How Important is Yamal

Recently there has been a bit of two-way extremism in blogland claiming that hockey sticks that depend on Yamal (don’t matter). A second group of people who are aware of the large quantity of serious flaws in climate science are ready at every new discovery to chuck the whole thing. Unfortunately for those who just want clear answers, neither of these is the case. The following studies are affected to some undetermined degree by Yamal, Quote by Steve McIntyre.

In summary, the apparent problems with Briffa’s Yamal series impact multiple other studies:
Briffa 2000, Mann and Jones 2003 (used in the recent UNEP graphic), Mann et al (EOS 2003), Jones and Mann 2004, Osborn and Briffa 2006, D’Arrigo et al 2006, Hegerl et al 2007, Kaufman et al 2009 (and of course, Briffa et al 2008).

It’s interesting to note that so many popular hockey stick reconstructions employ Yamal. On the other hand AGW advocates are far to quick to say reconstructions don’t matter either – Gavin Schmidt and Michael Mann at Real Climate’s latest, where several hockey sticks with even more severe problems are presented as supporting evidence of the Robustness of the Yamal paper group. Unfortunately for them, it cannot be denied, the Yamal find is a serious issue in climatoloty. Unfortunately for those of us at the mercy of government policy based on these papers, problems in climate science like this are NOT unprecedented.

This is a guest post by John F. Pittman which endeavors to explain the import of proxy temperature recontsructions in the context of the IPCC AR4 report.

Jeff Id

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Why Reconstructions Matter

Wahl and Amman Hockey Stick. Besides the obvious Nike swish popularity, and clear visual impact, there are scientific issues regarding the hockey stick graphs. --- Jeff Id

Introduction:

 

The AGW blogosphere is busily proclaiming that the recent problems with Briffa’s Yamal do not matter. With the debunking of the Mann MBH9x by M&M0x, and by the NAS and Wegman reports, reconstructions began using the Yamal chronologies. Despite the claim by AGW proponents, it does matter. We start not at the chapters on reconstructions, but rather with understanding and attributing climate change.

Section I

 

Understanding the Basic Claim

From IPCC AR4 WG1 Chapter 9 p665.

Understanding and Attributing

Climate Change

Greenhouse gas forcing has very likely caused most of the observed global warming over the last 50 years. This conclusion takes into account observational and forcing uncertainty, and the possibility that the response to solar forcing could be underestimated by climate models. It is also robust to the use of different climate models, different methods for estimating the responses to external forcing and variations in the analysis technique. … Anthropogenic influence has been detected in every continent except Antarctica (which has insufficient observational coverage to make an assessment), and in some sub-continental land areas. The ability of coupled climate models to simulate the temperature evolution on continental scales and the detection of anthropogenic effects on each of six continents provides stronger evidence of human influence on the global climate than was available at the time of the TAR. No climate model that has used natural forcing only has reproduced the observed global mean warming trend or the continental mean warming trends in all individual continents (except Antarctica) over the second half of the 20th century.

Probably, the most recognized claim dispute in the discussions between the AGW proponents and the skeptics is in this quote: No climate model that has used natural forcing only has reproduced the observed global mean warming trend or the continental mean warming trends in all individual continents (except Antarctica) over the second half of the 20th century.

However the first bolded quote of the section plays a more important point. While there is an admission that solar forcing could be underestimated, it is very likely that GHG forcing caused the observed global warming over the last 50 years. It is important to note that the most recognized bone of contention is about the last 50 years.

The point to remember is that their claim that their conclusion takes into account observational uncertainties and is robust to the use of different climate models, different methods for estimating the responses to external forcing and variations in the analysis techniques. This claim of robustness and the second half claim of anthropogenic will be examined starting in the next section.

