1. The use of the Penman‐Monteith PE, instead of the
Thornthwaite PE, in the Palmer model only has small effects
on actual evapotranspiration and thus the resultant PDSI, and
it only slightly reduces the widespread drying represented by
the PDSI during recent decades over global land. This result
confirms the finding of van der Schrier et al. [2011], who
found that the sc_PDSI does not change a lot when either
PE_th or PE_pm was used because of the insensitivity of the
CAFEC precipitation (equation (2)) to PE. I realize that large
uncertainties exist in historical data for surface net radiation,
wind speed, and humidity needed for computing the Penman‐
Monteith PE, and further work is needed to improve the