evidence: Global average sea level has risen throughout the 20th century and continues to rise at an accelerating rate. Sea level rise primarily results from glacial ice melting and the expansion of seawater as it warms. Scientists do not arbitrarily adjust sea level data, but instead compare sea level measurements to stable benchmarks to generate accurate estimates of sea level change over time. [...] Misleading: The claim that scientists were caught "adjusting" sea level data misrepresents the process scientists use to account for potential errors in historical sea level data. [...] The claim that "scientists were caught ‘adjusting’ sea level data to create false impression of rising oceans" misrepresents approaches used by scientists to account for potential errors in historical sea level data. Instruments used to measure sea level, called tide gauges, may be replaced or moved to new locations over time. To calculate actual changes in sea level despite movements of the tide gauges, sea level data is compared to a stable benchmark at each sampling site. The process of adjusting data based on benchmarks is not arbitrary, as Thomas Frederikse explains in the reviewer comments below.