  A recent study has suggested a link between the surface level diurnal
temperature range (DTR) and variations in the cosmic ray (CR) flux. As the DTR
is an effective proxy for cloud cover, this result supports the notion that
widespread cloud changes may be induced by the CR flux. If confirmed, this
would have significant implications for our understanding of natural climate
forcings. Here, we perform a detailed investigation of the relationships
between DTR and solar activity (total solar irradiance and the CR flux) from
more than 60 years of NCEP/NCAR reanalysis data and observations from
meteorological station data. We find no statistically significant evidence to
suggest that the DTR is connected to either long-term solar periodicities (11
or 1.68 year) or short-term (daily-timescale) fluctuations in solar activity,
and we attribute previous reports on the contrary to an incorrect estimation of
the statistical significance of the data. If a CR-DTR relationship exists,
based on the estimated noise in DTR composites during Forbush decrease (FD)
events, the DTR response would need to be larger than 0.03{\deg}C per 1%
increase in the CR flux to be reliably detected. Compared with a much smaller
rough estimate of -0.005{\deg}C per 1% increase in the CR flux expected if
previous claims that FD events cause reductions in the cloud cover are valid,
we conclude it is not possible to detect a solar related responses in
station-based or reanalysis-based DTR datasets related to a hypothesized
CR-cloud link, as potential signals would be drowned in noise.
