It's not global warming. It's flat earthal warming. And it's happening because the ice that rings the earth and holds in the ocean is melting because the turtle that carries the earth on his back is actually Gamera - and he's testing out his thrusters.
When that ice fully melts enough, and all the oceans drains out, it's gonna unbalance the earth and Gamera is is just gonna buck us off into space. No more surf for you. Just ask Bohter.