Section II

 

Bringing in the Reconstructions

 

 

This section explores how the reconstructions were a necessary and indispensible argument in the claim that GHG forcing caused the observed global warming over the last 50 years. The first item of interest is the title and the bolded quote below:

From P666:

Analyses of palaeoclimate data have increased confidence in the role of external influences on climate. Coupled climate models used to predict future climate have been used to understand past climatic conditions of the Last Glacial Maximum and the mid-Holocene. While many aspects of these past climates are still uncertain, key features have been reproduced by climate models using boundary conditions and radiative forcing for those periods. A substantial fraction of the reconstructed Northern Hemisphere inter-decadal temperature variability of the seven centuries prior to 1950 is very likely attributable to natural external forcing, and it is likely that anthropogenic forcing contributed to the early 20th-century warming evident in these records…

Why is there a need for increased confidence? From Section I, the claim was very likely. After admitting to the possibility that the solar forcing could be underestimated, support of the claim of “robust” and very likely was needed. Who hasn’t heard of all the claims that solar is not just underestimated, but severely underestimated? This is not an unusual claim. It is unsurprising with the sun as the heat source for earth that the sun should be considered the primary driver for climate. But this is the IPCC. This is about climate change. Thus to claim the need to address climate change, GHG must be forceful AND the claim of solar forcing being minor in a ROBUST, VERY LIKELY claim is needed. For if not, the human species has no need to worry about climate change. This is NOT an accusation of a conspiracy or wrong-doing. It is simply a fact that if climate change were a non-issue much of the past scientific efforts would have been unnecessary and directed elsewhere. Stating the constraints necessary for one to claim that climate change needs to be addressed should cause no one to claim someone else is reaching for their tin foil cap with antennae.

One of the key passages in this quote “While many aspects of these past climates are still uncertain, key features have been reproduced by climate models using boundary conditions and radiative forcing for those periods.” will be explored in another section. Readers need to pay attention to “key features have been reproduced by climate models using boundary conditions…” This will be explored after a proper foundation is laid. But this should not be forgotten as we examine the claim “A substantial fraction of the reconstructed Northern Hemisphere inter-decadal temperature variability of the seven centuries prior to 1950 is very likely attributable to natural external forcing, and it is likely that anthropogenic forcing contributed to the early 20th-century warming evident in these records. “

This last bolded section is the crux of the claim and the falsification of the AGW proponents claiming Briffa does not matter. Note the use of reconstructed, variability prior to 1950 is very likely attributable to natural external forcing. This is the time period with the least reliable records and least covered area of the earth for the shortest relative time used in determining the global climate signal based on temperature. With temperature records so sparse, another argument has to be made in order to support the claim of “natural”, since after this period the claim that it is anthropogenic must be supported or the IPCC claim of climate change should be ignored. It is their claim that it should NOT be ignored and the BURDEN of proof is on them. Thus it is not only the MWP that must be considered, a visible, but necessary consideration, it is the depth of the temperature changes for the period from what was considered to be the end of the MWP to the start of the modern temperature measurements WITH enough coverage and accuracy to support the “robust” claim of very likely….

Section III

 

Supporting the Models with the Reconstructions

 

At this point, a quick recap will help illuminate how models are dependent on reconstructions lest one misses the somewhat “sleight of hand” in this section. At this point, from the IPCC about reconstructions and their support of models, one can tentatively conclude that reconstructions are necessary to increase confidence to the “very likely” and “robust” regime. The subtitle claims that estimates of the climate sensitivity are now better constrained by observations. Here is where the recap is important. We started with the basic claim that espoused the bone of contention about the solar and natural forcings and their uncertainties. This uncertainty is part and parcel to the claim by the IPCC that it is manmade! If the uncertainty is too large, the claim of robust and very likely cannot be supported. The uncertainty was reduced by including the reconstructions. But the IPCC cannot limit itself to just talking of forcings. Climate sensitivity has to be determined. This poses a problem. There is natural forcings, and variability, and anthropogenic forcings. Add to this the consideration of sensitivity. The question to be answered is “Are the forcings big or small, and/or the sensitivity big or small? So many possibilities, so few independent variables!!!

From P666:

Estimates of the climate sensitivity are now better constrained by observations. Estimates based on observational constraints indicate that it is very likely that the equilibrium climate sensitivity is larger than 1.5°C with a most likely value between 2°C and 3°C.

