Trenberth and his NCAR colleague Aiguo Dai found just such a pronounced drop in precipitation — seen in terms of the world's stream and river flows — after the 1991 eruption of Mount Pinatubo.
There was a "singular decrease" in river discharges into the oceans, Trenberth told Discovery News. The researchers' work is published in the latest issue of Geophysical Research Letters.
Unlike the more gradual effects of global warming, droughts have been known to cause immediate famines along with political and economic instability.
"There is really a major ethical aspect to it," said Trenberth. "If you can really [dim solar radiation], who is in charge? Who plays God?" After all, he said, it's one thing to accidentally cause the climate to change, as has happened with global warming, and another to deliberately tinker with it.
"Any time you are talking about geo-engineering you have to be very careful," said climate researcher Robert Adler of NASA's Goddard Space Flight Center. "If you don't understand the system — and we do not fully understand this system — you can get perturbations."
Another problem with mimicking volcanoes is that you have to keep doing it or face potential trouble when the effect wears off in 18 months or so and the climate rebounds, said Trenberth.
Related Links:
The National Center for Atmospheric Research
NASA on volcanoes and climate change.
Explore a virtual volcano.
All about volcanoes from the USGS.
