We investigate historical and projected precipitation in Tanzania using observational and climate model data. Precipitation in Tanzania is highly variable in both space and time due to topographical variations, coastal influences, and the presence of lakes. Annual and seasonal precipitation trend analyses from 1961 to 2016 show maximum rainfall decline in Tanzania during the long rainy season in the fall (March–May), and an increasing precipitation trend in northwestern Tanzania during the short rainy season in the spring (September–November). Empirical orthogonal function (EOF) analysis applied to Tanzania’s precipitation patterns shows a stronger correlation with warmer temperatures in the western Indian Ocean than with the eastern-central Pacific Ocean. Years with decreasing precipitation in Tanzania appear to correspond with increasing sea surface temperatures (SST) in the Indian Ocean, suggesting that the Indian Ocean Dipole (IOD) may have a greater effect on rainfall variability in Tanzania than the El Niño-Southern Oscillation (ENSO) does. Overall, the climate model ensemble projects increasing precipitation trend in Tanzania that is opposite with the historical decrease in precipitation. This observed drying trend also contradicts a slightly increasing precipitation trend from climate models for the same historical time period, reflecting challenges faced by modern climate models in representing Tanzania’s precipitation.

Rice planthoppers are common insect pests in Taiwan, and they have caused significant damage in the past. The majority of rice planthoppers have seen a drastic decline in their population since the mid-2000s, a trend that has anecdotally attributed to widespread and better pest control, as well as improved rice cultivation management. By analyzing 40 years of the airborne net trap data of rice planthoppers collected in Southwest Taiwan, it was found that the pests’ yearly population, computed with a logarithmic transformation, resembles a signature climate pattern in the global oceans with a robust multi-decadal variability. An ocean temperature-based index derived from the patterns of multi-decadal variability shows a marked resemblance with the population change of common rice planthoppers, with overlapping peaks during the 1990–2010 period. The climate dynamics associated with the regional weather pattern in the vicinity of Taiwan are discussed. Phase reversal of this multi-decadal climate variability in the future may produce favorable climatic conditions for the rice planthopper population to increase back to its historical levels.