Polar Push and Pull



Guest post by Renee Hannon

Introduction
This post examines regional temperature reconstructions during the past several thousand years relative to different baselines and the responses of end member deviants, the Arctic and Antarctic polar extremes. And it’s a quite interesting tug of war.

Why use Temperature Baselines?
Regional and global reconstructions are frequently shown as temperature anomalies relative to a reference timeframe. According to NOAA, temperature anomaly means a departure from a reference value or long-term average. A positive anomaly indicates observed temperatures were warmer while a negative anomaly indicates observed temperatures were cooler than the reference value. Long-term for instrumental records typically means 30 years.

The World Meteorological Organization (WMO) suggests using the latest decade for the 30-year average and recent graphs and maps show temperature anomalies relative to a 1981–2010 base period. The baseline of 1961-1990 is also frequently used because it serves as a good tie point between older proxy datasets that overlap with recent instrumental data.

The New Oxford American Dictionary states that a baseline is a minimum or starting point used for comparisons. Baselines are commonly used in science and elsewhere. For instance, a shale baseline in log analysis of lithologies is a line drawn through the minimum deflection of impermeable shales. Baseline adjustments typically do not change the shape of the individual time series or affect the trends within it. However, baselines can have a significant visual effect on the spatial distribution of data and regional temperature reconstructions.

Recent Baselines Emphasize the Hockey Stick

The Pages 2K Consortium recently produced new global mean temperature reconstructions, presumably in preparation for the next climate symposium and IPCC report (Pages 2K, 2019). This update was basically a statistical exercise of calculating global mean surface temperatures over the past 2000 years. The results are shown in Figure 1, top graph. The global mean temperatures are shown relative to a 1961-1990 baseline and tie in nicely with the instrumental global temperature anomaly. The study used seven statistical methods ranging from Bayesian models, regression-based techniques to newer linear methods to which they assign catchy acronyms.

These global means highlight the significant cold period of the Little Ice Age (LIA) around 1600 AD which is followed by the rapid “industrial” warming trend. The Medieval Warm Period (MWP) also known as the Medieval Climate Anomaly (MCA) is nowhere to be found.

Figure 1: Top graph are global mean temperature anomalies (Pages, 2019). Bottom graph are four regional temperature reconstructions based on a 1961-1990 baseline with a 50-year loess filter applied.

Instead of using global means, this post focuses on spatial temperature reconstructions over the past thousands of years. Four regional reconstructions consisting of the Arctic by McKay, Northern Hemisphere (NH)/Europe by Luterbacher, Southern Hemisphere (SH) by Neukom, and Antarctic by Stenni are plotted in Figure 1, bottom graph. Links to the datasets and a brief description of the temperature reconstructions are listed at the bottom of this post.

Using the 1961-1990 baseline highlights the LIA which shows large temperature divergences between the four regional reconstructions. This is consistent with the deviations of Pages 2K various global mean temperatures around the time of the LIA. The present warming is pronounced, and all the regional reconstructions appear to merge visually creating the so-called hockey stick effect. It’s very difficult to see the MWP or past warm temperature events when using this baseline.

What seems unusual about this baseline normalization is the position of the Antarctic temperature anomaly. Antarctic temperatures plot about 1 deg C warmer than Northern regions. Positioning of regional temperature reconstructions seem completely reversed with Arctic and NH anomalies plotting colder than Antarctic anomalies. Whether by design or chance, using the 1961-1990 baseline visually amplifies present day warming and suppresses known past natural events like the MWP.

LIA Baseline Reveals Arctic Amplification
The same regional temperature reconstructions in Figure 1 are shown in Figure 2. The only difference is the baseline. A baseline was chosen using the LIA cold period or average minimal temperatures during the past 2000 years. The timeframe of 1600-1700 years AD appears to be a semi-stable period where temperatures are not significantly increasing or decreasing. This is different from the 1961-1990 and 1981-2010 baselines which occur during a non-stable rapidly increasing temperature trend.

Using the LIA baseline shows Arctic/NH temperature anomalies generally warmer than Antarctic/SH as they logically should be. Now regional temperature reconstructions show separation during warm periods like MWP and Present. Spatial heterogeneity shown in Figure 2 is evidence of Arctic amplification. Arctic amplification events occur about 400 years AD, during the MWP, during smaller unnamed bursts between 1400-1600 years AD and present day. The present period appears to be part of a warming trend that began with Arctic and NH temperatures rising over 150 years ago after recovery from the cold LIA.

