date: Fri, 31 May 1996 09:16:30 +1200 from: Limin Xiong subject: Proposed Programme of Research to: Keith Briffa NZ Science & Technology Post-Doctoral Fellowships Application Form 6.0 PROPOSED PROGRAMME OF RESEARCH 6.1 Programme Title: Reconstruction of the climate since AD 1500 using tree-tings 6.2 Science Area (refer to section 6.2 of the Guidelines) H6 6.3 General Abstract: At present, the possibility that the climate is changing and that this may lead to unprecedented warming, is at the top of political agendas. Greater understanding of climatic fluctuations is necessary, not only for the last century, but also of earlier times. The longer the record of climate is, the more confidence we will have in determining how unusual recent events have been. The aim of this proposal is to provide the last five centuries of climate data for New Zealand derived from tree-rings. The reconstructed climate would be compared with patterns seen in other parts of the Southern and particularly the Northern Hemisphere (such as the Little Ice Age). Although there is voluminous indirect evidence that climatic conditions in the past 500 years were often different from our contemporary experience, the precise nature of these differences, and what caused them, remains elusive. Tree-rings provide the best hope for an answer. Keywords: Tree-rings; climate change; palaeoclimatology; dendroclimatology 6.4 Programme Goal: The goal of the proposed programme is to develop a network of existing and new tree-ring sites which best enable the reconstruction of New Zealand's past climate for the last 500 years. The programme is directly targeted to meet a priority research need identified in the September 1994 Report of the National Science Strategy Committee for Climate Change (p26). It will also contribute to the Past Global Changes project of the IGBP. This is important because international climatic data used in general circulation modelling is dominated by Northern Hemisphere information and dendroclimatology has the potential of significantly extending the climate record in New Zealand. 6.5 Ethical or Regulatory Obligations: Sampling new locations or updating some existing locations will require approval from the Department of Conservation (DOC). Permits have been obtained in the past and we would expect no problems for future sampling. 6.6 Programme Significance and Justification: New Zealand is of global significance due to the role of the Southern Oscillation in the climate of this region, and the opportunities the mid- and high Southern latitudes provide for understanding the role of the oceans and the continents in climate variability. Instrumental climate data has only been recorded for about 150 years and this is widely acknowledged as too short to detect the full range of natural variability likely to be present. Dendroclimatology has the potential for extending New Zealand quantitative climate records back several centuries (there are only two other Southern Hemisphere regions where this potential exists: southern South America and Tasmania). A workshop convened by the Royal Society of New Zealand on 'Palaeoclimates and Climate Modelling' (May, 1994) revealed that, while considerable knowledge exists on palaeoclimates in New Zealand, very little is in the quantitative form that is needed for understanding the present limits of climate variability and for validating hindcast regional climatic models. This research programme will address this by: (1) providing high quality, quantitative, palaeoclimate information for New Zealand, so that an improved balance of Southern Hemisphere data is achievable in global climate prediction models; (2) helping to ensure that the best possible quantitative data are available to define the limits of climatic variability and for calibration of climatic models; and (3) ensuring that such data are available to test the hindcast output from regional climatic models, thereby enabling greatest confidence to be placed in their capacity to forecast within acceptable levels of accuracy. All 84 tree-ring chronologies in New Zealand, produced by a range people and methods from several different species, will be screened and reanalysed (as a quality control measure). New Zealand tree-ring width chronology has been established by Ahmed & Ogden (1985), Fowler (1988), LaMarche et al. (1979), Norton (1983a,b,c), Palmer (1989), Xiong (1995) and others. The reanalysed information will then be lodged with the International Tree-Ring Data Bank (ITRDB; Colorado, USA) and be publicly available for the first time. In the data sparse Southern Hemisphere, such a contribution will be highly significant for global climate modelling and prediction. Some sites will also be extended and updated and some new sites developed. New tree-ring parameters - such as maximum and minimum wood intensity and earlywood/latewood ratios - will be derived and analysed from each species in an attempt to extract the maximum climatic information possible. No New Zealand species has had all these parameters investigated. The climate reconstructions will be compared with earlier published work (Ogden & Ahmed (1989), Norton et al. (1989), Palmer (1989), Salinger et al. (1994), Xiong (1995), Murphy & Palmer (1992)) for comparison of results and gauging the level of enhancement achieved. The proposed research builds on the experience of the applicant while at the same time taking full account of the research of others. 