Trees tell of past climates: but are they speaking less clearly today?
- Briffa, K. R. Climatic Research Unit, University of East Anglia, Norwich NR4 7TJ, UK
- Schweingruber, F. H Swiss Federal Institute for Forest, Snow and Landscape Research, Zürcherstrasse 111, CH- 8903, Birmensdorf, Switzerland
- Jones, P. D. Climatic Research Unit, University of East Anglia, Norwich NR4 7TJ, UK
- Osborn, T. J. Climatic Research Unit, University of East Anglia, Norwich NR4 7TJ, UK
- Harris, I. C. Climatic Research Unit, University of East Anglia, Norwich NR4 7TJ, UK
- Shiyatov, S. G. Institute of Plant and Animal Ecology, Ural Branch of the Russian Academy of Sciences, 8 Marta Street, Ekaterinburg 620219, Russia
- Vaganov, E. A. Institute of Forest, Siberian Branch of the Russian Academy of Sciences, Krasnoyarsk 660036, Russia
- Grudd, H. Naturgeografiska Inst., Stockholms Universitet, 106 91 Stockholm, Sweden
- 1998-1-29
Published in:
- Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences. - The Royal Society. - 1998, vol. 353, no. 1365, p. 65-73
English
The annual growth of trees, as represented by a variety of ring–width, densitometric, or chemical parameters, represents a combined record of different environmental forcings, one of which is climate. Along with climate, relatively large–scale positive growth influences such as hypothesized ‘fertilizationrsquo; due to increased levels of atmospheric carbon dioxide or various nitrogenous compounds, or possibly deleterious effects of ‘acid rain’ or increased ultra–violet radiation, might all be expected to exert some influence on recent tree growth rates. Inferring the details of past climate variability from tree–ring data remains a largely empirical exercise, but one that goes hand–in–hand with the development of techniques that seek to identify and isolate the confounding influence of local and larger–scale non–climatic factors.
By judicious sampling, and the use of rigorous statistical procedures, dendroclimatology has provided unique insight into the nature of past climate variability, but most significantly at interannual, decadal, and centennial timescales. Here, examples are shown that illustrate the reconstruction of annually resolved patterns of past summer temperature around the Northern Hemisphere, as well as some more localized reconstructions, but ones which span 1000 years or more. These data provide the means of exploring the possible role of different climate forcings; for example, they provide evidence of the large–scale effects of explosive volcanic eruptions on regional and hemispheric temperatures during the last 400 years.
However, a dramatic change in the sensitivity of hemispheric tree–growth to temperature forcing has become apparent during recent decades, and there is additional evidence of major tree–growth (and hence, probably, ecosystem biomass) increases in the northern boreal forests, most clearly over the last century. These possibly anthropogenically related changes in the ecology of tree growth have important implications for modelling future atmospheric CO
2
concentrations. Also, where dendroclimatology is concerned to reconstruct longer (increasingly above centennial) temperature histories, such alterations of ‘normal’ (pre–industrial) tree–growth rates and climate–growth relationships must be accounted for in our attempts to translate the evidence of past tree growth changes.
However, a dramatic change in the sensitivity of hemispheric tree–growth to temperature forcing has become apparent during recent decades, and there is additional evidence of major tree–growth (and hence, probably, ecosystem biomass) increases in the northern boreal forests, most clearly over the last century. These possibly anthropogenically related changes in the ecology of tree growth have important implications for modelling future atmospheric CO
concentrations. Also, where dendroclimatology is concerned to reconstruct longer (increasingly above centennial) temperature histories, such alterations of ‘normal’ (pre–industrial) tree–growth rates and climate–growth relationships must be accounted for in our attempts to translate the evidence of past tree growth changes.
- Language
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- English
- Open access status
- green
- Identifiers
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- DOI 10.1098/rstb.1998.0191
- ISSN 0962-8436
- Persistent URL
- https://sonar.ch/global/documents/139779
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