Pumping nitrogen into the ground produces food. As for the long or short term question, we're amputating our foot because we predict that a minor cut will be infected. Knowing what you don't know is the key here. Right now no one can predict how the world will look like in 5 years. War, disease, new weapons, new disruptive technologies being developed. Whatever the temperature and sea level change will be, it'll be the least of my concerns for a good few decades.