Even if all greenhouse emissions ceased overnight, global temperatures would continue climbing for another century before hitting equilibrium. We are already past the point of no return unless we start actively pulling carbon back out of the atmosphere.
Rising of the sea levels is problematic for nearly all coastal areas of the world. Another problematic result is more extreme weather scenarios. There are many more, but let's start there.
I'll do an eli5 summary:
Even if all greenhouse emissions ceased overnight, global temperatures would continue climbing for another century before hitting equilibrium. We are already past the point of no return unless we start actively pulling carbon back out of the atmosphere.