This is the first consideration. Once again it is based on observational constraints. This is the start of many of the dogfights between the skeptics and the AGW proponents. But one has to ask “What are these observational constraints?” Why guess? The IPCC provides some interesting information in the next quote.

The upper 95% limit remains difficult to constrain from observations. This supports the overall assessment based on modelling and observational studies that the equilibrium climate sensitivity is likely 2°C to 4.5°C with a most likely value of approximately 3°C (Box 10.2). The transient climate response, based on observational constraints, is very likely larger than 1°C and very unlikely to be greater than 3.5°C at the time of atmospheric CO2 doubling in response to a 1% yr–1 increase in CO2, supporting the overall assessment that the transient climate response is very unlikely greater than 3°C (Chapter 10).

At this point, this transcends to a different argument. We will stipulate that the sensitivity is correct within the constraints of their argument. However, in a later post it may be illustrative to question this sensitivity, and examine it in more detail, as we show the basis is questionable. We will need to bring in Lucia’s and treesfortheforest.wordpress.com/2009/09/26

/ar4-model-hypothesis-tests/ among others such as Dr’s Schmidt and Browning.

Section IV

 

Proving that Briffa Matters

 

This section is the most important to the argument that Briffa matters, or not! Not because I say it is, nor because others say that it is not, but because the IPCC stated that “”Indirect indicators (‘proxy data’ such as tree ring width and density) must be used to infer climate variations (Chapter 6) prior to the instrumental era (Chapter 3).”” Why? Because “”Past periods offer the potential to provide information not available from the instrumental record, which is affected by anthropogenic as well as natural external forcings and is too short to fully understand climate variability and major climate system feedbacks on inter-decadal and longer time scales.”” The complete quote in order is provided below this discussion such that this most important point can be assimilated by rereading what the IPCC stated. The AGW proponents who are claiming that Briffa does not matter are contradicting the IPCC. But a recap at this point shows why the IPCC had to make this claim. Remember that there are both natural and anthropogenic forcings according to the IPCC. In order to state that climate change is real, big, and manmade, and that the “”Greenhouse gas forcing has very likely caused most of the observed global warming over the last 50 years”” the BURDEN OF PROOF requires that uncertainty, especially solar forcing uncertainty is small enough that it can be ignored past 1950. This “ties” the IPCC’s hands when it comes to supporting their own claims. As we have seen, it repudiates the claims that Briffa doesn’t matter; the GCM’s, according to the IPCC must use indirect indicators. For those who like me get forgetful, all of these quotes from AR4 are from the section on AR4 WG1 Chapter 9 Understanding and Attributing Climate Change. Not to make too fine of a point, understanding and attribution requires Indirect indicators (‘proxy data’ such as tree ring width and density) (that) must be used to infer climate variations (Chapter 6) prior to the instrumental era (Chapter 3) in order to understand the potential information not available from the instrumental record which is too short to fully understand climate variability and major climate system feedbacks on inter-decadal and longer time scales. In other words we cannot understand inter-decadal or longer time scales without this information. Remember such understanding is necessary to attribute sensitivity such that sensitivity is constrained. If CO2 sensitivity, for example is too low or unknown, the IPCC claim of robust and solar forcing properly estimated are invalidated.

So here is the section in order:

P679

Past periods offer the potential to provide information not available from the instrumental record, which is affected by anthropogenic as well as natural external forcings and is too short to fully understand climate variability and major climate system feedbacks on inter-decadal and longer time scales. Indirect indicators (‘proxy data’ such as tree ring width and density) must be used to infer climate variations (Chapter 6) prior to the instrumental era (Chapter 3). A complete description of these data and of their uncertainties can be found in Chapter 6…

Section V

 

Nailing the Coffin on Briffa

 

We will start with the title again: What Can be Learned from the Past 1,000 Years. Remember this is what the IPCC learned. WG1 Ch 9 p679… states “”Nonetheless, there is evidence that climatic responses to forcing, together with natural internal variability of the climate system, produced several well-defined climatic events, such as the cool conditions during the 17th century or relatively warm periods early in the millennium. This is where the rubber meets the road as they say. The internal variability of the climate system has produced several well-defined climatic events that are based on MBH9x and Yamal (in chorus and all uses), for the most part. Most other proxies than these are not well defined nor extend with inter-decadal resolution necessary for the above IPCC claims. So let’s read the passage in order.

