by haakonsk
The United Nations’ Intergovernmental Panel on Climate Change (IPCC) published their latest assessment report (AR6) in 2021. In 2023, the Clintel Foundation published a report which criticizes AR6.
Clintel is short for Climate Intelligence, and the Clintel Foundation doesn’t think there’s a climate emergency. Overall, Clintel’s main criticism is that the IPCC hasn’t reviewed the scientific literature in an objective way, as is their stated mission.1)
This article focuses on the topic of chapter 2 of the Clintel report: The Resurrection of the Hockey Stick.
What is a “hockey stick” temperature graph?
The image below shows a “hockey stick” temperature graph for the past 1000 years. This particular version is from the Summary for Policymakers of the IPCC’s third assessment report from 2001, and it applies only to the Northern Hemisphere.
The graph is called a hockey stick graph because the shape somewhat resembles an ice hockey stick with a long, flat “shaft” and a big “blade” shooting up at the end. If there had been more variability in the temperature before the “blade” – meaning that the “shaft” wasn’t flat – then it wouldn’t be a hockey stick graph.
Short summary
A “hockey stick” temperature graph has made a comeback in the latest IPCC report from 2021 (AR6), after being absent in the fourth and fifth reports.
Unlike the previous two reports which included multiple temperature estimates, AR6 relies on just one temperature estimate for the past 1000-2000 years, sparking criticism.
Moreover, this single estimate has itself been criticized. The perhaps most important issue relates to a method that incorrectly generates hockey stick temperature graphs from non-hockey stick data.
In general, the quality and amount of data that can tell us something about past temperatures quickly decline when we go further back in time. Based on the currently available data, it might therefore be impossible to know whether the global temperature of the past 1000-2000 years has a hockey stick shape or not.
Why is the hockey stick important?
A hockey stick temperature graph is convincing evidence that human emissions of greenhouse gases have a big impact on the climate, and according to IPCC, humans are responsible for roughly 100% of all warming over the past 150 years.
For Clintel, who doesn’t think there’s a climate emergency, it would make their argumentation easier if past temperature variability were higher, as more of the recent warming could then be attributed to natural causes. They write that if past temperature variability has been high, then “the temperature rise of the past 170 years would have to be shared [between] anthropogenic and natural causes.” 2)
However, this way of thinking is a fundamental mistake, according to climate scientist Ulf Büntgen. He argues that a high pre-industrial variability would mean that the atmosphere is more sensitive to changes in e.g. greenhouse gases, than if pre-industrial temperature variability has been low.3)
In any case, what’s most important is, of course, to get a correct estimate (or “reconstruction”) of past temperatures — whose shape may or may not resemble a hockey stick. Let’s explore!
From Chapter 2 of the Clintel report:
One of the big surprises of the IPCC’s AR6 report was the comeback of the so-called “hockey stick“. This term refers to the northern hemispheric and global temperature development of the past 1000-2000 years. More than two decades ago, Mann et al. (1999) published a reconstruction in which the temperatures of the pre-industrial period 1000-1850 AD appear rather flat and uneventful (the “shaft” of the ice hockey stick), followed by a fast and allegedly unprecedented warming since 1850 (the “blade”). The hockey stick became world famous because it was featured prominently in the Summary for Policymakers (SPM) in the IPCC’s 3rd Assessment report [see image at the top of this article].
The hockey stick graph received a fair amount of criticism, and Clintel explains that the hockey stick graph was subsequently corrected — resulting in a temperature reconstruction with more pre-industrial variability, and thus without a hockey stick shape. IPCC’s fourth and fifth assessment reports did not include a hockey stick temperature graph, but in the most recent assessment report (AR6), the IPCC once again presents a temperature reconstruction with low pre-industrial variability – a new hockey stick:
The new hockey stick temperature reconstruction is based on the work of PAGES 2k, the flagship of the PAGES (Past Global Changes) project. Clintel writes:
The PAGES 2k group is specialised in climate reconstructions and back in 2013 was comprised of the majority of all active paleoclimatologists. In 2019, PAGES 2k published a new version of the temperature development of the past 2000 years (PAGES 2k Consortium, 2019 4) [hereafter “PAGES 2k 2019”]). Surprisingly, it differed greatly from the predecessor version. Even though the database had only mildly changed, the pre-industrial part was now suddenly nearly flat again. The hockey stick was reborn[.]
And:
Evidence suggests that a significant part of the original PAGES 2k researchers could not technically support the new hockey stick and seem to have left the group in dispute.
It would be very interesting to read more about this. Unfortunately, Clintel doesn’t provide a reference.5) Anyway, Clintel continues:
Meanwhile, the dropouts published a competing temperature curve with significant pre-industrial temperature variability (Büntgen et al., 2020)[.] On the basis of thoroughly verified tree rings, the specialists were able to prove that summer temperatures had already reached today’s levels several times in the pre-industrial past. However, the work of Ulf Büntgen and colleagues was not included in the IPCC report[.]. [Emphasis added]
Did they really prove it? Probably not.
PAGES 2k 2019 is a global multi-proxy temperature reconstruction. Büntgen et al. 2020, on the other hand, applies only to the extra-tropical Northern Hemisphere, uses only one proxy-type – tree rings, and only looks at summer temperatures, not yearly temperatures. Still, it may actually make sense to compare Büntgen et al.’s reconstruction with PAGES 2k 2019, but that’s not immediately obvious, and a discussion of this by Clintel could have been beneficial.
What’s a multi-proxy temperature reconstruction?
In the previous paragraph, the term multi-proxy temperature reconstruction was used. A proxy — in this case a proxy for temperature — is an alternative to a direct temperature measurement with a thermometer. We’ve only had thermometers for a few hundred years, so we have no direct measurements of temperatures before that. To be able to estimate past global temperatures, scientists thus have to use less accurate alternatives instead of direct temperature measurements. These alternatives are called proxies. One proxy that can be used for temperature is tree ring width. Trees will typically grow more in a warm year than in a cold year, so for certain temperature sensitive trees, bigger tree rings could mean higher temperature.
A multi-proxy temperature reconstruction is an estimate of past temperatures that’s based on multiple proxy types. Tree ring width is typically one of several proxy types used in a multi-proxy temperature reconstruction.
The reason it may still make sense to compare Büntgen et al. 2020 and PAGES 2k 2019 is that PAGES 2k 2019 is also biased towards the Northern Hemisphere, towards summer temperatures, and towards the use of tree ring proxies:
PAGES 2k 2019 used 257 6) proxies out of a total of 692 proxies in the PAGES 2k database. 210 of these are high-resolution proxies with yearly resolution. In the below image, which is parts A, B and C from Figure 2 of Anchukaitis and Smerdon 2022, we can see
A) that most of the proxies with yearly resolution are based on trees (tree rings),
B) that the average latitude is not the equator, but 47 degrees north, and
C) that most of the proxies capture summer temperature (the growing season for trees in the extra-tropical Northern Hemisphere), not yearly temperature.
