Drought in northern Nigeria: An indication of abrupt climatic change?
The Mann-Kendall-Sneyers trend test is used to examine the extent of climatic jumps in the rainfall series of six synoptic stations in northern Nigeria. A sequential version of the test which uses the intersection of two curves produced by the progressive forward and backward applications of the test is used to determine the approximate beginning points of trends in the series. The results indicate that the rainfall series exhibit a general downward trend with significant abrupt changes in the late 1960s and early 1970s. This downward trend is interpreted as an indication of an abrupt change in the mean climatic conditions over the region, and suggests bistable modes of oscillation in the climate. The discontinuous changes of rainfall in the region after the 1970s requires that agricultural and hydrological planning must take cognizance of the recent climatic normals.