Background
Climate alarmists typically claim that global warming will lead to increases in all kinds of storms, and that these storms will also become more intense as temperatures rise. One unique way of evaluating these contentions would be to analyze ocean wave heights over the past century to see how closely their temporal variations match those of the mean global air temperature.

What was done
In a study that allows us to make this type of comparison, Gulev and Grigorieva used the Voluntary Observing Ship wave data of Worley et al. (2005) to characterize significant wave height (HS) over various ocean basins throughout all or parts of the 20th century.

What was learned
The two Russian scientists report that "the annual mean HS visual time series in the northeastern Atlantic and northeastern Pacific show a pronounced increase of wave height starting from 1950," which finding sounds pretty much like it vindicates climate-alarmist thought on the subject.  "However," as they continue, "for the period 1885-2002 there is no secular trend in HS in the Atlantic," and "the upward trend in the Pacific for this period ... becomes considerably weaker than for the period 1950-2002."

Gulev and Grigorieva also note that the highest annual HS in the Pacific during the first half of the century "is comparable with that for recent decades," and that "in the Atlantic it is even higher than during the last 5 decades."  In fact, in the Atlantic the mean HS of the entire decade of the 1920s is higher than that of any recent decade, and the mean HS of the last half of the 1940s is also higher than that of the last five years of the record.  In the Pacific it also looks like the mean HS from the late 1930s to the late 1940s may have been higher than that of the last decade of the record, although there is a data gap right in the middle of this period that precludes us from conclusively proving this latter point.

What it means
All things considered, it is clear that annual mean wave heights over the last decade of the 20th century, the warmth of which climate alarmists claim was unprecedented over the last two millennia, were not higher than those that occurred earlier in the century.  Hence, it is likely that storminess is no greater now either, as indeed can be verified by other independent data on our website (see Weather Extremes (Storms) and Wind in our Subject Index).

References
Worley, S.J., Woodruff, S.D., Reynolds, R.W., Lubker, S.J. and Lott, N.  2005.  ICOADS release 2.1 data and products.  International Journal of Climatology, in press.