<i>So all we need to do in order to follow these stations, is filter out those in the northern hemisphere and re-run the job.</i><p>Isn't this the same sort of thing that the tree ring people did?  There were some statistical points that looked like they were going to mess with the results so they threw them out?  They only threw out a few outliers, which is standard practice, but here we're throwing out a whole class of data.<p>It's also interesting that the northern hemisphere is warming up faster (if the methodology chosen by the author is correct).  Since most of the earth's landmass is on the northern hemisphere (as well as most of the developed countries), doesn't that mean we're in trouble?<p><i>By looking at each station indiviually instead of compressing them to an unevenly weighted average, we will be able to clearly deduce how the weather has changed through the years recorded.</i><p>This still doesn't take into account the density of stations.  Also, trying to compare stations like that, with the curves obscuring each other, is a crime of presentation.  If you took the time to do a regression on the datapoints with the other data, it surely would not have took much longer to code for regression on each of the individual weather stations (incorrect as that may be).<p>On a different note, the use of clojure was enjoyable, which deserves an upmod.