The Hockey Stick is Bad Science

The hockey stick which started out in the earlier cited MBH98 citation (see Round 1) was predicated on the idea of extending the surface temperature record back beyond the current instrumental record which, at best is only about 150 years. The use of “proxy” data is what MBH and others over the past years have used to achieve this task. Proxies are merely items that contain some aspect that relates to some other physical attribute. Proxies are quite commonly used in all manner of paleoenvironmental and geochemical studies and are in no way controversial. The proxies in question for the hockeystick were chosen as temperature or climate proxies. Climate proxies include things like tree rings, corals, ice cores, lake sediment cores, speleothems, etc. Since the original MBH98 citation there have been numerous additional studies each of which shows the now famous “hockey stick” pattern as Roy described. A 2008 study by Mann et al. expanded the number of proxies to about 9 different types of temperature proxy [1]. Since the use of proxies is extremely common in paleoenvironmental analyses we cannot fault the reliance on proxies for the development of the hockey stick. If the choice of proxy is problematic then we must know exactly why this is the case. If there is objection to tree ring proxies then why do speleothems (cave formations) [2] show a hockey stick shape to the data? Why do glacier measurements show a hockey stick shape?[3] Why do borehole analyses [4] show a hockey stick shape? Why would coral or ice core paleoclimate proxies show a hockeystick shape? It is quite difficult to imagine how so many disparate techniques can show the same general trends and yet one or two are “controversial”. As for Pro’s contentions: “What's contested is whether it is entirely anthropogenic and has an exponential character as he Hockey Stick purported to show.” This is a mischaracterization. No serious climate scientist thinks climate change is solely due to anthropogenic factors as even a cursory examination of the IPCC report will show [5]. Natural forcings are explicitly considered and factored into the calculations. Many of these are actually positive forcings as well. The second contention: “ The Hockey Stick also made The Little Ice Age and the Medieval Warm Perid disappear. ..” Is also problematic. The MWP and LIA are known to be real and if they show up as less than Pro would prefer that is only due to how the data lined up. (The MWP is still under debate as to it’s geographic extent.) If Pro wishes to bring this point into the debate it will have to be in the context of the original debate. He will have to show that the relative temperature change due to the MWP compared to modern temperature increase is due to “bad science”. As such Pro bears the burden of showing the error in the science . SOURCES: Mann, M.E., Zhang, Z., Hughes, M.K., Bradley, R.S., Miller, S.K.,Rutherford, S., Ni, F., Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia , Proceedings of the National Academy of Sciences Vol. 105, No. 36, pp. 13252-13257, September 9, 2008. Smith, C.L, Baker, A., Fairchild, I.J., Frisia, S., Barsato, A., 2006, Reconstructing hemispheric-scale climates from multiple stalagmite records. International Journal of Climatology Vol. 26, Issue 10, pp. 1417 – 1424 Oerlemans, J., 2005, Extracting a Climate Signal from 169 Glacier Records, Science 29 April 2005: Vol. 308 no. 5722 pp. 675-677 Huang, S., Pollack H., Shen, P-O, 2000, Temperature trends over the past five centuries reconstructed from borehole temperatures, Nature, v 403 p 756 http://www.ipcc.ch...