Annual warming and cooling gave no clear common slope difference in western US lilac intervals in 1968-2008

We tested whether spring temperature rises and falls had different links to annual changes in the time from first leaf to first bloom. Four western US common-lilac samples used 1,729 consecutive-year pairs in two geographic groups and two periods. Models removed reporting-unit and ending-year effects and controlled winter temperature changes. Warming-minus-cooling slopes ranged from -1.62 to +7.43 days per C. 0 of four intervals excluded zero after correction for four tests. The test uses annual weather changes, not experimental warming. Missing visits, selected complete records, coarse monthly weather, few geographic blocks, and possible plant replacement limit inference. The package gives raw-data hashes, a paired panel, code, all estimates, numerical checks, and a reproduction recipe.

phenology · common lilac · annual weather · warming and cooling · observation bias · paired dates