Sycamores Puzzle Laura

Tree mysteries aren't resolved this year.  Some of the sycamores are already leafing out, mostly the grey trunked ones but also a few of the white trunked ones.  But they all still have some of their brown leaves stuck on the branches, stars high in the treetops.  So the game is over and neither the whites nor the greys won.  And furthermore, the strong generalization from last spring, that all the grey trunked ones leafed out first, followed two weeks later by the whites, has broken down.  Is it global warming?  Or simply an unjustified conclusion from a one-of test last year?  I'm frustrated, but the trees sit serenely on the boulevard, not bothered at all.