Nahle, N. 2009. Strong Correlation between Treerings Proxy of Temperature and Total Solar Irradiance. Biology Cabinet. San Nicolas de los Garza, N. L. MX. http://www.biocab.org/Insolation_Treerings_Growth.html

The authors are grateful to TS for his kind assistance with the text.

By Nasif Nahle
October 2nd, 2009


Treerings have been used as a source for the assessment of paleotemperatures. Nevertheless, the width of the growth rings of bristlcone pines change according to insolation rather than environmental temperature. Bristlecone pines are extremely sensitive to high levels of insolation, which determines their geographical distribution, placing them in cold environments where insolation is usually not higher than 50% of the total incident solar irradiance on the surface. As insolation increases to levels above 50%, the widening of treerings slows and stops. This latter physiological response of the plant propels us to false interpretations of environmental temperatures because they would tend to appear flat. In this assessment, I have made a comparison between the raw data of the Yamal treerings database (from the species Larix sibirica, Ledebour) and the total solar irradiance from three sources, Lean 2000, Lean 2004 and Svalgaard 2008. In addition, I have made  a reconstruction of temperatures covering the last two millennia by combining three temperature proxies, including records obtained by Yang, Moeberg, Calvo and from the Yamal mixed proxies, and compared them with Lean’s databases on TSI.


Taking the raw database from the Yamal region I obtained a change of temperature by employing the following formula:

ΔT = TRings Growth Index Recons (0.01 °C)

For example, the reconstruction indexes from treerings in 1996 is 136. Applying the algorithm, I obtained a change of temperature = 136 (0.01 °C) = 1.36 °C.

I then assembled the change of temperature obtained by instruments from 1997 up to 2008 and plotted it alongside the Yamal database.

The following graph illustrates the results:


Notice that the maximum temperature derived from the analysis of Siberian larch trees from the Yamal Peninsula, in Russia, occurred in 995 AD, which coincides with the well known Medieval Warming Period. One notable point is that the current warming is insignificant in comparison with past warming periods.

On the other hand, the maximum growth index could have been caused by changes of solar irradiance which could have modified the insolation in the area.

The combination of several proxies reveals that the maximum temperature was achieved in 980 AD, during the Medieval Warming Period. Again, the relevance of the current warming is quite low in comparison with past warming periods.

In the next graph, I plotted the combined databases from several non-treering proxies, as well as treerings, against the TSI reconstruction published by Dr. Lean in 2004:


There is a clear correlation between the Total Solar irradiance reconstruction of Dr. Lean (2004) and the variation of temperature obtained from several combined proxies.

I have also compared the combined proxies on variation of temperature with Dr. Svalgaard’s Total Solar Irradiance reconstruction (2007) depicted in the following graph:


The graph demonstrates the existence of a correlation between the variation of temperature from the combination of several proxy reconstructions and the total solar irradiance from Svalgaard’s reconstruction.


Notice that the width of the treerings is primarily a response to insolation rather than temperature. The reason being that Siberian Larch Trees are C3 plants, whose growth is more closely linked with insolation than it is with environmental temperature.

It is clear that C3 plants achieve better growth when the proportion of insolation does not exceed 50% of the total insolation; for values above 50%, the growth of Siberian larch trees, which are C3 plants, is slowed progressively as solar luminosity increases. The following diagram illustrates what happens to bristlecone pines as solar luminosity increases; something similar also happens to Siberian Larch Trees:


Notice that as the luminosity increases above 50%, the growth of the treerings slows until they achieve values close to the initial response from 10% luminosity. This characteristic of bristlecone pines makes treerings growth analysis a highly inadequate proxy for assessing paleotemperatures.

So how does this physiological pathway work? By means of a primitive physiological mechanism called Photorespiration. Photorespiration occurs on bright, hot and dry days. Under those conditions, the C3 plants close their stomata for preventing loss of water. As a result, the concentration of oxygen within the air spaces of the leaves increases and the concentration of carbon dioxide decreases. This change of concentration of oxygen and carbon dioxide makes the molecule of Ribulose-1, 5-bisphosphate carboxylase oxygenase (RuBisCO) to capture oxygen to be used in the Calvin cycle instead of carbon dioxide. Consequently, the plants produce less food and slow their growth. (Odum. 2006. Pp. 48-50) (Lodish et al. 2000. Pp. 667-669)

Photosynthesis is affected in the same way on gloomy, cold and wet days. For this reason we cannot know when the slowness of plant growth was due to high or low insolation, to high or low temperature, or to high or low humidity. (Odum. 2006. Pp. 48-50)

