Warm extreme months showed no clear six-month directional SST difference in detrended ERSSTv5 from 60 S to 60 N for 1982-2025

We tested whether SST six months after an extreme warm month differed from SST six months before it. We used 7,877 ERSSTv5 ocean cells from 60 S to 60 N in 1982-2025, with minimum SST above -1 C. We removed a separate linear year trend for each calendar month and cell. The area-pooled warm-tail difference was -0.0030 C. Its conditional 95% five-year block interval was -0.0430 to 0.0401 C. An interval with trends and tail thresholds fitted again was -0.0340 to 0.0298 C. Cold-tail and warm-minus-cold intervals also included zero. Planned lag, trend, region and block checks gave no clear warm-tail balance. This null result does not show equal onset and recovery rates. The statistic selects extreme months rather than event peaks. A short dependent record, one coarse reconstruction, spatial cancellation and conditional uncertainty limit inference. Code, source hashes, annual aggregate evidence, all main resampling draws and numerical checks support reproduction.

SST extremes · time reversal · ERSSTv5 · recovery · block bootstrap · null result