Criticism of PAGES 2k 2019 and IPCC
Anchukaitis and Smerdon 2022, where the above image is taken from, is an article that reviews “the strengths and limitations of existing global and hemispheric paleoclimate temperature reconstructions and highlight[s] likely sources of [existing] uncertainties, all in the context of [IPCC AR6].” They’re quite critical of the IPCC’s new hockey stick graph.
One thing they criticize IPCC for, is that the IPCC did not consider a variety of multi-proxy temperature reconstructions, which they had done in their previous two assessment reports (AR4 and AR5):
Despite the attempts in AR4 and AR5 to reflect uncertainties across multiple reconstruction efforts and to represent time-dependent uncertainties as they expanded back in time, these efforts were surprisingly abandoned in the most recent AR6 Working Group I (WG1) report in favor of a single ensemble-based reconstruction of global temperature with relatively static uncertainty bounds over the [past 2000 years.] […] The most recent assessment […] is thus a turn away from the attempts in previous reports to provide a full accounting of uncertainty in reconstruction efforts […], an incomplete representation of forward progress in both understanding and quantifying disagreement in temperature reconstructions of the [past 2000 years], and is an unnecessary return to a singular representation of large-scale temperature estimates that span all or part of the last several millennia.
Another point made by Anchukaitis and Smerdon, which they also touched upon in the above quote, is that the uncertainty range in the new hockey stick graph is far too narrow, especially when we get further back in time:
[T]he estimated uncertainties for this reconstruction used in AR6 only reflect the methodological differences as applied to the PAGES2k dataset at decadal and longer time scales. Much larger latent uncertainties are almost certainly present due to the change through time in proxy availability, sensitivity, and spatial distribution[.] Because the consequences of these uncertainties are poorly represented in AR6, which is intended to reflect an assessment of the current state of the science, the report fell short in its representation of what we know and what we have learned about Common Era [=past 2000 years] temperatures over the last two decades. [Emphasis added]
Clintel, of course, also criticizes PAGES 2k 2019:
Like its predecessor, the new hockey stick by PAGES 2k 2019 is based on a large variety of proxy types and includes a large number of poorly documented tree ring data. In many cases, the tree rings‘ temperature sensitivity is uncertain. For example, both PAGES 2k Consortium (2013) and PAGES 2k Consortium (2019) used tree ring series from the French Maritime Alps, even though tree ring specialists had previously cautioned that they are too complex to be used as overall temperature proxies (Büntgen et al. 2012; Seim et al., 2012).
In contrast, Büntgen et al. (2020) were more selective, relied on one type of proxy (in this case tree rings) and validated every tree ring data set individually. Their temperature composite for the extra-tropical northern hemisphere differs greatly from the studies that use bulk tree ring input.
In some cases, PAGES 2k composites have erroneously included proxies that later turned out to reflect hydroclimate and not temperature. In other cases, outlier studies have been selected in which the proxies exhibit an anomalous evolution that cannot be reproduced in neighbouring sites (e.g. [Medieval Warm Period] data from Pyrenees and Alboran Sea in [PAGES 2k 2013]) (Lüning et al., 2019b). Outliers can have several reasons, e.g. a different local development, invalid or unstable temperature proxies, or sample contamination.
However, starting from the third sentence, this text is virtually copy-pasted from a study by Lüning and Lengsfeld (2022). Clintel could have at least added a reference to that study. Also, it’s unclear whether the last paragraph applies to PAGES 2k 2019 or just to earlier PAGES 2k versions. If it does indeed apply to the 2019 version, then the Clintel report would have benefited from documenting it.
A new temperature reconstruction that includes short-term trends
As noted, PAGES 2k 2019 is a multi-proxy temperature reconstruction (although it may be biased towards tree-rings), while Büntgen et al. 2020 only uses tree rings. All things equal, multi-proxy reconstructions should be preferred over single-proxy reconstructions; according to Büntgen et al. 2022, there is “community-wide agreement that multi-proxy compilations are the most appropriate methodology to climate reconstructions“.
One reason that multi-proxy reconstructions are better is that some proxy types can reveal short-term temperature variability, but not long-term variability, while others can reveal long-term variability, but not short-term variability.
And while “tree rings are excellent at capturing short frequency variability, they are not very good at capturing long-term variability.” (Fundamentals of Tree-Ring Research, James H. Speer, 2009) This is also pointed out by Büntgen et al. 2020 itself, the study that used tree-rings only:
[Tree ring width] is particularly limited when reconstructing the amplitude and duration of climatic extremes[.]
And:
While we have no doubt about the timing of past summer cooling in our reconstructions, accuracy of the temperature amplitude remains somewhat challenging.
Since some proxy types are good for capturing short-term trends, while others are good for capturing longer-term trends, the best way to make a temperature reconstruction should be to use proxy-types that capture long-term variability for the long-term trends, and then use e.g. tree rings to show the short-term variations on top of the long-term trends.
Titled “A frequency-optimised temperature record for the Holocene“, Helen Essell et al. 2023 is a study that combines short-term and long-term proxies in this way. It’s the first study that attempts to “present […] temperature variability on interannual timescales over the past 12 000 years.” Previous studies have had a much lower (worse) time resolution, and hence the temperature graphs from those studies have been smoother and with less variability.
However, while “interannual signals ([less than] 10 years) are best captured by tree-ring chronologies (wood)“, only 3 tree-ring proxies were included in the study. Unfortunately, the study doesn’t discuss uncertainties related to the low number of short-term proxies.
The study performs a global temperature reconstruction, but like most other “global” reconstructions, there is a bias towards the Northern Hemisphere and summer temperatures.
Also note that the study looks at the time period 12,000 – 0 BP, where BP means “before present” and “present” is defined as the year 1950. This is a longer time period than we normally talk about for hockey stick temperature graphs, which is 1000-2000 years. Hockey stick temperature graphs also normally include the time period after 1950, which is often represented by thermometer data in addition to proxy data. Helen Essell et al. 2023 does not use thermometer data.
Although the time period is different, it’s interesting to compare IPCC’s hockey stick graphs with the new temperature reconstruction from Helen Essell et al. 2023, which looks like this (where light green shows the uncertainty range):
If the results of this study are broadly correct, then pre-industrial temperature variability has been high, which would mean that hockey stick temperature graphs are not correct.
Since Helen Essell et al. 2023 is a new and novel study, it may or may not contain important errors, but their criticism of the IPCC is very relevant regardless; the IPCC should not compare long-term average temperatures with recent yearly (high) temperatures:
[W]e remain critical of the interpretation of the smooth trajectories of existing Holocene temperature reconstructions, which have influenced policy debate. For instance, the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), and its ‘Summary for Policy Makers’ and ‘Technical Summary’ compared recent annual extremes against past centennial averages. Such unequal comparison has the potential to mislead portrayal of the threat of global warming as low- and high-frequency records reflect different aspects and amplitudes of the Earth’s climate system. [References removed]
Stephen McIntyre
Stephen McIntyre is a central figure in the hockey stick controversies. McIntyre thinks (as does Clintel) that the IPCC wanted to get a hockey stick temperature graph: “the IPCC remains addicted to hockey sticks“, he wrote in a 2021 article on his blog, ClimateAudit, where he explains some of his major complaints about the new IPCC hockey stick.
