Nobody predicted that sea levels would rise noticably yet – that’s still a few decades off. But glaciers are already retreating at an alarming pace around the world, as is the Arctic ice. Weather patterns in the last few years have also been erratic – warmer on the whole but significantly drier in some areas, significantly wetter in other areas, etc. It could be a natural anomaly, but it does fit in with the weather chaos predicted by the global warming models.
It all boils down to a colossal bet – if we bet that global warming is real and human caused and bet wrong, then we’ll have needlessly spent billions of dollars. That expenditure wouldn’t be a complete loss, though – a lot of high-tech jobs would be created, other types of pollution would likely also be diminished, and we would extend the life of our nonrenewable resources. However, if we bet that global warming is not real or is not human-caused and are wrong about that, then the results would be flooded coastal cities, dramaticly shifted weather patterns and a corresponding elimination of many species (as well as viable farmland), etc., etc. I’d rather bet that the vast majority of scientists are actually correct.
(Oh, by the way, as the oceans absorb the increased concentrations of carbon dioxide, the acidity of the oceans will increase, which will kill off coral reefs and the species that depend on them. So the sharks are screwed anyway.)