Monday, September 30, 2013

Dear Bjorn: if you spend money to reduce a problem and the problem's reduced, that doesn't magically mean the problem reduced itself

One piece of Lomborg's alleged evidence that climate change hasn't produced extreme weather:  "Damage from flooding in the United States has declined from 0.2 percent of gross domestic product in 1940 to less than 0.05 percent today."

I vaguely remembered seeing this lame argument before, and after I clicked his source link I saw a familiar piece of liver. Should've guessed.

The problem with this argument is that the vast majority of money spent on flood control activities happened after 1940, and the damage-reduction effect of those flood control expenditures is incremental (flood control projects typically last 30-50 years, and rebuilding is cheaper than the original building). Extreme storm precipitation could get worse and the damage could still decrease, if you put in some effort at flood control. There's no accounting in the data set for the cost of that effort.

That's only one of many problems with Lomborg, but it's in my bailiwick so I had to call it out. And btw, the data doesn't include Sandy damages (the NOAA flood loss data set ended in September 2012), so that also might end up being a disturbance in the Force of the trend line.