Stephen McIntyre is well-known for his criticism of Michael Mann’s original hockey stick graph. He has been reporting errors in the PAGES 2k temperature reconstructions since at least 2013, when the IPCC was set to use data from the PAGES 2k project in its 5th assessment report (AR5). Much of the proxy data was already familiar to McIntyre at the time, since many of the proxies used by PAGES 2k had also been used by Michael Mann and in other earlier temperature reconstructions.
So it’s safe to say that McIntyre is very knowledgeable when it comes to the proxies underlying the temperature reconstructions that have been published in the last few decades. And in 2019, McIntyre commented on Twitter that: “[…] I probably know the data better than the article lead authors[.]“
Asian tree ring chronologies: – It’s worse than anyone can imagine
What’s a tree ring chronology?
A tree ring chronology represents the year-to-year variations in tree growth within a geographical region. In a chronology for temperature sensitive trees, the variations in tree growth will roughly correspond to temperature variations. Scientists take samples from lots of temperature sensitive trees in a region, and you can think of the resulting chronology as an average of all those trees.
The most common tree ring proxy is tree ring width. There may be better tree ring proxies, but tree ring width is the one that’s easiest (cheapest) to measure.
Since the cross-section of the stem of a tree grows roughly the same amount each year, tree rings are typically wider for younger trees. For this reason, you can’t directly compare tree ring widths and say that, just because the tree ring was wider in a given year, that the temperature was also higher in that year. You have to first adjust for the age of the tree and potentially other factors. This adjustment is called standardization (or detrending), and it’s usually performed on data for each tree before the data from individual trees are combined into a chronology.
There are many problems with the chronologies included in PAGES 2k 2019. Here, I’ll just focus on the most important issue. But see footnote 7) for a summary of some other issues.
According to McIntyre, some of the tree ring chronologies included in PAGES 2k are incorrectly calculated:
It’s hard for a statistical methodology to be so bad as to be “wrong”. Mann’s principal components methodology was one seemingly unique example. PAGES2K’s Asian tree ring chronologies are another. It’s worse than anyone can imagine. [Emphasis added]
In a 2021 article, McIntyre writes about the Asian tree ring chronologies used by PAGES 2k. He writes that many chronologies were introduced without having been reviewed. The ones that made it into the latest PAGES 2k version were the ones that were the most hockey stick-shaped:
About 20% of the PAGES 2019 proxies are 50 Asian tree ring chronologies, all of which were originally published as chronologies in PAGES (2013). At the time, none of these series […] had ever been published in technical literature, peer reviewed or otherwise. Nothing in the Supplementary Information to any of these articles says who calculated these chronologies or how they were calculated. […]
PAGES (2013) was originally rejected by Science in 2012, because peer reviewers (including Michael Mann) objected to the introduction of so many new proxies in what was ostensibly a review paper; they sensibly recommended that components first be peer reviewed in relevant specialist journals. However, PAGES2K results had already been incorporated into a pending IPCC assessment (AR5), so the authors, now under a very short deadline, submitted to Nature, which was confronted by the same review problems that led to the rejection by Science. Keith Briffa had a clever, too clever, solution: publish the PAGES2K submission as a “Progress Article” – a classification that did not require the peer review procedure required for a Research Article. This would qualify the article for IPCC and nobody would notice the sleight-of-hand. (Even I didn’t notice it at the time; someone told me.)
One of the consequences of the 2013 manoeuvring was that several hundred Asian tree ring chronologies were introduced to paleoclimate archives with no technical publication or technical peer review, no information on how they were calculated or even who among the PAGES2K (2013) authors had calculated them.
Having been introduced through the back door, so to speak, nearly all of the 200+ Asian tree ring chronologies were carried forward into the PAGES (2017) compilation, and then a subset of 50 chronologies (more or less the most hockey stick shaped) was screened to become a substantial component of PAGES (2019) – the source of the IPCC Summary for Policy-makers Hockey Stick.
One of the new Asian tree ring chronologies is shown below. In addition to “Asia_207”, it also goes by the name “paki033” and “Asia-MUSPIG”:
The x-axis shows the year, and the y-axis shows ring width index, which corresponds to temperature in the region. The higher the ring width index, the higher the temperature. In an ideal world, at least.
Below are two chronologies that McIntyre calculated from the underlying tree ring widths using two normal standardization procedures (middle and right) compared with the PAGES 2k 2019 chronology (left):
As we can see, there is no hockey stick in the chronologies calculated using the standard procedures. And actually, temperature (or tree growth) seems to be going down rather than up in the 20th century, “so how did PAGES2K manage to get such a hockey stick? I have no idea“, wrote McIntyre in 2021.8) In 2023, however, Hampus Söderqvist (@detgodehab on Twitter/X) had been able to reverse engineer the algorithm used by PAGES 2k.
It turned out that the algorithm had a tendency to add upticks at the end — making hockey sticks from non-hockey stick data. This was verified by McIntyre and Söderqvist by cutting off the last 50 or 25 years of data before applying the algorithm. From Twitter:
bingo. Excluding the last 50 years of data, paki033 had an even bigger blade //50 years earlier//. For good measure, @detgodehab did test excluding 25 years and got same big blade //25 years earlier//.
It didn’t happen for all tree ring datasets, though, but the fact that it happened for some, means that the algorithm can’t be trusted and shouldn’t be used. However, the algorithm was used not only for this one site in Asia, but for several others as well, contributing significantly to the hockey stick shape of PAGES 2k’s (and IPCC’s) temperature reconstruction:
@detgodehab has verified that same flawed algorithm was used for at least 8 other Pakistan sites. Note that these sites (together with Columbia U’s Mongolia chronologies) dominate PAGES19 list of heavy contributors to closing blade.
(See this sub-thread on Twitter for more details on what the algorithm did for certain tree ring data.)
The “signal-free” procedure
The problematic standardization procedure used by PAGES 2k is called signal-free detrending.9) As we’ve seen, tree rings aren’t very good at preserving long-term temperature trends, and the signal-free procedure was created with the intention to at least partly solve this problem — to preserve medium-term (up to one century) variability in tree ring temperature reconstructions.10)
Looking to the scientific literature, we actually find a criticism of this procedure that’s very similar to McIntyre and Söderqvist’s; Pearl et al. 2017 found that
the signal-free detrending procedure increased the amplitude of the early and late ring-widths beyond reasonable growth patterns for the species[.]
and that
the use of [signal-free standardization] instead of traditional [negative exponential] chronologies results in an overestimation of recent temperature trends and a lack of reconstruction skill. [Emphasis added]
An overestimation of recent temperatures was exactly what McIntyre and Söderqvist found could happen.
How much can we actually know about past temperatures?