Figure 2: The top graph shows regional temperature reconstructions using LIA years 1600-1700 AD as a baseline and 50-year Loess filter applied. Bottom graph is the difference between Antarctic and Arctic temperature anomalies after 100-year Loess filter is applied.

During the present, Arctic and NH/Europe temperatures begin warming at approximately 1830 AD and before industrial times. SH temperatures begin to increase around 1925 AD and Antarctic temperatures recently began to increase around 1940. That’s over 100 years later than Arctic and NH temperature increases suggesting Arctic amplification and hemispheric temperature asymmetry.

The Arctic temperature anomaly shows an abrupt warming and gradual cooling during the MWP. NH/Europe temperature reconstructions do not show temperatures increasing as strongly during this time. This may be due to the sparseness of tree proxy data available pre-1000 years AD.

The other key difference between the Present and MWP is Antarctic temperature anomalies are colder during the Present. The Antarctic is just now approaching temperature anomalies seen during the MWP and are still lower than pre-1000 AD. Over the past two thousand years, Antarctic temperatures have been generally decreasing by 2 degrees C per 1000 years as described by Stenni. The Antarctic temperature anomaly continued to steadily decrease until about 1940 AD.

Both the MWP and Present have an abrupt warming signal characterized by an initial high rate of temperature increase coupled with a high interhemispheric difference between the Arctic and Antarctic reconstructions. The difference during the MWP is approximately 0.75 deg C and over 1 deg C for the Present. The smaller interhemispheric difference during the MWP is mostly due to higher Antarctic temperature anomalies of 0.35 deg C versus -0.1 deg C for the Present. Another element could be McKay’s Arctic temperature reconstruction where the use of multiple data proxies tends to smooth Arctic temperature peaks.

Both Present and MWP show Similar Latitudinal Trends
The MWP is the most recent analog for the Present warming. There are numerous articles debating the presence and absolute warmth of the MWP (Ljungqvist, Nuekom, Wilson). Most of the discussion is based on NH temperature reconstructions and lack of temperature response in southern latitudes.

Figure 3 is a histogram of the temperature differences between the MWP (950-1100 AD) and Present (1950-2000 AD) relative to the LIA (1600-1700 AD) for thirteen individual reconstructions. Ljungqvist, 2019 conducted a detailed study using similar temperature reconstructions of MWP using a longer timeframe for the LIA (1450-1850 AD). Surprisingly, both the MWP and Present show similar latitudinal temperature differences, larger in the northern hemisphere shown in greens and blues and smaller in the southern hemisphere shown in orange and reds.

Figure 3: Histogram of 13 temperature reconstructions of Present and MWP temperature anomaly differences from the LIA. Reconstructions from Pages 2K 2013 unless otherwise noted. Filled circles are reconstruction means and lines are the quartile range from Ljungqvist 2019.

Absolute temperatures tend to be slightly lower during the MWP than Present relative to the LIA. McKay’s Arctic temperature reconstruction shows that Present is about 0.2 deg C warmer than during the MWP. Pages 2K 2013 Arctic reconstruction shows the biggest discrepancy with Arctic temperatures of almost 0.6 deg C warmer during Present than MWP. Their Arctic reconstruction has recently been updated. Tree ring proxy data is sparse during the MWP leading to greater uncertainty for NH and Europe temperature reconstructions. Otherwise, most of the temperature differences between Present and MWP are within 0.2 to 0.3 deg C and almost within the error of the data.

Instrumental Data
Instrumental data using GISS Surface Temperature Analysis reveals diverging NH and SH trends around 1940 and again after 1980 as shown in Figure 4. The SH temperature anomaly in red is very similar to ocean surface temperatures in blue. Both are flat to decreasing until around 1930 and then begin to increase while NH temperatures are increasing.

Figure 4. Top graphs – GISS NH and SH surface temperature anomalies using a 1961-1990 baseline and 30-year lowess filter. Land and ocean surface temperature anomalies. Bottom graph are differences between the Arctic, NH, NH extratropics and the Antarctic, SH, and SH extratropics, respectively.


The NH and SH interhemispheric difference shows latitude divergence at 1940, convergence by 1980 and increasing divergence since. Arctic and Antarctic polar temperature anomalies show a large difference of almost 1 deg C at 1940.

