Sure, but it doesn’t matter. Confounding means that there’s an uncontrollable factor in the analysis. You can’t just assume that the uncontrollable factor is the same over all measurements in the dataset.
Just to illustrate the point, the trend you’re describing (which you haven’t correctly described, but I digress) could be due to warming, or it could be due to selection in favor of earlier blooming varieties in the last generation. You can’t know which explanation is true, so you can’t draw conclusions.
Just to illustrate the point, the trend you’re describing (which you haven’t correctly described, but I digress) could be due to warming, or it could be due to selection in favor of earlier blooming varieties in the last generation. You can’t know which explanation is true, so you can’t draw conclusions.