Abstract The observed increases in temperature and sea level are clearly driven by climate change, and these trends are projected to accelerate in the future. The ocean surface wave characteristics are projected to change depending on the climatic elements. However, the historical trends of the global ocean wave climate have not been accurately assessed owing to the limited duration (primarily starting from the 1980s) and insufficient number of wave observations. Previous numerical studies on the global wave climate using reanalysis data have focused on the period starting from the 1980s. To better understand long‐term global wave climate trends, this study conducted a global ocean wave hindcast using the latest atmospheric reanalysis and an unstructured grid wave model over an extended timeframe from 1948 to 2022. The global wave hindcast was validated using satellites, in situ observations, and another reanalysis. The trends of wave heights within the first (1948–1984) and latter (1985–2022) halves exhibit opposing patterns over the North Pacific, resulting in no overall trend across the entire period, which indicates large multidecadal variability. Positive trends in wave heights in the Southern Ocean are evident, with a slowdown in the latter half of the period. These wave climate trends are supported by trends in atmospheric circulation patterns. The estimated trends in the Northern Hemisphere are not consistent with previous future projections. Addressing the discrepancies between historical trends and future projections is important for increasing confidence in climate projections.
Shimura et al. (Mon,) studied this question.