I would dispute that even a sizeable increase in global average temperature, of say 5 degrees celsius by 2100, would make much of our infra-structure useless. I also don't buy that it would lead to some catastrophic rise in sea levels; I don't think this is being suggested even by the most alarmed "warmists". The IPCC forecasts a rise of 18 to 59cm, and even they refrain from stating it as a certainty.
Your hypothetical ability to dispute my claim is a piss-poor rejection of my claim.
18-59 was the projection for this century. It is also a world mean, and is amplified by tidal action and other factors in some parts of the world. If the icecaps and the Greenland icefield were to melt, the range according to the IPCC is 110-770. These projections are possibly true, quite possibly true, and such an actuality
would be catastrophic.
So my best guess is that warming would lead to problems in some areas and open opportunities in others. And have no effect in other areas (after all GW is not supposed to be uniform).
Your best guess is still a guess. You are simply presuming that everything will balance out in the end without a defense of that outcome. There are at least identifiable reasons to think there will be detriment if GW is true.
My take is that there is no real base to state that there will be a climate-induced catastrophe in the next century. Additionally, it is pretty silly to make forecasts about climate over a century from now because by then the technological level will be so vastly different that all bets are off. So claims along the lines of "by the year 3000 London will underwater!" are comedy, not science (and yes, I've read this).
The issue is that these forecasts are all that is available to us. We have to make decisions today about things in the future that we cannot know much about. Inaction is as much a decision as some other action and can be equally as misguided in retrospect. Using your argument to reject a claim that we ought to do x equally undermines the argument that we oughtn't to do x. Your point is thus absurd. A parallel example:
You are leading an army towards a field hoping to capture a strategic hill beyond it. A patrol has reported that the hill has been occupied, but this isn't certain and hasn't been established by more reliable recon.
There are two policy options available:
Policy A-- Continue moving forward in hopes of capturing the hill
Policy B--hold up in the field and wait for reinforcements and air support.
There are four possible outcomes:
1. The hill is occupied and Policy A = disaster
2. The hill is occupied and Policy B = eventual but costly victory
3. The hill is unoccupied and Policy A = best possible outcome
4. The hill is unoccupied and Policy B = 50% chance of 2 being eventual result as the enemy may take advantage of the delay and occupy the hill.
One of your staff (this is your position) says we can't justify B adequately because we don't have more reliable sources.
The problem is that we also can't justify A adequately because we lack more reliable sources to use as counterevidence. We do need to make a decision, however; we need to do this with current evidence. You can dispute the findings and significance of current evidence, but this isn't what your argument is doing. Your argument is throwing all evidence into the trash because it doesn't meet some here-to-fore undefended standard of reliability.