In light of the big differences between global temperature reconstructions, one might wonder how much we can actually be certain of when it comes to past global temperatures. In a 2021 article, The future of paleoclimate, Jan Esper and Ulf Büntgen address this issue:
Our understanding of natural climate variability rapidly declines over the Common Era (CE) [Common Era=past 2000 years] as the pre-instrumental temperature amplitude differs substantially among large scale reconstructions. Highlighting such differences and emphasizing paleoclimatic findings is crucial for placing [human-caused] climate change in a long-term context. We argue that more proxy records are needed to accurately reconstruct first millennium CE temperature variability[.] [Emphasis added]
The number of proxies as well as the quality of these series declines back in time, so that only a few records are available during the early centuries of the [Common Era]. All of these issues, i.e. the limited resolution, reduced replication, and increased dating uncertainty, affect our ability to accurately assess past temperatures and cause a blurring of the climate record back in time. [References removed]
In their opinion, we can know very little about global temperature variability prior to the year 1400:
Yet the circumstance that the next IPCC report will no longer include a paleoclimate chapter should not mistakenly be interpreted as evidence that natural climate variability is understood. The opposite is actually the case. We are in the dark already before 1400 CE, have a rather limited idea of the magnitude […] of pre-industrial warm periods, and know much less about the Southern Hemisphere[.] [Emphasis added]
Conclusion
Whether the average global temperature of the past 2000 years forms a hockey stick pattern or not might not be possible to determine from existing proxy records. And there’s disagreement in the scientific literature about how much the pre-industrial global temperature has varied since year 0.
Although the IPCC knew about the disagreement, they still chose to rely on a single temperature reconstruction for the past 2000 years (PAGES 2k 2019) in their latest assessment report. That in itself is unfortunate, since they’re supposed to make an objective assessment of the scientific literature. It’s even more unfortunate considering all the criticism PAGES 2k 2019 has received.
Did the IPCC want to present a hockey stick temperature graph? The Clintel Foundation and McIntyre believe so, and I wouldn’t be surprised, either. But it’s hard to prove.
Footnotes:
1) An objective review is at least one of IPCC’s stated missions. On their About page, one of the things the IPCC writes is:
An open and transparent review by experts and governments around the world is an essential part of the IPCC process, to ensure an objective and complete assessment and to reflect a diverse range of views and expertise.
2) Lüning and Lengsfeld 2022 has the same perspective as Clintel. They write:
As a rule of thumb, the larger[…] the pre-industrial temperature changes, the higher[…] the natural contribution to the current warm period (CWP) will likely be, thus, reducing[…] the CO2 climate sensitivity and the expected warming until 2100.
3) As part of Büntgen’s response to a question about whether his recent work would help the “climate deniers” or the “climate change proponents”, Büntgen argues that a high pre-industrial temperature variability would mean that the climate sensitivity is also high:
There is one thing that often gets taken wrong if we are reconstructing past climate and we show more natural variability. Some people, they don’t understand it fully, they would say “ah okay, you are able to show us that [the] climate system was always varying, so where is the problem?” This is the wrong assumption, the assumption is that this only indicates that the climate system is very sensitive, so it’s about the sensitivity. That means even without [varying amounts of] greenhouse gases, we had these fluctuations; we had cold and warm periods. So that means the sensitivity of the [Earth] system is very high, which makes the effect of greenhouse gases even bigger, right? So I think it is exactly the counter-argument. If we are able to show that pre-industrial temperature and precipitation changes were relatively big, it only means that the additional effect of greenhouse gases will be even further a problem.
I haven’t found a discussion in the scientific literature comparing the opposing perspectives of Clintel and Büntgen.
4) Unfortunately, you have to pay to read the main text of PAGES 2k 2019 at Nature. However, a free version of the main text is available here.
5) But an article by Swedish blogger Maths Nilsson may lend some support to Clintel’s claim. Nilsson had asked climate scientist and fellow Swede, Fredrik Ljungqvist, whether a new hockey stick had been commissioned by the IPCC, something that the Clintel report suggested might have happened. According to Nilsson, Ljungqvist’s answer was a categorical no:
So I contacted Fredrik Charpentier Ljungqvist (FCL), co-author of both the Page[s] 2k (2019) and Büntgen (2020)-papers. What did he say?
First of all, the IPCC did NOT in any way commission the Page[s] 2k-study as Clintel implies ([Ljungqvist] used the capital letters).
Nilsson’s next paragraph then hints at a possible justification for Clintel’s claim that some researchers seem to have left PAGES 2k in dispute — at the very least, there seems to have been disagreement:
[Ljungqvist] did however confirm that some leading [paleoclimatologists] do not think the Page[s]2k graph was properly used in the IPCC AR6-report. They don’t think there is sufficient data to even reconstruct a global mean temperature with precision 2000 years back (most data comes from northern [hemisphere]). [Ljungqvist] somewhat regrets putting his name on the Page[s]2k-study. [Emphasis added]
6) Stephen McIntyre has made available a folder with two files. One file, proxy_pages2019.csv, shows an overview of all 257 chronologies (although only the tree ring chronologies were visible to me by default — I had to unhide the others). The other file, info_pages2019.xlsx, includes all yearly values (temperature, ring width index or similar) for all 257 chronologies.
The PAGES 2k 2019 study also links to much of the same data, but in a harder-to-read data format.
7) Some of the other potential problems that McIntyre writes about:
The IPCC AR6 Hockeystick:
“The idea/definition of a temperature “proxy”“, McIntyre writes, “is that it has some sort of linear or near-linear relationship to temperature“. He argues that this is not the case for the proxies underlying e.g. PAGES 2k 2019. To illustrate his point, McIntyre visualizes random samples of 11 proxies from each of PAGES 2k 2017, PAGES 2k 2019, and tree ring chronologies from North America (used by PAGES 2k 2019), and compares them with PAGES 2k 2019’s resulting hockey stick graph. A few proxy chronologies have a hockey stick shape, but in those cases, according to McIntyre, the hockey stick shape was the result of errors in calculating the chronology. One chronology looks like an upside-down hockey stick. McIntyre suspects PAGES 2k 2019 flips it over (!), which means it would contribute positively to the final hockey stick shape.
PAGES2019: 30-60S:
PAGES 2k 2019 includes very few southern hemisphere proxies. In the 30-60 degrees south latitude band (southern extra-tropics), PAGES 2k has included only 8 proxies. Of the 8 proxies, 7 are tree rings, and none are ocean proxies despite 94% of the area being ocean. The 8 proxies had been reduced from 19 proxies in PAGES 2k 2017. Only one proxy goes back 2000 years, one goes back about 1200 years, and the rest are shorter than 600 years. The final PAGES 2k reconstruction has a much more pronounced hockey stick shape than any of the 8 proxies that it’s made up of.
PAGES19: 0-30S:
PAGES 2k 2019 includes 46 proxies in the 0-30 degrees south latitude band (southern tropics). However, only 2 of them go back 2000 or nearly 2000 years. Among the rest, none of the proxies go back further than the year 1500 AD, and about half have a start date after 1850. McIntyre comments: “None of these short series shed any light on whether the medieval period, for example, was warmer than modern period or not.” 43 of the 46 proxies are coral proxies, and strangely, there are only two proxies from land.
