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Stratospheric volcanic eruptions have far-reaching impacts on global climate and society. Tree rings can provide valuable climatic information on these impacts across different spatial and temporal scales. To detect temperature and hydroclimatic changes after strong stratospheric Common Era (CE) volcanic eruptions for the last 1500 years (535 CE unknown, 540 CE unknown, 1257 CE Samalas, 1640 CE Parker, 1815 CE Tambora, and 1991 CE Pinatubo), we measured and analyzed tree-ring width (TRW), maximum latewood density (MXD), cell wall thickness (CWT), and δ13C and δ18O in tree-ring cellulose chronologies of climate-sensitive larch trees from three different Siberian regions (northeastern Yakutia – YAK, eastern Taimyr – TAY, and Russian Altai – ALT). All tree-ring proxies proved to encode a significant and specific climatic signal of the growing season. Our findings suggest that TRW, MXD, and CWT show strong negative summer air temperature anomalies in 536, 541–542, and 1258–1259 at all studied regions. Based on δ13C, 536 was extremely humid at YAK, as was 537–538 in TAY. No extreme hydroclimatic anomalies occurred in Siberia after the volcanic eruptions in 1640, 1815, and 1991, except for 1817 at ALT. The signal stored in δ18O indicated significantly lower summer sunshine duration in 542 and 1258–1259 at YAK and 536 at ALT. Our results show that trees growing at YAK and ALT mainly responded the first year after the eruptions, whereas at TAY, the growth response occurred after 2 years. The fact that differences exist in climate responses to volcanic eruptions – both in space and time – underlines the added value of a multiple tree-ring proxy assessment. As such, the various indicators used clearly help to provide a more realistic picture of the impact of volcanic eruption on past climate dynamics, which is fundamental for an improved understanding of climate dynamics, but also for the validation of global climate models.

Radial tree growth at high-elevation and high-latitude sites is predominantly controlled by changes in summer temperature. This relationship is, however, expected to weaken under projected global warming, which questions the reliability of tree-ring chronologies for climate reconstructions. Here, we examined the growth–climate response patterns of five tree-ring width (TRW) and maximum latewood density (MXD) chronologies of larch (Larix sibirica) from upper-treeline ecotones in the Altai Mountains, which is a key region for developing millennial-long dendroclimatic records in inner Eurasia. The TRW and MXD chronologies exhibited significant year-to-year coherency within and between the two parameters (p < 0.001). While TRW is mostly influenced by temperature changes during the first half of the growing season from June to July (r = 0.66), MXD is most strongly correlated with May–August temperatures (r = 0.73). All seasonal temperature signals are statistically significant at the 99% confidence level, temporally stable back to 1940 CE, the period with reliable instrumental measurements, and spatially representative for a vast area of inner Eurasia between northeastern Kazakhstan in the west, northern Mongolia in the east, southern Russia in the north and northwestern China in the south. Our findings demonstrate the paleoclimatic potential of TRW and especially MXD chronologies and reject any sign of the ´divergence problem´ at these high-elevation, mid-latitude larch sites.

The goal of the study was to provide an analysis of climate impact before, during, and after the Little Ice Age (LIA) on the larch (Larix gmelinii) tree line at the northern extreme of Siberian forests. Recent decadal climate change impacts on the tree line, regeneration abundance, and age structure were analyzed. The location of the study area was within the forest-tundra ecotone (elevation range 170–450 m) in the Anabar Plateau, northern Siberia. Field studies were conducted along elevational transects. Tree natality/mortality and radial increment were determined based on dendrochronology analyses. Tree morphology, number of living and subfossil trees, regeneration abundance, and age structure were studied. Locations of pre-LIA, LIA, and post-LIA tree lines and refugia boundaries were established. Long-term climate variables and drought index were included in the analysis. It was found that tree mortality from the 16th century through the beginning of the 19th century caused a downward tree line recession. Sparse larch stands experienced deforestation, transforming into tundra with isolated relict trees. The maximum tree mortality and radial growth decrease were observed to have occurred at the beginning of 18th century. Now larch, at its northern boundary in Siberia, is migrating into tundra areas. Upward tree migration was induced by warming in the middle of the 19th century. Refugia played an important role in repopulation of the forest-tundra ecotone by providing a seed source and shelter for recruitment of larch regeneration. Currently this ecotone is being repopulated mainly by tree cohorts that were established after the 1930s. The last two decades of warming did not result in an acceleration of regeneration recruitment because of increased drought conditions. The regeneration line reached (but did not exceed) the pre-LIA tree line location, although contemporary tree heights and stand densities are comparatively lower than in the pre-LIA period. The mean rate of tree line upward migration has been about 0.35 m yr-1 (with a range of 0.21–0.58), which translates to a tree line response to temperature of about 55 m °C-1.

