For some Black Swan events there are clear definitions of strength (Richter, VEI ...) and location. We certainly don't mean to imply we are satisfied with seismic data, but at least there's no doubt about when and where (or even if) a recent earthquake occurred. Determining whether a drought has started (or ended) and its severity is quite a bit more challenging. This makes it nearly impossible to predict when either a current drought might end or a new one start. Ultimately, many African and western Asian governments are obliged to expect that each year will be a drought. There are many consequences of a drought: drops in agricultural production and rises in imports of foods;
disruptions as citizens move within the country or emigrate outside of it (or one can be obligated to accept refugees from other countries); less overall resistance to disease resulting in epidemics; and stresses on armed services and doctors as they struggle to save the citizens and country they are sworn to defend. Past history aside, were Eritrea to ask Ethiopia for help during a drought, it is not likely Ethiopia could do much even were there a will because Ethiopia would be likely to be having the same drought. That would leave the United Nations. So when we first heard about a volcano erupting somewhere in northeastern Africa our second concern (after the Red Sea trade rout being blocked) was would ash clouds make the existing drought worse? To take one example, Eritrea has an impressive array of difficult problems. In 2010 should President Isaias Afworki have spent a great deal of time on worrying about whether one of Ethiopia's 70-odd volcanoes was going to erupt? Probably not. How about whether one of his seven volcanoes was going to erupt? They'd been largely quiet for decades, so probably not. But Eastern Africa has been having horrific droughts for millenia - probably even millions of years. We'd assert the current drought started in 2005. There are two real worries that ought to preoccupy any leader - when would the drought or financial stagnation end AND will an earthquake, tsunami or volcanic eruption make whatever the present disaster is worse? Japan now knows the answer.