Comments on: Post-1980 Proxies #3: Chesapeake Bay Mg/Ca

By: Moderate Low Weight « Climate Audit

Moderate Low Weight « Climate Audit — Sun, 04 Dec 2011 20:35:23 +0000

[...] discussion of the topic from the early days of CA. Fourth series to enter the MJ03 portfolio is the Chesapeake Bay Mg/Ca proxy, also present in Figure 2. This series has declining temperatures since late 19th century. Finally, [...]

By: TCO

TCO — Sun, 11 Sep 2005 16:42:55 +0000

What is the implication of figure 2b (can’t really read it). Are there two series on here that are moving together? If so, can’t some numeric analysis (covariation?) be made?

Also, where is the feild study proof of the proxy relevance (direct measurement of temp and Mg/Ca) or at least the covariance versus local temp stations in 1900s? Does Steve agree that this proxy “works” in these terms?

By: Greg F

Greg F — Sat, 26 Feb 2005 03:46:01 +0000

The link in post #5 is broke. The ‘/’ after the ‘.GIF’ has to be removed.

Steve: Fixed.

By: Greg F

Greg F — Sat, 26 Feb 2005 02:49:14 +0000

"The plot of the 19th and 20th century data looks more volatile, but Cronin et al. [2003] do not discuss whether this is an artifact of sampling."

The data at WDCP (Cronin et al, 2003) is composed of 3 different proxy data sets with a total of 450 samples. Almost half the samples are post 1750 as is shown below:

1900 – 1995 Total samples = 130
69 – RD/2209
39 – PTXT-2
22 – PTMC-3

1750 – 1995 Total samples = 223
99 – RD/2209
71 – PTXT-2
53 – PTMC-3

Post 1750 is the only time span that all three proxies contribute significant samples, as is evident from this plot. I think this explains the volatility.

Steve: looks like a logical explanation.

By: Steve Funk

Steve Funk — Sun, 20 Feb 2005 04:19:12 +0000

I was just saying that Moberg, et. al., does not have nearly as much confidence in tree-ring data as did Mann, et.al, since Moberg considers tree-ring data unsuitable for long-term trends.

By: Jeff Norman

Jeff Norman — Fri, 18 Feb 2005 13:08:11 +0000

I may have missed the definition somewhere, but what is COADs? John writes: Ah, those pesky scientists and their acronyms! I think it means "Comprehensive Ocean-Atmosphere Data". Check out this site for more details.

By: John A.

John A. — Fri, 18 Feb 2005 00:11:18 +0000

My response to realclimate is: useful for what? Trees, we are told, are not sensitive to local temperature conditions, yet by some strange magic, can be used to measure something called the “global temperature”.

In climatic terms, 80 years is barely significant, let alone useful.

By: Steve Funk

Steve Funk — Thu, 17 Feb 2005 22:18:16 +0000

One thing that Real Climate mentions about this paper is that the authors consider tree ring data to be useful for short-term fluctuations, but not for long-term trends greater than 80 years. The paper evidently combines longer-term data from sediment cores with shorter-term tree ring data in the graph.