Climate Models Do Not Reproduce Antarctic and SH Temperature Reconstructions
The global spatial pattern of the Present suggests that internal variability plays a major role in driving heterogeneous warming and is underestimated in model simulations. Both Luterbacher and Ljungqvist state that NH and European temperature reconstructions have larger temperature differences between the Medieval period and the Little Ice Age than in climate simulations. Luterbacher states this discrepancy may be due to inflated variability of the reconstructions and/or an underestimation of climate model sensitivity to internal variability on centennial and longer time scales. Ljungvist suggests the disagreement is related to too-cold initial ocean conditions and too-weak internal variations.

Climate simulation results are also poor in matching Southern Hemisphere temperature reconstructions (Nuekom, 2018). In the SH, climate models show a much greater response to volcanic, aerosol and greenhouse gas forcings than seen in the temperature reconstructions. Also, climate models do not recognize the warming delay of the SH and Antarctic and therefore overestimate southern hemisphere warming. This suggests climate models have less interhemispheric variance and greater consistency between hemispheres than in actual temperature reconstructions. Nuekom speculates that temperature responses in the ocean-dominated SH are delayed and buffered by the large heat capacity of the oceans and by more monotonic oceanic processes. Pages 2K, 2015, agrees that better knowledge of internal and forced variability in the ocean is necessary to understand the influence of climate modes on temperature variability.

Conclusions
Baselines are important in the visual presentation of global climate heterogeneity. The 1961-1990 baseline commonly used emphasizes the LIA and the present rapid warming. Past warm anomalies are obscured. Conversely, converging spatial temperature anomalies during the cold LIA demonstrates separation of northern latitudes from southern latitude temperatures during warm events such as the MWP and Present.

The MWP analog is frequently questioned as to whether it is a global event and not having a global impact, especially in the southern latitudes. Ironically, the Present shows similar smaller temperature increases and delayed warming in southern latitudes. The Present warming began as an abrupt warm upturn from the cold LIA around 1830 initially in the Northern Hemisphere and Arctic.

The Arctic and NH are on different climate pathways than the SH and Antarctic. Northern latitudes respond rapidly to short-term influences such as volcanic activity, GHG and solar whereas ocean-dominated southern latitudes lack many of these signals. Until science and climate models can sort out natural underlying polar causes and effects, only then can science unravel the potential influence of anthropogenic intervention on climate change.

Acknowledgements: Special thanks to Donald Ince and Andy May for reviewing and editing this article. This article is dedicated to my Delaware friends.


References Cited:
Cowtan, K. & Way, R. G. Coverage in the HadCRUT4 temperature series and its impact on recent temperature trends. Q. J. R. Meteorol. Soc. 140, 1935–1944 (2014). https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/qj.2297Documents

Ljungqvist, F.C.; Zhang, Q.; Brattström, G.; Krusic, P.J.; Seim, A.; Li, Q.; Zhang, Q.; Moberg, A. Centennial-Scale Temperature Change in Last Millennium Simulations and Proxy-Based Reconstructions. J. Clim. 2019, 32, 2441–2482. https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-18-0525.1

Luterbacher J et al. European summer temperatures since Roman times. Environmental Research Letters 11, 024001, DOI: 10.1088/1748-9326/11/2/024001, 2016.

McKay, N. P. and Kaufman, D. S.: An extended Arctic proxy temperature database for the past 2,000 years, Scientific Data 1:140026, doi:10.1038/sdata.2014.26, 2014 Dataset: https://www1.ncdc.noaa.gov/pub/data/paleo/pages2k/arctic2014temperature-v1.1.txt

McIntyre, S. Climate Audit blog. https://climateaudit.org/?s=Pages

Neukom, R., Schurer, A. P., Steiger, N. J. & Hegerl, G. C. Possible causes of data model discrepancy in the temperature history of the last Millennium. Sci. Rep. 8, 7572 (2018). https://www.nature.com/articles/s41598-018-25862-2

PAGES 2k Consortium: Continental-scale temperature variability during the past two millennia, Nat. Geosci., 6, 339–346, Published online 21 April 2013, https://doi.org/10.1038/NGEO1797, 2013.1c PAYWALLED. Dataset available see above.

PAGES 2k-PMIP3 group: Continental-scale temperature variability in PMIP3 simulations and PAGES 2k regional temperature reconstructions over the past millennium, Clim. Past, 11, 1673– 1699, https://doi.org/10.5194/cp-11-1673-2015, 2015.

