Temperature and precipitation effects on the isotopic composition of global precipitation reveal long-term climate dynamics.

Earth's climate history is traced through the long-term covariance between the isotopic (δ O) composition of archived meteoric waters (groundwater, ice cores) with air temperature (T) and amount of precipitation (P). To assess recent multi-decadal climatic changes, we analysed δO, T and P, and the relationships between these parameters at 20 stations having 60 years of continuous monthly isotopic records. Using nonparametric regressions and time series modelling we found significant linear and non-linear relationships for δO with T and P and showed that the δO dependency on these two parameters varied over decadal scales, thereby revealing complex relationships related to recycled moisture, large-scale convective processes and atmospheric-oceanic oscillations. Due to multiple factors controlling the δ O composition of precipitation including P and T effects, we found that time-varying relationships between δO in precipitation P and T were better explained using the non-linear regressions. Our results affirmed that δO distributions in global precipitation are integrative indicators of climate dynamics whose patterns can be applied to better understand region-specific climatic changes in the present, past, and future.