Ocean Impact on Temperature Data and Temperature Homgenization

Pierre Gosselin’s notrickszone points looks at a new paper.

Temperature trends with reduced impact of ocean air temperature – Frank LansnerJens Olaf Pepke Pedersen.

The paper’s abstract.

Temperature data 1900–2010 from meteorological stations across the world have been analyzed and it has been found that all land areas generally have two different valid temperature trends. Coastal stations and hill stations facing ocean winds are normally more warm-trended than the valley stations that are sheltered from dominant oceans winds.

Thus, we found that in any area with variation in the topography, we can divide the stations into the more warm trended ocean air-affected stations, and the more cold-trended ocean air-sheltered stations. We find that the distinction between ocean air-affected and ocean air-sheltered stations can be used to identify the influence of the oceans on land surface. We can then use this knowledge as a tool to better study climate variability on the land surface without the moderating effects of the ocean.

We find a lack of warming in the ocean air sheltered temperature data – with less impact of ocean temperature trends – after 1950. The lack of warming in the ocean air sheltered temperature trends after 1950 should be considered when evaluating the climatic effects of changes in the Earth’s atmospheric trace amounts of greenhouse gasses as well as variations in solar conditions.

More generally, the paper’s authors are saying that over fairly short distances temperature stations will show different climatic trends. This has a profound implication for temperature homogenization. From Venema et al 2012.

The most commonly used method to detect and remove the effects of artificial changes is the relative homogenization approach, which assumes that nearby stations are exposed to almost the same climate signal and that thus the differences between nearby stations can be utilized to detect inhomogeneities (Conrad and Pollak, 1950). In relative homogeneity testing, a candidate time series is compared to multiple surrounding stations either in a pairwise fashion or to a single composite reference time series computed for multiple nearby stations. 

Lansner and Pederson are, by implication, demonstrating that the principle assumption on which homogenization is based (that nearby temperature stations are exposed to almost the same climatic signal) is not valid. As a result data homogenization will not only eliminate biases in the temperature data (such a measurement biases, impacts of station moves and the urban heat island effect where it impacts a minority of stations) but will also adjust out actual climatic trends. Where the climatic trends are localized and not replicated in surrounding areas, they will be eliminated by homogenization. What I found in early 2015 (following the examples of Paul Homewood, Euan Mearns and others) is that there are examples from all over the world where the data suggests that nearby temperature stations are exposed to different climatic signals. Data homogenization will, therefore, cause quite weird and unstable results. A number of posts were summarized in my post Defining “Temperature Homogenisation”.  Paul Matthews at Cliscep corroborated this in his post of February 2017 “Instability og GHCN Adjustment Algorithm“.

During my attempts to understand the data, I also found that those who support AGW theory not only do not question their assumptions but also have strong shared beliefs in what the data ought to look like. One of the most significant in this context is a Climategate email sent on Mon, 12 Oct 2009 by Kevin Trenberth to Michael Mann of Hockey Stick fame, and copied to Phil Jones of the Hadley centre, Thomas Karl of NOAA, Gavin Schmidt of NASA GISS, plus others.

The fact is that we can’t account for the lack of warming at the moment and it is a travesty that we can’t. The CERES data published in the August BAMS 09 supplement on 2008 shows there should be even more warming: but the data are surely wrong. Our observing system is inadequate. (emphasis mine)

Homogenizing data a number of times, and evaluating the unstable results in the context of strongly-held beliefs will bring the trends evermore into line with those beliefs. There is no requirement for some sort of conspiracy behind deliberate data manipulation for this emerging pattern of adjustments. Indeed a conspiracy in terms of a group knowing the truth and deliberately perverting that evidence does not really apply. Another reason for the conspiracy not applying is the underlying purpose of homogenization. It is to allow that temperature station to be representative of the surrounding area. Without that, it would not be possible to compile an average for the surrounding area, from which the global average in constructed. It is this requirement, in the context of real climatic differences over relatively small areas, I would suggest leads to the deletions of “erroneous” data and the infilling of estimated data elsewhere.

The gradual bringing the temperature data sets into line will beliefs is most clearly shown in the NASA GISS temperature data adjustments. Climate4you produces regular updates of the adjustments since May 2008. Below is the March 2018 version.

The reduction of the 1910 to 1940 warming period (which is at odds with theory) and the increase in the post-1975 warming phase (which correlates with the rise in CO2) supports my contention of the influence of beliefs.

Kevin Marshall


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