Stratospheric volcanic eruptions have had significant impacts on the radiation budget, atmospheric and surface temperatures, precipitation and regional weather patterns, resulting in global climatic changes. The changes associated with such eruptions most commonly result in cooling during several years after events. This study aimed to reveal eco-physiological response of larch trees from northeastern Yakutia (YAK), eastern Taimyr (TAY) and Altai (ALT) regions to climatic anomalies after major volcanic eruptions CE 535, 540, 1257, 1641, 1815 and 1991 using new multiple tree-ring parameters: tree-ring width (TRW), maximum latewood density (MXD), cell wall thicknesses (CWT), δ13C and δ18O in tree-ring cellulose. This investigation showed that TRW, CWT, MXD and δ18O chronologies recorded temperature signal, while information about precipitation and vapor pressure deficit was captured by δ13C chronologies. Sunshine duration was well recorded in δ18O from YAK and ALT. Tree-ring parameters recorded cold, wet and cloudy summer anomalies during the 6th and 13th centuries. However, significant summer anomalies after Tambora (1815) and Pinatubo (1991) eruptions were not captured by any tree-ring parameters

Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850–2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python. Design Type(s) observation design • data integration objective • time series design Measurement Type(s) archaeal metabolite • calcification • glacial ice • radiance • sediment • stable isotope analysis • temperature of environmental material • trace metal analysis • wood Technology Type(s) data acquisition system Factor Type(s) measurement method • environmental material • geographic location • temporal_interval Sample Characteristic(s) Democratic Republic of the Congo • Tanzania • South Africa • Antarctica • United States of America • Russian Federation • Canada • Greenland • Finland • Norway • Iceland • Sweden • Bhutan • China • Indonesia • India • Japan • Kyrgyzstan • Kazakhstan • Mongolia • Nepal • Pakistan • Afghanistan • Thailand • Taiwan Province • Viet Nam • Australia • New Zealand • Slovakia • Romania • Austria • Switzerland • France • Spain • Germany • Estonia • Mexico • Atlantic Ocean • Pacific Ocean • Indian Ocean • Southern Ocean • Arctic Ocean • Chile • Argentina • Peru • lake sediment • speleothem • glacial ice • borehole • marine sediment • coral reef • marine sponge reef Machine-accessible metadata file describing the reported data (ISA-Tab format)

Dendroclimatic studies based on the use of various indicators of annual tree-ring structure (width, maximum density, cell wall thickness, lumen size etc.) have become widespread over the past decade. However, reconstructions of climatic characteristics revealed limitations associated with the use of both the width and density of annual rings. In particular, annual ring width, in the high latitudes of the Northern Hemisphere and in mountain regions, is usually closely related either with June, or June and July air temperature. The tree-ring maximum density is closely related with June-August or May-August temperature, which relationship improves past climate reconstruction. Structural characteristics at a cell level (cell wall thickness, lumen size, etc.) are more suitable for dendrophysiological and dendroecological studies. Blue intensity (BI) is a new parameter of annual ring structure used in dendrochronological studies. BI correlates well with annual ring maximum density. BI key advantages are in that it is fairly inexpensive, user-friendly and timesaving concerning data acquirement. Studies done in Europe and North America show a high BI potential regarding reconstruction of past climate, in particular, of that of air temperature. This paper discusses the problems of use of BI as a paleoclimatic indicator for the mountainous areas of southern Siberia (Altai Region, Russia). BI was calculated for tree-rings of the Siberian larch trees growing in Altai mountains. As a result, a local 232-yr (1783-2014) BI-chronology of Larix sibirica L. was built for an area located in Altai Mt., southern Siberia. BI-chronology was tested for quality by standard statistical methods used in dendrochronology. Mean sensitivity (MS), standard deviation (SD), first order autocorrelation (AC1) and other indicators were used to test BI time series. The correlation between individual time series ranged 0.5 to 0.65, whereas the ranges were 0.11-0.21 for MS, 0.16-0.21 for SD, and 0.86-0.88 for AC1. The statistical data were similar regarding tree-ring maximum density (MXD). AC1 was similar to that for tree-ring width (TRW). A linear regression, negative exponential line, and different spline functions were used to calculate standard (STD) and residual (RES) BI-chronologies. STD-chronology had an autocorrelation and RES-chronology had a negative autocorrelation. Preliminary studies of Siberian larch showed a high potential of BI as a paleoclimatic proxy for dendroecological and dendroclimatological studies conducted in the mountain regions of southern Siberia (Altai Mt., Russia).