There are two different coral temperature proxies, δ18O and Sr/Ca. δ18O looks at the ratio of two different oxygen isotopes in the coral, the common 16O and the much less common 18O. The Sr/Ca proxy looks at the ratio of two different chemical elements in the coral, Strontium (Sr) and Calcium (Ca). According to McIntyre, “PAGES2K is primarily populated with d18O series – which, in specialist articles, are seldom, if ever, used as temperature proxies, as Sr/Ca is usually preferred. Changes in 20th century coral d18O are nearly always much more pronounced than corresponding changes in coral Sr/Ca. Perhaps that’s why they were selectively chosen into the PAGES2K network.” A little speculation at the end there, but from having read many of McIntyre’s articles, the speculation is certainly very understandable.
PAGES 2019: 0-30N Proxies:
PAGES 2k 2019 includes 41 proxies in the 0-30 degrees north latitude band (northern tropics), which is down from 125 proxies in PAGES 2k 2017. The removed proxies were mostly ocean sediments and tree rings, “all of which were much longer than the retained coral proxies“. Among the 41 remaining proxies in PAGES 2k 2019, only one extends back 2000 years, while two others go back around 1000 years. 8 of the proxies are from tree rings, two of which had upticks at the end. However, the upticks didn’t appear when standardizing the raw data using normal detrending-algorithms. “In response to a recent inquiry, the PAGES2019 authors were unable to identify how the chronology was calculated and refused to find out.” Presumably, they were calculated using the same flawed algorithm that was used for the Asian tree ring chronologies discussed in the main text (the signal-free procedure).
8) The reason McIntyre didn’t know was that PAGES 2k hadn’t documented which standardization (or detrending) method was used to create each tree ring chronology. I already quoted McIntyre saying this (“Nothing in the Supplementary Information to any of these articles says who calculated these chronologies or how they were calculated“), and Klippel et al. 2020 confirms it:
[T]he PAGES2k database contains no information regarding the detrending method used to produce the tree-ring chronologies in its collection[.]
Also, when McIntyre asked two of the PAGES 2k authors about the standardization method on Twitter, Nick McKay replied that he didn’t know which method had been used.
9) Here’s a technical explanation from McPartland et al. 2020 for why the algorithm is called signal-free:
The term “signal-free” refers to the creation of detrending curves that do not contain the common signals shared across the trees in a chronology, and are thus ‘free’ from common variance and should preserve this signal in the resulting chronology.
In its original formulation, [signal-free standardization] was primarily intended to improve the expression of medium-frequency (i.e., decades to one century) variance associated with climate forcing.
Those “error bars” in that graph are total bullshit.
Typical climate science lies.
So they are telling the same lie, just using new graphics. Got it.
This article is too long and may HAVE MISSED SOME IMPORTANT POINTS
Local climate reconstructions should not be compared with modern instrument temperature statistics, or even placed on the same chart
When local proxies are averaged to create a fake global average, the variations are reduced to a point where they often become statistically insignificant
I have no idea what a reasonable margin of error is for local proxies, but my personal Rule of Thumb is to ignore variations less than +/- 1 degree C.
The first IPCC report claims the past 1000 years had average temperatures within a one degree C, range (0.5 degree cycles). I consider that statically insignificant as a global average based on local proxies
In 1995 the IPCC declared all natural causes of climate change added up to “noise”, except in the very long run.
They already thought that in 1988 but waited a few years to pretend they were studying all natural and manade causes of climate change
In 1998 Mann used cherry picked incompetent proxies for his Fraudulent Hockey Stink Tree Ring Circus Chart. The past 1000 years (pre 1961) suddenly showed only a 0.4 degree C, range of the estimated average temperatures. Just what the IPCC wanted to hear, so they bought what Mann was selling.
Are Siberian tree rings a good proxy for the average NH temperature or the global average temperature? No. Not when they are cherrypicked and you have no idea how much growth was related to precipitation in the growing season.
The goal of the Hockey Stink Tree Ring Circus Chart is the false claim that natural causes of climate change are tiny and don’t matter, which is what the IPCC was formed to claim in the first place. They started with that conclusion. And that’s junk science.
Yes, it is long because there is a lot of patented IPCC baloney to expose.
The whole IPCC Summary for Policymakers is baloney and does not even accurately summarize the back up science reports which used to be released months later.
Now the so called journalists don’t even read the 12 page Summary. They only read and reprint the IPCC press releases. Maybe they change a few words and create an exciting headline, such as:
“IPCC Scientists Say Climate Change Will Kill Your Dog”
I was going to point out the mathematic maleficence of tacking hi-res thermometer data onto lo-res proxy data.
Also the many other things that can effect tree growth (apart from very low CO2 levels)
Glad I read your post first.. saves me the bother. 🙂
Are you trying to confuse me by agreeing with me?
That is a violation of Al Gore’s Rules of the Internet, which requires bitter arguments among strangers to continue and escalate until one compares the other to H i t l e r, after which the Moderator wakes up and ends the argument.
You get some things correct…Probably by accident…..
other things totally wrong.
Still waiting for that evidence of warming by human CO2.
Totally lacking !!
Since the resolution of the proxies are 100+ years. The instrumental record from 1850 should be at least reduced to a single averaged point as rough offering
Don’t get me started on 1800s instrument records. They are mainly infilling with a few measurements in the US, Europe eastern China and eastern Australia and some NH shipping lanes. No more accurate than pulling a number out of a hat.
Here’s where the land weather stations were located
The Honest Climate Science and Energy Blog: Sparse coverage of Earth’s land surface with land weather stations in the old days
“No more accurate than pulling a number out of a hat.”
So all those thermometer readers over the decades were just wasting their time?
a/ small sample size
b/ poor spatial dispersion
c/ no Stevenson screens. Australia’s BoM doesn’t use pre-1910 records.
The written record is better than nothing. It’s better than making it all up in a computer.
The BoM doesn’t use pre-1910 records because it would destroy their “hotter and hotter and hotter” human-caused climate change meme.
Here’s a Tmax chart for Australia that shows pre-1910 temperatures:
Certainly. But there is considerable uncertainty for at least the reasons I gave
The stated reason is largely related to standardisation of met stations. It does seem a little odd that other organisations use pre-1910 Australian figures.
“…were just wasting their time?”
No, not necessarily. Local temperature measurements may be quite useful over a long period of time for understanding local weather (or even ‘local climate’) patterns. Hell it’s highly likely that’s why they were being measured to begin with e.g. to help understand ‘local weather/climate’
One of the reasons I credit Stephen McIntyre with a legitimate approach to paleo climate reconstructions is because I closely identify and embrace his ‘old-school’ auditor discipline and procedures.
Strip away the “end-result” theatrical stuff and forensically analyse where every input value came from, who provided it, and what confirming observations render it trustworthy.
From my (fairly limited) experience in auditing, I can observe that sphincters often turn out to be the most prolific sources of “data”.
Modern climate science
Start with a conclusion
Data mine to support the conclusion
Change the data if necessary
Focus mainly on predictions of future CAGW doom, for which there are no data.
Be confident that few people know that science always requires data, but there are no CAGW data, because CAGW has never happened, despite being predicted since 1979
Focus on warming by human CO2.. for which you have proven that you have no evidence.
The IPPC should be done and disbanded because they send out the same type of reports that says the same basic thing over and over since 1990 it has been exposed too many times to be promoting pseudoscience and modeling fantasies, they defend hard with a barrage of half-truths and lies.
