I have not seen any peer-reviewed economic studies indicating extreme weather costs are trending lower. Please share those complete references with our readers; I am sure  many will be interested.  I am not an economist, but I thought that adjusting all losses to the consumer price index, as the NOAA analysis does, is indeed a commonly used economic technique to normalize costs that have been incurred in different time periods.

But even if I were to accept that your point is true--that relative to GDP, the cost of extreme weather losses has gone down--it doesn't follow that statistics such as NCEI keeps about the rising absolute costs of such disasters are "worthless." For one thing, such statistics would serve as the basis for more sophisticated analyses.

But also, from a public policy perspective, it's useful to know that the absolute costs of natural disasters are rising: billions of dollars in damages are still billions of dollars in damages, and they sap growth from the economy. Even if it's true that growth in other areas has been enough to offset those losses, it would still be still better for the economy if the absolute costs of disasters went down, not up.