PAGES 2k Consortium- Neukom, R., Barboza, L.A., Erb, M.P. et al. Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era. Nat. Geosci. 12, 643–649 (2019). https://doi.org/10.1038/s41561-019-0400-0. Paywalled, but shared by the author at the following link. http://pastglobalchanges.org/science/wg/2k-network/nature-geosc-2k-july-19

Stenni, B., Curran, M. A. J., Abram, N. J., Orsi, A., Goursaud, S., Masson-Delmotte, V., Neukom, R., Goosse, H., Divine, D., van Ommen, T., Steig, E. J., Dixon, D. A., Thomas, E. R., Bertler, N. A. N., Isaksson, E., Ekaykin, A., Werner, M., and Frezzotti, M.: Antarctic climate variability on regional and continental scales over the last 2000 years, Clim. Past, 13, 1609–1634, https://doi.org/10.5194/cp-13-1609-2017, 2017.

Wilson, R. et al. Last millennium northern hemisphere summer temperatures from tree rings: Part I: The long-term context. Quat. Sci. Rev. 134, 1–18 (2016). https://www.st-andrews.ac.uk/~rjsw/N-TREND/Wilsonetal2016.pdf


Temperature Reconstruction Datasets
Surface temperature reconstructions over the past thousands of years are numerous (Luterbacher, McKay, Nuekom, Stenni, and Wilson) to name a few. Most of these authors, if not all, are part of the Pages 2K Consortium. Pages 2K compiled a temperature proxy database that includes almost 700 records from ice cores, sediment, corals, tree rings, and pollen in 2013 and updated it in 2017.

Regional reconstructions used in this post are the Arctic by McKay, Northern Hemisphere (NH)/Europe by Luterbacher, Southern Hemisphere (SH) by Neukom, and Antarctic by Stenni. The Arctic reconstruction by McKay utilizes proxy records consisting of ice cores, tree rings, lake and marine sediments north of 60 deg N. The Europe reconstruction used is tree based and like Wilson’s NH reconstruction. Wilson’s NH data ends at 900 AD and includes a couple of peak temperature differences during the MWP (not used). Neukom’s SH reconstruction is based on ice cores, tree rings, and corals and ends at 1000 AD. Stenni used mostly ice core isotope data to produced Antarctic temperature reconstructions.

There is a notable shift is data quantity and quality of temperature datasets around 1000 AD especially tree rings. The number of tree ring records are reduced significantly from 400 records post-1600 AD to less than 30 records pre-1000 AD. Unfortunately, this reduction of proxy data occurs in the middle of the past analog warm period, the MWP. For an objective review of Pages 2K datasets, I recommend reading Steve McIntyre’s articles particularly in reference to tree ring data. He discusses the accuracy of tree ring data, the divergence problem and cherry picking of data.

Arctic McKay, 2016. https://www1.ncdc.noaa.gov/pub/data/paleo/pages2k/arctic2014temperature-v1.1.txt

Antarctic Stenni, 2017. https://www1.ncdc.noaa.gov/pub/data/paleo/pages2k/stenni2017antarctica/CPSrecons/All_regions_recons_CPS.csv

Europe Luterbacher, 2016. https://www1.ncdc.noaa.gov/pub/data/paleo/pages2k/EuroMed2k/eujja_2krecon_nested_cps.txt

NH Wilson, 2016. https://www.ncdc.noaa.gov/paleo-search/study/19743

SH Nuekom, 2014. https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/neukom2014/SH_Fig2_recons_Ens-means_wrt1000-2000.txt

Pages 2K 2013 dataset. www.ncdc.noaa.gov/paleo/pages2k/pages-2k-network.html

Pages 2K-Nuekom Ensemble Means 2019. https://www.ncdc.noaa.gov/paleo-search/study/26872.

Instrumental Data. https://data.giss.nasa.gov/gistemp.



49 thoughts on “Polar Push and Pull

  1. Something strange is going on with the changing baselines between Fig. 1 and Fig. 2. There is no way
    that changing the baseline will change which temperature anomaly is greatest. If the antarctic anomaly is greater than the arctic anomaly using one baseline then it will be great using all baselines. The maths is simple:

    Suppose that x>y then you add some constant a to both and you will still have x+a>y+a.

    Perhaps the author is applying a different baseline to each hemisphere in which case the curves should not be on the same graph and any comparisons are meaningless.

    • “The maths is simple:
      Suppose that x>y then you add some constant a to both and you will still have x+a>y+a.”

