Warming Island / Greenland Sea Regional Climate and Arctic Sea Ice Reconstruction

Guest post by David Middleton

The recent return of the Warming Island AGW myth inspired me to build a climate reconstruction for the Greenland Sea region.

Temperature Reconstruction

I performed a GISS station search centered on 71.4 N latitude, 23.5 W longitude and downloaded the 12 GISS/GHCN instrumental records with at least 60 years of continuous data up to 2011.

Fig. 1) Station Location Map

Next I calculated a temperature anomaly relative to 1961-1990 for each of the 12 stations and then averaged them together to create a temperature reconstruction. The climate in the Warming Island area is statistically indistinguishable from that of the 1930’s.

Fig. 2) Warming Island Area: Instrumental temperature reconstruction.

Then I took that reconstruction back to 1000 AD with the GISP2 ice core d18O data (Kobashi et al., 2010)…

Fig. 3) Warming Island Area: Instrumental reconstruction combined with GISP2 ice core reconstruction.

The Modern Warming is also statistically indistinguishable from the Medieval Warm Period in the Warming Island / Greenland Sea region.

Arctic Sea Ice Reconstruction

It occurred to me that there might just be a relationship between the temperature anomaly and the Arctic sea ice extent. So I went to Wood for Trees and downloaded the historical NSIDC Arctic Sea Ice Index. Then I cross plotted an annual 13-month running average of the sea ice index against the average of the station anomalies and the GISP2 reconstruction (Kobashi et al., 2010) and found a pretty good correlation (R-squared = 0.67)…

Fig. 4) Warming Island Temperature Anomaly vs. NSIDC Arctic Sea Ice Index.

Using the equation “Sea Ice Index = (-0.5976 * Temp. Anom.)+12.374″ I calculated a Model Sea Ice Index.

The “Model Sea Ice Index” (white curve) is very similar to the measured sea ice index (cyan curve)…

Fig. 5) Arctic Sea Ice Extent Model: 1880 AD to present.

Using the same equation, I extrapolated the Model Sea Ice Index back to 1000 AD using the GISP2 temperature data from Kobashi et al., 2010…

Fig. 6) Arctic Sea Ice Extent Model: 1000 AD to present.

The model suggests that Arctic sea ice had been steadily expanding from ca. 1150 AD up until ca. 1800 AD and has been declining since ca. 1800 AD.

Next, I carried the model back to the Early Holocene using the Alley, 2000 GISP2 reconstruction…

Fig. 7) Arctic Sea Ice Extent Model: Holocene

This suggests that the sea ice contraction during the instrumental era (1979-2011) is not particularly remarkable.

Calibrating the Model

Realizing that my model has been extrapolated about 8,000 years away from real data, I decided to compare it to some real data. McKay et al., 2008 demonstrated that the modern Arctic sea ice cover is anomalously high and the Arctic summer sea surface temperature is anomalously low relative to the rest of the Holocene…

Modern sea-ice cover in the study area, expressed here as the number of months/year with >50% coverage, averages 10.6 ±1.2 months/year… Present day SST and SSS in August are 1.1 ± 2.4 8C and 28.5 ±1.3, respectively… In the Holocene record of core HLY0501-05, sea-ice cover has ranged between 5.5 and 9 months/year, summer SSS has varied between 22 and 30, and summer SST has ranged from 3 to 7.5 8C (Fig. 7).

McKay et al., 2008

Fig. 8) Chukchi Sea Ice Extent: Holocene.

My GISP2 (Alley, 2000) sea ice model is generally consistent with McKay et al., 2008…

Fig. 9) Comparison of Arctic sea ice extent model to Chukchi Sea ice cover.

Conclusion

“Move along, there’s nothing to see here.” The Arctic sea ice has “been there and done that” many times over the last 10,000 years without any anthropogenic assistance.

References

Alley, R.B. 2000. The Younger Dryas cold interval as viewed from central Greenland. Quaternary Science Reviews 19:213-226.

