evidence: An alternative procedure to compute the sea-level acceleration from long-term-trend tide gauge records [...] The thermosteric effect attributed to global warming is responsible for the acceleration of the sea levels. This acceleration should be computed by clearing the tide gauge signal of the natural oscillations to avoid interpreting a part of a periodic movement as unprecedented sea-level change. This requires time series long enough to discover the longer periodicities and the amplitudes of the oscillations. Specific examples are given for the Fort Denison tide gauge record in Sydney, New South Wales, Australia, and Fremantle, Western Australia, Australia. Aggregate statistics are presented based on the tide gauge records hosted by the Permanent Service for Mean Sea Level (www.psmsl.org). Parabolic fitting of the raw and processed data with the removal of fitted sinusoids only converges in the acceleration estimate for record lengths of 110 + years. The revised procedure provides reliable estimations of the acceleration already with a record length of 90 + years. [...] Boretti, A. An alternative procedure to compute the sea-level acceleration from long-term-trend tide gauge records.