Re-evaluation of the effects of precipitation amount and temperature on precipitation δ18O at the monthly and interannual timescales

Proxy records of the oxygen isotope ratio of O-18/O-16 of past precipitation (delta O-18(p)) have played an important role in revealing past hydroclimatic changes, on the basis of global observed relationships between monthly precipitation delta O-18(p) and both precipitation amount and temperature only of a few years as reported by Dansgaard in 1964. It is therefore crucial to systematically re-evaluate the relationships using modern instrumental data. We analysed monthly and annual mean correlations from 108 global stations over the past about 60 years. Consistent with previously reported results, monthly delta O-18(p) values in the high latitudes (>= 60 degrees) show a significant positive correlation with temperature (referred to as 'temperature effect') and a negative trend with precipitation amount in the low latitudes (<= 20 degrees) ('amount effect'). However, these correlations do not hold for true for yearly mean data for more than three-quarters of the stations evaluated. This indicates that the relationships between the different temporal resolutions could be more complicated than previously thought. For the related natural archives, such as ice cores, sediments, and carbonates, further careful evaluation is required to establish the robustness of their paleoclimatic implications.