Long-term trend of precipitation stable isotopic compositions under global warming conditions

Based on observation data from the Global Network of Isotopes in Precipitation, the temporal variations of precipitation oxygen isotope compositions (delta O-18) are estimated globally, by using the methods of non-parametric Mann-Kendall test and Sen's slope estimator. The results show statistically significant long-term delta O-18 increasing and decreasing at about two thirds and one third sites, respectively. For most temperature effect dominated sites, the delta O-18 changes can be attributed to the changes of surface air temperature. Therefore, the delta O-18 is predicted to rise with global warming for these sites, which has great implications in application of isotopes as traces of hydrology.