Kobashi, T., J.P. Severinghaus, J.-M. Barnola, K. Kawamura, T. Carter, and T. Nakaegawa. 2010. Persistent multi-decadal Greenland temperature fluctuation through the last millennium. Climatic Change, Vol. 100, pp. 733-756.

McKay, J.L., A. de Vernal, C. Hillaire-Marcel, C. Not, L. Polyak, and D. Darby. 2008. Holocene fluctuations in Arctic sea-ice cover: dinocyst-based reconstructions for the eastern Chukchi Sea. Can. J. Earth Sci. 45: 1377–1397

Michaels, P. 2008. “Warming Island”—Another Global Warming Myth Exposed.World Climate Report.

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52 thoughts on “Warming Island / Greenland Sea Regional Climate and Arctic Sea Ice Reconstruction

  1. You do realize that McKay et al 2008 was about the Chukchi Sea and not the entire Arctic?

    Could you also do a temperature reconstruction for the North coast of Ellesmere Island where apparently ice shelves that have been there for 3000-5500 years are rapidly disappearing?

    Cheers!

  2. David Middleton

    Nice work-well done!

    My own study showed considerable arctic ice melting around 1800 to 1860 which fits in nicely with your own paper. At that time the Royal Society mounted an expedition to investigate the causes.

    http://wattsupwiththat.com/2009/06/20/historic-variation-in-arctic-ice/#more-8688

    There then seems to have been a partial recovery, with a further notable down turn from 1919-1939 which my colleague Dr Arnd Bernaerts wrote about here

    http://www.arctic-heats-up.com/chapter_1.html

    There then seems to have been another partial recovery until the advent of the satellite era which marked a relative high point in the amount of arctic ice, which has declined ever since..

    Arctic ice melt is a regular occurrence with a downwards trend probably from around 1750 or so, which Hubert Lamb and others mark as being the start of the glacier retreat we can witness today. As well as the Vikings a thousand years ago we also have the evidence of Arctic civilisation in the form of the Ipiatuk some 3000 years ago, so we really should stop thinking about the current episode as being unique.
    tonyb

  3. Beautifully and comprehensively presented in a way that even this non-scientist can understand. Thank you David.

  4. Nice work!

    This rightly makes a mockery of this latest AGW myth, which seems to have duped a lot of people into thinking it’s both unprecedented and a new name for Warming Island – both of which are wrong.

    The well-known fact that the Vikings settled there and called it Greenland at a time when they could grow crops, raise livestock, and bury their dead in ground which is now permafrost, rarely seems to see the light of day amidst the MSM AGW hysteria.

    Sadly, as I say, lots of people have been duped – just as they were by the Row To Pole jokers. Most Hanoi-ing, as they say in Vietnam. }:o(

  5. The alarmist method of choosing summer to measure ice loss and scream ‘AGW’ but ignore the winter freeze, regardless of the depth of that freeze, shows a complete one sided cherry picked system of argument which proves nothing.

    The cyclicity of climate would dictate ice area changing to follow the cycles.

    Thanks for making the seemingly obvious more obvious for the alarmists who might change the habits of a lifetime and actually read this.

  6. Scottish Sceptic says:
    September 29, 2011 at 1:05 am
    That’s worth a paper. I will look for it in around 3-4 years after (if) it gets through the buddy peer review.
    ————————
    Why so long? I would expect a pal/peer reviewed paper by Friday.
    By today’s standards. /sarc off

  7. A textbook example of loss of high frequency information in ice data. Nice work Willis. It seems this sort of analysis is out of the reach of anyone with the term “climatologist” in their CV. Perhaps that’s the issue that will be the most challenging scientific investigation.

  8. Ergo: The actual intent of Mann, Gore, Jones, et al, is to make the next natural cooling event much stronger and thereby initiate the next glacial cycle ASAP. The overall impact will be a tremendous reduction in human population, the destruction of modern civilization, a significant reduction in sealevels, a fantastic expansion in the population of ‘desireable’ species, and an absolutely phenominal expansion in new beachfront property for the rich-n-famous worldwide.

