Tree-ring Based Temperature Reconstructions Research Articles

Temperature variability over Dokriani glacier region, Western Himalaya, India

Long-term climate records which help decipher past climate variability and its impact are scarce in the tough terrain of the Himalayan region. Therefore, in order to fill the climate data gap and understand the glacier climate linkage, we developed a 231 year long (1785–2015 CE) March–June temperature record using ring-width chronology of Himalayan fir (Abies pindrow (Royle ex D.Don) Royle) for the Din Gad valley, Dokriani glacier region, Uttarkashi, Uttarakhand, in the Western Himalaya. The Din Gad, originating from the Dokriani glacier, is a meltwater river contributing to Bhagirathi catchment in the headwaters of the socio-economically vital Ganga River. The 21-year running mean of the temperature record showed 1978–1998 CE as the coldest period followed by 1925–1945 CE, and 1890–1910 CE as the warmest period followed by 1946–1966 CE over the entire time series. The reconstruction matches well with tree-ring based temperature records available from the Garhwal Himalaya. It also shows similarity to tree-ring based temperature reconstructions from the Western Himalaya, Nepal, Tibetan Plateau and Bhutan, thus displaying a regional scale climate signal. The low frequency fluctuation patterns of the March–June temperature also matches with Asia and Northern hemisphere temperature records. Reconstructed March–June temperature record showed a statistically negligible warming temperature trend during 1901–1989 CE in the 20th century. It, however, captured a warming spike from 1990s CE which continues rising into the 21st century, which is also evident in the Northern hemisphere temperature record. Moreover, temperature rise is not anomalous in the past 231 years and well within range of the rest of the series. The present temperature record exclusively from the glacier region revealed a strong linkage with the benchmark Dokriani glacier's winter mass balance (November–April) revealing mass loss (gain) episodes occurred in warm (cool) phases. This first such record from the glacier valleys in Ganga headwaters would be of great value at providing insight into past climate variability and glacier behaviour with respect to climate change in long term perspective, and thus would provide valuable information for water resource management in light of climate change.

Common Era treeline fluctuations and their implications for climate reconstructions

Two hundred years after von Humboldt's pioneering work on the upper treeline, and many fundamental studies thereafter, the rate of past elevational changes in one of the most fascinating biogeographic boundaries on our planet remains poorly understood. Here, we distinguish conceptually between realised and potential treeline positions and present an ensemble model approach to simulate mean elevational treeline fluctuations for the past 2000 years. Based on dendrochronological summer temperature records, our simple, though efficient model emulation shows that alpine treelines across the Northern Hemisphere were, on average, about 50 m higher after the Roman and medieval warm periods compared to their lowest mean position in the 1760s, which reflects the accumulated effects of repeated cold spells during the Little Ice Age. We suggest that the simulated mean differences between realised and potential treeline positions can affect the amplitude and variance of tree ring-based temperature reconstructions. Contrary to common belief, we also argue that the current offset between lower realised and much higher potential treeline positions, which appears unprecedented in the past two millennia, does not account for the yet unexplained ‘Divergence Problem’ in dendroclimatology, a decoupling between increasing temperature measurements and tree-ring chronologies since the 1970s. • Potential and realised treelines were simulated over the past 2000 years. • Treelines were highest after the Roman and medieval warm periods. • The lowest treeline positions of the Little Ice Age were in the 1760s. • Treeline fluctuations can bias tree ring-based temperature reconstructions.

