New, and Old, Explainers on Temp Adjustments

July 19, 2017

Favorite hobby horse of deniers. Evil scientists adjust temperature measurements to suit their one-world-government agenda.
Reality more boring.

Fortunately, Berkeley Earth Alumnus Zeke Hausfather is one of our most lucid explainers.

Zeke Hausfather in Carbon Brief:

These adjustments have long been a heated point of debate. Many climate sceptics like to argue that scientists “exaggerate” warming by lowering past temperatures and raising present ones.

Christopher Booker, a climate sceptic writing in the Sunday Telegraph in 2015, called them “the greatest scientific scandal in history”. A new report from the rightwing US thinktank, the Cato Institute, even claims that adjustments account for “nearly all the warming” in the historical record.

But analysis by Carbon Brief comparing raw global temperature records to the adjusted data finds that the truth is much more mundane: adjustments have relatively little impact on global temperatures, particularly over the past 50 years.

In fact, over the full period when measurements are available, adjustments actually have the net effect of reducing the amount of long-term warming that the world has experienced.

Raw data shows more global warming

Land and ocean temperatures are adjusted separately to correct for changes to measurement methods over time. All the original temperature readings from both land-based weather stations and ocean-going ships and buoys are publically available and can be used to create a “raw” global temperature record.

The figure below shows the global surface temperature record created from only raw temperature readings with no adjustments applied (blue line). The red line is the adjusted land and ocean temperature record produced using adjusted data from the US National Oceanic and Atmospheric Administration (NOAA), with the difference between the two in grey.


You can see that adjustments to the data have relatively little effect on global temperatures after 1950. The rate of warming between 1950 and 2016 in the adjusted data is just under 10% faster than the raw data, and only 4% faster since the start of the modern warming period in 1970.

The adjustments that have a big impact on the surface temperature record all occur before 1950. Here, past temperatures are adjusted up – significantly reducing the warming over the past century. Over the full 1880-2016 period, the adjusted data actually warms more than 20% slower than the raw data. The large adjustments before 1950 are due almost entirely to changes in the way ships measured temperatures (more on that later).

My video from last year goes a bit more into depth – but definitely read Carbon Brief if you want to deep dive.

6 Responses to “New, and Old, Explainers on Temp Adjustments”

  1. Adjustments to the GHCN land station data modestly increase warming, largely for the following reason: the adjustments correct for the movement of hundreds of temperature stations from city centers to outlying airport (and other) locations during the mid 20th-Century.

    Drill down into the GHCN data (using very mundane programming techniques) and you will find over 400 “airport” stations that have data records going back prior to the Wright Brothers’ first flight in 1903. Those stations obviously did not start their lives at airports; they were later moved out to airports when those airports were constructed (largely during and immediately after WWII).

    Process the “airports only” GHCN data (lots of moved stations) and “non-airport” GHCN data (fewer moved stations) separately, and you can see the station-move effect very clearly. For the early 20th-Century, the raw (i.e. no corrections) “non-airport” results will line up a lot more closely to the adjusted data results than the “airports only” results will. This is a nice (if informal) validation of the homogenization adjustments that NOAA applies to the data.

    I wrote up a detailed (and hopefully easy understand) document that demonstrates all of the above with actual raw-data results — link here:

  2. Sir Charles Says:

    Christopher Booker isn’t a “climate sceptic”, he’s a die-hard climate change denier who is relying on bloggers like Tony Heller AKA “Steven Goddard”. These guys are just a bunch of evil liars.

    • toby52 Says:

      Booker is also a known anti-science nut, who denies the threat of dangers such as asbestos on totally specious grounds. Google George Monbiot’s demolitions of this puffed-up ignoramus.

  3. Sir Charles Says:

    Zeke Hausfather’s article above at Carbon Brief is worthwhile reading in full length.

    The graph below shows that adjusted data represent anything but a warmer trend than pristine data:

    Comparison of the distribution of temperature trend differences between proximate raw (blue), adjusted (red), and reference network (green) station pairs. If the raw or adjusted data had identical trends to the reference network, they would match the green shaded area perfectly.

    => No climate conspiracy: NOAA temperature adjustments bring data closer to pristine

  4. Sir Charles Says:

    Also read => Understanding Adjustments to Temperature Data

    Histogram of all PHA changepoint adjustments for versions 3.1 and 3.2 of the PHA for minimum (left) and maximum (right) temperatures.

  5. indy222 Says:

    So here’s the key question – Does the GISS GISTMP data you can pull off of the GISS website corrected for this, so that the adopted “pre-industrial” baseline (avg of 1880-1910), has these corrections incorporated? It makes a difference when asking how close we are to the +1.5C tipping point for permafrost inevitable melt as found by Anton Vaks et al 2013. As of March 2017, that data set said we were at +1.4C above the 1880-1910 average, when including a .254C correction to go from the 1950-1981 average which they prefer to baseline to, back to the 1880-1910 average

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