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. (C) 2015 Elsevier Ltd. All rights reserved.