This is an open-access publication: anyone clicking the above "doi" link can read our article, no need for a subscription.
An annually resolved and absolutely dated ring-width chronology spanning 4,500 y has been constructed using subfossil, archaeological, and living-tree juniper samples from the northeastern Tibetan Plateau. The chronology represents changing mean annual precipitation and is most reliable after 1500 B.C. Reconstructed precipitation for this period displays a trend toward more moist conditions: the last 10-, 25-, and 50-y periods all appear to be the wettest in at least three and a half millennia. Notable historical dry periods occurred in the 4th century BCE and in the second half of the 15th century CE. The driest individual year reconstructed (since 1500 B.C.) is 1048 B.C., whereas the wettest is 2010. Precipitation variability in this region appears not to be associated with inferred changes in Asian monsoon intensity during recent millennia. The chronology displays a statistical association with the multidecadal and longer-term variability of reconstructed mean Northern Hemisphere temperatures over the last two millennia. This suggests that any further large-scale warming might be associated with even greater moisture supply in this region.
Significance. This paper describes the production and climatic interpretation of a tree-ring width chronology that is currently the longest, absolutely dated series produced for the northeastern Tibetan Plateau and one of the longest in the world. The method of chronology construction enables comparison of variations in precipitation totals over long timescales as well as shorter periods. Precipitation in this region during the last 50 years has been historically high -- likely higher than for any equivalent length period in at least 3,500 years, even when considering the chronology and interpretational uncertainty. Notable dry periods occurred in the 4th century BCE and in the second half of the 15th century CE.
This study has assembled a network of tree-ring width measurements, combined these into several tree-ring width chronologies, and calibrated the main chronology to produce an estimate of annual precipitation (prior-July to June). These data are available below (see "Data Files") and at the World Data Center for Paleoclimatology. The main chronology and the calibrated precipitation reconstruction are also provided here:
When using any of these data, please cite:
Yang B, Qin C, Wang J, He M, Melvin TM, Osborn TJ and Briffa KR (2014) A 3500-year tree-ring record of annual precipitation on the northeastern Tibetan Plateau. Proceedings of the National Academy of Sciences, in press.
Extensive supplementary material is provided in the article's Supplementary Information appendix, available from the publisher's website and also provided here for convenience. This material provides additional detail about the tree-ring measurement data, the construction of the regional chronology and the regional precipitation series, the correlations between the chronology and climate variables locally and across fields of data, the calibration of the chronology and its comparison with other records.
The tree-ring chronologies were constructed using the CRUST (CRU Standardisation of Tree-ring data) software. A separate article has been published that describes the processing methods that CRUST implements, and the full CRUST software (including source code) is now available.
The data files and this NE Tibetan Plateau version of CRUST are available in this zip file. It contains all the raw tree-ring data and the regional climate data (the raw weather station series are available from the Chinese Meteorological Administration). The zip file contains executable versions for Linux and Windows. It also includes the Fortran source code, from which it can be compiled. We are not able to offer any technical support, but it does include a "makefile" to assist with compiling the software (though we recommend using the pre-compiled, executable versions if they work on your computer system).
The full-functionality version of CRUST is available from the CRUST software page.