date: Mon, 5 Mar 2001 13:51:29 -0800 from: Chick Keller subject: Quick question to: k.briffa@uea.ac.uk Keith, I'm reading reprints Phil Jones sent me. One of them by you, "Trees Tell of past climates: but are they speaking less clearly today?, Phil. Trans. R. Soc. Lond. 1998, 65-73. Two things--you argue persuasively that "standardization" problems severely degrade our ability to infer low freq. trends from tree rings (even with improvements such as RCS and even though density seems less affected than TRW. But you conclude, it doesn't matter, we can rely on the tree rings anyway?? At least that's how the article comes across. Do you base this on comparisons with other proxy data? Second, to show how new I am to all this, I can't follow the reasoning about Possible long-term anthropogenic changes in tree growth. Figure 6 compares instrumental data (1880-1990+), with Proxy density and width curves in which the proxy temperatures diverge (go lower) from the instrumental curve after 1960. You go on to say that this might be due to increased growth due to CO2 or some combinations of factors (similarly on p. 101, Briffa, Annual climate variability in Holocene, Quaternary Sci Rev, 19 (2000). But I'm now in the dark because figure 6 seems to show that the effect has tree rings being narrower for a given temp after 1960 (because the temperature from these curves isn't increasing as much as the instrumental record), but Fig 7 seems to show them wider???? then figure 8 seems to be showing them stable or getting smaller after 1950. (although you don't define BAI I inferred it to be area increments at the base of the tree due to tree ring growth (using area to minimize ring width dependence on diameter). Now if increased CO2 and other fertilizers are at work, ring width should increase, but I can't make Figure 6 work then. Also despite the increases shown in Fig 7 and 8, they seem to have no effect in Fig 6 prior to 1960??? Sorry to be so opaque. Regards, Chick Charles. "Chick" F. Keller, IGPP.SIO.UCSD - Attn: Chick Keller 9500 Gilman Drive La Jolla, CA 92093-0225 (858) 822-1510 office (858) 456-9002 home Is the noticeable increase in surfers off Scripps Beach a possible indication of global warming?