From: mann@snow.geo.umass.edu To: p.jones@uea.ac.uk Subject: Re: Straight to the Point Date: Thu, 6 May 1999 13:09:36 -0400 (EDT) Cc: k.briffa@uea.ac.uk, mhughes@ltrr.arizona.edu, rbradley@geo.umass.edu, t.osborn@uea.ac.uk Hi Phil, SOrry that you have taken such a negative spin from this. I had hoped it was all resolved pretty amicably, and emphasized to Keith and Tim that I was being perhaps overly picky this time PRECISELY to avoid the misunderstanding that happened last time around w/ Science. Trust that I'm certainly on board w/ you that we're all working towards a common goal. That is what is distressing about commentarys (yours from last year, and potentially, without us having had approprimate input, Keith and Tim's now) that appear to "divide and conquer". The skeptics happily took your commentary last year as reason to doubt our results! In fact, your piece was references in several commentaries (mostly on the WEB, not published) attacking our work. So THAT is what this is all about. It is in the NAME of the common effort we're all engaged in, that I have voiced concerns about language and details in this latest commentary--so as to avoid precisely that scenario. Please understand the above to be a complete and honest statement about the source of my concerns. It really doesn't have anything to do about who did what first, etc. I trust that history will give us all proper credit for what we're doing here. The millennial-scale trend issue appears to be a source of contention. Malcolm can address the replication issue better than any of us--it's not a problem w/ our reconstruction. Furthermore, WE HAVE EXPLICITLY TAKEN INTO ACCOUNT THE LOSS OF LOW-FREQUENCY VARIANCE IN OUR ESTIMATES OF UNCERTAINTY. I don't know how many times I need to stress this. It is of fundamental importance in framing our conclusions. Our own analysis convinces me that things are already quite uncertain a millennium back in time. With regard to longer timescale variations, the evidence is all over the place. At EGS I saw some convincing evidence that many new paleo proxies indicate steadily decline at least over several millennia, and so do, in large part, the available long borehole estimates (though we should all take that w/ a good dose of NaCl). So I'm skeptical of estimates more than a millennium back in time until we have multiple proxies we can trust at that timescale, and can verify somehow the DC component of the estimates, or at least replicate them. This was my concern about the latest 2000 year recon that was shown. You are right, the Milankovitch forcing argument is ONLY A NULL HYPOTHESIS. I hope I haven't argued anything more than that. That our millennial scale trend, which we reasonably trust, and have some idea of the uncertainties in, is in line w/ that null hypothesis is information that cannot be ignored. That Kutzbach, Berger, and others are showing increasingly convincing model integrations over several millennia suggesting this, is more evidence. In the real word, anything *could* have happened. But lets not loose site of the appropriate null hypothesis here. I hope the above clears things up somewhat. I'm sorry things have been construed in more negative light than I had ever intended. Call me anytime to discuss, here at the office (not sure how well our schedules overlap though). Thanks, and sorry for the miscommunication here, mike _______________________________________________________________________ Michael E. Mann ________Current_____________________________Starting Fall 1999_________ Adjunct Assistant Professor | Assistant Professor Department of Geosciences | Dept. of Environmental Sciences Morrill Science Center | Clark Hall University of Massachusetts | University of Virginia Amherst, MA 01003 | Charlottesville, VA 22903 _________________________________|_____________________________________ e-mail: mann@geo.umass.edu; memann@titan.oit.umass.edu (attachments) Phone: (413) 545-9573 FAX: (413) 545-1200 http://www.geo.umass.edu/climate/mike