    Who said these guys were flakes? I really can’t get it out of my head that Soros is behind all this somewhere, and I just can’t imagine how he himself expects to profit from it all. When ‘Fat Albert’ starts talking about everyone chipping in to build a pyrimid for ‘Big George’ you’ll know the cat’s out of the bag.

    I just don’t get it! WHY?

  9. If YOU can do it, then THEY should be able to do it too, but, as we all know, that would be VERY inconvenient, indeed.

    They’re really not interested in testable science, or historical fact (or likelihood), only the religion and pandering to their funders.

  10. Not much grant money on the horizon for your efforts. However if you could do a Jones/Mann obfuscation and show a potential but untrue 21st Century Arctic AGW meltdown you could gather squillions of dollar/pound/euros to continue the lie!

    Inconvenience notwithstanding.

  11. Michael D Smith says:
    September 29, 2011 at 4:42 am
    “A textbook example of loss of high frequency information in ice data. Nice work Willis.”

    err… I know Willis E. does great work around here, but give credit to David Middleton where credit is due… :)

  12. I am not sure to mix instrumental record with GISP2 data. More, GISP2 ends in 1905 (but not on your graph) so not easy to calibrate them against each other.
    There is a nice relation between Arctic SST and ice extent. In the past I did the ice extent reconstruction back to 1900 based on Arctic SST as well. Add the albedo amplifying effect and it might be not far off.

  13. Günther Kirschbaum says:
    September 29, 2011 at 12:39 am
    You do realize that McKay et al 2008 was about the Chukchi Sea and not the entire Arctic?

    I meant to point that out..

    The Greenland Sea temperature derived sea ice model’s consistency with a foram-derived Chukchi Sea ice reconstruction is a good check on the validity of the model.

    Could you also do a temperature reconstruction for the North coast of Ellesmere Island where apparently ice shelves that have been there for 3000-5500 years are rapidly disappearing?

    Cheers!

    I don’t think there are that many long record-length GISS stations and I’m not aware of any decent ice core records for the Ellesmere Island area.

  14. RR Kampen says:
    September 29, 2011 at 3:45 am
    Same empty fruitbowl with some picked cherries. BTDT.

    http://tamino.wordpress.com/2011/09/17/cold-cherries-from-joe-daleo/

    I used the “after combining sources at same location” version. I did not use the “after cleaning/homogeneity adjustment version.”

    The only criteria for “cherry picking” I used were…

    -At least 60 years of continuous data.
    -Data for 2011.
    – North of 60 deg. latitude.

    If the data records were discontinuous, short or ended prior to 2011, I did not use them.

  15. Dr Mo says:
    September 29, 2011 at 6:07 am
    Michael D Smith says:
    September 29, 2011 at 4:42 am
    “A textbook example of loss of high frequency information in ice data. Nice work Willis.”

    err… I know Willis E. does great work around here, but give credit to David Middleton where credit is due… :)

    I consider it a compliment of the highest order to be confused with Willis!

    The amplitude attenuation with frequency loss is also pretty obvious. I often wonder if the Hockey Team ever heard of Nyquist… And I seriously doubt any of them has ever processed seismic reflection data.

  16. Juraj V. says:
    September 29, 2011 at 6:26 am
    I am not sure to mix instrumental record with GISP2 data. More, GISP2 ends in 1905 (but not on your graph) so not easy to calibrate them against each other.
    There is a nice relation between Arctic SST and ice extent. In the past I did the ice extent reconstruction back to 1900 based on Arctic SST as well. Add the albedo amplifying effect and it might be not far off.

    The Kobashi N2-Ar reconstruction goes up to 1950 and has temperature data up to 1993 (modeled from borehole temperatures).

  17. Brian Johnson uk says:
    September 29, 2011 at 6:01 am
    Not much grant money on the horizon for your efforts. However if you could do a Jones/Mann obfuscation and show a potential but untrue 21st Century Arctic AGW meltdown you could gather squillions of dollar/pound/euros to continue the lie!

    Inconvenience notwithstanding.