      But it isn’t the same constant. For NH, say, it is the difference between 1961-90 and 1600-1700 in the NH. And for Antarctica, it’s the corresponding difference in Antarctica.

        • “Nick :Still suggesting these major warm and cold periods were local events?”

          I’m pointing out some basic math. But yes, this article confirms that they were locally very different. Just look at Fig 3. Or look at Fig 1, trying to match events. You see an MWP marked for Arctic at 1000 AD. What happens then to NH? It’s in a local slide. SH? It only starts in 1000 AD, but no sign of a peak there. Antarctica? Just a continuous slide from about 500 AD to about 1925. None of this matches up.

          • Nick,
            “What happens to the SH?”
            No data during the MWP, and the SH is pretty dismal during the Present also, a whopping 0.25 deg C increase.

            “Antarctic?”
            The Antarctic is actually warmer during the MWP than it is during the Present.

          • “using the 1961-1990 baseline visually amplifies present day warming and suppresses known past natural events like the MWP.”

            It is not the baseline which “suppressing” MWP. That does not make sense.

            It is probably how they are blending SH record which starts half way through MWP. Their first graph has a questionable fluffy “blending” around 1000AD, which is suspiciously flat. My bet is that they are doing some Mannian blending here, like the way he grafted proxies to observed temps and then ran a lowpass filter over the splice to blend it all together.

            They have three records before 1000AD and four after, the difference being the entire SH outside Antarctica. That means they have inhomogeneous data which they are artfully “blending” together and presenting as a homogeneous record.

            SH proxy does not start a zero so when it in introduces it will pull the average down. Enough to clip MWP and provide a grey homogenised mess.

            The art is always the same, if you mix enough unreliable proxy data with large uncertainties erroneous swings and put them all through the sausage machine, you uniform blended sausage meat out the other end. You then tack on the observational temperature record produce your hockey stick.

            More data frauwwd by the globalist data manipulation industry.

          • Ah, I think I get Renee’s point about baselines.

            It is still what I was saying about slicing incompatible datasets. In Renee’s reworking in figure SH kicks in with a smaller but positive offset rather than the authors significant negative offset.

            The baselines should have been selected so that SH kicked in at zero and thus would not introduce a bias ( and then try to hide it with some blending ).

            It is still yet another form of the usual sausage machine which mashes wobbly error laden proxies in a grey homogeneous mess with no analytic value.

          • Renee,
            “The Antarctic is actually warmer during the MWP than it is during the Present.”

            But it was even warmer earlier. You would not look at that period and say that there was a MWP. As your Stenni reference says, Antarctic temperatures show a fairly uniform cooling trend over the last 2000 years, as expected from the orbital causes of the Holocene.

          • Nick,
            “You would not look at that period in the Antarctic and say there was a MWP”

            And can also say that the Antarctic is not responding to the Present warming either.

      • So the 1961-1990 temps for Antarctica were almost exactly the same as 1600-1700. The value of “a” looks almost precisely 0 for the Antarctic data.

        • Michael,
          Yes, the Antarctic data is pretty much the same for both baselines. It’s the other temperature reconstructions, Arctic, NH and SH that are shifted up to where the temperature from 16-7000 AD averages zero. The Arctic data for example is shifted higher by over 1 deg C, from -1.2 to 0.

  2. About 10 years ago McShane and Wyner put together a thoughtful and pretty condamming statistical analysis of proxie data:
    “We find that the proxies do not predict temperature significantly better than random series generated independently of temperature.”
    There was a lot of loud words about this paper and a rejoinder by McShane and Wyner, which in my opinion defended and validated every point they made earlier.
    Then 10years of silence about this.
    How can it be possible to have ANY proxie reconstruction as long as that paper is not refuted?

    LoN

  3. I’m a bit sceptical about accuracy even of the current Arctic data, so when someone quotes temperature data with resolution of one year (crude interpolation?) for Arctic area for 2 millennia I’m prepared to dismiss it out of hand.
    But to be fair, I decided to look at spectral composition which might revel a bit more, and indeed it did, since decadal peaks are in the same range as those for the CET with the much higher data quality, as shown here:
    http://www.vukcevic.co.uk/ArcticSpec.htm
    Hence, appears to be a degree of credibility to the Arctic data reconstruction which I did not expect at the start.

