Why is global warming bad?

It will cause flooding in some coastal areas and result in more powerful storms. It will destroy some farm land and inhabitable areas while opening up some new ones forcing migration.

How detrimental these effects really are is up for debate. For instance to avoid flooding we could just move inland or build better flood control.
Answer
If scientists do not find a way to prevent global disasters from happening we will be severely devastated,scientists are working on making our earth more green and not you so much oil so there is less pollution.

Most of us are unaware of the massive, continual movement of our oceans' water. It's a very very important thing. It allows many millions of us to live where we would have great difficulty living otherwise. There's a conveyor belt or river of water in our planet's oceans that moves the cold water to the deepest areas which brings warmer water to places, helping those places stay in moderate, livable, temperature ranges. It ALSO allows the trillions of krill to reproduce and feed the small and larger fish. If the krill all die, so will many many fish!

Both will suffer the immediate effects first; both of the Predator and the Prey.