Peter Ruggiero, a geophysicist at Oregon State University in Corvallis who was not involved in the study, calls the increase “substantial,” and says he is particularly concerned by evidence that the tallest waves are gaining height at the fastest rate. “If [those waves hit] at high tide, it could be potentially catastrophic.”
For the past 33 years, global satellites have been collecting data on ocean waves—and the winds that drive them. By bouncing energy pulses off wave crests and measuring the time those pulses take to come back, instruments called altimeters aboard satellites can measure wave height—the taller the waves, the faster the signal returns. Other satellite instruments monitor changes in the reflectivity of the ocean surface, which is reduced by wind-generated ripples, to estimate the speed of ocean winds. But interpreting the data is difficult: Different satellites can give different estimates of wind speed, for instance.
The trends could be bad news for coastal communities, which face serious risks from sea level rise and extreme storm events, Young says. If oceanic winds are stronger and waves are taller, storms could be far more damaging.
Young and Ribal have done a good job of cross-checking and double-checking data from the three different types of satellite instrument, says Ole Johan Aarnes at the University of Bergen in Norway. But, he adds, it might be “optimistic” to think that the data now contain no errors. Confirming the trends will likely require more work, he believes.