nations also do agree on the threat to our whole existence and start doing a annual meetup to discuss on this. #COP

Years 40 to 60 (2000 to 2020)

1. Scientific community also devised ways to deflect the Asteroid. But the methods are highly advanced and costs a hell lot. It requires all countries, who are at war with each other, to work together holding hands.
2. All nations also understand and agree that immediate action is required to deflect the Asteroid and save Earth. But the Asteroid deflection plan is too expensive that no one wants to take the burden.
3. The general public is unaware of total destruction earth in next 50 years, goes on in their daily schedule.
4. Because of the influence of nearing Asteroid, Earth already started showing symptoms of Heavy drought and Heavy floods.
5. The NGOs, Volunteers and Social activists, unaware of the Story of the incoming Asteroid, do Tree plantation drives, monitors govt on their Mass tree plantation drives, with their #limited Vision of Saving Planet Earth. Noble but poor souls, blinded from Truth!
6. 200 nations come together on Paris in the year 2015 to sign an Agreement to do something about the Asteroid.
7. The Former President of a Developed nation, USA says “We are the first generation to feel the impact of the Asteroid and we are the last generation to do something about it”.
8. Then USA selects their next President, Trump who says “The whole asteroid thing is Hoax created by Chinese govt. to disturb our growth.” AND THIS FKING SHIT pulls the plug out of Paris Agreement.
9. The Prime minister of the Developing nation, India says, “We have 30% of our population without Electricity. So we need to take care of them. Developed nations should take responsibility of deflecting the asteroid.” He clearly knows not just the 30%, but the whole 100% is gonna be wiped away in next couple of decades.
10. Everyone speaks, but only little action is taken.

Years 60 to 80 (2020 to 2040)

1. Scientific community cries out trying to push the govt to take action, arrange mass demonstrations to convey the impending danger to Public.
2. The asteroid entered the Solar system and the symptoms are getting too heavy. Oceans getting acidic, Glaciers getting melted, rising ocean sea levels, Sea water entering cities like Miami, Mumbai, Calcutta, New york, Bangkok.
3. Many animal species getting WIPED OUT as the Asteroid nears the Earth. Extreme symptoms also wipes out all people in lower economic class.
4. This is a very critical stage. Putting every resource, technology, money in Asteroid deflection plan might help, but the Governments and Corporates could never make a decision that would bankrupt the entire planet.

Years 80 to 99 (2040 to 2059)

1. Scientific community has probably achieved in gaining Public attention to some extent, but not enough to move the Governments.
2. The people who first discovered the Asteroid are long gone, this is their great grandchildren on Earth. 
3. The great grandchildren are the ones who are now in agreement that Earth screwed up. It’s clear, It’s all doomed. They curse the great grand parents, grand parents and parents for screwing up the Earth. They are counting the final days, in the harshest environment that Humanity has ever faced.

Years 100 (2060)

Booom!

It’s too little too late. There’s nothing that can be done, even with our 100 year advancements. We spent too long bickering.

Good story? For Fun: Replace the word `Asteroid` with `Climate change` and this becomes a True story. But dont replace it word by word, but just the context. We, Humans are driving Sixth Mass Extinction.

Nature played a Dice to create a Intelligent species. But it failed. Don’t know how many millions of years, how many light years away, till another Intelligent life form evolves!