Why is there a "controversy" about Global Warming, and why is there none about "Terrorism"?
For starters, it's hard to make a defensible argument for terrorism. Any "controversy" is usually concocted from the AGW side trying to avoid defending their positions.
My question is: From a risk management point of view, shouldn't it be the other way 'round?
If one is going to do a risk management assessment properly, one must enumerate the risks, enumerate the benefits, enumerate the costs, figure the impact of any mitigation and figure the probability of the event in the first place (and this list is just off the top of my head - I'm sure there's a couple more that I am forgetting). Your example is a very poor example - Terrorism IS NOT a imagined problem - there are several buildings missing from NYC and several large passenger planes destroyed just from 9/11. Contrast that with Global Warming, where it's not clear it's even a bad thing - warmer climates mean that plants are better off and people freeze to death less often. There seems to be less violent storms. Why would you do risk management on something that is beneficial?
Plus your simplistic scenario leaves out the cost of the mitigation. When "doing something" means you are forcing the poor of the world to live with the cost of higher energy prices (ie, higher food costs), one really has to question the motivation of the ones proposing these ideas (and if you don't think this is a the case, just look at what the production of ethanol and the diversion of corn to make this "green" fuel have caused).
Also high cost, but climate changes can be mitigated to the point where only little/no damage has to be suffered.
Excuse me? There is no reasonable mitigation strategy that I've seen where the results of the mitigation would stop AGW.
The latter can literally cost millions of lives with coastal areas becoming uninhabitable for decades, if not forever, with storms causing damages in the billions and unforeseeable effects to agriculture and nature (and of course tourism, but I guess that's the least of our concerns then). And we're not talking about some brown bodies being killed, that could well be millions of AMERICANS dead, so the usual "Anyone outside the US doesn't count as human to the US" won't apply.
And what SCIENCE are you basing this off of?! Look at: http://en.wikipedia.org/wiki/Current_sea_level_rise where it says that the rise in sea level between 1870-2004 is 7.7 INCHES. Yes. Like millions have died from the 7.7 inches that has already happened. Good Grief. Statements like what you said is why I'm saying that you can replace "Global Warming" with "The Angry God" in many of the AGW arguments without changing any of the meaning, since there are no facts to back them up.
Yet we pump billions into the defense against terrorism, but we keep bickering on whether or not Global Warming may or may not happen. Anyone able to explain the sense in that?
If you are trying to compare a real problem (terrorism) to something you aren't even sure exists or not, you aren't making an apples to apples comparison. I would change the question and ask you, "well, we *KNOW* that asteroidd hit the Earth and that this has very, very bad effects. Why are we spending so much time worrying about global warming than we do about that?"