{
  "evidence_edition": "winter-experimental-1-20260924",
  "prebuild_attestation_sha256": "431c2d2b4bb5d79359caa7fa287825d1e23950a1a8cb59c3aaee5fa986ee020e",
  "source": {
    "attribution": "Source: Met Office Hadley Centre, www.metoffice.gov.uk/hadobs. Parker, D.E., T.P. Legg, and C.K. Folland (1992), A new daily Central England Temperature Series, 1772-1991, International Journal of Climatology 12, 317-342. Contains public sector information licensed under the Open Government Licence v2.0. CoryVu derived analysis; no endorsement implied.",
    "dataset": "HadCET daily mean and minimum regional temperature series",
    "document_hashes": {
      "hadcet-download.html": "14bacb273b290f535c47565091d5d1728e42eede231a6507748c2c1ab534a53e",
      "hadcet-format-0.html": "f660f73233fa4ebecb33121910a658592d2af2dafdf4e192f568ad77ac41836e",
      "hadcet-format-1.html": "09ec0cdcfb86f153bd917c469e1be0ac13378ccdfda310e91456c795d6e4760d",
      "hadcet-home.html": "aa659d386a08aea95919142ddc082bc25d57e23cdaabcd2d9074f396740e65e0",
      "hadcet-terms.html": "1feded3fa5d97b621aa234f3f6ec21be1cfbf0629b3d7da321593833420c4b6b",
      "ogl2.html": "f43b76732008f9cf9b51d6a8dc45db23289b784e79691e0de04cc08c51f6d9be"
    },
    "geography": "Central England regional index",
    "licence": "OGL-2.0",
    "limits": [
      "Regional, homogenised temperature indices, not every station or garden",
      "Below-zero regional-minimum days are not ground-frost counts",
      "Fixed December-February winters and 1961-1990 reference-ending years",
      "Reference is equally weighted winter means, not pooled baseline days",
      "Historical comparison, not a forecast or future probability",
      "No planting, heating, health, household-cost or safety recommendation",
      "Source precision 0.1 Celsius; exact zero is not counted below zero"
    ],
    "method_sha256": "3fb031d968a835ab8f0bfb45c8d13e0fbc9312c67585fa425bce49684d149e7f",
    "method_version": "winter-experimental-1",
    "publisher": "Met Office",
    "raw_hashes": {
      "mean.txt": "64fcd343f7ec5608d1b30321ecc8d51067e1df39857779ffdb489c06a10bf73e",
      "min.txt": "62461c1c724e79d28bfed2200ac5a1add80ff1d574d4f2f2df3c672b53c5a0da"
    },
    "units": "degrees Celsius; days with regional minimum index below zero",
    "version": "HadCET v2.1.1.0; 2026 provisional portion excluded"
  },
  "method": "Question: Did every Central England winter milder than its 1961-1990 winter average also have fewer air-frost days than the corresponding average? Frozen population: all complete December-February winters ending in 1879 through 2025 (December 1878-February 1879 through December 2024-February 2025). Reference winters end in 1961..1990, exactly 30. Source: HadCET daily mean and daily minimum regional indices, paired by actual calendar date. Winter mean is exact arithmetic mean of daily mean index (Celsius as supplied with one decimal place); air-frost-index day is daily minimum regional index strictly below 0 Celsius. This does not count every station or garden frost. Baseline is equally weighted average of the 30 winter means, and mean of the 30 winter frost-day counts; do not pool all baseline days. Milder means strictly above baseline mean; fewer frost days strictly below baseline count. Equality is explicit. Enumerate every expected calendar date including leap days. Missing/nonfinite/duplicate observations fail or exclude the winter with detailed reasons; baseline incompleteness fails entire gate. Treat -99.9 (documented missing marker in related HadCET formats), -999, or NaN as missing, never a temperature; audit any occurrence explicitly. Require both fields for every day. Derive full winter population, quadrant counts, baseline, extrema, all contrary/ordinary cases. Preserve regional-index, daylight/minimum and source homogenisation qualifications. No local planting, heating, household-emission, hazard, future-probability or causal recommendation. Adjacent winters do not overlap, but the baseline and historical sequence are not independent trials. Do not choose reference or scope after looking at results.\n",
  "verified_result_sha256": "51d816fc9314dac7c6c71249db9a26c48f3feb6f154938b6f6657e520d083556",
  "downloads": {
    "daily.csv": "e0577faa555911c5e06fed8be5eb32c60e98842c799a186a1743b6bad1082788",
    "data-dictionary.json": "7d727985a0c9fb3b1509a4117be5e6c8e265470a276dd0f6070c70a75ef63b76",
    "rows.csv": "c8b407a1fe08a892b55e351d7080f5b2fc3a4fe7e1f2d4a94dfa151423dd7b60"
  }
}