Over the next 200 years sea level changes due to greenhouse gas emissions are projected to reduce global real GDP by 0.19 percent in present value terms

See Further estimates on the cost of climate change and global warming by Tyler Cowen.

"Sea level rise will cause spatial shifts in economic activity over the next 200 years. Using a spatially disaggregated, dynamic model of the world economy, this paper estimates the consequences of probabilistic projections of local sea level changes. Under an intermediate scenario of greenhouse gas emissions, permanent flooding is projected to reduce global real GDP by 0.19 percent in present value terms. By the year 2200, a projected 1.46 percent of the population will be displaced. Losses in coastal localities are much larger. When ignoring the dynamic response of investment and migration, the loss in real GDP in 2200 increases from 0.11 percent to 4.5 percent.

That newly published paper is from Klaus Desmet, Robert E. Kopp, Scott A. Kulp, Dávid Krisztián Nagy, Michael Oppenheimer, Esteban Rossi-Hansberg and Benjamin H. Strauss in American Economic Journal: Macroeconomics.  Am I wrong to feel a little…underwhelmed by those estimates?  Here is an earlier recent paper on other cost estimates."