This is a really interesting thread.
It happens to be my field…

The interesting thing about this issue is that there is data on both sides of the argument. Best muddled by Michael Crichton in his book “State of Fear”, where he used IPCC data coupled with information from “The skeptical environmentalist” written by Bjorn Lomborg (Both are worthy reads). The reality is that there are woefully few scientists that think global warming is not REAL. I would submit though that the pressure to fund environmental research is orders of magnitude less than the power of corporations to influence legislation. So although climate scientists have vested interest in keeping public interest in science high, I would say our abilities to really influence legislation at the national level is pretty weak.

The issues relevent to this posting are the economic ones.
There is healthy skepticism about the magnitude of the changes, and the projections of change especially from the numerical models. BUT, the cost of doing nothing, and not planning for the changes will be much higher than making smart changes now.

There are a number of events (more than two or three life times in length) that should concern all of us regardless of whether we believe the simple trends in CO2 (and dumping hummers etc).

There is no doubt that the north polar ice cap is melting. This will have a huge positive economic influence in shipping. It will have other direct effects. 1) The reflection of the suns energy into space (albedo) will decline. This will increase the amount of heat into the water (heating it and expanding it). 2) It will NOT raise sea level. This is because the north polar cap displaces water like an ice cube. 3) The warming of the northern polar regions will melt the permafrost. The result of this could be huge and is not well understood. But the amount of methane that will be released will be enormous as bacteria begin to actively remineralize the highly organic soil (Think all of siberia, not Canada). Methane is hugely more influential in climate than CO2.

Understanding and mitigating the impact of this change will be critical.

2) High altitude glaciers in a number of places (think africa), are major sources of water through percolation. Many of these glaciers will be gone over the next 20-100years. Result. This has the potential to displace hundreds of millions of people. It has the potential to start a large number of wars. Mitigating this impact will cost money regardless of the reason for the loss of the glaciers, but who cares about africa! Now think Afghanistan, Pakistan!

3)Notwithstanding the failure of the army corp, congress and the fed agencies responsible for the levies in New Orleans, Katrina is the future. Not necessarily because of hurricane cycles, but because over the last 35years, few huge storms hit the gulf and florida coasts. At the same time these areas experienced huge increases in both people and investment. If the number and intensity of storms had been as great as they have been over the last 15 years before the development occurred actuaries would not have created the risk table that allowed the development. Just bad timing is enough to screw us in the south. The displacement of a few hundred thousand people overwhelmed our ability to deal effectively. A few more storms like Rita, or others could greatly impact insurance and the potential to rebuild. Of course the government will than subsidize insurance in those regions and we will all pay the bill (just like flood insurance).

4) Out here, we will see the effects of climate change. Small changes in precipitation over long periods of time will effect the water flow in the Colorado, the snow pack in the sierras, and the aquifers through out west. This will directly impact food production, it will impact development as we fight for water rights, and will increase friction with our southerly neighbor. All of that requires a lot of thought, and money to mitigate.

5)The smog issues are local, changes in climate may increase the number of bad air days. The cost will be high in terms of healthcare. Vistas, that we enjoy, could erode. That is direct real estate effects. The sunsets will prettier though.

6) In the antarctic the changes are more complicated. There is evidence that over the last 50 years air temperature in many locations (more coastal than inland) have increased. deep water temps have seemed to increase. Until recently indices of ice extent have shown a decline (although some areas ahve increased their ice).

The big issue for antarctic is whether the loss of the ice shelves will increase the rate of movement of glaciers. If this happens sea level rises immediately. More scary is what will happen to greenland. That has a very huge potential for acceleration of glaciers. Think, short term more bergs floating south, potentially impacting shipping. Sea level will rise from that. Light freshwater will sit on the top of the ocean.

The other issues with climate change and sea level are 1) if you warm the ocean it expands. This directly impacts coastal regions; 2) If temps in the atlantic warm or cause large amounts of freshwater to enter areas of the Labrador sea, or the areas southeast of Greenland, deep convection could slow or stop, affecting the gulf stream (There are at least two events within recorded history where his has happened). The direct impact of this scenario is the huge cooling of western europe. That will be a major economic factor.

There are a number of other things will occur, and the global economy will be affected. It may not happen in your life time, but if you have kids it will probably affect them in theirs.

For the doubters or those that do not believe the correlational nature of the data. Why then do you believe economic trends? This real estate bubble was built on the premise that exponential growth was sustainable. That is why, average people put themselves at risk to buy more than they could afford in the hopes of doubling or tripling their money over just a few years. The government, did not enforce rules that protected consumers from themselves and allowed sub prime mortgages to be made available to everyone. RE agents, banks, and shareholders benefitted. Because of a trend line!!

Now the trend is down, yet everyone sees the end of this downward cycle already. It is a lot of wishful thinking. And a lot of hard working people will lose a lot because of it. In terms of climate change, it is easy to do nothing and hard to do something. The climate is changing, we impact the climate, and one thing we can do is become more efficient. Increasing efficiency will do two things 1) clean the air; 2) eliminate a source of instability in the world centered in the middle east.