Comments on: The Three-Core Chronology

By: bender

bender — Thu, 17 May 2007 00:33:12 +0000

Re: Li et al’s Fig. 3.
The 1944-45 event is exerting large leverage on the reconstruction calibration. Take those years away and watch the significance of the reconstruction drop. Meanwhile dry episodes in 1948-51, 1961-63, 1981-83 are not well reconstructed at all. Looks like the reconstruction might actually be failing in the decadal range. The 1970s and 1990s events are reasonably well-reconstructed. Wet events in 1959, 1988 are not at all well-reconstructed.

By: bender

bender — Thu, 17 May 2007 00:18:21 +0000

Re #21

How much physiological process modeling is being currently performed regarding TRW ‘€” lets say as compared to crop plant modeling to predict yields?

Very little, IMO. I could answer quantitatively via a literature search, but it’s hardly worth the effort. I do not think the physiologists have tuned into this particular gem of a debate. Not yet.

By: bender

bender — Wed, 16 May 2007 23:49:59 +0000

1. The link between solar cycles (bidecadal and decadal) and drought in the continental US has been reported in the literature, and is well-known. So why not China?
2. Are the tree-ring data archived? They don’t actually show their data in this paper, just the reconstruction.
3. They are using Picea. In N. America that would be a bad idea for the number of outbreaking insects that feed on Picea, many of these genera occurring in Asia. How do they rule out insect outbreaks as a source of variation? The word “insect” is not even in that paper. Many insects are more prone to outbreak during droughts. Including species that feed on Picea.
4. They show the spectrum of the reconstruction, but not the data on which the reconstruciton is based. It would be interesting to see where in the frequency domain there is gain and loss of signal.

By: Mark T.

Mark T. — Wed, 16 May 2007 23:33:59 +0000

I wonder, Steve M., if the 11.4 year cycle in that paper is perhaps indicative of the solar cycle?

Interesting, btw, that 47.5% of the variability in tree-rings is attributed to _moisture_, not temperature, in this study. Also interesting is that the variability is increasing, i.e. it is not stationary.

Mark

By: jae

jae — Wed, 16 May 2007 19:30:36 +0000

40: Now THATS the type of study where tree ring information is useful, IMHO. An R2 of 47.5% ain’t bad and makes good sense.

By: Steve McIntyre

Steve McIntyre — Wed, 16 May 2007 17:54:57 +0000

Current Int JClimatology:

Drought reconstruction for North Central China from tree rings: the value of the Palmer drought severity index
Jinbao Li 1 2, Fahu Chen 1 *, Edward R. Cook 2, Xiaohua Gou 1, Yongxiang Zhang 1
1CAEP, MOE Key Laboratory of West China’s Environmental System, Lanzhou University, Lanzhou 730000, China
2Tree-Ring Laboratory, Lamont-Doherty Earth Observatory, Columbia University, NY 10964, USA
email: Fahu Chen (fhchen@lzu.edu.cn)

*Correspondence to Fahu Chen, CAEP, MOE Key Laboratory of West China’s Environmental System, Lanzhou University, Lanzhou 730000, China.

Keywords
dendroclimatology ‘€¢ drought ‘€¢ PDSI ‘€¢ north central China

Abstract
We present a drought reconstruction for north central China based on a tree ring-width chronology developed from two sites of the Chinese pine (Pinus tabulaeformis) in the northern Helan Mountains. The drought reconstruction, spanning 1788-1999 A.D., was developed by calibrating tree-ring data with the Palmer drought severity index (PDSI), an index that describes the regional moisture condition properly. The reconstruction was verified with independent data, and accounts for 45.7% of the actual PDSI variance during their common period (1941-1999). The full reconstruction indicates that the regional drought variability was relatively stable during the nineteenth century, but became more variable and persistent during the twentieth century. The drought epoch in the late 1920s was the most severe one in our reconstruction. In contrast to a wetting trend in the western area of northwest China, a clear drying trend has occurred in north central China since mid-1930s. The multitaper method (MTM) spectral analysis indicates the existence of some decadal (11.4 year) and interannual (9.1, 6.8, 4.0, 2.7 and 2.1-2.0 year) cycles, which may potentially be the fingerprints of some proposed climate change forcings. Copyright ⧠2006 Royal Meteorological Society

By: Don Keiller

Don Keiller — Sat, 14 Apr 2007 17:19:58 +0000

RE #26 “As much fun as criticising the Bristlecones may be, the science of climate change does not stand or fall on the reliability of this proxy”. No, but as Steve said, the continued use by the IPCC of such questionable data as factual proof of AGW casts doubt on their other endorsements. Loehe’s(Ecol. Mod. 171, 433-50) 2004 paper casts more doubt- as does Svensmark’s Solar Climate connection (e.g J. of Atm. and Solar-Terrestrial Phys., 59 (11) (1997) 1225-1232. AGW, as a theory, has a number of competitors- credible ones at that. I and many others have yet to see a knockout blow from the AGW camp. Dodging the contenders is an old (and past it) boxing champion’s modus operandii. But sooner or later you have to face up to reality.

By: Kenneth Fritsch

Kenneth Fritsch — Sat, 14 Apr 2007 13:43:29 +0000

Re: #26

As much fun as criticising the Bristlecones may be, the science of climate change does not stand or fall on the reliability of this proxy.

The science of climate and how the reliability of its outputs are to be evaluated do, in my judgment, stand on how the scientists of climate change (and their layperson supporters) react to such criticism. In the consensus of scientists on climate change one needs to know if there are any prejudices and cherry picking of results. I think a number of supporters of the current state of science on climate change do not necessarily see this aspect of the issue very clearly.

By: esceptico

esceptico — Sat, 14 Apr 2007 09:20:24 +0000

it is completely proven that close to 100% of the recent warming is due to man.

In science never exist the last word

By: Andrey Levin

Andrey Levin — Sat, 14 Apr 2007 09:08:39 +0000

Twq:

Depends on what you are calling “recent warming”.

Climate is on warming trend for 150+ years, CO2 is noticeably rising for less than 100 years, antropogenic CO2 emissions rose noticeable for only 50 years, from 1.2 Gt C per year in 1950 to 6.5 Gt in 1990 (and about leveled off since):

http://en.wikipedia.org/wiki/Image:Global_Carbon_Emission_by_Type.png

If “recent warming” is for 150 years, antropogenic emissions of GHG could cause it only from the point of view of somebody traveling back in time.

If “recent warming” is for last 30 years ‘€” yes, it is theoretically possible.