Abstract: Assessments of global wave power have been receiving increasing attention currently; however, a
characterization of the global resources that holistically consider the different temporal scales that influence
wave climate (monthly and seasonal, interannual and long-term) is still lacking. Moreover, the
debate around the global figure of available resource is still widely open. This study provides a new global
wave power assessment using a dataset that covers the period from 1948 to 2008, which was corrected
using altimetry data and validated with buoys in terms of wave power. This study characterizes the mean
wave power globally as well as its monthly and seasonal variability. Furthermore, it provides a link with
the most relevant climate indices globally. The effect of the interannual variability is especially noteworthy
for the Northern Hemisphere, where the seasonality is strongest. Additionally, we detect decadal
long-term changes and determine that natural variability could explain a few of the differences found
between decades. Lastly, we provide an assessment of the global theoretical wave power that covers
the last six decades, compare approaches and estimates, and discuss factors of discrepancy. The global
offshore wave power is estimated at 32,000 TW h/yr, which is reduced to 16,000 TW h/yr when considering
the direction of the energy. The historical average change is 580 TW h/decade. Our results indicate
that the global natural variability could be a more relevant factor in the lifetime of wave farms than
the historical long-term changes in wave energy.