What is the main topic of discussion in the poem below?

Fire and Ice
by Robert Frost

Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.
But if I had to perish twice,
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice.

Frost, Robert. "Fire and Ice." Harper's Magazine, December 1920.

The poem discusses global warming.
The poem discusses the end of the world.
The poem discusses the creation of the world.
The poem discusses war.