The temperature sensitivity along elevational gradients is more stable in maximum latewood density than tree-ring width

Tree ring-based temperature reconstructions are preferably derived from maximum latewood density (MXD) compared to tree-ring width (TRW). Although temperature signals in MXD are less dependent on site ecology, systematic analyses of the effects of elevation and slope aspect on ring formation are still lacking. Here, we assess the climate sensitivity of MXD and TRW chronologies from six larch (Larix decidua Mill.) sites across the Simplon valley in the southwestern Swiss Alps, representing elevations from 1400 to 2150 m asl on both north- and south-facing slopes. We find decreasing temperature signals with decreasing elevation in MXD and TRW, though correlation coefficients are generally higher for MXD and on the warmer and dryer south exposed slopes. While the greatest temperature signals are found for MJJA at highest elevations with r = 0.71 for MXD and r = 0.57 for TRW (both p < 0.05 and for the 1928–2009 common period), MXD still correlates significantly positive at the lowest elevation site that is ~750 m below the treeline. Our findings indicate the suitability of MXD over TRW for temperature reconstructions when using historical wood sources of unknown origin.

Stationarity of climate-growth response is only marginally influenced by the soil moisture regime in Western Siberia

Stationary (time-stable) relationships between a tree-ring proxy and climatic drivers are a prerequisite for using tree rings as paleo-climatological archives, but non-stationarity has been detected worldwide. Here we use a classical, temperature-sensitive treeline site in Western Siberia to specifically test the influence of micro-site conditions (wet versus dry) on the stationarity of climate-growth relationships in three co-existing conifer species: Larix sibirica Ledeb., Picea obovata Ledeb., and Pinus sibirica DuTour. We test two commonly used tree-ring proxies, annual tree-ring width (TRW) and maximum latewood density (MXD), using moving windows and the bootstrapped transfer function stability test (BTFS). Summer temperature is the main driver of tree growth in all three species, but non-stationarities exist in all species and both tree-ring proxies. For TRW, we found stationarity only for larch from both micro-sites, while for MXD, we found stationarity for spruce from both micro-sites, and for pine from the wet micro-site. Micro-site variability did not seem to affect stationarity in any systematic way. We highlight the necessity to systematically test the influence of different methods of stationarity tests, since BTFS was more sensitive than moving-window analysis. Taken together, our results underscore the importance of testing the assumption of stationarity for diverse micro-sites, different species and proxies at all sites prior to any tree-ring based temperature reconstruction, since even within one site results can be drastically different.

The effect of provenance of historical timber on tree-ring based temperature reconstructions in the Western Central Alps

Millennial-length tree-ring width chronologies are used to reconstruct temperature and place recent warming into historical context. The Simplon valley in the Western Central Alps is an ideal region for such a study as it provides historical timber back to medieval times which can be combined with temperature sensitive living larch trees. However, the exact provenance of the historical timber is unknown, but might origin from different elevations which potentially biases derived temperature reconstructions. To study the effect of elevation on tree growth and climate sensitivity, approximately 250 trees at three elevational levels (1500, 1700, and 2000 m a.s.l.) were sampled. Results indicate that the overall growth rate decreases with increasing elevation. Significant correlations between tree-ring width and summer temperature are recorded at tree sites ≥ 1700 m a.s.l. The comparison of the growth patterns between living trees and historical timber from Simplon Village (1476 m a.s.l.) reveals a most likely origin of the historical samples between 1700 and 2000 m a.s.l. When combining the data from the living trees at the different elevational levels with the historical timber, to produce three separate chronologies spanning the past 1200 years, substantial low frequency differences are recorded after RCS detrending the data. This finding demonstrates that the origin of samples in combined (living + historical) chronologies has a strong influence on long-term summer temperature reconstructions. It is thus important to analyse the growth characteristics of historical timber, and estimate their provenance in comparison to living trees, when producing millennial length chronologies.

Setting the tree-ring record straight

Tree-ring chronologies are the main source for annually resolved and absolutely dated temperature reconstructions of the last millennia and thus for studying the intriguing problem of climate impacts. Here we focus on central Europe and compare the tree-ring based temperature reconstruction with reconstructions from harvest dates, long meteorological measurements, and historical model data. We find that all data are long-term persistent, but in the tree-ring based reconstruction the strength of the persistence quantified by the Hurst exponent is remarkably larger (hcong 1.02) than in the other data (h= 0.52–0.69), indicating an unrealistic exaggeration of the historical temperature variations.We show how to correct the tree-ring based reconstruction by a mathematical transformation that adjusts the persistence and leads to reduced amplitudes of the warm and cold periods. The new transformed record agrees well with both the observational data and the harvest dates-based reconstructions and allows more realistic studies of climate impacts. It confirms that the present warming is unprecedented.

