More Yamal tree ring temperature data

More Yamal tree ring temperature data

http://wattsupwiththat.com/

Today while looking for something else I came across an interesting web page on the National Climatic Data Center Server that showed a study from 2002

A continuous multimillennial ring-width chronology in Yamal, northwestern Siberia (PDF) by Rashit M. Hantemirov and Stepan G. Shiyatov

That study was tremendously well done, with over 2000 cores, seemed pretty germane to the issues of paleodendroclimatology we’ve been discussing as of late. Jeff Id touched on it breifly at the Air Vent in Circling Yamal – delinquent treering records?

A WUWT readers know, the Briffa tree ring data that purports to show a “hockey stick” of warming in the late 20th century has now become highly suspect, and appears to have been the result of hand selected trees as opposed to using the larger data set available for the region.

OK,  first the obligatory Briffa (Hadley Climate Research Unit) tree ring data versus Steve McIntyre’s plot of the recently available Schweingruber data from the same region.

Red = Briffa's 12 hand picked trees Black = the other dataset NOT used

 

The Hantemirov- Shiyatov (HS) tree ring data that I downloaded from the NCDC is available from their FTP server here. I simply downloaded it and plotted it from the present back to the year 0AD (even though it extends much further back to the year 2067 BC) so that it would have a similar x scale to the Briffa data plot above for easy comparison. I also plotted a polynomial curve fit to the data to illustrate trend slope, plus a 30 year running average since 30 years is our currently accepted period for climate analysis.

Compare it to the Briffa (CRU) data above.  

Click for larger image

 

When I first saw this plot, I thought I had done something wrong. It was, well, just too flat. But I double checked my data import, the plot, the tools used to plot, and the output by running it 2 more times from scratch. Then I had Jeff Id over at the air vent take a look at it. He concurs that I’ve plotted the data correctly.

The trend is flat as road kill for the past 2000 years, though it does show an ever so slight cooling.

So the next task was to look at more recent times. Here’s the last 200 years of the data:

Zoomed to last 200 years - click for larger image

 

Still flat as road kill.

Finally, since Tom P made a big deal out of the late 20th century with his analysis where he made the mistake of combining two data sets that had different end points, I thought I’d show the late 20th century also:

Zoomed to last 50 years - click for larger image

 

Still flat.

Note that in the graph done by Steve McIntyre showing both Briffa and Schweingruber data, both of those data sets are also quite flat until we get into the late 20th century. So out of the 3 data sets we’ve looked at, the Briffa data, the data kept hidden for almost 10 years,  is the only one that shows any propensity for sudden 20th century warming.

But don’t take my word for it that this record is so flat. Look at the authors results. Their results seem identical to what I’ve plotted. Here is the last 2000 years of data charted taken from their paper:

Figure 8 Reconstructed southern Yamal mean June–July temperature anomalies relative to mean of the full reconstructed series.

But for those that want more close up views, I’ve done some additional graphs. Since the authors used a 50 year window in one of their graphs I did the same. I also changed the Y scale to show a zoomed in +/- 0.3°C as the range rather than the +/- 4.0°C the authors used in the plot above. Some details begin to emerge, but once again the trend is essentially flat, and slightly negative.

Click for a larger image

 

And here are the last 200 years zoomed

Click for a larger image

 

The period around 1800 was warmer than the late 20th century according to the data viewed this way, but we can see that slight rise in temperature for the 20th century. However compared to the rest of the Yamal HS data record it appears insignificant.

The authors insist that this wood contains a valid climatological record.

Holocene deposits in the southern Yamal Peninsula contain a large amount of subfossil tree remains: tree trunks, roots and branches. This is the result of intensive accumulation and the good preservation of buried wood in the permafrost. The occurrence of this material in the present-day tundra zone of the Yamal Peninsula was described for the Žfirst time by Zhitkov (1913). Later, Tikhomirov (1941) showed that, on the evidence of remains of trees preserved in peat, during the warmest period of the Holocene, the northern tree-line reached the central region of the Yamal Peninsula (up to 70°N), whereas today the polar timberline passes through the southernmost part of the peninsula at a latitude of 67°309 N.

By 1964, attention had been drawn to the potential significance of Yamal subfossil wood for reconstructing climatic and other natural processes over many thousand years, as a result of Ž fieldwork carried out within the valley of the Khadytayakha River in the southern part of the Yamal Peninsula (Shiyatov and Surkov, 1990).

I was impressed with the amount of field work that went into this paper. The authors write:

We travelled by helicopter to the upper reaches of the river to be sampled. Small boats were then used for locating and collecting cross-sections from wood exposed along the riverbanks. It was also possible, when going with the stream, to explore the nearest lakes.

The best-preserved material from an individual tree is usually found at the base of the trunk, near to the roots. However, many of these remains are radially cracked and it is necessary to tie cross-sections, cut from these trunks or roots, using aluminum wire before sawing. This wire is left in place afterwards as the sections are air-dried.

Here’s how they got many of the tree samples using a rubber boat:

And here is how they sum up the last 2000 years from a tree line analysis they did:

From the beginning of the first century bc to about the start of the sixth century ad, generally warm conditions prevailed. Then began a quasi 400-year oscillation of temperature, cooling occurring in about 550–700, 950–1100, 1350–1500 and 1700–1900. Warming occurred in the intermediate periods and during the twentieth century. The more northerly tree-line suggests that the most favourable conditions during the last two millennia apparently occurred at around ad 500 and during the period 1200–1300. It is interesting to note that the current position of the tree-line in Yamal is south of the position it has attained during most of the last three and a half millennia, and it may well be that it has not yet shifted fully in response to the warming of the last century.

Interestingly while the authors note some warming in the last century, they don’t draw a lot of attention to it, or refer to it as being “unprecedented” in any way. There’s no graphs of nor mention of “hockey stocks” either.

Here’s the link to the source data:

ftp://ftp.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/asia/russia/yamal_2002.txt

Feel free to make some plots of your own.