> There are many global > temperature records. > [such as] borehole records.
Thanks for reminding me of borehold records. Tamino recently had an interesting post on them: http://tamino.wordpress.com/2007/05/20/notes-from-underground/#more-259 They are indeed a beautiful measure, because they naturally provide a long term average and they circumvent the fact that satellite/balloon data are very recent and even the longest surface series only goes back some 300 years. Not that they are without problems, but my feeling is that borehole data must be the critical piece of evidence for constraining the pre 1940 rise to above 0.2C, and below 0.6C (and therefore the overall range to 0.7 +/- 0.2C). They kind of had slipped my mind when I wrote the post. I've got a question though: http://www.geo.lsa.umich.edu/climate/core.html http://www.globalwarmingart.com/wiki/Image:Global_Warming_Map_jpg The graph presented comparing borehole data with surface data suggests an extremely good fit of surface station data and borehole data. What I wonder is how you can actually calculate a global average from boreholes with such a low visually claimed uncertainty (+/- standard deviation indicated in pink)), when borehole coverage is so spotty (for starters, there aren't any in the oceans, for obvious reasons)? Looking at the map for coverage, Greenland isn't covered at all, North Africa with 1 single borehole. In South America there are 4 boreholes for Peru, a little over 10 for Brazil and none for the rest of the continent. North of 60 degrees latitude there are 6 boreholes in North America and something like 5-10 for Siberia and there are none north of 70 degrees. There are some heavy concentrations (England, the Urals) with many boreholes, but 90% of the land area is either not covered at all, or covered with a coverage of 5-10 boreholes per USA size land block. And a spot check of some of those stations shows vastly different trends, eg look at Canada North of 60 degrees. The first station in the list North of 60 degrees is http://www.geo.lsa.umich.edu/climate/RECONSTRUCTION/CA-066-0.html And it gives a downward drop of 2.5C. The next one http://www.geo.lsa.umich.edu/climate/RECONSTRUCTION/CA-289-1.html gives a 1.5C increase with virtuall all the increase affter 1900. And the next one http://www.geo.lsa.umich.edu/climate/RECONSTRUCTION/CA-289-2.html gives 1C, but with virtually all the increase before 1900. And the fourth borehole gives http://www.geo.lsa.umich.edu/climate/RECONSTRUCTION/CA-289-4.html 3C, with virtually all the increase before 1800. How can one extract something useful out of that? I mean how do you convert these 6 completely different temperature graphs for Canada North of 60 degrees latitude into some measure of average temperature trend for that region? And it's not as if the difference between a downward trend of 2.5C and an upward trend of 3C for that region didn't matter for the global average. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. Posts will be admitted to the list if and only if any moderator finds the submission to be constructive and/or interesting, on topic, and not gratuitously rude. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/globalchange -~----------~----~----~----~------~----~------~--~---