Ranking of tree-ring based hydroclimate reconstructions of the past millennium

To place recent hydroclimate changes, including drought occurrences, in a long-term historical context, tree-ring records serve as an important natural archive. Here, we evaluate 46 millennium-long tree-ring based hydroclimate reconstructions for their Data Homogeneity, Sample Replication, Growth Coherence, Chronology Development, and Climate Signal based on criteria published by Esper et al. (2016) to assess tree-ring based temperature reconstructions. The compilation of 46 individually calibrated site reconstructions includes 37 different tree species and stem from North America (n = 29), Asia (n = 10); Europe (n = 5), northern Africa (n = 1) and southern South America (n = 1). For each criterion, the individual reconstructions were ranked in four groups, and results showed that no reconstruction scores highest or lowest for all analyzed parameters. We find no geographical differences in the overall ranking, but reconstructions from arid and semi-arid environments tend to score highest. A strong and stable hydroclimate signal is found to be of greater importance than a long calibration period. The most challenging trade-off identified is between high continuous sample replications, as well as a well-mixed age class distribution over time, and a good internal growth coherence. Unlike temperature reconstructions, a high proportion of the hydroclimate reconstructions are produced using individual series detrending methods removing centennial-scale variability. By providing a quantitative and objective evaluation of all available tree-ring based hydroclimate reconstructions we hope to boost future improvements in the development of such records and provide practical guidance to secondary users of these reconstructions.

Were medieval warm-season temperatures in Jämtland, central Scandinavian Mountains, lower than previously estimated?

Today few high-quality tree-ring based temperature reconstructions extending over the past millennium exist, and those have, in general, low replication in their early parts. Here we present a new and updated maximum latewood density (MXD) chronology extending over the last 1200 years, built from local Scots pine wood sources (living trees, drywood preserved the ground, and subfossil wood extracted from lakes) all collected within 20 km in the Scandinavian Mountains in Jämtland. The MXD data was used to reconstruct April-September mean temperatures, where 60% of the variance in observed temperatures could be explained. The reconstruction exhibited distinct multidecadal variability, with the coldest periods centred on ca. 900, 1450, 1600 and 1900 CE, and the warmest periods on ca. 1160, 1250, 1500, 1660 CE. The last part of the 20th – early part of 21st century was the warmest period throughout the whole record, and the reconstruction suggests that, on average, the Medieval Climate Anomaly (MCA, 950–1250 CE) was only slightly warmer than the Little Ice Age (LIA, 1450–1900 CE). In fact, compared to earlier reconstructions from the region, the new reconstruction suggested lower MCA warm-season temperatures. However, despite sufficient replication during that period, high inhomogeneity among the MXD series makes this period slightly uncertain. The unique drywood on which the chronology was built, displayed a distinct regeneration pattern, where changes in Scots pine establishment was interpreted as responses to changes in forest fire activity and climate throughout the past millennium.

Century-scale temperature variability and onset of industrial-era warming in the Eastern Tibetan Plateau

