Winter NAO rainfall slope changes were not resolved in three British countries in 1951-2025

We tested a linear change with year in the link between winter North Atlantic Oscillation (NAO) and log rainfall. We used 75 winters from Met Office country rainfall and NOAA CPC NAO. The slope changes per decade were -0.0051 in England, -0.0109 in Wales and -0.0085 in Scotland. Joint 95% five-winter residual block intervals were -0.0524 to 0.0422, -0.0588 to 0.0370 and -0.0389 to 0.0218. Each interval includes zero. Changing the block length or adding squared NAO did not resolve a change. Raw rainfall gave small positive point estimates with wide intervals. The result does not prove a constant link. It gives a joint uncertainty check on a common assumption in simple circulation adjustments. One rainfall product, country averages, revised data, a linear change model and stationary residual assumptions limit the result. The package includes source records, numeric inputs, code, draws, an independent audit and a figure.

winter rainfall · NAO · changing sensitivity · block bootstrap · null result