For example, if the insolation is 210 W/m^2 on average, the growth of pines would be optimal; let us say some 140% per year, according to the diagram above these lines. If we deduced the environmental temperature anomaly from this data, we would say that that year would have been a fairly warm year, let us say 1.4 °C above the standard temperature. However, supposing that the insolation increases up to 100 %, i.e. to 420 W/m^2 on average. This would mean that the pine trees’ growth would be dramatically slowed, so the annual pines’ rings growth actually would be fairly lessened, let us say -30% a year. If we continue with the same criterion for calculating the annual temperature anomalies, this would represent an anomaly of -0.3 °C, which would be absolutely false because the insolation would have been at its peak intensity (100%) and consequently the environmental temperature would have been higher than if the pine treerings would have grown up to 140 mm a year.

The works of Michael Mann, Keith Briffa and colleagues on paleotemperatures are based absolutely on the treering growth of pines, which explains why their results always show flat temperatures for periods prior to the use of thermometers. Because of this, their graphs give false results. The latter is revealed when we compare the treerings growth from the Yamal Peninsula with the instrumental data in the last 30 years. This comparison gives a 100 % correlation which is clear indication on hard manipulation of the data to give the false impression that the pine’s treerings growth is a reliable proxy on the tropospheric temperature when in reality it is not.

On the other hand, when properly examined, the databases of other non-treering proxies always show the Medieval Warming Period.

This analysis demonstrates also that the combination of the databases from treering proxies with the databases from other proxies such as sediments, pollen, Hematite Stained Grains, etc. is always more appropriate for obtaining reliable records on variation of temperature than simply treering growth alone, which is affected by many other factors such as humidity, insolation, concentration of carbon dioxide, altitude, temperature, etc.



Hantemirov, R.M. and S.G. Shiyatov. 2003. Yamal Peninsula Multimillennial Summer Temperature Reconstruction. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2003-029. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

Lean, J. 2004. Solar Irradiance Reconstruction. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2004-035. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. Reviewed by Nasif Nahle ©2008.

Lodish, H., Berk, A., Zipursky, S. L., Matsudaira, P., Baltimore, D. and Darnell, J. Molecular Cell Biology. W. H. Freeman and Company; 1999, New York, New York. Pp. 667-669

Yang, B., A. Braeuning, K. R. Johnson, and S. Yafeng (2002). General characteristics of temperature variation in China during the last two millennia. Geophys. Res. Lett., 29(9), 1324.

Moberg, Anders, Sonechkin, Dmitry M.; Holmgren, Karin; Datsenko, Nina M.; Karlén, Wibjörn; Lauritzen, Stein-Erik. (2005). Highly variable Northern Hemisphere Temperatures Reconstructed from low- and high Resolution Proxy Data. Nature, 433: 613-617.

Svalgaard, L. 2008. Reconstruction of Total Solar Irradiance. Research Analysis. Last reading on May 12, 2008.

Sutton, David B., Harmon, N. Paul. Ecology: Selected Concepts. 2000. John Wiley & Sons, Inc. New York.

Odum, Eugene P. and Barrel, Gary W. Fundamentos de Ecología-Quinta Edición. 2006. International Thompson Editores, S. A. de C. V. México, Distrito Federal. Pp. 48-50.

Mann, Michael E., Bradle, Raymond S. and Hughes, Malcolm K. Global-scale temperature patterns and climate forcing over the past six centuries. Nature, Vol. 392. Pp. 779-787. 23 April 1998.

Campbell, Neil A., et al. Biology. Addison Wesley Longman, Inc. 1999, Menlo Park, CA.


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For the next assessment I averaged three databases from different proxies to those of the treerings growth of Siberian larch trees and combined them with the data from the Yamal Peninsula. The databases used were compiled by Moeberg, Yang and Calvo. I also collated the database of change of temperature from instrumental records for the period 1997-2008 AD. The resulting graph barely differs with respect to the graph drawn from the database of the Yamal Peninsula:

In the next graph, I have plotted the raw database on treerings width of Siberian Larch trees from Yamal Peninsula, Siberia Russia:

This graph illustrates the periods when the growth of the Siberian Larch trees achieved maximum and minimum growth indexes derived from the rate of photosynthetic production.

The photosynthesis of Siberian Larch trees, bristlecone pines, Canadian pines or C3 plants in general, is affected by insolation, in the first place, followed by environmental temperature and humidity (Lodish et al. 2000. Pp. 667-669)
the width of the treerings is primarily a response to insolation rather than temperature. The reason being that Siberian Larch Trees are C3 plants, whose growth is more closely linked with insolation than it is with environmental temperature.