To improve our understanding of climate variability in the Tibetan Plateau (TP) and its sensitivity to external forcings, recent temperature changes need to be placed in a long-term historical context. Here, we present two tree-ring based temperature reconstructions: a 1003-year (1000–2002 CE) annual temperature reconstruction for the northeastern TP (NETP) based on seven series and a 522-year (1489–2010 CE) summer (June–July–August) temperature reconstruction for the southeastern TP (SETP) based on 11 series. Our reconstructions show six centuries of generally warm NETP temperatures (1000–1586 CE), followed by a transition to cooler temperatures (1587–1887 CE for NETP and 1588–1930 CE for SETP). The transition from the Medieval Climate Anomaly to the Little Ice Age thus happened in the 1580s in NETP and SETP, which is about 150 years later than in larger-scale (e.g. Asia and the Northern Hemisphere) temperature reconstructions. We found that TP temperature variability, especially in SETP, was influenced by the Atlantic multi-decadal oscillation and that the twentieth century was the warmest on record in NETP and SETP. Our reconstructions and climate model simulations both show industrial-era warming trends, the onset of which happened earlier in NETP (1812 CE) compared to SETP (1887 CE) and other temperature reconstructions for Western China, East Asia, Asia, and the Northern Hemisphere. The early NETP onset of industrial-era warming can likely be explained by NETP’s faster warming rate and by local feedback factors (i.e., ice–snow cover-albedo). Comparisons between climate model simulations and our reconstructions reveal that cooler TP temperatures from 1600 to 1800 CE might be related to land-use and land-cover change.

Climate changes reconstructed from a glacial lake in High Central Asia over the past two millennia

Climatic changes in Arid Central Asia (ACA) over the past two millennia have been widely concerned. However, less attention has been paid to those in the High Central Asia (HCA), where the Asian water tower nurtures the numerous oases by glacier and/or snow melt. Here, we present a new reconstruction of the temperature and precipitation change over the past two millennia based on grain size of a well-dated glacial lake sediment core in the central of southern Tianshan Mountains. The results show that the glacial lake catchment has experienced cold-wet climate conditions during the Dark Age Cold Period (∼300–600 AD; DACP) and the Little Ice Age (∼1300–1870 AD; LIA), whereas warm-dry conditions during the Medieval Warm Period (∼700–1270 AD; MWP). Integration of our results with those of previously published lake sediment records, stalagmite δ18O records, ice core net accumulation rates, tree-ring based temperature reconstructions, and mountain glacier activities suggest that there has a broadly similar hydroclimatic pattern over the HCA areas on centennial time scale during the past two millennia. Comparison between hydroclimatic pattern of the HCA and that of the ACA areas suggests a prevailing 'warm-dry and cold-wet' hydroclimatic pattern over the whole westerlies-dominated central Asia areas during the past two millennia. We argue that the position and intensity of the westerlies, which are closely related to the phase of the North Atlantic Oscillation (NAO), and the strength of the Siberian High pressure (SH), could have jointly modulated the late Holocene central Asia hydroclimatic changes.

Climate Response of Larch and Birch Forests across an Elevational Transect and Hemisphere-Wide Comparisons, Kamchatka Peninsula, Russian Far East

Kamchatka’s forests span across the peninsula’s diverse topography and provide a wide range of physiographic and elevational settings that can be used to investigate how forests are responding to climate change and to anticipate future response. Birch (Betula ermanii Cham.) and larch (Larix gmelinii (Rupr.) Kuzen) were sampled at eight new sites and together with previous collections were compared with monthly temperature and precipitation records to identify their climate response. Comparisons show that tree-ring widths in both species are primarily influenced by May through August temperatures of the current growth year, and that there is a general increase in temperature sensitivity with altitude. The ring-width data for each species were also combined into regional chronologies. The resulting composite larch chronology shows a strong resemblance to a Northern Hemisphere (NH) tree-ring based temperature reconstruction with the larch series tracking NH temperatures closely through the past 300 years. The composite birch ring-width series more closely reflects the Pacific regional coastal late summer temperatures. These new data improve our understanding of the response of forests to climate and show the low frequency warming noted in other, more continental records from high latitudes of the Northern Hemisphere. Also evident in the ring-width record is that the larch and birch forests continue to track the strong warming of interior Kamchatka.

