Global hydroclimatic changes from 1950 to 2018 are analyzed using updated data of land precipitation, streamflow, and an improved form of the Palmer Drought Severity Index. The historical changes are then compared with climate model-simulated response to external forcing to determine how much of the recent change is forced response. It is found that precipitation has increased from 1950 to 2018 over mid-high latitude Eurasia, most North America, Southeast South America, and Northwest Australia, while it has decreased over most Africa, eastern Australia, the Mediterranean region, the Middle East, and parts of East Asia, central South America, and the Pacific coasts of Canada. Streamflow records largely confirm these precipitation changes. The wetting trend over Northwest Australia and Southeast South America is most pronounced in austral summer while the drying over Africa and wetting trend over mid-high latitude Eurasia are seen in all seasons. Coupled with the drying caused by rising surface temperatures, these precipitation changes have greatly increased the risk of drought over Africa, southern Europe, East Asia, eastern Australia, Northwest Canada, and southern Brazil. Global land precipitation and continental freshwater discharge show large interannual and inter-decadal variations, with negative anomalies during El Niño and following major volcanic eruptions in 1963, 1982, and 1991; whereas their decadal variations are correlated with the Interdecadal Pacific Oscillation (IPO) with IPO’s warm phase associated with low land precipitation and continental discharge. The IPO and Atlantic multidecadal variability also dominate multidecadal variations in land aridity, accounting for 90 % of the multidecadal variance. CMIP5 multi-model ensemble mean shows decreased precipitation and runoff and increased risk of drought during 1950–2018 over Southwest North America, Central America, northern and central South America (including the Amazon), southern and West Africa, the Mediterranean region, and Southeast Asia; while the northern mid-high latitudes, Southeast South America, and Northwest Australia see increased precipitation and runoff. The consistent spatial patterns between the observed changes and the model-simulated response suggest that many of the observed drying and wetting trends since 1950 may have resulted at least partly from historical external forcing. However, the drying over Southeast Asia and wetting over Northwest Australia are absent in the 21st century projections.

使用更新的土地降水，水流量和改进形式的Palmer干旱严重性指数，对1950年至2018年全球水文气候变化进行了分析。然后将历史变化与气候模型模拟的对外部强迫的响应进行比较，以确定最近的变化中有多少是强迫响应。发现中高纬度欧亚大陆，大多数北美，南美东南部和澳大利亚西北部的降水从1950年到2018年增加了，而在大多数非洲，澳大利亚东部，地中海地区，中东和东亚，南美中部和加拿大太平洋海岸的部分地区。流量记录在很大程度上证实了这些降水变化。在澳大利亚南部的夏季，澳大利亚西北部和南美东南部的湿润趋势最为明显，而在所有季节中都可以看到非洲的干燥和中高纬度欧亚大陆的湿润趋势。再加上由于地表温度升高引起的干燥，这些降水变化极大地增加了非洲，南欧，东亚，澳大利亚东部，加拿大西北部和巴西南部干旱的风险。全球陆地降水和大陆淡水排放量显示年际和年代际变化很大，在厄尔尼诺现象期间以及在1963年，1982年和1991年的重大火山喷发之后均出现负异常。而它们的年代际变化与年代际太平洋涛动（IPO）相关，而IPO的暖期与土地降水低和大陆排放有关。IPO和大西洋地区的多年代际变化也主导着土地干旱的多年代际变化，占多年代际变化的90％。CMIP5多模型总体平均数显示1950–2018年期间，北美西南部，中美洲，南美洲北部和中部（包括亚马逊河），南部和西非，地中海地区以及东南部地区降水和径流减少，干旱风险增加亚洲; 而北部中高纬度地区，南美东南部和澳大利亚西北部则出现降雨和径流增加的情况。观测到的变化与模型模拟的响应之间一致的空间格局表明，自1950年以来，许多观测到的干燥和湿润趋势可能至少部分是由历史外部强迫造成的。然而，