One possible consequence of a change in climate over the past several decades is an increase in wave heights, potentially threatening coastal areas as well as the marine industry. But the difficulties in observing wave heights exacerbates a general problem of climate-change detection: inhomogeneities in long-term observational records owing to changes in the instruments or techniques used, which may cause artificial trends. Ground movements with periods of 4-16 seconds, known as microseisms, are associated with ocean waves and coastal surf, and have been recorded continuously since the early days of seismology. Here we use such a 40-year record of wintertime microseisms from Hamburg, Germany, to reconstruct the wave climate in the northeast Atlantic Ocean. For the period 1954-77, we detect an average of seven days per month with strong microseismic activity, without a significant trend. This number increases significantly in the second half of the record, reaching approximately 14 days of strong microseisms per month. The implied increase in northeast Atlantic wave height over the past 20 years parallels increased surface air temperatures and storminess in this region, suggesting a common forcing.

The Institute for Geophysics (IfG) at Hamburg University and the Research Center for Marine Geoscience (GEOMAR) of Kiel University have developed new, wideband ocean bottom seismic stations (OBS) for long‐term, deep‐sea deployments of up to 1 year. A first long‐term pilot experiment of these stations was conducted in the Tyrrhenian Sea north of Sicily, in‐cooperation with the first long‐term, deep‐sea test of the European Ocean Bottom Observatory GEOSTAR [Beranzoli et al., 2000] by Istituto Nazionale di Geofisica e Vulcanologia (INGV). The seismic data retrieved prove that the new OBSs are useful for seismological studies. A large number of tele‐seismic earthquakes have been recorded in good quality; waves originating from such events pass the mantle and crust below the network, and thus provide important constraints on their structure.

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