I have a few questions regarding Alley 2000...?

Question

- Are the temperature reconstructions given often by skeptics to show a large temperature variance (such as)
http://i90.photobucket.com/albums/k247/dhm1353/Climate%20Change/Moberg_Mann_Esper_Alley.png
of temperatures as measured in Greenland ice cores, or are they extrapolations to the planet?

- Is there a more updated record of Greenland temperatures, since the data set used in Alley 2000 ended at the beginning of the twentieth century? Also, do these two use the same time frame (and thus base temperature) as a reference, or would they have to be shifted up or down?

- Is there actually an Alley 2004? Alley 2000 comes up in a Google search, but not Alley 2004.

- How appropriate is a comparison between studies that use different proxies in different locations to determine which one is more accurate?

Answer 1

If you have access to the SkS Authors forum, which I believe you do, you can read a discussion about Alley's GISP-2 Greeland ice core data here:

http://www.skepticalscience.com/thread.php?t=320&r=23



To make a long story short, it's just representative of Greeland temps, not global or northern hemisphere (NH), and although it's the most up-to-date ice core record from Greeland, it ends around 1850. There is of course instrumental temperature data from Greenland as well:

http://data.giss.nasa.gov/cgi-bin/gistemp/findstation.py?lat=61.2&lon=-48.2&datatype=gistemp&data_set=1



You are correct that the reference should be to Alley (2000). There is no Alley (2004).

http://www.geosc.psu.edu/people/faculty/personalpages/ralley/index.html



These data should not be compared. The others shown (Moberg, Esper, and Mann) are NH temperature reconstructions (and contrary to the figure, do not show the MWP as warm as today). They're graphed here:

http://www.ncdc.noaa.gov/paleo/globalwarming/medieval.html



And Moberg is here:

http://www.skepticalscience.com/Do-critics-of-the-hockey-stick-realise-what-theyre-arguing-for.html

http://www.ncdc.noaa.gov/paleo/globalwarming/images/moberg-2005-large.jpg



The figure in question conveniently leaves off the instrumental temperature record. Proxy data usually ends in early to mid 20th century, so all the figure is showing is that the MWP was roughly as warm as 1900-1950, which is at least a half degree cooler than today. Moberg even includes the instrumental record in his paper on Figure 2b:

http://coast.gkss.de/staff/storch/pdf/moberg.nature.0502.pdf



To answer your final question, if you're trying to determine which is the most accurate temperature reconstruction, you can't compare a Greeland reconstruction to NH reconstructions, as was done in the figure you linked. Comparing Moberg to Mann, for example, would be valid. Like the spaghetti graph:

http://www.ncdc.noaa.gov/paleo/globalwarming/medieval.html



I also wish deniers would get over their obsession with Loehle, whose paper failed peer review, had to be completely revised with assistance from a statistician, at which point it showed today about a half degree warmer than the MWP, and only used 18 proxy records. The only reason deniers like it is that it ends in 1935 and doesn't include instrumental data, so it looks like the MWP is as hot as today, and particularly because pre-statistical revision the MWP looked hotter than "today". But there is no reason whatsoever to reference Loehle when there are a dozen reconstructions available which did pass peer-review. But you can see Loehle's revised paper superimposed on the "spaghetti graph" here:

http://farm3.static.flickr.com/2666/3914214320_261cba1cf2_o.png



As you can see, it's quite similar to all other reconstructions. Except Loehle's is clearly flawed. For example, his has the MWP peaking in 800 AD as opposed to 1000 AD. See here:

http://tamino.wordpress.com/2010/09/28/vindication/



*edit* don't mind jim, I think he's just here for comic relief. Honestly I can't even figure out what he's babbling about. I thought we were talking about ice cores and temperature records, but he's talking about glaciers and tree rings and plant stomata.



Stomata, by the way, are used as an atmospheric CO2 proxy, not a temperature proxy, so they have nothing whatsoever to do with this question. And there's a reason ice core records are the preferred CO2 record - they're a direct measurement via trapped air, whereas stomata are an indirect proxy which can be influenced by a number of factors. But of course deniers like jim prefer stomata because they show a larger atmospheric CO2 variability, precisely because they're influenced by a number of other factors.

http://www.skepticalscience.com/Plant-stomata-and-CO2-levels.html



Of course none of this has anything to do with the question you asked, but I have a hard time letting deniers get away with making incorrect statements.

