  Maunakea is one of the world's primary sites for astronomical observing, with
multiple telescopes operating over sub-millimeter to optical wavelengths. With
its summit higher than 4200 meters above sea level, Maunakea is an ideal
location for astronomy with an historically dry, stable climate and minimal
turbulence above the summit. Under a changing climate, however, we ask how the
(above-) summit conditions may have evolved in recent decades since the site
was first selected as an observatory location, and how future-proof the site
might be to continued change. We use data from a range of sources, including
in-situ meteorological observations, radiosonde profiles, and numerical
reanalyses to construct a climatology at Maunakea over the previous 40 years.
We are interested in both the meteorological conditions (e.g., wind speed and
humidity), and the image quality (e.g., seeing). We find that meteorological
conditions were, in general, relatively stable over the period with few
statistically significant trends and with quasi-cyclical inter-annual
variability in astronomically significant parameters such as temperature and
precipitable water vapour. We do, however, find that maximum wind speeds have
increased over the past decades, with the frequency of wind speeds above
15~m~s$^{-1}$ increasing in frequency by 1--2%, which may have a significant
impact on ground-layer turbulence. Importantly, we find that the Fried
parameter has not changed in the last 40 years, suggesting there has not been
an increase in optical turbulence strength above the summit. Ultimately, more
data and data sources-including profiling instruments-are needed at the site to
ensure continued monitoring into the future and to detect changes in the summit
climate.
