I'd say abandoning entire coastal regions is pretty damn catastrophic, even if it's an orderly retreat and nobody drowns. That's still billions (trillions?) of dollars worth of real estate vanishing under the waves, not to mention the immense cultural loss.
The real estate itself: as much ocean-front real estate is created by sea-level rise as is destroyed, approximately. So at this point, it is only the improvements upon the real estate which are lost. With sea level creeping slowly up, these losses should be minimal. Structures have various economically useful lifetimes ranging from years to many decades depending on the structure.
And it should be noted that sea levels have been rising for longer than human civilization has existed. Loss of real estate and improvements because of natural shifts in land vs water levels is nothing new.
as much ocean-front real estate is created by sea-level rise as is destroyed, approximately.
There isn't a substantial change in the amount of ocean-front real estate, but there is a substantial change in the total amount of real estate. Super-crude model: you have a square island of side 1 unit; rising sea level reduces the side by 0.01 units of length, which by coincidence is also how near the sea something needs to be to be "ocean-front". Before, the total amount of land is 1 unit and the total amount of sea-front land is 0.0396 units. After...
Note: Please see this post of mine for more on the project, my sources, and potential sources for bias.
I have written a couple of blog posts on my understanding of climate forecasting, climate change, and the Anthropogenic Global Warming (AGW) hypothesis (here and here). I also laid down the sources I was using to inform myself here.
I think one question that a number of readers may have had is: given my lack of knowledge (and unwillingness to undertake extensive study) of the subject, why am I investigating it at all, rather than relying on the expert consensus, as documented by the IPCC that, even if we're not sure is correct, is still the best bet humanity has for getting things right? I intend to elaborate on the reasons for taking a closer look at the matter, while still refraining from making the study of atmospheric science a full-time goal, in a future post.
Right now, I'm curious to hear how you formed your views on climate change. In particular, I'm interested in answers to questions such as these (not necessarily answers to all of them, or even to only these questions).