    I guess I’ll have to keep my “day job”… /Sarc

  18. Pascvaks says: @ September 29, 2011 at 5:21 am

    “…….Who said these guys were flakes? I really can’t get it out of my head that Soros is behind all this somewhere, and I just can’t imagine how he himself expects to profit from it all. When ‘Fat Albert’ starts talking about everyone chipping in to build a pyrimid for ‘Big George’ you’ll know the cat’s out of the bag.

    I just don’t get it! WHY?…”
    _________________________________________________________________________
    First David, Great article, I hope you can expand and publish. Given all the Viking artifacts the melting is uncovering you would think the CAGW types would get a clue.

    About WHY

    MONEY and POWER of course with the added benefit of wiping out the excess “Useless Eaters” (you and me) cluttering up the landscape they want to “Rewild”

    Big Al , Monsanto, and the World Bank will clean-up big bucks with planting eucalyptus forests for carbon credits as I just explained in this comment It is an invasive allelopathic monoculture tree, uneatable to most animals so it also wipes out the food supply of the wildlive while sucking up water and nutrients and leaving the land unfit for crops. Eucalyptus globulus Is also classified as the worst fire hazard tree to top it off.

    I explain the push for power and control of the world food supply with comments starting http://wattsupwiththat.com/2011/09/26/ipcc-resistance-is-futile/#comment-752960“>here.

    All you have to do is a search on Soros, Rothschild and farmland to see what is considered the next big money maker. The plan has been in the works for decades and scares the {selfsnip} out of me because they are now beginning to “cash in ” on their plans as the big corporations buy up more and more farmland worldwide.

    Making BIG money from starvation:

    http://www.bread.org/hunger/global/

    http://www.independent.co.uk/opinion/commentators/johann-hari/johann-hari-how-goldman-gambled-on-starvation-2016088.html

    http://www.globalissues.org/article/758/global-food-crisis-2008

  19. Thanks for the good work. The role of time in all geoscience endeavors must never be underestimated. The geosciences are simply one huge set of models that are continually being recalibrated to new empirical data. Many it seems are so focused on their own navels they completely forget about geo-time.

  20. Dennis Nikols, P. Geo. says:
    September 29, 2011 at 8:33 am
    Thanks for the good work. The role of time in all geoscience endeavors must never be underestimated. The geosciences are simply one huge set of models that are continually being recalibrated to new empirical data. Many it seems are so focused on their own navels they completely forget about geo-time.

    We geo’s also tend to appreciate the fact that the Earth is one heckuva low-pass filter.

  21. Dr Mo says:
    September 29, 2011 at 6:07 am

    Michael D Smith says:
    September 29, 2011 at 4:42 am
    “A textbook example of loss of high frequency information in ice data. Nice work Willis.”

    err… I know Willis E. does great work around here, but give credit to David Middleton where credit is due… :)

    Duly noted… Sorry about that David! I read it and it was so well done and easy to follow I guess I just assumed it was Willis. I too would take that as a huge compliment! Nicely done, I look forward to your next article… Mike S.

  22. Thanks for the Kobashi et al. David. So the whole catastrophic warming occurred up there before 1950, then cooled a bit, then warmed a bit to previous level. Here are all Greenland stations via the KNMI Climate Explorer:
    Monthly: http://climexp.knmi.nl/data/icrutem3_300-340E_55-85N_n_sua.png
    Annual means: http://climexp.knmi.nl/data/icrutem3_300-340E_55-85N_n_su_mean1a.png
    Here is the CMIP3+ model average for the same area:

    Those cutting-edge-coupled-state-of-the-art models can not replicate recent history, because they are purely based on hypothetical “greenhouse forcings” and dismiss any natural changes. Unbelievable, that someone is still ready to argument with them.

  23. I don’t see the obvious and predictable 60-70 year ice cycles discussed by Joe D’Aleo on here a couple of weeks ago. What’s up with that?

  24. Did you look up Walsh & Chapman 2001, Annals of Glaciology, 33, 444-448 and compare their reconstruction of arctic ice to yours?

  25. Well done David! I am in agreement. The most important/dominant time scale for humans is the last ~8000 years (since the interglacial maximum peak to the LIA minimum and present). The linear trend is COOLING. I don’t see the trend reversing in the future.

