Two L2SWBM releases gave no clear rise in June-September evaporation share at two Great Lakes from 1950-1986 to 1987-2022

We tested whether June-September net evaporation took a larger share of annual net evaporation in 1987-2022 than in 1950-1986. We used monthly L2SWBM medians for Superior and Michigan-Huron from two releases on the same 73 years. In v3.0, share changes were -1.12 and -1.20 percentage points. Their conditional 97.5% five-year block intervals included zero. In v2023.2, changes were -3.09 points for Superior (-5.66 to -0.64) and -2.17 points for Michigan-Huron (-4.94 to 0.27). Thus, neither release supported the proposed rise. The revision changed the Superior contrast by -1.97 points, mainly through larger early-period summer estimates. The newer Superior decrease held in all planned checks. These are tests of reconstructed medians, not direct flux measurements. Model-run boundaries, related source inputs, short records and uncertainty outside the conditional intervals limit physical interpretation. The result does not refute warming or earlier findings for shorter periods. We provide exact inputs and hashes, paired resamples, all checks, code, a figure and offline audit results.

Great Lakes · evaporation · seasonal change · data revision · L2SWBM · null result