We investigate the observational signatures of an idealized double-ring and double-torus system orbiting a Schwarzschild black hole, allowing the two emitting components to have mutually inclined symmetry axes. Using general-relativistic ray tracing, we construct frequency-shift maps, bolometric flux maps on the observer's screen, and the corresponding spectral line profiles of the emitted radiation. The single equatorial torus is used as a reference configuration in order to isolate the effect of the second emitting component and of the mutual misalignment of the two structures. We show that the presence of two non-coplanar emitting structures produces characteristic multi-peak spectral profiles and asymmetric bolometric-flux distributions. These signatures are imprinted both in the line-profile morphology and in the \\(\\)-profiles of the bolometric flux, providing simple diagnostic features of non-coplanar multi-component accretion structures.

We analyzed the dynamics of Lake Teletskoye water level and attempted to use data on bottom sediment geochemistry in combination with Siberian larch (Larix sibirica) tree-ring width chronology to reconstruct it for late Holocene. In particular, we studied the links among the water level characteristics, precipitation amount, bottom sediment geochemistry, and tree-ring width chronology available for Russian Altai. A correlation analysis revealed the annual water level fluctuations to correlate closely with mean annual temperature and annual precipitation (67% and 33%, respectively). The fluctuations exhibited a negative correlation with the regional tree-ring width chronology. As for the bottom sediments, two components were identified, one of which correlated closely with air temperature and the other with precipitation. Combining these three components, including tree-ring width chronology, provides new possibilities for a complex reconstruction of the lake water level fluctuations occurred during middle and late Holocene based on a regression model. A regression reconstruction model of the dynamics of the Lake Teletskoye water level was calculated for the last millennium. We defined ~60-, ~100-, ~200-year cycles of water level variability in Teletskoye Lake and supposed that the observed fluctuations are due to long-term climatic changes. Of the greatest interest are the identified interdecadal and decadal climate-caused water level fluctuations, since they will enable to estimate indirectly, in the long term, climatic changes in southern Siberia for the past 2-5 thousand years.

To better understand past climate variability of vast terrestrial regions, reconstructions of different climate parameters are needed. Different types of climate proxy data may provide season-, time resolution-, and longevity-specific information. In this paper, we present a reconstruction of summer temperature and ablation of Malii Aktru glacier variability, Altay Mountains, for the past four centuries inferred from lake Teletskoe sediments and the maximum density of the tree-rings of Siberian larch trees found at the upper timberline. The Teletskoe lake is situated close to both the Malii Aktru glacier and the tree-ring-maximum-density-chronology site (approxinately 50.29N, 87.39E). Lake Teletskoe sediments provided seasonal climatic information for the late Holocene, especially regarding summer and annual temperature variations. Ablation of the Malii Aktru glacier was also clearly sensitive to summer temperature (correlation was 0.8; p=0.05; n=32). The tree-ring maximum density chronology was well correlated with summer temperature (r=+0.65-0.72; n = 60). Ablation of Malii Aktru glacier was reconstructed using the linear regression from the tree-ring maximum density chronology (r=+0.68; n=32; p=0.05 for the calibration period) for the period since '60' AD. The summer temperature reconstructed from the data on the lake sediments was compared with the reconstructed ablation of Malii Aktru glacier for 1601-1994. A common low-frequency variability (100-200-year long cycles) was identified in the summer temperature and ablation for the reconstructed series. For example, a decrease in ablation of Malii Aktru coincided well with a temperature decrease that was found around 1700 AD and middle of 1850AD. The cold periods during LIA (Little Ice Age) were clearly pronounced in Altai Mountains climate reconstructions obtained from different climate proxies. Our study showed that various sources (tree-rings, glaciers and lake sediments) may be based upon to extract common information on climate low frequency variables, which helps better understand regional climate changes.

We review recent calculations of quasinormal modes and asymptotic tails of the Bardeen spacetime interpreted as a quantum corrected Schwarzschild-like black holes. Massless electromagnetic and Dirac fields and massive scalar field are considered. The first few overtones are much more sensitive to the change of the quantum correction parameter than the fundamental mode, because such correction deforms the black hole geometry near the event horizon. While the asymptotic tails of massless fields are identical to those for the Schwarzschild case, the tails for a massive field differs from the Schwarzschild limit at both intermediate and asymptotic times.