When empires rise and fall and plagues sweep over the land,
people have traditionally cursed the stars. But perhaps they
should blame the weather. A new analysis of European tree-ring
samples suggests that mild summers may have been the key to the
rise of the Roman Empire—and that prolonged droughts, cold
snaps, and other climate changes might have played a part in
historical upheavals, from the barbarian invasions that brought
about Rome's collapse to the Black Death that wiped out much of
medieval Europe. "Looking back on 2500 years, there are examples
where climate change impacted human history," says the study's
lead author, Ulf Büntgen, a paleoclimatologist at the Swiss
Federal Research Institute for Forest, Snow and Landscape in
Zurich. "This kind of information is not only relevant for
ancient agrarian societies, it might also impact modern
societies." The study, published online today in Science,
examined nearly 9000 pieces of wood, mostly collected over the
past 30 years by archaeologists who use tre