Sometimes valid concerns are blown out of proportion by panicky people, it's pretty clear you understand the issues involved, but exaggerated concerns are often pointed to by ideologues on both sides in order to advance their own agendas: One to instill fear, the other to reassure and debunk.

For example, global warming could cause sea level rises, but this does not necessarily mean that thousands of square miles and hundreds of coastal cities would necessarily be swallowed up. However, a rise of even a few feet could make the occasional 100 year flood a 10 year flood, perhaps even a yearly event. In places like Miami, London or Venice this means billions of dollars in economic damage. Many people don't realize how marginal most of our coastal settlements are. The most valuable real estate in Florida is located in places where any form of construction should be strictly forbidden, even without taking sea level rise into account.

Just because we don't have a global catastrophe doesn't mean we can't have severe economic consequences.