The problem is that if there is a serious accident with a nuclear power plant, the damage is localized. If global warming gets to a point where sea level rises 2 or 3 feet, tens, maybe hundreds of millions of people are going to be affected, not to mention the tremendous death and misery that would be caused by the disruptions to agriculture. If things get to that point, there's no way humankind could undo the damage without tremendous cost, and that's assuming it would even be possible (currently the technology does not exist).

If solar and wind power could meet energy needs around the world better than nuclear then great. The fact is that they're not even close and no good alternatives will be ready in the foreseeable future.