There are also “interrupted” forms of the Mollweide that slit the N and S halves of the map along selected latitudes to reduce distortion of the continents.

The top two equirectangular projections are Mercator-like in that they enlarge areas in high latitudes, but are not true Mercator, in that they only stretch distances horizontally and not vertically as well.

The Lambert Cylindrical Equal Area projection I had suggested in #22 above compresses distances vertically in order to make up for the horizontal stretching, while preserving NS and EW directions. A 2:1 aspect ratio, as suggested on CA by John Bell, then gives the same average detail as the equirectangular, while eliminating shape distortions at 40.08° N and S. See comment 107 of the earlier post.

But the Mollweide or interrupted Mollweide are equally good from an equal-area point of view. They distort NS directions, but nicely invoke the sphericality of the earth.

have a look at the side bar. Steve has posted code and data and a learning/training page.

Why not break out of the Hellenistic era and into the 2nd millenium, by using the far more advanced equal area cylindrical or azimuthal polar projections of Lambert of Alsace??

I can think of two reasons,

a) they’ve always used these projections and don’t understand the problem (although given Jeff K’s comments this seems unlikely)

b) it suits them just fine to have the distortions, ie big red Siberia, big white Greenland icecap etc because it puts across a ‘message’ to the unaware

c) I guess Steve will snip this because of b

David, I did an analysis of the anomaly differences between the UAH/RSS satellite and GISS surface (land and ocean) data sets for the period 1998-2007 on another thread here at CA (along with more extensive analysis in the 1979-2007 period). I did it on an annual basis and thus did not include 2008. What I am not certain from viewing your graph is whether you are subtracting the average of the surface records from the satellite ones.

I think these more recent time descrepancies are important, since, while UAH and RSS differ over the long term trends from 19979-2007, in recent times (1998-2007) the re-nornmalized trends for UAH and RSS correlate very closely. If indeed the satellite MSU measurements are independent of the surface ones, as I have tentatively concluded, then I think these recent differences with the surface records deserve some detailed analyses.

If you want to look at the whole globe at the same time, you have to sacrifice something – data or geography *has* to be distorted.

Why not simply have two globes side by side and make the second the part that’s hidden by the first? Then everything is present at all times and while the material around the edges would be distorted, you can move whatever point you want to the center.

There appears to be a shift circa March of 2008. Or, maybe not – perhaps it is random movement. A global map comparing the satellite vs surface difference for March thru October 2008 versus the same period in 2007 would be interesting.

I guess, if you want to project global data with the most geographic accuracy, IMO, you need three displays; Lat/Lon, North Polar Stereographic and South Polar Stereographic.

Rectangular and Polar projections are fine, but why cling, like Hansen of NASA/GISS, to the equirectangular lat/lon projection of Marinus or Tyre, or to the Stereographic polar projection of Hyparchus of Nicaea? Why not break out of the Hellenistic era and into the 2nd millenium, by using the far more advanced equal area cylindrical or azimuthal polar projections of Lambert of Alsace??

See comment 107 of the CA equal area projection thread for the Lambert Cylindrical equal area projection (adjusted to a 2:1 aspect ratio in the middle image), and comment 43 of the same thread for the Lambert Az equal area projection (albeit from an interesting whole earth equatoral rather than hemispheric polar viewpoint).

– Hu of Ohio State