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The dendroclimatic divergence phenomenon: reassessment of causes and implications for climate reconstruction

树木气候分歧现象：重新评估原因及其对气候重建的影响

基本信息

批准号：
NE/G018863/1
负责人：
Keith Briffa
金额：
$ 29.49万
依托单位：
University of East Anglia
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FG018863%2F1
关键词：
dendroclimatic divergence phenomenon reassessment causes

项目摘要

Palaeoclimate reconstructions extend our knowledge of how climate varied in times before expansive networks of measuring instruments became available. These reconstructions are founded on an understanding of theoretical and statistically-derived associations acquired by comparing the parallel behaviour of palaeoclimate proxies and measurements of varying climate. Inferences about variations in past climate, based on this understanding, necessarily assume that the associations we observe now hold true throughout the period for which reconstructions are made. This is the essence of the uniformitarian principle. In some northern areas of the world, recent observations of tree growth and measured temperature trends appear to have diverged in recent decades, the so called 'divergence' phenomenon. There has been much speculation, and numerous theories proposed, to explain why the previous temperature sensitivity of tree growth in these areas is apparently breaking down. The existence of divergence casts doubt on the uniformitarian assumption that underpins a number of important tree-ring based (dendroclimatic) reconstructions. It suggests that the degree of warmth in certain periods in the past, particularly in medieval times, may be underestimated or at least subject to greater uncertainty than is currently accepted. The lack of a clear overview of this phenomenon and the lack of a generally accepted cause had led some to challenge the current scientific consensus, represented in the 2007 report of the IPCC on the likely unprecedented nature of late 20th century average hemispheric warmth when viewed in the context of proxy evidence (mostly from trees) for the last 1300 years. This project will seek to systematically reassess and quantify the evidence for divergence in many tree-ring data sets around the Northern Hemisphere. It will establish a much clearer understanding of the nature of the divergence phenomenon, characterising the spatial patterns and temporal evolution. Based on recent published and unpublished work by the proposers, it has become apparent that foremost amongst the possible explanations is the need to account for systematic bias potentially inherent in the methods used to build many tree-ring chronologies including many that are believed to exhibit this phenomenon. This proposal is designed to build on recent innovations in tree-ring chronology production techniques, also developed by the proposers. These new methods will produce tree-ring chronologies whose variability is unbiased, either by temporal changes in the age structure of the constituent sample series, or by any distortion in the data that can arise when using the previously applied techniques. The extensive reprocessed and improved data sets will then form the basis for many detailed, site-by-site comparisons of local climate and various tree-growth parameters in order to re-characterise the nature, strength and temporal stability of the climate/growth associations. This will represent a systematic and objective re-assessment of the evidence for divergence in different forest contexts. The project will then explore all of the current theories for the cause(s) of divergence employing both statistical and process-modelling techniques. The project will go on to use the reprocessed tree-ring data sets to re-calibrate many important climate reconstructions, with varying levels of spatial detail, and carefully assess the implications of the divergence effect, as newly characterised, on reconstruction uncertainty. This project will provide results that will inform the international scientific debate and widespread public perception of the reliability of tree-ring-based climate reconstructions in particular, but also our current understanding of the reliability of current evidence for high-resolution temperature changes during the late Holocene.

古气候重建扩展了我们对气候如何在测量仪器的大规模网络出现之前的时代变化的了解。这些重建建立在对通过比较古气候指标的平行行为和对不同气候的测量而获得的理论和统计派生的关联的理解之上。基于这一理解，关于过去气候变化的推论必然假定，我们所观察到的关联在整个重建期间都是正确的。这就是统一主义原则的本质。在世界北部的一些地区，最近对树木生长的观察和测量的气温趋势在最近几十年似乎出现了分歧，即所谓的“分歧”现象。有很多猜测和许多理论被提出，以解释为什么这些地区以前对树木生长的温度敏感度明显下降。分歧的存在使人们对支撑一些重要的树轮(树枝气候)重建的统一性假设产生了怀疑。它表明，过去某些时期的温暖程度，特别是在中世纪，可能被低估了，或者至少受到比目前接受的更大的不确定性的影响。由于缺乏对这一现象的明确概述和普遍接受的原因，一些人对目前的科学共识提出了质疑，这体现在气专委2007年的报告中，从过去1300年的代理证据(主要是来自树木)的角度来看，20世纪末半球平均温度可能是史无前例的。该项目将寻求系统地重新评估和量化北半球许多树轮数据集中的差异证据。它将建立对分歧现象的本质的更清晰的理解，表征空间模式和时间演变。根据提出者最近发表和未发表的工作，很明显，在可能的解释中，最重要的是需要解释用于建立许多树轮年表的方法中潜在的系统性偏差，包括许多据信展示这种现象的方法。这项建议旨在建立在树轮年表制作技术的最新创新的基础上，该技术也是由提出者开发的。这些新方法将产生树轮年表，其变异性是无偏差的，要么是由于组成样本系列的年龄结构的时间变化，要么是由于使用以前应用的技术时可能出现的数据扭曲。然后，经过广泛处理和改进的数据集将成为许多详细的、逐个地点比较当地气候和各种树木生长参数的基础，以便重新表征气候/生长关联的性质、强度和时间稳定性。这将是对不同森林情况下的差异证据进行系统和客观的重新评估。然后，该项目将使用统计和过程建模技术来探索目前关于分歧原因(S)的所有理论。该项目将继续使用重新处理的树轮数据集，以不同程度的空间细节重新校准许多重要的气候重建，并仔细评估新特征的分歧效应对重建不确定性的影响。该项目将提供的成果将使国际科学辩论和公众对基于树木年轮的气候重建的可靠性的广泛看法有所了解，但也将使我们目前对目前关于全新世晚期高分辨率温度变化证据的可靠性的理解有所了解。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

A tree-ring reconstruction of East Anglian (UK) hydroclimate variability over the last millennium

DOI：
10.1007/s00382-012-1328-x
发表时间：
2013-02-01
期刊：
CLIMATE DYNAMICS
影响因子：
4.6
作者：
Cooper, Richard J.;Melvin, Thomas M.;Briffa, Keith R.
通讯作者：
Briffa, Keith R.

Old World megadroughts and pluvials during the Common Era.

DOI：
10.1126/sciadv.1500561
发表时间：
2015-11
期刊：
Science advances
影响因子：
13.6
作者：
Cook ER;Seager R;Kushnir Y;Briffa KR;Büntgen U;Frank D;Krusic PJ;Tegel W;van der Schrier G;Andreu-Hayles L;Baillie M;Baittinger C;Bleicher N;Bonde N;Brown D;Carrer M;Cooper R;Čufar K;Dittmar C;Esper J;Griggs C;Gunnarson B;Günther B;Gutierrez E;Haneca K;Helama S;Herzig F;Heussner KU;Hofmann J;Janda P;Kontic R;Köse N;Kyncl T;Levanič T;Linderholm H;Manning S;Melvin TM;Miles D;Neuwirth B;Nicolussi K;Nola P;Panayotov M;Popa I;Rothe A;Seftigen K;Seim A;Svarva H;Svoboda M;Thun T;Timonen M;Touchan R;Trotsiuk V;Trouet V;Walder F;Ważny T;Wilson R;Zang C
通讯作者：
Zang C

CRUST: Software for the implementation of Regional Chronology Standardisation: Part 2. Further RCS options and recommendations