Monsoon season in Asia brings the rains vital for crops that feed nearly half the world’s population. Climate change appears to be affecting the monsoon, though the effects differ from region to region and time to time: sometimes in the form of more extreme rains, at others in extended dry periods, or inconvenient changes in the season’s timing.
To gain insight into the history of the monsoon and its potential future, scientists at the Columbia Climate School’s Lamont-Doherty Earth Observatory have spent decades sampling and studying the rings of old trees across wide areas. Because tree rings respond to annual precipitation, these can be read like books, documenting dry and wet periods year by year, going back centuries. The research has revealed punishing droughts of the past, including some that probably contributed to the overthrow of entire civilizations.
The sampling work takes place mostly in remote mountain areas, where huge, old trees have survived human intrusions. It is a race against time; many are now finally being cut down. The audio slideshow below, which originally appeared in 2009, takes viewers on an expedition to the highlands of Vietnam, where behemoth thousand-year-old cypresses still stand―at least for now.