9.3.3 What Can be Learned from the Past 1,000 Years?

External forcing relative to the present is generally small for the last millennium when compared to that for the mid- Holocene and LGM. Nonetheless, there is evidence that climatic responses to forcing, together with natural internal variability of the climate system, produced several well-defined climatic events, such as the cool conditions during the 17th century or relatively warm periods early in the millennium.

So, now we can positively conclude that understanding and attributing climate change depends on the “well-defined events, such as cool conditions during the 17^th century or relatively warm periods early in the millennium. After all the IPCC learned it, and then taught us in the AR4. BUT WHAT IF cool was actually cold and relatively warm were absolutely hotter? Just what could be learned? The answers or contentions are specified above in the first four sections.

Section VI

 

The IPCC claiming Robust and Independent

 

As we examine the IPCC’s claims, remember that this section is understanding and attributing climate change. Not Yamal, or MBH9x., or whether Steve McIntyre is trying to make a mountain out of a mole-hill. This is about the IPCC’s claims. Let’s examine the text first. It is VERY long, because it includes the next section! The next section binds the models to the reconstructions. Thus the quotes are broken into smaller more understandable pieces.

9.3.3.1 Evidence of External Influence on the Climate Over the Past 1,000 Years

A substantial number of proxy reconstructions of annual or decadal NH mean surface temperature are now available (see Figure 6.11, and the reviews by Jones et al., 2001 and Jones and Mann, 2004). Several new reconstructions have been published, some of which suggest larger variations over the last millennium than assessed in the TAR, but uncertainty remains in the magnitude of inter-decadal to inter-centennial variability. This uncertainty arises because different studies rely on different proxy data or use different reconstruction methods (Section 6.6.1).

Two points: The first is that a “substantial number of proxy reconstructions of annual or decadal NH mean surface temperature are now available (see Figure 6.11, and the reviews by Jones et al., 2001 and Jones and Mann, 2004). As the reader should now be aware the question is, “Are they renditions of MBH9x or Briffa’s Yamal?” These can be discarded. They can be discarded because of what NAS and Wegman reported for the MBH9x series. They can be discarded for Briffa’s admission “My colleagues and I are working to develop methods that are capable of expressing robust evidence of climate changes using tree-ring data. We do not select tree-core samples based on comparison with climate data.” Which Briffa gave to explain his use of Yamal when problems were found by Steve McIntyre at CA after years of stonewalling. The IPCC‘s claims depend on robust evidence of climate change using proxies (tree-ring data). Without this robust evidence understanding and attributing climate change cannot be accomplished according to the IPCC in IPCC AR4 WG1 Chapter 9.

The second point is “This uncertainty arises because different studies rely on different proxy data or use different reconstruction methods (Section 6.6.1).” This is the moment to savor. This is why all those AGW proponents are wrong when they claim Briffa doesn’t matter. Steve McIntyre has had to scratch and posit and work without the code or the data to get a handle on the uses of different proxies and different reconstruction methods. As the data or code became available, he has been able to prove that the uncertainties expand and often methods are incorrect (MBH) or the methods were followed incorrectly (Briffa). But remember, if the uncertainties are too great, the whole purpose of this chapter “understanding and attributing climate change” cannot be done in the robust and very likely claims of the IPCC which is necessary for the attributing the anthropogenic rather than the natural external forcing for the second half of the 20^th century.

In order to re-iterate their claim, the IPCC repeats the discredited MBH9x claim

Nonetheless, NH mean temperatures in the second half of the 20^th century were likely warmer than in any other 50-year period in the last 1.3 kyr (Chapter 6), and very likely warmer than any such period in the last 500 years. Temperatures subsequently decreased, and then rose rapidly during the most recent 100 years. This long-term tendency is punctuated by substantial shorter-term variability (Figure 6.10). For example, cooler conditions with temperatures 0.5°C to 1°C below the 20^th-century mean value are found in the 17^th and early 18^th centuries. And of course, these reconstructions include Briffa (chorus and all).