Ranking of tree-ring based temperature reconstructions of the past millennium

Tree-ring chronologies are widely used to reconstruct high-to low-frequency variations in growing season temperatures over centuries to millennia. The relevance of these timeseries in large-scale climate reconstructions is often determined by the strength of their correlation against instrumental temperature data. However, this single criterion ignores several important quantitative and qualitative characteristics of tree-ring chronologies. Those characteristics are (i) data homogeneity, (ii) sample replication, (iii) growth coherence, (iv) chronology development, and (v) climate signal including the correlation with instrumental data. Based on these 5 characteristics, a reconstruction-scoring scheme is proposed and applied to 39 published, millennial-length temperature reconstructions from Asia, Europe, North America, and the Southern Hemisphere. Results reveal no reconstruction scores highest in every category and each has their own strengths and weaknesses. Reconstructions that perform better overall include N-Scan and Finland from Europe, E-Canada from North America, Yamal and Dzhelo from Asia. Reconstructions performing less well include W-Himalaya and Karakorum from Asia, Tatra and S-Finland from Europe, and Great Basin from North America. By providing a comprehensive set of criteria to evaluate tree-ring chronologies we hope to improve the development of large-scale temperature reconstructions spanning the past millennium. All reconstructions and their corresponding scores are provided at www.blogs.uni-mainz.de/fb09climatology.

Two centuries temperature variations over subtropical southeast China inferred from Pinus taiwanensis Hayata tree-ring width

High-resolution long-term temperature reconstructions in subtropical southeast China (SSC) are very scarce, yet indispensable for the comprehensive understanding of climate change in China, even in East Asia. We reconstructed the first previous growth-season temperature in the Sanqingshan Mountains (SQS), southeast China since 1806 based on tree-ring width data. The reconstruction accounts for 56.4 % of the total variance in the instrumental record over 1954–2009. Unlike the Northern Hemispheric warming during recent two centuries, the reconstruction captured a slowly cooling trend from 1806 to 1980, followed by a rapid warming afterward. 2003–2009 was the warmest period in the reconstruction. 1970–2000 was colder than the last stage of the Little Ice Age (LIA). Most of the warm and cold periods in this reconstruction could be found in the tree-ring based temperature reconstructions of vicinity area, indicating that the temperature variations in SSC were almost synchronous at least at decadal scale. This regional coherence of temperature variation was further confirmed by the spatial correlation patterns with the CRU TS3.22 grid dataset. A strong positive relationship between the temperature over SQS region and sea surface temperature (SST) over the North Pacific Ocean (NP) has been noted, suggesting that SST variations over NP and the related Pacific Decadal Oscillation significantly influenced the temperature variability over SSC. To better understand the climate variability during the LIA and the regional differences in temperature variations over SQS and northern Hemisphere, long data sets from more diverse areas of southern China are needed.

How similar are annual and summer temperature variability in central Sweden?

Tree-ring based temperature reconstructions have successfully inferred the past inter-annual to millennium scales summer temperature variability. A clear relationship between annual and summer temperatures can provide insights into the variability of past annual mean temperature from the reconstructed summer temperature. However, how similar are summer and annual temperatures is to a large extent still unknown. This study aims at investigating the relationship between annual and summer temperatures at different timescales in central Sweden during the last millennium. The temperature variability in central Sweden can represent large parts of Scandinavia which has been a key region for dendroclimatological research. The observed annual and summer temperatures during 1901–2005 were firstly decomposed into different frequency bands using ensemble empirical mode decomposition (EEMD) method, and then the scale-dependent relationship was quantified using Pearson correlation coefficients. The relationship between the observed annual and summer temperatures determined by the instrumental data was subsequently used to evaluate 7 climate models. The model with the best performance was used to infer the relationship for the last millennium. The results show that the relationship between the observed annual and summer temperatures becomes stronger as the timescale increases, except for the 4–16 years timescales at which it does not show any relationship. The summer temperature variability at short timescales (2–4 years) shows much higher variance than the annual variability, while the annual temperature variability at long timescales (>32 years) has a much higher variance than the summer one. During the last millennium, the simulated summer temperature also shows higher variance at the short timescales (2–4 years) and lower variance at the long timescales (>1024 years) than those of the annual temperature. The relationship between the two temperatures is generally close at the long timescales, and weak at the short timescales. Overall the summer temperature variability cannot well reflect the annual mean temperature variability for the study region during both the 20th century and the last millennium. Furthermore, all the climate models examined overestimate the annual mean temperature variance at the 2–4 years timescales, which indicates that the overestimate could be one of reasons why the volcanic eruption induced cooling is larger in climate models than in proxy data.