    • Vuk,
      I attempted to use temperature reconstructions that utilize multiple proxy data with both low and high resolution proxy data and were recently referenced in the literature. The Arctic reconstruction by McKay uses ice cores such as GISP2 and GRIP combined with tree rings, lake and marine sediments. It’s one one the better Arctic datasets I’ve run across.

  4. Its the same old story, thing are still far worse than we thought.

    The present problem with the Crown virus will massively reduce the money available to governments, and will result long term in far less for the myth of climate change.

    Expect lots more scare talk, but right now the World is far more into surviving the next 12 months, than in saving the Planet for our grandchildren.

    VK5ELL MJE

    • But the wonderful thing with this Crown Crisis is that it is a microcosm of the same industry as the CAGW industry but much faster.
      As such I think we will be able to calibrate the BS factor.

      We in NZ have the ruling cluster talking 50K to 80K dead I pick 1500 is more likely so there we have it.

      If I am wrong and its 5000 they live in the world of 10% and me 25% but still kind of there, if its 2000 dead I am credible they remain in the 4% class fully busted. Now watch the numbers, the silence on chloroquine says it all its still not a silver bullet but it looks better than 90% effective. And really cheap but no left wing grab in that story.

  5. “…between Present and MWP are within 0.2 to 0.3 deg C and almost within the error of the data.”

    Renee, this was a lot of work and I thank you for it. However, with the ‘local’ nature of all proxies, the picking and choosing among them to fit the narrative, the resolution of proxy data in some cases a century or several, the unconscionable fiddling by ideologues with the instrumental data, I’m afraid the quote above gives the imprimatur of science to what continues to be a shoddy political exercise.

    Even giving the modern temperature record a pass, the 150 years of its existence should be averaged to one data point and then compared to the MWP. You must know that disappearing the MWP (and the Roman WP, etc.) and the LIA until recently (after a barrage of info from this relatively recent period) was discussed in the Climategate emails.

    History, like the growing of grains and raising sheep and other animals in Greenland (not to be tried today), the medieval wine industry in Scotland, etc. are better than proxies. Likewise, the even warmer Roman period (Hannibal would have had a grand time getting his military elephants over the Alps today.

    • Gary P

      Right on, what you say: average the data and create a point makes sense. This splicing together of data sets with different smoothing (effectively) is really misleading.

      In real science it is not allowed.

  6. “Regional and global reconstructions are frequently shown as temperature anomalies relative to a reference timeframe. According to NOAA, temperature anomaly means a departure from a reference value or long-term average. A positive anomaly indicates observed temperatures were warmer while a negative anomaly indicates observed temperatures were cooler than the reference value”

    The use of temperature anomalies assumes that the seasonal cycle is invariant even over long time spans.

    Here is a test of that assumption.

    https://tambonthongchai.com/2018/08/17/trendprofile/

  7. “These global means highlight the significant cold period of the Little Ice Age (LIA) around 1600 AD which is followed by the rapid “industrial” warming trend. The Medieval Warm Period (MWP) also known as the Medieval Climate Anomaly (MCA) is nowhere to be found”

    A new MWP angle is that “it may have been warmer but it was a local europe thing and not a global thing and so it doesn’t count”. (Neukom 2019)

    https://tambonthongchai.com/2020/03/24/unprecedented/

    • Chaamjamal,
      “A new MWP angle is that it may have been warmer but it was a local Europe thing and not a global thing so it doesn’t count” .

      Unfortunately, the Nuekom, 2019 article is paywalled. However, he does state in the abstract that the rapid global warming seen in observations over the past 150 years does show NEARLY global coherence. SH temperatures are barely increasing and Antarctic temperatures have been decreasing to stable. In fact Present Antarctic temperature anomalies are still colder than MWP Antarctic temperature anomalies. So, is Present warming just a local Northern Hemisphere thing?

  8. The Hockey Stick is a lie and its perpetrators are enemies of humanity who should suffer the most severe penalties. They have the blood of millions on their foul hands.

  9. Thank-you Renee Hannon
    You bring a clarity, transparency and honesty to late Holocene proxy temperature reconstruction that is entirely – and deliberately – lacking in the disgraceful PAGES 2k project.

  10. Using actual temperatures from the Antarctic and Arctic paints a very different picture (see data in my paper in the Elsevier volume (2016). Using data from all weather stations in Greenland show a clear picture of the Arctic closely following global patterns, high temps during the 1915-1945 warm period, cooling during the 1945-1980 cool period, and warming during the 1980-2000 warm period. But Arctic temperatures in the 1930s were warmer than the latest warm period (1980-2000).