  26. jakers says:
    September 29, 2011 at 11:40 am
    I don’t see the obvious and predictable 60-70 year ice cycles discussed by Joe D’Aleo on here a couple of weeks ago. What’s up with that?

    Kobashi et al. found them…

    4 Multi-decadal temperature fluctuations

    4.1 Comparison with hemispheric temperature trend

    The reconstructed temperature record shows a quasi-periodic multi-decadal temperature
    fluctuation (Fig. 19). The spectrum shows three significant peaks with periods of
    ∼330, ∼70, and ∼40 years (Fig. 19). Wavelet analyses show 60–70 year multi-decadal
    fluctuations in the thirteenth century, late eighteenth century to the early nineteenth
    century (90% confidence level) (Fig. 20a). Also, decadal temperature variations with
    shorter period of ∼32 years are significant at the beginning of eleventh century,
    early seventeenth century, and early twentieth century (Fig. 20a).

    Davis & Bohling, 2001 also found a prominent 60-70-yr cycle.

  27. Edim says: @ September 29, 2011 at 11:59 am

    “Well done David! I am in agreement. The most important/dominant time scale for humans is the last ~8000 years (since the interglacial maximum peak to the LIA minimum and present). The linear trend is COOLING. I don’t see the trend reversing in the future.”
    __________________________________________________________________________

    All you have to do is LOOK at the long term Geo scale record of temp. and you can see the earth is in the best shape it has been for an extended period of time. I am talking about the nice FLAT Holocene instead of a spike and crash back to an Ice age of the previous couple of interglacials. The believers of CAGW are so busy looking at the temp vs CO2 data they never notice that we don’t even have a problem.

  28. Gail Combs,

    Yes, it’s much flatter cooling than the previous couple of interglacial, but I take these ice core records with a grain of salt. There may be unknown artifacts, or maybe not. What I find interesting is that on those timescales warming seems to be steeper than cooling.

  29. jakers says:
    September 29, 2011 at 11:49 am
    Did you look up Walsh & Chapman 2001, Annals of Glaciology, 33, 444-448 and compare their reconstruction of arctic ice to yours?

    Walsh & Chapman’s reconstruction starts in 1880. It wouldn’t be of much use in trying to reconstruct the Little Ice Age & Medieval Warm Period.

    Walsh & Chapman’s reconstruction disagrees with the NSIDC real data much more than my model and shows an expansion of Arcitc sea ice during the 1930’s & 1940’s… A period of Arctic warmth during which Soviet ships routinely plied the Northeast Passage.

    Otherwise it indicates ~4% more ice than my reconstruction from 1880-1930, up to 17% more ice from 1930-1960, ~4% more from 1960-1970. The two reconstructions are in agreement with the satellite record from 1980-1990 and then Walsh & Chapman deviate above the the satellite record from 1990-2000 and then drop ~10% below the satellite record from 2000-2010. My reconstruction is within 3% of the satellite record in 28 out of the 32 years….

    1980 -6%
    1995 +6%
    2003 -4%
    2007 +5%

  30. Looks like you are tossing away loads of information by not using shorter records. As JeffId and Romanm and Tamino and Nick Stoke and Richard Muller’s team shows there is no need to
    throw away this information as they can be combined effectively.

    Also, it looks like you are averaging over 90 degrees of longitude and if you are simply averaging them that will tend to give you a spatial bias.

    Finally, you’ve got a geographically inhomogenous group WRT ( many island stations for example. )

    In any case, there is more data that might tighten up you analysis and of course.. code and data posted or it doesnt count as science. Same rules for everybody

  31. @steven mosher says:
    September 29, 2011 at 2:19 pm

    It’s a hobby… Not a Ph D thesis… /Sarc

    If I had an unlimited amount of time for this hobby, I would have used the shorter records… Or at least all of the records with data from 1961-1990.

    On the spatial biasing… The data are where the data are. Ideally, I would have plotted the anomalies on annual map horizons, gridded & contoured the anomalies and then put together an animated time slice volume… But that would have been too much like work.

