Removing linear trend, as suggested in comments, it is almost a one-liner:

    data=Import["https://pastebin.com/raw/aWYk1Jba"];
    lm=LinearModelFit[data,x,x];
    ListLinePlot[Transpose[{data[[All,1]],lm["FitResiduals"]}],
    PlotLabel->lm["BestFit"],PlotTheme->"Detailed"]

[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/UZhs9.jpg