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Index of Subjects Hi Dave, On 11-Jun-08, at 9:17 PM, David & Alison Webster wrote: > Hi Again, June 11, 2008 > Let me assure you that I know do something about reading graphs, > approaches that can be used to minimize noise in measurements and a > couple of other things. I've no at all doubt of this! > But it seems some printers are more equal than others and one or > both of us may be to some degree dealing with printer artifact. My > printout of methane, for whatever reason, was useless, which is why > I stuck with CO2. > > My graph is 93 mm/800,000 years or 8600 years/mm and where the > variates increase rapidly (i.e. the points of interest in this case) > the lines are as thin as 0.34 mm (measured by ocular micrometer at > 40X). > > But the precision of measuring an average offset, between a > printed line and a drawn line, is not constrained by the width of > either line provided the imaginary dimensionless ideal line is on > average in the middle of the printed and drawn lines and provided > care is taken to measure from the middle of one line to the middle > of the other. I think that trying to eke out conclusions from data that are at (or below) the minimal level of the graph's resolution is skating on very thin ice. One doesn't know the precision of the software program used to generate the graph in the first place (how accurately does it place the center of the imaginary dimensionless ideal line in generating the graph?) and different web browsers running on different computers under different operating systems will render this differently (i.e., 71.5 mm vs 93 mm) depending on screen resolution and other factors. This information will then be variably reproduced with different printers (ink jet, laser, etc.). Given this, I'm not convinced that it is possible to reliably make measurements that are at or below the threshold line width. Because the line is thicker than the imaginary dimensionless line doesn't mean there is any mathematical meaning (or precision) to this dimension. It's like trying to infer meaning from variations in a pencil track that are caused by irregularities in the carbon core of the pencil, or vibrations in the hand of the person drawing it, rather than by any actual changes in the values of the variables being plotted. > A brief search failed to locate that graph that we discussed several > years ago but I did find this commentary to the effect that warming > preceeds CO2 by about 800 years. > http://www.realclimate.org/index.php/archives/2004/12/co2-in-ice- > cores/ > > As noted previously this initial reversed order (first temp then > CO2) does not rule out a greenhouse effect that further increases > temperature by feedback. > > Qualitatively, the model that seems to fit is a warming that is > initiated by the solar cycle, a subsequent increase in CO2 & CH4 > that is caused by this warming (and based on Ruddiman, probably > even more warming due to greenhouse effect which of course generates > more of these gasses). Yt, DW You may well be correct, but I'm not sure that the graph supports this conclusion. Cheers! Chris Christopher Majka - Atlantic Canada Coleoptera http://www.chebucto.ns.ca/Environment/NHR/atlantic_coleoptera.html c.majka@ns.sympatico.ca
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