Easiest is probably geom_col. For the above, the mapping would just be aes(year, SPEI)
Or you could e.g. use geom_segment, with something like aes(x = year, y = 0, xend = year, yend = year). If you combine with geom_point you get something more like the examples here: Plot discrete sequence data - MATLAB stem, which we also call a lollipop chart.