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.

We developed a 50‐year tree ring δ¹⁸O chronology for each of three tree species (Juniperus indica, Larix griffithii, and Picea spinulosa) using a total of 12 trees (four trees per species) from the Bhutan Himalaya. Despite originating from different species sampled at two different altitudes, the δ¹⁸O chronologies are highly correlated with one another (r = 0.76–0.89). Response analyses reveal that tree ring δ¹⁸O values are controlled mainly by summer precipitation, irrespective of species. Based on these results, a robust 269‐year δ¹⁸O chronology was established to reconstruct the amount of May–September precipitation based on data from four larch trees. Our tree ring δ¹⁸O data show significant correlations with those from other regions of the Himalaya and the Tibetan Plateau, indicating that common signals related to monsoon activity are recorded in the data. However, at centennial timescales, our data from Bhutan show normal conditions during the 20th century, whereas records from sites in western Nepal and the southern/eastern Tibetan Plateau show weakening trends in monsoon intensity during the last 100–200 years; the weakening trends may be the result of a reduction in the meridional sea surface temperature gradient in the Indian Ocean during this time. At continental scales, the tree ring records show that areas more from ocean basins are particularly sensitive to reduced monsoon circulation. Correlation analyses suggest that the El Niño–Southern Oscillation (ENSO) plays an important role in modulating summer precipitation. However, the teleconnected relationship disappears during the period 1951–1970, coinciding with a negative phase of the Pacific Decadal Oscillation (PDO), implying interdecadal modulation of the PDO on the influence of the ENSO on precipitation in Bhutan.

A tree ring cellulose oxygen isotope (δ¹⁸O) chronology for the period 1870–2011 was established using samples from four Fokienia hodginsii trees with the aim of exploring the potential to use tree ring δ¹⁸O records to reconstruct climatic variations in Fujian, a subtropical region of southeast China. We believe that this is the first tree ring δ¹⁸O chronology from this area. Response analysis revealed that tree ring δ¹⁸O is significantly correlated with precipitation between April and September, relative humidity between August and October, and the Palmer drought severity index between April and October. Our δ¹⁸O chronology accounts for 37.4% (24.6%) of actual variation in precipitation between April and September during the period from 1951 to 2011 (1901 to 2011). Spatial correlation analysis revealed that tree ring cellulose δ¹⁸O is a suitable proxy for reconstructing April–September precipitation in Fujian, as well as in parts of Guangdong and Jiangxi, southeast China. In addition, significant correlations between δ¹⁸O chronology and the Indian summer monsoon index show that large‐scale atmosphere circulation also influences tree ring δ¹⁸O. Comparisons between the tropical Pacific sea surface temperature (SST) and tree ring δ¹⁸O, during the period from 1895 to 2009, indicate that the tropical Pacific SST is positively correlated with tree ring δ¹⁸O in the study region over the last 110 years, except between 1920 and 1960. Reduced El Niño–Southern Oscillation (ENSO) variance from 1920 to 1960 may result in collapsed relationship between tree ring δ¹⁸O in Fujian and tropical Pacific SST.

We have constructed a regional tree-ring cellulose oxygen isotope (δ¹⁸O) record for the northern Indian sub-continent based on two new records from northern India and central Nepal and three published records from northwestern India, western Nepal and Bhutan. The record spans the common interval from 1743 to 2008 CE. Correlation analysis reveals that the record is significantly and negatively correlated with the three regional climatic indices: all India rainfall (AIR; r = −0.5, p < 0.001, n = 138), Indian monsoon index (IMI; r = −0.45, p < 0.001, n = 51) and the intensity of monsoonal circulation (r = −0.42, p < 0.001, n = 51). The close relationship between tree-ring cellulose δ¹⁸O and the Indian summer monsoon (ISM) can be explained by oxygen isotope fractionation mechanisms. Our results indicate that the regional tree-ring cellulose δ¹⁸O record is suitable for reconstructing high-resolution changes in the ISM. The record exhibits significant interannual and long-term variations. Interannual changes are closely related to the El Niño–Southern Oscillation (ENSO), which indicates that the ISM was affected by ENSO in the past. However, the ISM–ENSO relationship was not consistent over time, and it may be partly modulated by Indian Ocean sea surface temperature (SST). Long-term changes in the regional tree-ring δ¹⁸O record indicate a possible trend of weakened ISM intensity since 1820. Decreasing ISM activity is also observed in various high-resolution ISM records from southwest China and Southeast Asia, and may be the result of reduced land–ocean thermal contrasts since 1820 CE.