@krellin
Of course climate change happens without people around, which isn't to say that it can't also happen with us around, or with us influencing it.
Regardless of the cause, the climate is warming and the ocean are rising, which will affect our way of life. Maybe catastrophically, maybe just a burp. But throwing as much science at the problem to see if it is a problem, and how much, is a logical thing to do. Maybe with our level of science and understanding of climate we will only get 60% or 80% or whatever accuracy and that's what we will have to work with. That's still better forecasting than say, with the stock market, the economy past a couple of years in the future, and so on, and yet that still doesn't keep governments and corporations from using long-range economic forecasts to plan ahead. A poor tool is still better than no tool, which is in turn better than throwing away the tool and denying there is a need for the tool.
Granted, this is a theory, not a proven thing, but here is a likely example of catastrophic climate change from greenhouse gases:
http://www.nature.com/news/archaeageddon-how-gas-belching-microbes-could-have-caused-mass-extinction-1.14958
In 2011, methane "volcanoes" up to a kilometer wide were spotted off of the Russian coast. Not scary in itself; that is just a blip, but there will be more of that as the oceans warm up, which adds to everything else.
I don't have a problem with looking at the models, getting projections, and planning for the future based on that. Maybe the solution is to curb greenhouse gases, but maybe the best economic solution is to educate people on low lying coastal areas on when they will likely need to take a hike. It's government's duty to plan ahead for potential crisis and come up with rational solutions; it's what they are paid to do. Insurance companies have already adjusted for increased severe weather activity. Governments at all levels generally have not.