Here comes the rain again. The skies darken and the winds howl; storms of a kind that should show up only once every half-millennium now arrive every 10 years. The world is warming up. The hotter the oceans get, the faster they evaporate, and the hotter the air gets, the more moisture it holds, with one devastating result: When the clouds let go of their watery load, it now pounds the earth for days at a time, washing away hillsides and flooding valleys and plains. Even when it isn't raining — the terrible storms alternate with equally terrible droughts — the glaciers go on melting, relentlessly raising sea levels and pushing waves farther and farther inland.