Divergence Problem

For the problem of divergences in quantum field theory, see Renormalization.

In climate science, the divergence problem is the apparent disagreement between the temperatures measured by the thermometers (instrumental temperatures) on one side and the temperatures reconstructed from the width of tree rings on the other side.

While the thermometers indicate a rather substantial warming trend, the tree rings don't seem to display the expected corresponding changes in their width. In other words, the temperature extracted from the tree rings doesn't seem to show any substantial warming.

The temperature graphs calculated in these two ways "diverge" from one another, especially since the 1950s, which is the origin of the term.