HadSST4 and knock on effects

The new version of the HadSST4 has reassigned ship based  measurements from before WW II  into the early 1990s. Bias adjustments depend on the fraction of measurements using wooden or canvas buckets and engine room intakes (ERI), which are partly defined by the metadata in ICOADS based on ship logs. The assignment of each measurement to the type of bucket or ERI is sometimes uncertain. HadSST4 now use instead the diurnal temperature dependence of the measurements (time of day) to identify which measurement type was used by each ship. The overall bias adjustment to SST will change if this procedure changes the fraction of data falling into into each category since each adjustments is different.

They claim that 75% of measurements could be classified in this way, and that buckets were still in use in US ships into the early 1990s. Since then measurements are based on floating buoys and Argo buoys and these recent temperatures measurements are unaffected. However that doesn’t matter because the crucial 1961-1990 normalisation period certainly is affected and HadSST4 only publishes temperature anomalies – not absolute temperatures. So the net effect of the new assignments  is to to lower the zero line (normals) from which anomalies are calculated,  and as a result all recent  anomalies have indeed increased in ‘temperature’. Hey presto the oceans have now warmed by an extra 0.1C.

We saw in the last post how moving from V3 to V4C had boosted warming when global temperatures are calculated in 3D using HadSST3. So what happens if instead we now use HadSST4 instead of HadSST3?

V4C/HadSST4 calculated with spherical triangulation covering poles. C&W would give similar result.

Recent temperatures get a boost increasing the apparent 2016 temperature by 0.25C  compared to the latest HadCRUT4. The record 2016 now stands at 1.05C or 1.45C above the pre-industrial era. Temperature anomalies are wonderful things. Changes to the past can affect the future. So expect to see alarmist headlines in the press soon once HadSST4 gets integrated into Berkeley Earth or into a future HadCRUT5?

V4/HADSST4 also kind of gazumps the Paris Agreement since the 1.5C target seems to have been almost been reached already in 2016.

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15 Responses to HadSST4 and knock on effects

  1. Lou Maytrees says:

    Clive, just wondering yet your ‘Turbocharging’ graph shows GHCN-V4C/HadSST4 started +.1*C above Hadcrut4 so shouldn’t that be a 0.15 difference, not 0.25?

  2. A C Osborn says:

    Clive, I just saw your tweet at Rog Tallblokes account and the graph from here.

    Do you have any earlier data, ie 1997 & 1998?
    I have been trying for quite a few years to understand how Global Temperatures in 1997 & 1998 have been lowered by over 5 Degrees F since 2001.
    Take a look at
    and compare to
    look at the Table down the page placing 1998 in 9th place.

    • A C Osborn says:

      ps, note that 1997 will drop off of the list this year and their mistake of quoting the Actual Temperature instead of just the Anomaly will disappear forever.
      I have take a screenshot of it, but that is not the same as the real thing.
      I have converted their 1997 anomaly to obtain their original 1901- 1990 baseline and then converted to an anomaly based on their current baseline.

    • Clive Best says:

      I think maybe your last link is wrong. It looks like originally NOAA quoted absolute temperatures (1997 = 62.5f), then thought better of it.

      This is what I get relative to 1961-1990 baseline

      1997 1998
      0.35C 0.53C HadCRUT3
      0.39C 0.54C HadCRUT4
      0.38C 0.53C V3/HadSST3
      0.48C 0.62C V4/HadSST4

      Everything including C&W pivots around 1998. Only HadSST4 breaks the pattern.

      • A C Osborn says:

        Why did it take them years to identify that they had made a mistake and then not going back and clarifying what it should have been?
        Instead they just said that the baseline and “Calculation method” had changed.
        They hardly ever quote the Actual Temperature, it is usually anomalies unless they wish to make a point about it being a record, how could Scientists make such a major blunder?

        • Windchaser says:

          They hardly ever quote the Actual Temperature, it is usually anomalies unless they wish to make a point about it being a record

          You don’t need actual temperatures to make a point about a record. The anomaly is enough.

          Actual temperatures are a bit harder to calculate accurately than anomalies, and anomalies is mostly what we care about (in terms of impact on ecosystems, sea level, etc.), so scientists generally report in terms of anomalies.

  3. jarves says:

    Why doesn’t Met Office comply with WMO Technical Regulations?

    “Under the current WMO Technical Regulations, recognising the realities of a changing climate, climatological standard normals are defined as averages of climatological data computed for successive 30-year periods, updated every ten years, with the first year of the period ending in 1, and the last year, with 0. That is, consecutive 30-year normals include: 1 January 1981 to 31 December 2010, 1 January 1991 to 31 December 2020, and so forth. Countries should calculate climatological standard normals as soon as possible after the end of the decennium. Climatological standard normals periods should be adhered to whenever possible in order to allow for a uniform basis for international comparison.”


    • jarves says:

      Wait…, WMO regulations apply only to national climatological data.

    • jarves says:

      AFAIK, for global temps these base periods are in use. Are there others? Standardization needed?

      GISS, 1951-1980
      NOAA, 20th Century
      Met Office, 1961-1990
      UAH, 1981-2010
      RSS, 1979-1998

      • jarves says:

        BEST, 1951-1980

      • Clive Best says:

        My list was

        NASA GISS 1951 – 1980
        Berkeley (BEST) 1951 – 1980
        Hadcrut4.5 1961 – 1990
        NOAA 1971 – 2000
        UAH 1979 – 2010
        RSS 1979 – 1984

        each should be a linear offset from the other. However the number of stations that can calculate normals will change. NOAA are cheating somewhat. They need to specify a minimum number of years a station must appear within the normalisation period.

  4. David R says:


    UAH data page states “New Reference for annual cycle 1981-2010”

    NOAA Global Anomalies and Index Data page states “Anomalies are with respect to the 20th century average (1901-2000).”

    • Clive Best says:

      I think both are now using 1981- 2010 to calculate the normals. This is new to me. NOAA then adjust the result down to get a 20th century average. One reason NOAA like to use a recent 30y period is that it maximises the number of stations they can use, since to calculate anomalies you must have values in the normalisation period.

    • Nick Stokes says:

      What NOAA says is:
      “he global maps show temperature anomalies relative to the 1981–2010 base period. This period is used in order to comply with a recommended World Meteorological Organization (WMO) Policy, which suggests using the latest decade for the 30-year average. For the global-scale averages (global land and ocean, land-only, ocean-only, and hemispheric time series), the reference period is adjusted to the 20th Century average for conceptual simplicity (the period is more familiar to more people, and establishes a longer-term average). The adjustment does not change the shape of the time series or affect the trends within it.”

      It’s a two stage process. To get an anomaly average, you need a reference period for which as many stations as possible have data. That is, if you aren’t using the greatly superior least squares method. Once you have the average, you can adjust by subtracting the mean for some other period, if the result seems more natural to you. That is what they do.

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