Current and next-summer warmth gave no clear nitrogen slope difference in four British butterfly samples in 1986-2011

We tested whether a summer-temperature, nitrogen-deposition and host-plant contrast in butterfly indices was specific to the current summer. Joint models included current and next-summer temperature. Four regional and time samples used 337,406 British site-species-year records in 1986-2011. All four current-minus-next-summer intervals included zero after correction for four tests. All eight sensitivity intervals also included zero. The later southern result had an unadjusted p value of 0.049, but did not persist after correction or removal of filled-in zero records. Fixed effects removed site-year, site-species and regional species-year differences. Source checks and an independent sparse regression check passed. The result does not establish equivalence or the absence of climate-pollution effects. Static deposition, coarse temperature, selected sites, uncertain traits and species-specific detection limit inference. Next-summer weather is an imperfect comparison for shared climate and spatial patterns. The package includes data, source hashes, code, covariance matrices, a figure and offline reproduction instructions.

butterflies · nitrogen deposition · temperature · temporal specificity · observation bias · negative control · null result