Section VII

 

The IPCC Ties it All Together and Falsifies the AGW Proponents Excuses

A number of simulations of the last millennium (Figure 6.13) have been performed using a range of models, including some simulations with AOGCMs (e.g., Crowley, 2000; Goosse and Renssen, 2001; Bertrand et al., 2002; Bauer et al., 2003; Gerber et al., 2003; see also Gonzalez-Rouco et al., 2003; Jones and Mann, 2004; Zorita et al., 2004; Weber, 2005; Tett et al., 2007). These simulations use different reconstructions of external forcing, particularly solar, volcanic and greenhouse gas forcing, and often include land use changes (e.g., Bertrand et al., 2002; Stendel et al., 2006; Tett et al., 2007). While the use of different models and forcing reconstructions leads to differences, the simulated evolution of the NH annual mean surface temperature displays some common characteristics between models that are consistent with the broad features of the data (Figures 6.13 and 9.4). For example, all simulations show relatively cold conditions during the period around 1675 to 1715 in response to natural forcing, which is in qualitative agreement with the proxy reconstructions. In all simulations shown in Figure 6.13, the late 20th century is warmer than any other multidecadal period during the last millennium. In addition, there is significant correlation between simulated and reconstructed variability (e.g., Yoshimori et al., 2005). By comparing simulated and observed atmospheric CO2 concentration during the last 1 kyr, Gerber et al. (2003) suggest that the amplitude of the temperature evolution simulated by simple climate models and EMICs is consistent with the observed evolution of CO2. Since reconstructions of external forcing are virtually independent from the reconstructions of past temperatures, this broad consistency increases confidence in the broad features of the reconstructions and the understanding of the role of external forcing in recent climate variability. The simulations also show that it is not possible to reproduce the large 20th-century warming without anthropogenic forcing regardless of which solar or volcanic forcing reconstruction is used (Crowley, 2000; Bertrand et al., 2002; Bauer et al., 2003; Hegerl et al., 2003, 2007), stressing the impact of human activity on the recent warming.

While there is broad qualitative agreement between simulated and reconstructed temperatures, it is difficult to fully assess model-simulated variability because of uncertainty in the magnitude of historical variations in the reconstructions and differences in the sensitivity to external forcing (Table 8.2). The role of internal variability has been found to be smaller than that of the forced variability for hemispheric temperature means at decadal or longer time scales (Crowley, 2000; Hegerl et al., 2003; Goosse et al., 2004; Weber et al., 2004; Hegerl et al., 2007; Tett et al., 2007), and thus internal variability is a relatively small contributor to differences between different simulations of NH mean temperature. Other sources of uncertainty in simulations include model ocean initial conditions, which, for example, explain the warm conditions found in the Zorita et al. (2004)simulation during the first part of the millennium (Goosse et al.,2005; Osborn et al., 2006).

By this time the reader should be able to pick out the part that is most appropriate:

For example, all simulations show relatively cold conditions during the period around 1675 to 1715 in response to natural forcing, which is in qualitative agreement with the proxy reconstructions. In all simulations shown in Figure 6.13, the late 20th century is warmer than any other multidecadal period during the last millennium.

In order to understand and attribute climate change, the relatively cold conditions around 1675 to 1715, and that the late 20th century is warmer than any other multidecadal period during the last millennium is required. Not because the proxies say so, but that the simulations agree with the proxies. This is required for the robust and very likely claim to counter the uncertainties of the solar forcing.

The out that will be claimed by the AGW proponents will be “”The role of internal variability has been found to be smaller than that of the forced variability for hemispheric temperature means at decadal or longer time scales.”” However, this is a circular argument at this point because the internal variability that was found to be smaller depends on the proxies being correct for the last millennium such that the IPCC admitted uncertainties of the solar forcing do not overwhelm the attribution of solar in the last half of the 20^th century. If it overwhelms the attribution, then by this chapter the understanding is incorrect. Truly with the temperatures relatively flat and SC24 weak so far, we live in interesting times.