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‘800 years of cooling’

This post is a very delayed issue of a conversation a year ago (a lot happened this year so it stayed in draft, seemed a waste not to publish it).

During my conversation on twitter with Paul Carfoot another statement popped up, this time from ‘Friends of Science‘, who describe themselves as “A group of earth, atmospheric, solar scientists and engineers” – Warren Blair is ‘President’ but they are sketchy on who they are. More here & here.

So lets take a look…..

The 1990 IPCC report ‘acknowledges’ MWP/MCA (they call the MWP the Medieval Climate Anomaly) but does not acknowledge that it was ‘as warm as today’.  The red arrows above have of course been added by someone else. From FoS;


From the IPCC;

IPCC 1990 graph.jpg

So I’ve marked the dotted line as c1900 and the vertical scale on the right (please let me know if this is incorrect).

On a later page (pg. 254) of the same 1990 IPCC report are the details from the last 130 or so years to 1990, split into north & south hemispheres.

IPCC 1990 graph p254.jpg

So that was the limit of knowledge in 1990, but to quote this report as proof that there has been ‘800 years of cooling’ is surely a bit simplistic when we know an awful lot more about global temperatures now, some 26 years later. Would you use data this old to ‘prove’ your theory of cooling? Only if you are a fake sceptic perhaps?

Some work suggests that the origins of the graph are actually from 1965, a whole 51 years ago. And based on data from just Central England, not global at all.


Comparison of MBH99 40-year average from proxy records, as used in IPCC TAR 2001 (blue), with IPCC 1990 schematic Figure 7.1.c (red) [based on Lamb 1965 extrapolating from central England temperatures and other historical records]; central England temperatures to 2007 shown from Jones et al. 2009 (green dashed line).[114] Also shown, Moberg et al. 2005 low frequency signal (black).

From the 5th IPCC report (2013), showing that current knowledge is vast and that temperatures have climbed well above the Medieval Warming Period.


Not exactly ‘800 years of cooling’, is it?

Carfoots’ tale

In response to my previous twitter conversation, and analysis of the poor ‘H&M’ graph here, Paul Carfoot responded.

So I went to look. The conversation with ‘sceptics’ revolves around AGW being ‘nothing new’ as it has been warmer in the past. So despite the graphs I refereed to previously clearly showing a 2004 temperature much higher than the MWP or other ‘peaks’, that point in my commets is assiduously ignored. So I looked at Paul’s blog to see his evidence for wny he thinks the H&M graph is OK as a reference.

The argument around current temperatures looks at this graph (linked by Carfoot to WUWT but actually from Alley)

Alley graph


Easterbrook graph


Carfoot says “As you can clearly see it has been much colder in the past and much warmer too.

But the Alley graph & Easterbrook graph are for Greenland, not global, and the dates are to 1855, not present.

The second graph links to Ice Age Now, but the original is by Easterbrook.

Ice Age Now say “Created by Cuffy and Clow in 1997, and based on Greenland ice core records, this chart shows global temperatures for the past 15,000 years.” Carfoot says of these graphs “so why are we being told that it is warmer today than ever before in history? I will leave that question unanswered and for you to decide.

The graph is Easterbrook graph is based on GISP2. However, the GISP2 “present” follows a common paleoclimate convention and is actually 1950. So the most recent temperature in the GISP2 series is therefore 1855. (more here and another critique here)

Here is the Cuffey (sp) & Clow paper from 1997. Carfoots graph is probably via WUWT here. Here is a version of the same, generated from the original data, plus the average temperature at the summit for the decade 2001-2010 – from here.


Data source: Alley, R.B..  2004. GISP2 Ice Core Temperature and Accumulation Data. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2004-013. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

So, finally, it doesn’t show global and it doesn’t show todays temperature, so that argument is disproved. You cannot rely on temperatures at the top of the Greenland ice sheet as a proxy for global temperatures. Easterbrook’s claim that “most of the past 10,000 [years] have been warmer than the present” is not true for central Greenland, let alone the global record.

There is another detailed analysis here, this graph is pertinent.


And finally;


Temperatures over most of the past 2000 years compared to the 1961-1990 average, based on proxy data (tree rings, ice cores, corals) and modern thermometer-based data. Over the past two millenia, climate warmed and cooled, but no previous warming episodes appear to have been as large and abrupt as recent global warming. NOAA graph by Fiona Martin, adapted from Figure 34.5 in the National Climate Assessment, based on data from Mann et al., 2008.





Comparing ‘data’

A tweet annoyed me! Oh dear, this always leads to an eating up of time as I research & plot. I know I shouldn’t bite but when I’m exceptionally busy at work its inevitable I want to distract myself. This time it was a crudely drawn graph posing as ‘history’.

And the usual pile-on of lukewarmers & fake sceptics appear. As the graph was SO crude and full of distracting words a mash up of this against actual measured data was messy. Here’s where the time consumption begins!

The graph comes (H&M) from “Climatologist Cliff Harris and Meteorologist Randy Mann” (though it appears that Harris probably isn’t a climatologist at all – here & here) and can be found here & purported to be ‘based upon thousands of hours of research done by Dr. Raymond H. Wheeler and his associates during the 1930s and 1940s at the University of Kansas.’

The graph shows a timescale going back to 2400BC but with no x-axis scale, apart from a reference to 58.3F in 98 & 57F as ‘normal’ and a prediction for 2019 to be considerably colder, then 2038 being as hot as the peak of 1100BC…. it didn’t look very convincing to me. So I dug out the Holocene records from here, based on this paper.

Result 1 – 2500 year records – shows pretty clearly how wrong the peaks in Harris’s graph are. NB. the largest peak & largest trough on H&M were used to scale the two graphs, as it had no defined x-axis apart from the points at the very end. (see note at the end on comparison).


Result 2 – past 1000 years, shows Harris & R.Mann bizarre predictions to larger scale.


Result 3 – with slightly more detail, trying to show the complexities of the data record v crude sine wave (& perhaps failing to do so!)


I can understand the desire to show an oscillating pattern to support a theory but H&M is pretty hopeless when it comes to accuracy.


I made this more emphatic graph as a result of the usual twitter convos – it went like this;

So, just for completeness, here is the ‘match’:


Here is the copied plot, marked white for clarity:


And for completeness, this is why the graph needed to be redrawn:


And now the twittersphere has gone quiet, will report back if further comments appear.

UPDATE: Paul Carbrook has responded, to keep the above information specific to the H&M graph I have responded to his comments on a new page.