A new study suggests that droughts in Africa, without any human causes, have been much worse than the present. NY Times:
For at least 3,000 years, a regular drumbeat of potent droughts, far longer and more severe than any experienced recently, have seared a belt of sub-Saharan Africa that is now home to tens of millions of the world’s poorest people, climate researchers reported in a new study.
That sobering finding, published in the April 17th issue of Science, emerged from the first study of year-by-year climate conditions in the region over the millenniums, based on layered mud and dead trees in a crater lake in Ghana. Although the evidence was drawn from a single water body, Lake Bosumtwi, the researchers said there was evidence that the drought patterns etched in the lakebed extended across a broad swath of West Africa.
More such mega-droughts are inevitable, the research team that studied the patterns said, although there is no way to predict when the next may unfold.
The lead authors of the report, Timothy M. Shanahan of the University of Texas at Austin and Jonathan T. Overpeck of the University of Arizona, warned that global warming resulting from human-generated greenhouse gases was likely to exacerbate those droughts and that there was an urgent need to bolster the resilience of African countries in harm’s way.
The study said that some of the past major droughts appeared to be linked to a distinctive pattern of increases and reductions in surface temperatures of the Atlantic Ocean, known as the Atlantic multidecadal oscillation.
Typically over the last 3,000 years, a severe drought developed every 30 to 65 years, they researchers said. But several centuries-long droughts in the climate record, the most recent persisting from 1400 to around 1750, are harder to explain, they said.
While that extraordinary drought occurred during a cool spell in the Northern Hemisphere called the “little ice age,” other extreme droughts appear to have hit West Africa at points when the world was relatively warm over all.
The article goes on to say how important it is to lower greenhouse gas emissions to try to smooth out these changes, but the real story is that when the Earth decides to start changing its temperature, there will not be a thing humans can do about it.