Answer 2

I certainly wouldn't assume any of the proxies are correct. How appropriate is it using different proxies in different locations? As opposed to using fewer proxies from one location?



Ottawa Mike provided a good answer so I don't need to repeat it. I am not so enamored as you are apparenlty with tree ring proxies. I would recommend to you to actually read his link. After that read this one about plant stomata.



http://www.geocraft.com/WVFossils/stomata.html



When you have lots of proxies showing you different results, you know what that means, right?

That means that there is a lot of uncertainty.



Dana claims that the Greenland core data isn't valid after 1800 something. Gee I wonder why that is. I will tell you why it probably is. There would be no use in testing the poorly formed ice formed since then. It would be unreliable. For the same reason, the ice core data provides only an average of CO2 over "hundreds" of years. It takes a long time for fern to form trapping the little bubble in the ice. CO2 is soluble in water and more so in cold water. There is water in glaciers. There are lots of problems with getting all your CO2 eggs in one basket. The ice core CO2 data has become a large part in the the AGW belief system so I realize challenging it is going to win me a lot of thumbs down.

Answer 3

Strangely the very same jim z who here says proxies like the one you have listed here shouldn't be trusted used the exact same link in a question just 2 hour before you posted this (I think you may have known that)

https://answersrip.com/question/index?qid=20101118093542AAWykx4

How fickle the denier mind is !

as I said in that question there is a reason such diagrams are sourced from photobucket rather than a real site it avoids awkward questions like how come Moberg's paper is actually about only the NH yet the diagram implies it's about global climate

http://www.nature.com/nature/journal/v433/n7026/full/nature03265.html

As Moberg points out in his header text his work only covers up to 1990 (20 years ago) why deniers use it is painfully obvious. If the graph included temperature to the present it would look quite different this is a trick deniers have used a number of times it was on open display in their little documentary TGGWS (till they got caught) "swindle" being quite prophetic given the number of mistakes found in that documentary and the number of re-edits they were forced to make, one reason I find it quite funny when they pick on ICT for errors.

Asking why deniers carry on with this rubbish is like asking why Jim gets so many thumbs up for answers that are obviously rubbish, even his own logic is fatally flawed if the proxy record is so bad then what are his references to the Younger Dryas (in the previous question) based on (tea leaves)

These guys seem unable to make up their minds, if the proxy is not accurate, then we have no idea what the Younger Dryas or the MWP were like (warmer or colder) but deniers seem to have this strange idea that proxies are only accurate when they reference them and inaccurate for the rest of us.

This graph below covers most of the sources mentioned (plus a number of others) and instrumental temperature data as well up to 2004

http://en.wikipedia.org/wiki/File:2000_Year_Temperature_Comparison.png

Fourteen years more information than the photobucket image

and where is 2004 in reference to the ten warmest years

http://www.ncdc.noaa.gov/sotc/?report=global&year=2009&month=13&submitted=Get+Report#gtemp

Eighth !

Answer 4

Well I'll start by describing Loehle (2007), A 2000-Year Global Temperature Reconstruction Based on Non-Treering Proxies.



Loehle specifically does not use tree rings (or Greenland ice cores for that matter) and explains why dendro proxies may not be sufficient. He uses 18 other proxies from Central Alps stalagmite oxygen isotope data to SST reconstruction in the Norwegian Sea. This page has a .pdf download link to that paper: http://www.ncasi.org/publications/Detail.aspx?id=3025



Here is a link to the main graph: http://www.co2science.org/articles/V11/N5/Loehle2007small.gif



As for the appropriateness of the comparisons between proxies, I'm not well educated in that area to answer. However, it seems to me that Loehle's approach for a global temperature reconstruction is pretty robust compared to just tree rings or just Greenland ice cores. Again, that's from limited knowledge of proxies.



Edit: I forgot that Loehle expanded on his thoughts about tree rings for temperature reconstruction in a paper dedicated to the topic here: http://icecap.us/images/uploads/Loehle_Divergence_CC.pdf

Answer 5

I'm not very well informed on that topic but I did find a general reference to Alley 2004 @ climate audit. No links, urls or reasons were offered as to why Thompson archived instead of Alley other then Steve M's persistance.

Whether its standing I haven't a clue.

http://climateaudit.org/2006/03/06/alley-at-the-nas-panel