Their climate crisis is all SCAM!
The current climate is the best climate for humans, animals and especially plants, in at least 5000 years.
Amazing how the GAT has not varied more than 0.2 or so degrees for almost a thousand years! A thousand years!!!
Just amazing. I certainly believe that. Michael Mann is a genius. Being able to destroy the LIA and the MWP means he is really smart and good and righteous. I heard him speaking on the radio the other day. He said it was ”nonsense” to believe otherwise….So, that’s that then.
Not new news, but well worth repeating.
Complex proxy reconstructions of the past 1000 year climate are fertile ground for confirmation bias driven or downright fraudulent statistical shenanigans.
There is ample historical and actual measurable material evidence that the NH Medieval Warm Period was at least a warm as the 20th century, for example:
Climate change and the northern Russian treeline zone (G.M MacDonald,* K.V Kremenetski, and D.W Beilman 2008).
From the Abstract: “The location of the treeline is largely controlled by summer temperatures and growing season length …,,, conifers have not yet recolonized many areas where trees were present during the Medieval Warm period (ca AD 800–1300) or the Holocene Thermal Maximum (HTM; ca 10 000–3000 years ago”.
Higher-than-present Medieval pine (Pinus sylvestris)treeline along the Swedish Scandes. (Leif Kullman 2015).
From the Abstract: “Radiocarbon-dated megafossil pines revealed that the treeline was consistently positioned as much as 115 m higher during the Medieval period than today (AD 2000-2010), after a century of warming and substantial treeline upshift … it may be inferred that Medieval summer temperatures were about 0.7 °C warmer than much of thepast 100 year”.
I love the way he just assumes that the only possible thing that can explain changes in the Earth’s temperature is changes in greenhouse gases.
This is the raison d’être of the IPCC.
Trees, up until humans started releasing CO2 in earnest, were CO2 deprived.
They are totally useless as a form of “thermometer”.
Anything produced pretending to use “tree-ometers” is garbage.
There is data from all around the world showing the MWP was warmer than today.
Plenty of art and literature from the LIA age well.
Frost Fair on the River Thames 1683–4. Painting by Thomas Wyke.
Or imagine the amount of ice required to strand a fleet in the Marsdiep strait.:focal(325x389:326x390)/https://tf-cmsv2-smithsonianmag-media.s3.amazonaws.com/filer/80/d5/80d5985f-5340-4e11-b81c-c7556d95d8ab/helder_morel-fatio.jpg)
The 21st of January 1795, the French attacked and captured a Dutch fleet… With horses. The 14 ships were caught in the ice at Helder, and the French general attempted this bold move. It is the only documented occurence of a cavalry charge against ships in History
From page 6 of the 6AR SPM: “The grey shading with white diagonal lines shows the very likely ranges for the temperature reconstructions.”
By “very likely” the authors very likely mean a 95% confidence interval. But the ±0.25 C bounds are smaller than is achievable in a laboratory using a good quality 1C/division LiG thermometer. Mindless doesn’t cover a scientific failure of that magnitude.
Doubling the indicator of competence, there were no thermometers 500 years ago, much less 100,000 years ago.
And tripling the indicator of competence, the supposed temperatures were not calculated using any physical theory — they’re physically meaningless.
The worst of it is that these people do not rise to the level snake-oil purveyors. Snake-oil retailers knew they were pulling a scam. These promoters — the iPCC professionals — truly think they’re doing science.
Ludicrous doesn’t begin to describe it.
Treemometers have an instrumental uncertainty of ±0.25°C, this is essentially what they are claiming.
I had the (mis)fortune to meet someone big in “Climate Change” from the University of Exeter. He seemed to have no idea of the concept of instrumental resolution or random and systematic errors. For him there was nothing absurd about quoting paleotemperatures to two decimal places. I had the clear impression he was totally clueless about physical measurements and had never read a thermometer in his life.
I’ve had the same experience, Graeme. Clueless captures it well.
Climate “Science” actually fulfils most or all of Irving Langmuir’s criteria for distinguishing what he called Pathological Science:
Gosh, doesn’t that sound familiar!
It should be classified as a liberal art and not a physical science.
The Liberal Arts have real value and are rooted in reality. Climate “Science” is mendacious drivel.
True this.
Please excuse a repeat of my comment at Climate Etc.
‘These words by Stephen McIntyre are death to PAGES2k.
Quote by SMcI: “The final PAGES 2k reconstruction has a much more pronounced hockey stick shape than any of the 8 proxies that it’s made up of.”
I have studied the data and reached the same, rather unavoidable conclusion.
Now, let’s hear some justification for belief in PAGES2k.’
………………..
Personally, I know of no valid method by which 8 proxies without any or much hockey stick shape can result in a combination with a pronounced hockey stick shape.
The hockey stick concept should have been dead and buried at that stage.
Geoff S
Same way with the instrumental temperature record.
The regional temperature records don’t show a Hockey Stick temperature profile, but when they are combined in climate alarmist computers into a global temperature profile, they show a Hockey Stick “hotter and hotter and hotter” temperature profile.
It’s all a scam to justify the UN IPCC. The IPCC was formed to find a human cause to climate change and they are going to find it whether it is there or not.
Tom,
Yes. Here are most of the longest Australian official temperature series, starting 1856.
Tmax, raw, daily, unadjusted are shown.
Is there a sign of the hockey stick shape? No!
Why not? Tree rings are said to show it better than thermometers.
Geoff S
Could you post the equivalent chart for minima, please?
old miner to old cocky,
Here is the Tmin graph.
Pleased to oblige.
Geoff S
Thank you, good sir.
“Is there a sign of the hockey stick shape? No!”
That’s right! No Hockey Stick shape.
All the temperature data mannipulators had as far as data was written temperature records from around the world, none of which showed a Hockey Stick temperature profile, yet when the climate alarmists came out with their computer-generated “global” temperature data set it showed a Hockey Stick profile.
So how do you get a Hockey Stick “hotter and hotter and hotter” temperature profile out of data that does not have a Hockey Stick profile?
I’m thinking someone is playing fast and loose with the numbers in their computers. That’s the only way it could occur, because the data the mannipulators had available to them does not have a Hockey Stick profile.
Here is strong reason number two why the hockey stick is invalid. Hide the decline.
It became obvious from the Climategate years that selected time periods were used by Briffa et al when constructing the elements of the hockey stick graph.
“We used simple linear regression, fitting the regression equations over the period 1881-1960, or over the total available period prior to 1960 when the instrumental record was shorter. The period after 1960 was not used to avoid bias in the regression coefficients that could be generated by an anomalous decline in tree density measurements over recent decades, that is not forced by temperature [Briffa et al 1998b: Nature 391, 678-682]”.
This became known as part of “Hide the Decline”. People do not claim that there was no decline. People do not claim that it was NOT hidden. The graphs used by IPCC show the hidden decline, in colour.
It is beyond comprehension why dendrothermometry was allowed to continue in use, when there was clearly a problem shown by Briffa for data after 1960. Scientific prudence would dictate that there be a search for a similar data problem before 1960. This has never been done. It reeks of deliberate academic fraud to create the hockey stick shape.
