Land Use - Land Amplification and General Data Confusion

The land and ocean instrumental temperature data is a measure of something with a mean error of about +/- 0.125 C degrees.  If all the data where measured in exactly the same way, that data would be a uniform measure of whatever it is measuring.  When you mix methods you begin to add a different kind of uncertainty that is not included in the standard published error.  Part of the problem with "Global" land and ocean data is that land is measured with a (Tmax +Tmin)/2 average where Tmax and Tmin have different influences.  Oceans are measured as a simple average of spot readings at a location that has less variability or noise.  You have apples and oranges if you can't tease out the "other" factors that are being measured.

With all the issues each of the data sets have it is hard to "convincingly" illustrate that there is an "other" influence that is not properly considered.  This is an example of land use changes and their impact on northern hemisphere land "surface" temperatures.  Land use, mainly mechanized farming and snow removal impact the land hydrological cycle.  CDIAC has estimates of land use impact on the carbon dioxide cycle that are far from perfect but useful to show how land use may have have a larger than anticipated impact on land surface temperature measurement.  There may be less "real" impact on land surface temperature, but ther appears to be a significant impact on the measurement of land surface temperature at least.

So how well can models be performing if they cannot find simple anomalies like land use impact.

Note:  The 15 year lag is an indication that land drying and general deterioration over time has the more significant impact.