HadCRUT5 increase in global temperatures

The HadCRUT5 data show about a 0.1C increase in annual global temperatures compared to HadCRUT4.6. There are two reasons for this.

  1. The change in sea surface temperatures moving from HadSST3 to HadSST4
  2. The interpolation of nearby station data into previously empty grid cells.

Here I look into how large each effect is. Shown below is a comparison of HadCRUt4.6 with HadCRUT5.

Comparison of standard  HadCRUT4 and HadCRUT5 showing a ~0.1C increase in recent years, 

Next we estimate the effect of both HadSST4 and interpolation. The previous post showed that my 3D triangulation method agrees almost exactly with HadCRUT5, so I now apply it to HadCRUT4.6. Any differences identifies the HadSST4 component.

Comparison of HadCRUT4, Interpolated HadCRUT4 and HadCRUT5

Conclusion: There is an increase of recent global temperatures of about 0.1C when moving from HadCRUT4.6 to HadCRUT5. Half of this increase is due to interpolation and half is due to using HadSST4 instead of HadSST3.

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8 Responses to HadCRUT5 increase in global temperatures

  1. Scott says:

    Have you seen the website temperature.global.
    I would be interested in your thoughts on their approach to trending the global temperature. I understand they are using 2000-2010 as their baseline.
    This seems to be a very robust approach to getting an average that is not subject to tampering with the data.

  2. Tor Ole Klemsdal says:

    Thank you for illustrating the differences so clearly!
    If I remember correctly, every new version of HadCRUT (3,4 5), GISS, NOAA and RSS that has been developed the last 20 years has resulted in an increasing warming trend compared to the previous version, the only exception is UAH (5,6 vrs 6.0) .
    Now, if we assume that all these revisions are genuine improvements and that the absolute temperatures measured by the metereological stations and boyes are not changed (from which tha anomalies are calculated), the actual change is that the new versions estimate past decades to have been colder than the previous version did. Is there a reasnable explanation for such a phenomenen – that we systematically have been overestimating temperature levels in the previous 2-5 decades?

    • Clive Best says:

      Yes that is more or less true.

      The fundamental problem is that modern measurements have much larger coverage than earlier years. The temperature anomalies are calculated typically against a 30 year climatology sometime in the past. Berkeley actually use stations which have no data within that normalisation period by fitting a spatial temperature field each month/year. and then use that value.

      So as we go backwards in time the temperature becomes less and less precise. However the fitting process into unmeasured areas (interpolation if you like) is designed to also include parts of the world warming the most such as the Arctic. The problem is that before say 1950 we have very little or no data in these areas so the fit makes less sense early on. Therefore if you include the early 20th century data it tends to systematically cool the past.

      The old Hadcrut4 analysis had one advantage of being agnostic to spatial trends. Of course they may have felt under pressure to update this so as to better align with the other groups

      • Tor Ole Klemsdal says:

        Thank you so much for this valuable explanation and comment! The problem is of course how to evaluate changes in temperature trends (e.g. degrees per decade) when new verssions replace the old ones several times within the time interval examined.

  3. Hugo says:

    Adjusting for consensus:
    The main problem is that there is no unbiased system. No double blind testing. The major consensus is temperatures are rising. Funding / politics are build on fear. Similar to corona and like the most money goes to weapons for “defense” But we need to sell stuff to others to keep up the threat. .If data does not confirm consensus, there must be something wrong so things always are adjusted upwards. Towards the bigger funding. and consensus If principal theories encounter anomalies for that we invent dark solutions, mass, matter and energy. Temperature climate wise over 30 years is nothing. Quality consistency and placement of measuring devices and points is crucial. We do not put them in the middle of no where all the same model and type. We do not collect data identical or even at the same time. There is no single unbiased organization or identical calibrated global system.
    While world population growth over 30 years is around 30-40% Around 2 billion, cutting of trees killing of big grazers and paving more and more space with concrete has grown along . So its a little short sighted to state temperature rising and even try to blame it on a single input source Like burning of fossil fuel only, which in it selves has never been from outside the existing system. But e.g. people are.
    Then again we have no clue what affects our planet inside our solar system. Or the travel and path placement of the system in it selves. Even its circular path is pretty unclear. We claim to know so much about everything. But as i see its news and internet media crying wolf about anything. For that Trump still has a principal point, yes fake media exist. That he extensively used it and was part of it too only makes it more valid.
    I do not say efforts are fake wrong or useless, totally not. But we must step down of our thrones and say we are doing our best and make sure that political power or money is not the path, and or make assumptions on things which we hardly understand or try to influence large populations while temperature rising is not a a major concern of the poor and really not of the rich while they say so yes. And politicians the keep busy with what ever likes sensitive matter not important how stupid or ill placed it is. Population growth is a real concern. Countries like India and Pakistan and many African countries are growing out of proportion. While western countries are suffering of old age with populations over 30% aged over 60. wand politicians keep the world hostage to protect that rich political influencer’s group.
    But anyway back to climate, what will the weather be tomorrow. Ask the Indian. He knows he watches the daily Internet podcast.

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