Governments will act when there is sufficient public will. I think I mentioned before that bureaucrats above all want to preserve their budgets, and politicians want to get re-elected. The politician sends a powerful message to the bureaucrat, "do not embarrass me". These powerful forces hamper the progress of mega-projects that span more than four years (one election cycle). The spectre of failure is just too horrible for the bureaucrat or the politician to face.
When a radical new program captures the public will (i.e. homeland security), taxes typically isn't raised. The budgets of existing programs are quietly scooped to pay for it. Imagine how the career bureaucrat feels about that.
Global warming is one of those urgent threats, too big and too far in the future, for the public to get too excited about. A radical government response will likely happen, too late, when we are thick in the middle of the crisis.