  Computation of propagation effects in the neutral atmosphere, namely path
delay, extinction, and bending angle is a trivial task provided the 4D state of
the atmosphere is known. Unfortunately, the mixing ratio of water vapor is
highly variable and it cannot be deduced from surface measurements. That fact
led to a paradigm that considers path delay and extinction in the atmosphere as
a~priori unknown quantities that have to be evaluated from the radio astronomy
data themselves. Development of our ability to model the atmosphere and to
digest humongous outputs of these models that took place over the course of the
21st century changed the game. Using the publicly available output of
operational numerical weather model GEOS run by NASA, we are in a position to
compute path delay through the neutral atmosphere for any station and for any
epoch from 1979 through now with accuracy of 45 ps * cosec elevation. We are in
a position to compute extinction with accuracy better than 10 pro cents. We are
in a position to do it routinely, in a similar way how we update apparent star
positions for precession and nutation. Moreover, we are in a position to do it
now. As a demonstration of current capabilities, I have computed time series of
path delays for all radiotelecopes that I was aware of (220 sites) since 1979
with a step 3-6 hours. Results of the validation tests are presented. A new
paradigm of data analysis assumes that we know the atmosphere propagation
effects a priori with the accuracy higher that one could deduce them from radio
astronomy observations.

Instrumentation and Methods for Astrophysics