Have reprocessed the data from yesterday, and graphed it.
Africa has some problems with station counts – there are none producing daily data in the 1950s or the early 1970s. I believe this might be different in the monthly GHCN dataset, but I’ve been using the GSOD figures instead – another strand to check. The station counts are shown below:
As a result, I’ve had to trim the data somewhat. 1956 and 1968 show major differences from the adjacent years, so are too volatile to include, and most of the other removed years have at most a dozen stations. There are some differences in station placement from the 1957-1967 series to the post-1973 one, but the latter seems quite stable:
All in all, I’d say this doesn’t show any particular trend in station placement in Africa w.r.t the ocean.
In Europe, we have:
which is a rather different story. The station counts are good for the entire period, and – aside from some difficulties immediately after WW2 – stations seem to have moved significantly closer to the water. Something like 100km/20% closer to the ocean between the early 1960s and the mid/late 1970s, and stable ever since.