6.7 Programme Objectives and Method(s): Tree-rings are widely recognised as one of the most important proxy-climate records for analysing recent climate change, because they are annual, widespread and easy to sample. The research proposed here will follow well established methodology in dendroclimatology (Fritts 1976; Cook & Kairiukstis 1990) and adopt techniques and analytical approaches that are now largely standardised at the international level. This will ensure consistency of results with international research and permit global comparisons to be made. The goal of this project is to produce climate reconstructions from high-quality tree-ring chronologies. Therefore, as much climate detail as possible will be extracted from selected chronologies of long-lived species. This will provide data to compare with other indicators of climate (e.g. glacier advance and retreat, bore hole temperature, speleothems) and other international studies. The first methodological step involves quality control of all available New Zealand tree-ring chronologies and the extension of some of the key ones (Oct. 1996- July 1997). Of the 84 known tree-ring chronologies, many are of uncertain quality. Recently developed computer cross-dating and standardisation program (Grissino-Mayer et al. 1992) will be used as a quality control, screening, reanalysing where appropriate and prepared into a consistent format. Tree-ring width chronologies using Nothofagus menziesii, N. solandrii, Phyllocladus trichomanoides, P. glaucus, and Libocedrus bidwillii have been extended back to 1500 AD, with a number of chronologies back to the 13th century. Because of the relatively small number of older samples in many of the chronologies, older samples will be taken from some of the above species to improve the reliability of this early data. To maximise the climate signal, chronologies produced from areas that have contrasting climate will be updated to allow a longer period of calibration with the modern climate record. The focus of additional collections will be on Libocedrus bidwillii and Agathis australis. These are the two species in which the chronologies could be extended back more than 1000 years. The original collections of many of the NZ chronologies (Dunwiddie 1979) are hold by the Tree-Ring Laboratory, University of Arizona, Tucson, Arizona, but have not been re-evaluated. As a result, it will be a advantage to travel to USA for one month to screen these samples during the middle of the first year (about March-April 1997). All the available chronologies will be standardised using techniques that maintain as much of the low-frequency variance in the tree-rings as possible (Briffa and Jones, 1990) so as to extract climatic variability on the longest possible timescales. The second methodological step will be the development of new chronologies based on different aspects of the tree-rings such as earlywood and latewood (Aug. 1997-Mar. 1998). Because none of this kind of work has been tried in New Zealand, the initial focus will be on the methodology using the new image analysis equipment (Windendro scanner; Lottery Board funded to Dr Palmer 1995) at Lincoln University. During this methodological phase emphasis will be on Libocedrus bidwillii and Agathis australis over the period 1900-present. Once having evaluated the approach for the two species, research will concentrate on density chronologies over the period 1500-1900, and then extend to study a range of species (e.g. Halocarpus biformis, Phyllocladus trichomanoides etc.). The third methodological step will be establishing statistical relationships between climate and tree-ring widths and wood density for the period of instrumental record (i.e. response function analysis) (Apr. 1998-May 1998). Response function analysis (Fritts 1976) will be used to investigate the climatic factors influencing tree growth at each site. This is a principal component regression using a bootstrap technique relating monthly climate variables to tree growth. The response function analysis will identify the chronologies to use in the climate reconstructions. The sequence will be: (a) Derive time series of selected climate data (air temperature and precipitation), including derived variables (e.g. Palmer drought index) from the instrumental database. (b) Derive climate - tree-ring width, wood density response functions for each tree-ring chronology site using established response function techniques. (c) Analysis of response functions obtained for multiple sites and multiple species to identify spatial patterns and variations associated with different environmental conditions. The fourth methodological step will be the reconstructing of past climate for earlier periods when only tree-ring data are available (June 1998-Sept. 1998). Transfer function will be used to estimate the climate (Fritts, 1991). Here, the principle component regression with bootstraping techniques of Guiot (1991, 1995) will be used to relate the selected network of tree-ring chronologies separately to temperature, circulation indices and precipitation data. Care will be taken to avoid artificial predictability. The reconstructions will be calibrated and verified against relevant high-quality data from the instrumental record. The results will be compared with longer term reconstructions from other parts of the globe. In the late of the second year(about June 1998), the applicant will spent one month at the Climate Research Unit, University of East Anglia, UK , working with Dr. Briffa to apply the new statistical technique for standardising the chronology and reconstructing the climate. Information transfer: The results will be passed to the research community by a paper at the end of the first year (annual conference of NZ ecological society or NZ climatological society in August 1997) and by a presentation in the second year (international conference of tree-ring society; about May of 1998). The results will also be published in refereed journals. The raw chronology data and reconstructed climate data will be lodged with the International Tree-Ring Data Bank in the World Data Centre-A, Boulder, Colorado, USA, for use by researchers. Future plans: The initial focus will be on the period 1500-1900. Future plans include extending the reconstruction to sub-fossil material and to additional species. The eventual aim is to be able to reconstruct the climate of the Holocene. =============================================================== Limin Xiong, Plant Science Department, Lincoln University, Canterbury, New Zealand. Phone: ++64-3-343,5198 (home); Fax: ++64-3-325,3843 (dept.); Internet: liminx@lincoln.ac.nz =============================================================== When raw wood is carved, it becomes a tool; When a man is employed, he becomes a tool; The perfect carpenter leaves no wood to be carved. -- Lao-tzu, Tao Te Ching