Albert Parker doesn’t want (you) to believe that the rise in sea-level is accelerating (spoiler – it is) so he hides it. In a post at WUWT, he shows maps of trends in sea-level for the period 1900-1975 and 1900 to 2014. He argues that the trends are very similar for both periods, and hence that there is no acceleration in sea level rise.
Fairly obviously, the two time periods overlap to a large extent so they are forced to share the same trend. This will make it very difficult to detect any change in trend between the two maps. If the trend in sea-level had been constant for the period 1900-1975 and then doubled for the period 1976-2014, the trend for the entire time period would only have gone up by a third. Even this large acceleration would be difficult to spot by eye.
A more honest approach would have been to compare (wait for it) the 1900-1975 trend with the 1976-2014 trend.
Compare these trends with the trends for 1900-2014. Many records report higher trends – look for example at Bergen – evidence of the acceleration that Parker is so desperate to hide.
Of course, if you really want to test for acceleration, you have to download and analyse the data.