Friday, August 08, 2008

Mucking my way through Pielke Jr. (and the Volokhs)

I haven't paid too much attention to Roger Pielke Jr. lately, as it's just too much work to sort through his stuff. I don't even know how to categorize him - not a denialist, exactly. Maybe just contrarian for the sake of it, a climate change nihilist.

But let's go through the exercise. Jonathan Adler at the Volokhs does his usual uncritical citing of RP Jr. to take potshots at Joe Romm who pushes for rapid action. This is how it works, by the way. Even if RP Jr. doesn't directly oppose attempts to mitigate climate change, he's used extensively by people like Adler who does.

RP says a new climate study doesn't support the idea of emphasizing how climate change makes weather more extreme. A casual reader might think RP is saying that weather won't get more extreme, so RP gets to send that message without actually saying it. To support his argument, he says the study finds in the US that

3. Despite increases in some measures of precipitation , there have not been corresponding increases in peak streamflows (high flows above 90th percentile).

Again a casual reader might think this means that things aren't getting worse. What RP leaves out is this compares high flows within a single period, not against the past. If total precipitation increases, the 90th percentile can also increase compared to what would have been a 90th percentile flood, fifty years ago. In other words, things are getting worse and it supports the opposite of what RP implies (this could be wrong, see updates below).

Another example - RP says the study (available here) emphasizes flooding when in fact "there has been no increase in streamflow" and is therefore ignorant or misleading (RP also says damage has decreased as a percentage of GDP, but he's ignoring the effect of flood control measures). TokyoTom valiantly tries to figure out in the comments what he's talking about regarding "no increase" in streamflow. RP says, "The report is not discussing flooding when it says it is discussing flooding. It is discussing precipitation. They are not at all the same thing, and implying that precip = floods is in error, and misleading." RP is accusing the study of doing what he just did - implying (not saying directly though) that streamflow is a proxy for extreme weather and it's not getting worse. Eventually RP cites to yet something else he wrote, but I'd had enough by this point.

UPDATE: Good grief, that was quick - Roger has a response in the comments. I'm not satisfied. And in somewhat related news, "Scientists studying variations in tropical heat and rainfall since the mid-1980s have found a strong link between warm periods and a rise in the frequency of the most extreme downpours."

UPDATE 2: Thinking some more about the comments, I did the same wrong leap from more extreme precip = more extreme flooding. It does ceteris parabis, but not over time with heavily managed and altered watersheds. Going back to the study itself, it's pretty measured on streamflow issues (p. 53), so I don't see the problem. More broadly, extreme events and their possibilities do motivate people, and is an important part of the economic analysis. They shouldn't be overplayed or downplayed.

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