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Loehle Temperature Reconstruction

The Loehle Temperature Reconstruction is a narrowly scoped loosely constructed picture that due to its limitations, is deceptive in its depiction of past climate. When placed in context of more strongly validated science it's weaknesses become more obvious. In that sense, one may go as far as to say the paper, in and of itself, is scientifically inappropriate with regard to what it is claimed to represent.
Loehle Temperature Reconstruction

Loehle Temperature Reconstruction

The most important point in understanding past climate is that single assessments and narrowly scoped research is not sufficient to understand the big picture of climate.

The Loehle temperature reconstruction is inadequate in its assessment and results. The simple fact that his chart is now out there without proper context is a distraction to the relevant contextual science that has survived peer response. Peer review is necessary but not sufficient when examining the validity of data. Loehles work does not hold up to peer response.

"Loehle has issued a correction that fixes the more obvious dating and data treatment issues, but does not change the inappropriate data selection, or the calibration and validation issues."
- Gavin Schmidt NASA/GISS

What this indicates is that Loehle is willing to leave his flat earth proposal out there for denialists to use to support scientifically unsupportable positions. But in reality it is a paper that will fade into the oblivion of irrelevant science. In the mean time, it wil be used by denialists of AGW to make false claims.

Let's take a look at what Loehle's paper is based on, and what relevant climates scientists look at when evaluating past climate temperatures from 'Past reconstructions: problems, pitfalls and progress'

"These encompass tree ring width, density and isotopes, some ice cores, corals, and varved lake sediments. The next most useful set of data are sources that have up to decadal resolution but that can still be dated relatively accurately. High- resolution ocean sediment cores can sometimes be found that fit this, as can some cave (speleothem) records and pollen records etc."
- Gavin Schmidt NASA/GISS


"The Loehle paper was published in Energy and Environment - a journal notable only for its rather dubious track record of publishing contrarian musings. The reconstruction itself is based on a network of 18 records that are purportedly local temperature proxies, and we will use those as examples in the points below. More discussion of this paper is available here."
- Gavin Schmidt NASA/GISS

Overall, the data concentrated on by Loehle seems to have low resolution which does not allow more accurate assessment. He used averages to represent data points. Times scales were misrepresented without reasonable context, he used proxy data with short period calibration with no validating data, he used out of date data, he composited data with different averaging periods, different spatial representation and noise levels and seems to have assigned weighting in a random pattern out of context to better validated reconstructions... all in all a very confused assessment.

To be fair it is difficult to reconstruct past climate, but Loehle seems to have scoped his assessment based on randomness rather than validated proxies. The lack of alignment in time is also a problem.

"What does this imply for Loehle's reconstruction? Unfortunately, the number of unsuitable series, errors in dating and transcription, combined with a mis-interpretation of what was being averaged, and a lack of validation, do not leave very much to discuss. Of the 18 original records, only 5 are potentially useful for comparing late 20th Century temperatures to medieval times, and they don't have enough coverage to say anything significant about global trends. It's not clear to me what impact fixing the various problems would be or what that would imply for the error bars, but as it stands, this reconstruction unfortunately does not add anything to the discussion."
- Gavin Schmidt NASA/GISS


It is important to state that if a scientist limits the scope of his analysis, narrows his view, or simply does not include the known relevant factors and scope, he/she can prove almost anything wrong based on such limitation ... even that the earth is flat. But in the big picture we know the earth is round and such limited analysis should be ignored. The incorrect nature of the Loehle temperature reconstruction is a disservice to the public and to science in general. One must wonder as to why he would ignore the relevant science?

Climate science is about the 'big picture' based on all the 'little pictures', not the little picture ignoring the big picture.

Here is what the relevant science reconstructions have on the medieval warm period (MWP). The global mean temperature is clearly warmer today that in the MWP.

IPCC Temperature Reconstruction

Source: IPCC


Past reconstructions: problems, pitfalls and progress


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