Dendroclimatic reconstruction of temperature in the eastern Qilian Mountains, northwestern China

Understanding the extent to which climate has varied in the past is a prerequisite to assessing current trends. In this study, we present a 225 yr tree-ring width record of Qinghai spruce Picea crassifolia from a mesic site in the eastern Qilian Mountains of northwest China. This tree-ring record showed significant positive correlations (p < 0.05) with temperature for most months from the preceding May to the current September, but none with precipitation or the Palmer Drought Severity Index. Based on the correlation relationships, we developed a regression model to reconstruct the average July temperatures over the period AD 1785-2009, which accounted for 45% of the observed temperature variation during the calibration period (1957-2009). This is the first tree-ring based temperature reconstruction in the eastern Qilian Mountains. The reconstruction indicated a warming trend that began around 1900 and continued through the late 20th century. Eight of the 10 warmest years were recorded during the period 1990-2009. The longest cool period occurred in 1894-1916. Comparisons of our reconstruction with other independent tree-ring based temperature reconstructions from the northeastern Tibetan Plateau suggest coherent variance patterns in these warm season temperature reconstructions regardless of the positive or negative correlation relationships between tree-ring records and temperatures. The results of comparisons also indicated that the warm season temperature variances lag behind the winter temperature variability by about 20 yr in this region.

Erratum to: Eight-hundred years of summer temperature variations in the southeast of the Iberian Peninsula reconstructed from tree rings

July-to-October temperature variations are reconstructed for the last 800 years based on tree-ring widths from the Cazorla Range. Annual tree-ring width at this site has been found to be negatively correlated with temperature of the previous summer. This relationship is genuine, metabolically plausible, and cannot be explained as an indirect correlation mediated by hydroclimate. The resulting reconstruction (NCZ Tjaso ) represents the southernmost annually resolved temperature record based on tree-rings in Europe and provides detailed information on the regional climate evolution during the Late Holocene in the southeast of the Iberian Peninsula. The tree-ring based temperature reconstruction of Cazorla Range reveals predominantly warm summer temperatures during the transition between the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) from the 13th to the mid of the sixteenth century. The LIA spanned a slightly longer time (1500–1930 CE) than in other European summer temperature reconstructions from the Alps and Pyrenees. The twentieth century, though warmer than the preceding centuries, does not show unprecedented warmth in the last 800 years. Three ensembles of climate simulations conducted with two global atmosphere–ocean general circulation climate models (GCMs), considering different external forcings, were used for comparison: ECHO-G (Erik) and MPI-ESM (E1 and E2). Additionally, individual simulations were available from GCM included in the fifth Coupled Model Intercomparison Project, as well as single-forcing simulations performed with MPI-ESM. The comparison of the reconstructed and simulated temperatures revealed a close agreement of NCZ Tjaso with the simulations performed with total solar irradiance forcing with wider amplitude. Furthermore, the correlations with single-forcing simulations suggest volcanism as the main factor controlling preindustrial summer temperature variations in the Cazorla Range over the last five centuries. The persistent anti-correlation between NCZ Tjaso and simulated temperatures during the MCA–LIA transitional period underlines the current limitations for attributing temperature variations during that period to internal variability or external forcing.

