Assessing and Comparing Long-term Precipitation Trends Worldwide

In the face of anthropogenic climate change, there is particular interest in how rising global temperatures affect water availability. Higher temperatures lead to increased rates of evaporation and raise the saturation humidity. Both phenomena lead to more intense precipitation events. However, a critical question is how changes in terrestrial water-dependent variables, such as runoff, soil moisture, and vegetation, will differ from precipitation trends. Will warming global temperatures result in scarcer or more plentiful water resources? Therefore, our broader research effort will be to compare local precipitation trends with local trends of other water-dependent variables in as many places as feasible. Yet, this cannot be achieved without first understanding the reliability of historical precipitation trends. Many other studies have simulated precipitation trends as global temperatures rise, but this study aims to use observational data from the Climatic Research Unit Time Series (CRU TS) and the Global Precipitation Climatology Centre (GPCC) databases, which cover common years of 1901 to 2020. From these gridded monthly datasets, long-term changes in precipitation are compared over several standard time intervals. Methods are developed to strictly use data constrained by observational stations. The precipitation trends computed using the CRU and GPCC databases show similar regional patterns, but the GPCC database has more spatial coverage. These precipitation trends will then be applied to our broader research efforts, which will compare them to local trends of other water-dependent variables.