“It reeks of deliberate academic fraud to create the hockey stick shape.”
That’s the way I see it.
The Hockey Stick was created for political purposes. The Climate Alarmists had to bastardize the data to get the temperature profile they wanted and needed in order to sell the Human-caused Climate Change narrative.
Without the Hockey Stick, the climate alarmists have nothing to scare people with.
One should just read McIntyre on each latitude band in his website. Succinct. The HS is a fraud I understand that AR6 doesn’t discuss it anywhere in the text?
Strong reason to suspect the hockey stick, number 3, starts with the example of Joule drift in liquid-in-glass thermometers. These thermometers can change shape over time, to create an error in their observed temperature.
As Pat Frank notes in a rather important, thorough 2023 paper,
“The 20th century surface air-temperature anomaly, 0.74 ± 1.94 °C (2σ), does not convey any knowledge of rate or magnitude of change in the thermal state of the troposphere. Climate alarm on that account is unjustifiable. The Joule-drift that certainly plagued all LiG thermometers manufactured prior to 1885 obviates the reliability of earlier air-temperature measurements. The global averaged surface air-temperature anomaly record cannot sustain any notion of unprecedented climate warming over the last 200 years, or over any other timespan.”
https://www.mdpi.com/1424-8220/23/13/5976
….
In most proxy study, there is a calibration step when the proxy response is converted to a related temperature by use of instrumental temperatures applicable to the proxy region. If these local temperatures are in error, so is the derived proxy temperature. There are no ifs and buts about this.
This is strong evidence that the proxy record is likely to be wrong.
There appears to be a lack of interest in this possibility.
….
Scientists with long experience in earth science measurements are usually aware of the curse of slow drift (such as Joule-drift). Many proxy studies might have this error, because there are few ways to determine it. An example is the presence or absence of frost in historic measurements of minimum land temperatures. If available, that should be able to stabilise the result. There are few other available natural reference points like the freezing of water of which I am aware, for this Hockey Stick form of thermometry. The drift problem is unresolved.
Geoff S
Jolly hockey sticks
Great for tripping people up
Essential for tripping people up.
Climate Alarmists have nothing else.
The Hockey Stick chart is the BIG LIE of climate science.
“Large-scale temperature reconstructions are nevertheless created almost exclusively from proxy data – including tree-rings, corals, ice cores, speleothems, and marine and lake sediments – each of which contain various biases in how they record temperatures, are heterogeneously sampled through time and space, and need to be statistically calibrated against instrumental data to provide estimates of past climate. These factors infuse Common Era temperature reconstructions with uncertainties that are inherent to the indirect representation of past climate by imperfect biological, physical, and geochemical archives, as well as from specific seasonal biases in proxy sampling of past climate, the relatively sparse availability of proxies in both space and time, and the wide range of statistical methods and assumptions used to transform a diverse set of proxy data into quantitative estimates of past temperatures”
https://www.sciencedirect.com/science/article/pii/S0277379122001688
New and improved! And, worse than we thought!
Difficult reading considering the definition is wrong. The blade is horizontal the shaft vertical.
It walks like a duck it quacks like a duck but according to the author he can’t find any proof that it’s a duck … so a very long post that ends up right where it started … I have no idea what the author believes… he seems to always hedge his opinion with the useless “no proof” cop out …
Cherry picked data is all they have supporting their false assumptions. Scientific fraud is standard operating procedure for the climate establishment. When will this become news to the brainwashed?
I’m an agronomist, arborist and orchard farmer with a background in geology. I’ve studied plant biology down to the sub-cellular level and I’ve been in the business of growing and maintaining trees for the last 40 years. I’m also a ‘tree doctor’ where I am professionally called upon to diagnose and treat diseases, insect infestations and nutritional issues.
This doctrine that tree ring widths are a proxy for temperature is utter nonsense. Tree ring widths are a measure of the amount of growth over a particular year, yes, but that is not entirely dependent on temperature. Growth is due to a number of factors, such as both rainfall AND temperature at very least. There can be years of high temperature and abundant rainfall which would have accelerated growth and produced wide rings. True. But the very next year could have been very warm but with very low rainfall, thus the result would have produced thin and spindly rings. Another year could have been cool but very rainy and thus ring widths would have been medium to wide. Tree ring width cannot be correlated exclusively with temperature.
What are entirely unknown are the surrounding conditions of those selected trees that are used for temperature proxies. Were there years where animal flocks, deer for instance, that repeatedly browsed underneath their sampled trees and did they leave their manure as fertilizer? If so, all other factors being equal, that alone would have accelerated growth and produced wider rings, independent of temp. And what about competition from surrounding trees? Root competition from other species of nearby trees would reduce growth no matter what the temperature was. So too, would a lessening of sunlight if the selected tree would have been shaded by the canopies of other fast growing trees. Root and sunlight reduction from competing trees would certainly reduce growth having nothing to do with temperature.
And then recent research has shown that the roots of forest trees of the same species can intertwine. As the roots of both trees increase in width and they can end up pressing against one another to the point of actually grafting into one another. Should that happen the sap flows from one to another, often the stronger tree donates sap to the weaker tree, thus the stronger one sacrifices its own vitality for the sake of the weaker. Should that happen the rings of the stronger tree would be thinner than they would had such a grafted relationship not existed.
Trees are very complex biological systems and to ASSUME that only one factor, temperature, determines the rate of growth is simply silly and born out of near complete ignorance of the multiple organic processes and influences that affect all arboreal life.
I tend to think that those who push the catastrophic climate narrative find it easy to make a gross oversimplification of what makes trees grow. For in a similar way, they oversimplify the entire complex climate system by claiming that one and only one influence, CO2, is behind all climate change. I hate to burst their bubble but as complex as biological processes of trees are, the climate system is infinitely more nuanced and complex. So to claim that one factor, decreasing or increasing CO2, determines all of climate is downright preposterous. For those who think that CO2 is the control knob for temperature ignores 680 million years of geological history to the contrary. It’s a history that shows that temperature and CO2 levels are not even correlated, much less engaged in a causative relationship.
Even the temperature record of the 20th C. shows that global temps cooled between 1940 and 1976 despite CO2 having consistently risen over that 37 year period. The bottom line is that without correlation there cannot be causation.
The whole of alarm-oonsensus climatology is filled with self-serving assumptions that make life very easy for the promoters.
“So to claim that one factor, decreasing or increasing CO2, determines all of climate is downright preposterous.”
Great post, Dale!
if Climate Alarmists took everything you mentioned into account, then they couldn’t scare anybody about CO2, and it’s their job to scare people about CO2, so they distort the truth to advance their goal.
As always, the contrarians love to decry hockey sticks, but they can’t seem to produce any paleo reconstructions that aren’t hockey sticks themselves. Leading us all to wonder if perhaps they aren’t just whinging for the hell of it.
Why do you try so hard to be stupid, here are a few of many of NO hockey stick papers you manage to miss:
LINK
I don’t think he has to try very hard.
