date: Mon, 05 Mar 2001 17:20:13 -0500 from: "Michael E. Mann" subject: Re: RSB Broecker response to: "Raymond S. Bradley" , mhughes@ltrr.arizona.edu, p.jones@uea.ac.uk, k.briffa@uea.ac.uk, tom@ocean.tamu.edu Ray, Do Pollack et al really say that in the 2000 article you cite (I don't have a copy)? If so, how do they rectify w/ the conclusion to the contrary expressed in Huang et al '97??? mike p.s. this is strongest either as a single authored piece (Ray only), or w/ *all* our names. In the latter case, I am happy to be on board... At 03:50 PM 3/5/01 -0500, Raymond S. Bradley wrote: >Here's what I propose to send to Science. I have just focused on a few >major points rather than trying to address all of the egregious errors & >distractions in his article. Join me if you wish...but I don't plan to >spend much more time on multiple iterations! I believe Scott Stine is >also writing a response (basically saying that what Broecker said about >his data is true, but irrelevant to the question he poses). >ray >____________________________________________________________________________ >__________________________________________ > >Paleoclimate reconstructions (1-4) using all available climate proxies >indicate that temperatures were warmer in Medieval times than during the >subsequent “Little Ice Age” (~1550-1850). But there is very little >evidence outside of Greenland and western Europe that temperatures in >Medieval times exceeded those of recent decades (5,6). All studies of >large scale climate variations reveal regions which do not follow the >global or hemispheric trend (e.g. 7) so selecting a few data points, as >Broecker does, (8) adds little to resolving the question he poses (“Was >the Medieval Warm Period Global?”). Furthermore, his claim that only >borehole temperatures and snowlines can reconstruct temperatures to within >0.5ºC is not supported in the literature. Reconstructing global >temperature requires a geographically extensive network of data, not just >a few points. Could you begin to appreciate the beauty and complexity of >a symphony by just listening to the percussion section of an >orchestra? Studies that have listened to all the “instruments” that are >currently available (1-4, 9,10) conclude that 20th century warming is >unprecedented in both rate and magnitude, compared to the last 1000 >years. This view may change as additional records become available, but >that is the state of play right now. >I could add: >Medieval climate was clearly unusual in some areas (cite Stine) and >further regional studies are needed; these may help to determine if >Broecker's hypothesis of a change in thermohaline circulation holds water. >[This may be too confusing an allusion for non-English Science readers!!] > >1. M. K. Hughes and H. F. Diaz, Clim. Change 26, 109 (1996). >2. P. D. Jones et al., The Holocene 8, 455 (1998). >3. Mann, M.E., et al., Geophys. Res. Lett. 26, 759 (1999). >4. T.J. Crowley and T.S. Lowery, Ambio 29, 51 (2000). >5. Dahl-Jenssen et al., Science, 282, 268 (1998). >6. Pfister, C. et al., The Holocene, 8, 535 (1998) >7. Jones, P.D. et al., Reviews of Geophysics, 37, 173 (1999). >8. Broecker, W.S., Science, 291, 1497 (2001). >9. K. Briffa et al., J. Geophys. Res., (2001) >10. Pollack, H.N. and S. Huang, Ann. Rev. Earth and Planet. Sci., 28, 339 >(2000). > > >Raymond S. Bradley >Professor and Head of Department >Department of Geosciences >University of Massachusetts >Amherst, MA 01003-5820 > >Tel: 413-545-2120 >Fax: 413-545-1200 >Climate System Research Center: 413-545-0659 >Climate System Research Center Web Page: > >Paleoclimatology Book Web Site (1999): >http://www.geo.umass.edu/climate/paleo/html > > > _______________________________________________________________________ Professor Michael E. Mann Department of Environmental Sciences, Clark Hall University of Virginia Charlottesville, VA 22903 _______________________________________________________________________ e-mail: mann@virginia.edu Phone: (804) 924-7770 FAX: (804) 982-2137 http://www.evsc.virginia.edu/faculty/people/mann.shtml