Comments on: Hughes at NAS

By: John Lish

John Lish — Thu, 09 Mar 2006 13:53:37 +0000

Hughes asked: what is needed? More records; better records; better understanding of the records. He said that we can only get back to AD1500 with spatiotemporal reconstruction and that there can be no substantial progress until data improves. (SM- this is interesting. Hughes said that spatiotemporal maps are needed to check physical reasonableness, but he says here that this can’t go prior to about 1500.)

Better understanding of the records – can’t disagree with that statement. However doesn’t this imply a more open process with proper archieving of data in order to create the spatio-temporal map required. I just find this frustrating given the extrapolation of the Hockey Stick from the data MBH had. It’s bizarre to find these health warnings occuring now. Equally, it isn’t surprising that Hughes places a health warning on going beyond AD1500 but it is inconsistant with previous behaviour.

By: kim

kim — Thu, 09 Mar 2006 12:05:35 +0000

Briffa’s ozone explanation is only one of a large multitude of factors that could be imagined once circularity is established and accepted. Those are straws in the cyclone at which they are grasping to stuff the bogeyman of anthropomalevolence.
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By: John A

John A — Wed, 08 Mar 2006 19:37:38 +0000

He brought up two possible explanations for the Divergence Problem (I don’t recall how this topic came up.) He first referred to the explanation of Vaganov et al [1998], that the divergence was due to growth delayed die to increasing snowpack; and secondly to Briffa’s speculation that trees may be damaged due to ozone.

There are two words that come to mind at this: “straws” and “grasping”

Why does Hughes sound like a used car salesman explaining why some of his cars sold are unfit to drive yet asserting that as a whole they are of high quality?

Not six months ago you’d have had Mann pontificating on RealClimate about “false uncertainty” with such language.

By: John Hekman

John Hekman — Wed, 08 Mar 2006 19:12:00 +0000

So if some trees grow faster after 1850, e.g. bristlecones, it’s due to AGW, but if some trees grow more slowly after 1970 it’s due to ozone and is not inconsistent with AGW?

By: Steve McIntyre

Steve McIntyre — Wed, 08 Mar 2006 19:10:35 +0000

I’ll ask the BBC guys to check the exact wording on this point so I’m accurate on it. Here’s what my notes say…
" doesn’t 20th century disconnect mean that proxies…. 3rd explanation that I wasn’t going to discuss". Snowpack and ozone were the first two explanations. I didn’t finish the sentence in my notes and do not absolutely exclude the possibility that I might not have the exact nuance here. I’ll try to see if the BBC guys have this exactly.

Now that I think about it, the rest of the sentence might have been more that such de-coupling didn’t occur in the past (which has the same import in the present situation.) I’ve edited to reflect this.

By: Armand MacMurray

Armand MacMurray — Wed, 08 Mar 2006 19:03:44 +0000

Hughes was asked whether the 20th century disconnect means that tree proxies can’t be relied on. Hughes said “That’s the third explanation that I wasn’t going to discuss”.

Wow!

By: Ross McKitrick

Ross McKitrick — Wed, 08 Mar 2006 18:22:35 +0000

Steve, I thought Hughes’ point regarding trees and ozone was that maybe the post-1980 divergence arose due to stratospheric ozone depletion, not ground level ozone increases. Ground level O3 would hardly matter in remote mountain sites or northern treelines. The idea that small increases in surface UV flux would harm trees is a stretch too, esp. since the maps produced by the WMO place the significant trends in O3 depletion in the poles in their local Spring, and little or no significant depletion in Summer in midlatitudes.

By: David Stockwell

David Stockwell — Wed, 08 Mar 2006 18:01:34 +0000

When Hughes was asked whether the 20th century disconnect means that tree proxies can’t be relied on, and Hughes said “That’s the third explanation that I wasn’t going to discuss”, what did he say after that? Was that it?