Here is an analysis from a data-driven organization dedicated to listing, understanding and reducing biases in science records. They have covered the National Climate Data Center data (which apparently GISS uses).
Edit: this discussion does focus on the U.S. network, where some of the articles you listed referred to data from Africa and South America, but assumedly the corrective techniques are similar.
Has that impacted OCW availability? I was noticing a lack of newer OCW material, but I have no data to substantiate that perception.