Tree-ring based temperature reconstruction for the west Qinling Mountains (China): linkages to the High Asia, solar activity and Pacific-Atlantic Ocean

We developed a Faxon fir (Abies faxoniana) tree-ring width chronology at the timberline in the western Qinling Mountains, China. Herein February–July mean temperature was reconstructed for Zhouqu in the western Qinling Mountains back to AD 1650 based on the standard chronology. The climate/tree-growth model accounts for 43.5% of the instrumental temperature variance during the period 1972–2006. Spatial correlation analyses with the gridded temperature data shows that the temperature reconstruction captures regional climatic variations over central and southeast China, and strong teleconnections with the nearby High Asia. There is a good agreement with cold and warm periods previously estimated from tree-rings in Nepal, India and southwest China. The temperature re-construction indicates that there was pronounced cooling in Zhouqu during the Maunder Minimum (late 1600s to early 1700s). The cold period (1813–1827) of the temperature reconstruction coincide with the volcanic eruptions. Significant spectral peaks are found at 56.9, 22.3, 11.4, 2.9, 2.8, 2.6, 2.2 and 2.0 years. The spatial correlation patterns between our temperature reconstruction and SSTs of the Atlantic and Pacific Oceans suggest a connection between regional temperature variations and the atmospheric circulations. It is thus revealed that the chronology has enough potential to reconstruct the climatic variability further into the past.

Tree ring-based temperature reconstruction over the past 186 years for the Miyaluo Natural Reserve, western Sichuan Province of China

The mountain range of western Sichuan Province of China runs roughly north to south defining the eastern edge of the Tibetan Plateau, where high-resolution climate records are essential for understanding regional climatic phenomena. Unfortunately, instrumental records in this region are too short in duration to confidently gauge the long-term variability of climate change. This paper presented a temperature reconstruction for the western Sichuan Province based on a tree ring width chronology developed from a tree line site (4,150 m) of the Faxon fir (Abies faxoniana) at the Miyaluo Natural Reserve. This reconstruction, spanning the years from 1824 to 2009, could account for 46.7 % of the actual variance of annual mean temperature during the calibration period from 1950 to 2002. The reconstruction could be essentially divided into two distinct subperiods: a relatively cold and stable period in the late nineteenth century and a relatively warm and unstable period in the twentieth century. Years 2001 and 1911 were the warmest (6.32 °C) and coldest (4.87 °C) years in the reconstruction, respectively, while 1960s (5.77 °C) and 1980s (5.08 °C) were the warmest and coldest ten consecutive years within the past 186 years. Close coupling observed with other temperature proxies (tree rings, ice cores, and glaciers) from surrounding areas emphasized the high degree of confidence in our reconstruction.

树轮宽度记录的松潘地区年平均气温变化

Three tree-ring STD chronologies of Abies faxoniana were developed from Songpan region Sichuan Province, and a regional chronology(RC) was established based on the three STD chronologies. The calculation shows that the tree-ring width was significantly correlated with temperature, and the RC had the highest correlation( r =0.576, P R adj2=32%, N =59, F =28.33). In the past 310 years, there were 8 warm periods and 7 cool periods. According to analysis of temporal and spatial correlation, it indicated that the reconstructed series with good spatial and temporal representation. Our reconstruction was validated by other tree-ring based temperature reconstructions from the surrounding area, glacier advances and retreats, and the documented climate disaster events. MTM analysis shows that there exist periods of 2-3 a, 26 a, quasi-33 a and quasi-40 a cycles.

Tree-Ring Based May-July Temperature Reconstruction Since AD 1630 on the Western Loess Plateau, China

Tree-ring samples from Chinese Pine (Pinus tabulaeformis Carr.) collected at Mt. Shimen on the western Loess Plateau, China, were used to reconstruct the mean May–July temperature during AD 1630–2011. The regression model explained 48% of the adjusted variance in the instrumentally observed mean May–July temperature. The reconstruction revealed significant temperature variations at interannual to decadal scales. Cool periods observed in the reconstruction coincided with reduced solar activities. The reconstructed temperature matched well with two other tree-ring based temperature reconstructions conducted on the northern slope of the Qinling Mountains (on the southern margin of the Loess Plateau of China) for both annual and decadal scales. In addition, this study agreed well with several series derived from different proxies. This reconstruction improves upon the sparse network of high-resolution paleoclimatic records for the western Loess Plateau, China.