  32. TomRude,

    The funding for these fellows has been drying up now since the Conservatives took a majority and naturally gravity has reasserted its tugging on the sky.

  33. Günther Kirschbaum says:
    September 29, 2011 at 12:39 am

    Take a look at your link. Then go to the Ward Hunt ice shelf pictures at:

    http://http-server.carleton.ca/~dmueller/iceshelves/WHIS2011.html

    Now tell me whether you can see any difference between the 2011-8-26 an 2011-09-22 state of the ice shelf. They have failed to indicate (by red outline) that the ice joining the two parts of the shelf is still there in the September picture. They are showing a decrease when there is none!

    Sloppy work.

  34. Somewhat OT, but I notice the temperature trend graph of Reno, Nevada, as posted at surfacestations.org in January 2008:
    (1) http://gallery.surfacestations.org/main.php?g2_itemId=33587
    has apparently been morphed into this one (at the GISS site):
    (2) http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=425724880000&data_set=1&num_neighbors=1

    On the current GISS site I’m unable to find any trend graph that is similar to (1), and the direction of “manipulation”, if any, appears to be “past years drastically upward”, as opposed to their “traditional manner”.

    Anyone in the know please tell me about the background of this enigmatic change of the graph.
    When the story becomes clear, I’m incorporationg it into a book (titled “The Global Warming Myth”, in Japanese) to be published in February or March 2012.

    Thank you in advance for your help.

  35. Billy Liar says:
    September 29, 2011 at 4:43 pm
    “Now tell me whether you can see any difference between the 2011-8-26 an 2011-09-22 state of the ice shelf”
    Look at the high resolution picture. What was joined in August is broken up in September.
    Just look at the orientation of the “texture” of the shelf.
    ==> NO sloppy work. Sloppy comment only.

  36. “Recent (ice shelf) loss has been very rapid, and goes hand-in-hand with the rapid sea ice decline we have seen in this decade and the increasing warmth and extensive melt in the Arctic regions,” said Ted Scambos, lead scientist at the National Snow and Ice Data Center at the University of Colorado, remarking on the research.

    […]

    Ice shelves, which began forming at least 4,500 years ago, are much thicker than sea ice,

    […]

    Between 1906 and 1982, there has been a 90 percent reduction in the areal extent of ice shelves along the entire coastline, according to data published by W.F. Vincent at Quebec’s Laval University.

    Sounds like the ice shelf loss is slowing down.

    “Between 1906 and 1982, there has been a 90 percent reduction in the areal extent of ice shelves along the entire coastline”… 1.2% per year. The ice shelves should have vanished in 1990, two years before the Canadian Arctic started to warm.

  37. RE: John Marshall observed that…

    “The alarmist method of choosing summer to measure ice loss and scream ‘AGW’ but ignore the winter freeze, regardless of the depth of that freeze, shows a complete one sided cherry picked system of argument which proves nothing.”

    I do tend to concur that the figures pertaining to Arctic Sea Ice Extent at the end of melt season (i.e. September) may take undue pride of place in the publicity stakes. (Although a variety of Naval forces and shipping companies may beg to differ.)

    If it is indeed the case that there exists somewhere a dataset which paints a completely different picture during the winter months, then I’m sure may people would love to see said data. However, if this conjecture is merely predicated upon a personal view of how the world ought to behave, then a measure of “steeling ones’s self for disappointment” may well be in order.

    A variety of sources for the relevant Sea Ice data exist, and, for example, it is straightforward to download monthly figures from the National Snow & Ice Data Centre stretching back to November 1978. Calculating the annual linear trends in Sea Ice Extent (with the equivalent Antarctic figures shown alongside for comparison) yields the following results…

    (numeric values in thousands of square kilometres per annum, Arctic figures precede Antarctic)

    Jan -49 8
    Feb -46 5
    Mar -43 12
    Apr -39 16
    May -33 23
    Jun -44 17
    Jul -68 13
    Aug -72 10
    Sep -81* 14
    Oct -57 15
    Nov -53 10
    Dec -47 15

    Ave -51 16

    *The September 2011 figures should become available in the next couple of days, and as a consequence, the mean rate of ice loss for the month will change to approximately -84,000 sq km/annum.