    Satellite (UAH, RSS) temperatures from Antarctica show no warming (in fact slight cooling) over the past 37 years and ground temps at two stations near the South Pole show no warming since 1957.

    This is the reality of what is happening in the Antarctic and Arctic–anything else is nonsense.

  11. Thank you, Renee, for the post. Well done.
    And thank you, Andy, for posting it here at WUWT.

    To all those reading this thread, STAY SAFE AND HEALTHY.

    Regards,
    Bob

  12. “The World Meteorological Organization (WMO) suggests using the latest decade for the 30-year average and recent graphs and maps show temperature anomalies relative to a 1981–2010 base period. The baseline of 1961-1990 is also frequently used because it serves as a good tie point between older proxy datasets that overlap with recent instrumental data.”

    Thats not why 1961-1990 is used

      • Andy May

        It is used because it has been formerly an offcial reference period, like has been 1971-2000 as well.

        Japan’s JMA introduced WHO’s most recent proposal (1981-2010) for external publication, but their internal 5° gridded Globe data still contained last year anomalies wrt 1971-2000.

        J.-P. D.

  13. “Instrumental data using GISS Surface Temperature Analysis reveals diverging NH and SH trends around 1940 and again after 1980 as shown in Figure 4. The SH temperature anomaly in red is very similar to ocean surface temperatures in blue. Both are flat to decreasing until around 1930 and then begin to increase while NH temperatures are increasing.”

    who knew that land warms faster than water, and that the SH has more water!

  14. “The Present warming began as an abrupt warm upturn from the cold LIA around 1830 initially in the Northern Hemisphere and Arctic.”

    The Central England Temperature database and many reconstructions show the present warming period starting in the late 1600s with a massive 1C rise in about 80 years, then cooling again until about 1830.

    Check out Wikipedia reconstruction graph for “Little ice age” which show most reconstructions showing warming started in late 1600s and the two that don’t are Michael Mann’s hockey stick and his apprentice, Briffa.

    It is important that the earlier date is used because it highlights that our current warming was not started by an increase in CO2 and it was only around 1950 that CO2 could theoretically have had any significant effect on global temperatures.

    However, the planet cooled from 1940 until the late 1970s , so it’s really only the last 40 years that an argument could be made for CO2 causing higher temperatures.

    However, the warming from 1910 to 1940 was just as significant as the 1980 to 2020 warming so it is impossible to scientifically establish that CO2 has had any significant effect on global warming.

    Historical reconstructions of the Holocene tell us that what’s happening now has had many precedents and rather than demonising CO2, we should be celebrating it because another ice age is just around the corner.

  15. Dear Renee Hannon,

    It is like you are completely unaware that these ‘reconstructions’ are nothing but mathematical anomalies created by using high noise data and sorting it through various correlation mechanisms to temperature.

    These are mathematical scribbles with no more meaning than a parasitic cat dragging its ass on the ground.

  16. Renee Hannon,
    Thank you for your excellent article… and your polite, to-the-point responses to commenters here, even to the ones that are less than polite to you.

  17. Renee Hannon

    Thanks for your interesting presentation & evaluation.
    It was nice to experience a guest post free of any dumb polemic concerning this poor hockey stick 🙂

    Please don’t bother about more or less aggressive comments here and there, showing the usual mix of arrogance and ignorance. Most of these ‘commentator’s (quotes needed) would never be able to replicate your work.
    *
    I have been wondering about a rather secondary point: that you seem to consider Antarctic’s anomalies unusual if not even incorrect when they are higher than those computed, wrt the same period of course, for the Arctic.

    Why should anomalies computed for a colder region be automatically lower than those computed for a warmer one?

    I apologise: this makes few sense to me, just because
    – the choice of a reference period is arbitrary;
    – wether anomalies for a region / a latitude band are higher / lower than those for another one solely depends on the regional / latitudinal average of all singular anomalies computed out their own data for the common period.

    Rgds
    J.-P. Dehottay

  18. An article popped up today about how tropical it was at the South Pole during the Cretaceous. Not much new there for anyone interested in Gondwanan etc flora. However, the temperatures were then modelled to see what the CO2 levels had to be for such temperatures to arise.

    There were two comments by others. One said Antarctica must have been further north then and drifted south since.

    Another said that reptiles evolved at higher temperatures than mammals and mammals are therefore more threatened by AGW because they can’t handle heat.

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