File talk:Mauna Loa Carbon Dioxide-en.svg

Old discussion

Wikipedia:Don't draw misleading graphs. I believe the Y origin of this graph should be at 0 in order to accurately represent the slope. Currently the Y origin is placed just below the low point of the data, sensationalizing the trend. Tempshill (talk) 19:41, 20 June 2008 (UTC)

I see your point, but I disagree. You can not really "accurately represent the slope", because it depends on the dimensions of the plot, which are arbitrary. If the same units were used on the X and Y-axis, then the slope would be accurately represented if the same length (on the graph) was used for one unit on both axis (note also that this would not depend on whether the Y origin is at 0 or not !). Here, I don't see any way to favour one representation of the slope over another. But what you really mean, I guess, is that the current Y origin prevents us from accurately comparing the increase over the years with the actual baseline. I have tried to make a similar graph, with the Y origin at 0, but it consists almost only of white space, and it becomes difficult to see the seasonal trend in the data (or the graph should be made much larger to compensate for the loss of detail). I side with Edward Tufte on this one: it would be nice to have the Y origin at 0, but using all the space to display the data instead of emptyness is more important. Also, this is just pure speculation on my part, but I have no idea if "0" is really the baseline here: it may be the case as temperature charts (in a hospital) which never start at O degrees (K, F or C) because it is an unrealistic value. Schutz (talk) 12:34, 31 July 2008 (UTC)

0 is the baseline here, just as 0K is a temperature baseline —Preceding unsigned comment added by 74.197.176.46 (talk) 02:30, 10 January 2010 (UTC)

You're right about 0 being an unrealistic value, but the graph currently tells the viewer, with the slope, that CO2 levels are up over 1000 percent, which is untrue. Tempshill (talk) 21:27, 1 April 2010 (UTC)

The baseline is hard to decide upon because back when the curve hadn't started yet it was still very hard to measure carbonic acid concentrations correctly, but a reasonable ballpark figure is 290 ppm, courtesy Callendar. The vertical axis should really contain a sawtooth to signify that it isn't zero based. —Preceding unsigned comment added by 82.139.87.57 (talk) 17:33, 8 April 2010 (UTC)

Update

Current data is available here, if someone has the drawing tool to update the graph:

• ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_mlo.txt

--Pjacobi (talk) 10:41, 11 May 2013 (UTC)