    Graphical representations showing trends across the entire year (as opposed to the supposedly cherry-picked summer months) are easily available from sites such as the NSIDC itself (using the average of the 1979-2000 figures as its baseline), Nansen Environmental (baseline 1979 – 2006) or the University of Bremen (baseline 1972 – 2008 for the Arctic, 1973 – 2008 for the Antarctic.)

    Obviously, if the above datasets from NSIDC and the others have been falsified, then the original assertion may indeed be valid. Otherwise, it would appear to be somewhat lacking in merit.

  38. Edim wrote…

    “The most important/dominant time scale for humans is the last ~8000 years (since the interglacial maximum peak to the LIA minimum and present). The linear trend is COOLING. I don’t see the trend reversing in the future.”

    Aha, good old “lies, damned lies and Statistics”.
    The above assertion is, strictly speaking, correct. Unfortunately, it is also complete nonsense.

    Edim, I’m quite happy to assume that you are making a genuine mistake here: however it is well past time for you to reassess your understanding of Statistics. Your starting figure of 8,000 years suggests pretty unambiguously that you are talking about the length of time from the Holocene Thermal Optimum up until today. Now, that represents a rather extended X-axis on a graph, and that is at the heart of your misunderstanding.

    Can we, for the sake of simplicity, assume that the LIA petered out around 1850? The reason for choosing this figure is to allow the scale to be brought down to more manageable proportions. If we can agree that the LIA ended about 160 years ago, this gives us a rather obvious cancellation factor.

    Instead of talking 8,000 years ago, we can divide this by 160, thus giving us a mere 50 or so “time units” to work with. (Each of these being a somewhat non-standard 160 years long.)

    Now try out the following steps on Excel. (NOTE you can either do this on a chart, and ask for a linear trend line and formula, or, even easier, just use the SLOPE function.)

    STEP 1: Along Row 1, enter the numbers 1 – 54. (This represents each of the 160-year units, and will simply provide a base for the X-axis in the chart and/or the SLOPE calculation.)

    STEP 2: Starting in the same column as above, but along Row 2, enter the sequence 50, 49, 48, ….. 3,2,1 (This is a gross simplification, but is meant to be representative of declining temperatures from the Thermal Optimum. This will be the Y-axis time-series data values. The actual scale of the Y-axis is unimportant here if one is merely looking at the sign of the trend.)

    STEP 3: Using either a chart and trend line, or the SLOPE function, calculate the trend. With the above figures, this will, unsurprisingly, produce a trend of -1/unit time.

    STEP 4: Insert an additional entry of value 50 at the end of the Row 2 values, such that it now reads “…3,2,1,50″. Recalculate the trend, and it will now read -0.89

    STEP 5: Add further values of 100,150, 200 into the next three cells of Row 2, such that it now has 54 entries and ends with “…3,2,1,50,100,150,200″. Recalculate the trend and it will STILL be negative!

    Let’s try a put that into some physical perspective shall we? If you think that the difference in global average temperature between the Holocene Thermal Optimum and the Little Ice Age was (say) 3 degrees, then, if the temperatures over the next 5 centuries rose steadily to 9 degrees ABOVE the Holocene Thermal Optimum, then the trend over the 85 centuries would STILL be negative!

    The problem with your reasoning, if you haven’t worked it out for yourself, is that the data from the end of the LIA till today only represents about 2% of the time series. When fitting a linear trend to the time series, this small proportion becomes utterly swamped by the other 98%. Even when we extrapolate out another 500 years, this only takes us up to about 7.5% of the whole series.

    I obviously do not know what age you are, but I would be prepared to bet vast sums of money that you will not live to “see the trend reversing in the future”. For the trend to reverse sign during your lifetime, the Sun would need to go nova, and you would need to have found some method of surviving this cataclysm. (If you didn’t survive, it wouldn’t be happening within your lifetime.)

    Under such extreme circumstances, I would certainly be prepared to admit that CO2 was just an unimportant trace gas.

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