Most of these papers show a single regional series, which, if combined with numerous other regional series, would show the same hockey stick. Some of the papers with global reconstructions encompass the Holocene climate optimum, which is much broader than the period defined as the “shaft” of the hockey stick.
Why would you even want to combine regional temperature series? If the Hockey Stick were real, ALL would show it.
You exhibit a fundamental misunderstanding of basic statistics and of paleoclimate proxies. The series *might* all show a common signal (some might not), but they *also* show regional variability, which might be much larger in amplitude than the common signal. The only way to extract the common signal is to combine the proxies. The hockey stick is a *global* reconstruction (that is, it contains only the common *global* climate signal). Thus to compare like with like you need to extract the global signal from the set of individual proxies you link.
It’s strange then that worldwide proxies all show clear evidence for the MWP, LIA, RWP etc without having to be combined.
Of course, they don’t. But you could only know that by… extracting the global signal from the individual proxies.
A demonstrable lie.
https://wattsupwiththat.com/2018/11/03/yet-another-study-illustrates-that-the-medieval-warming-period-was-not-regional-but-global/
Kindly notice that all these proxies individually and in isolation show a warming signal. No need to combine them.
You have to follow the ball for this hat trick. First, any study that does not show evidence of medieval warmth is omitted. Second, there is no indication anywhere of the timing of the purported medieval warm events. The evidence suggests that many regions on earth did experience some measure of abnormal warmth at some point during the long period defined as the MWP (although mostly concentrated in the north Atlantic), but that at no point was the globe as a whole abnormally warm or warmer than today (i.e. it might have been abnormally warm in one place and abnormally cold in another at the same time).
Of course, it’s completely impossible to ascertain this by looking at a scattered map of individual proxies without any dates attached. Which is exactly what the creator of that map wants.
If you had bothered to read the legend of the graph, you would have seen that the proxies are ALL from the period 1000 AD to 1200 AD, in other words essentially contemporaneous as well as global in extent.
Right, “at some point during a 200 year interval this place was warmer than usual, or wetter than usual, or dryer than usual. We don’t know about any of the places without a marker.” Nothing about this map suggests a contiguous period of global warmth exceeding the modern day, although we are meant to infer that it does.
What is this nonsense about “markers”? The dating of the proxies is solid.
Everything about this map suggests a contiguous period of global warmth exceeding the modern day.
Sorry, yes, important distinction you’ve drawn. The map is very suggestive. The author clearly wants us to infer something that the data being presented doesn’t support. The map does not show a contiguous period of global warmth exceeding the modern day, it does suggest it, as designed.
Evidence of proxies from the remote past can never be definitive, and must always be suggestive and provisional.
How would the chart differ if the MWP was global and synchronous?
You couldn’t tell from the map if the MWP was global and synchronous and warmer than present day, you need to perform a global time series analysis to do that, like the many multi-proxy reconstructions available.
Er, no, the map is multi-proxy and demonstrates precisely that the MWP was global and synchronous.
Be honest, for once. Fundamentally, the problem is that you really, really don’t want to acknowledge the existence of the MWP.
The MWP was a thing, there just isn’t any evidence that it was similar to the thing happening today, that’s the big lie WUWT is spreading.
I’ve just spotted yet another lie: you claim that studies showing cooling or no warming are omitted. Take another look at the map: do you see those little blue dots? They are proxies showing cooling.
Again, the map covers 200 year period, it is completely impossible to demonstrate synchronous changes in a map covering two centuries. You need to look at a time series. But thanks, I guess, for pointing out my error and confirming that in fact the map does not appear to confirm coherent global warmth?
Thanks for confirming you’re a cretin as well as a liar. What is the ratio between the numbers of red and blue dots? Rather more of the former than the latter, no?
Why should every single spot on Earth show synchronous warming? Is it not possible that most of the Earth warms and a few spots cool at the same time?
The dots don’t all happen at the same time, that’s the whole issue. And “warmer than usual” in the map does not equal “warmer than the present day.” There’s also more empty space than dots, and you don’t have any inkling of what’s happening in the empty spaces unless you do some sort of reconstruction of all the dots and extract the common signals. If you do the reconstruction using all the dots (including all the dots the author has opted not to show) across all the times represented by the dots, you will get the same exact answer as everybody else, which is that the MWP was not a globally synchronous warming event comparable to today (see, again, Neukom et al., 2019, which you keep ignoring).
Because the claim being made is that the earth was warmer during the MWP than it is today. For that to be true, the majority of the earth during the MWP needs to have been warmer than today at the same time. It doesn’t count if just one patch in the north Atlantic was warmer than today for a brief period, and then that patch cooled down and a patch in the equatorial Pacific or someplace was warmer for a bit, those two consecutive periods combined don’t make a single congruous period of global warmth. Those are just two distinct regional warming events occurring at different times.
The amount of effort needed to explain this childishly simple concept to you is quite astounding.
You claimed that the studies were cherry picked to exclude those showing cooling. You lied.
You genuinely believe proxies record instantaneous temperatures rather than decades or centuries of average temperature at a given location? The proxies require decades to register changes, so a period of 200 years is representative.
The Earth doesn’t have a “temperature” or a “climate”, and average global temperature is unphysical nonsense, as is saying the Earth was warmer or cooler than today. If the Northern Hemisphere warms by (say) 2 degrees and Antarctica cools by 5 degrees, the “average” temperature has not changed. Does that represent warming, cooling, or no change?
The many papers in the link doesn’t support your lie, why don’t you stop lying?
Here are 35 published in a single year 2019 that has ZERO HS in them which was in the link I gave you.
LINK
LOL
AlanJ
Try here.
Geoff S
Hi Geoff, those are not paleoclimate reconstructions.
AlanJ,
Then what are they?
They are absolutely paleoclimate reconstructions, with the advantages (2) of using original, unadjusted data and measuring temperature, the subject of interest, directly and not by proxy.
They should be as good as it gets.
Geoff S
Geoff, these are instrumental temperature records covering the modern era, a paleoclimate reconstruction is a dataset built from various climate proxies that reconstructs the temperature history of the pre-instrumental period.
Hope that this helps.
What are the real measurement uncertainties of these paleo reconstructions, pray tell?
You’ll want to refer to the literature.
In other words, you don’t have a single clue.
Something that might astonish you to learn is that I don’t walk around carrying a list of uncertainty estimates for global paleoclimate reconstructions in my back pocket, so to answer your question I would go pick up the papers and read them. Since you are equally capable of this, I simply refer you to the literature up front.
What always got me about the hockey stick graphs isn’t so much the spike at the end (the “blade”), but the fact that the reconstructions show virtually no temperature change for a thousand years. Look at the y-axis. I’d like to know how the Earth’s temperature could be that stable for that long, especially given the reams of proxy data that show otherwise (those Vikings in Greenland must have pulled off one hell of a parlor trick).
History clearly demonstrates that it was warmer in the past (the period covered by the bogus Hockey Stick chart) than it is today.
Tree ring temperature estimates are a joke, a very bad, misleading, destructive joke.
Averaging (and smoothing) loses information, each time one is performed.
The concept of the Hockey Stick Graph was so popular that it will never just lie down and die as it ought.