AN ANCIENT piece of wood has revealed how humid the air was 45 million years ago.
Hope Jahren from Johns Hopkins University in Baltimore, Maryland, and her team studied a metasequoia tree from the Fossil Forest, a 40-kilometre-long stretch of Arctic desert on Axel Heiberg island in Nunavut, Canada.
The researchers found the cellulose of the well-preserved wood was unusually high in the light hydrogen and oxygen isotopes that plants selectively lose by evaporation (Geology, vol 31, p 463). That means the air must have been humid enough to suppress evaporation – about as wet as today’s Pacific Northwest rainforests…
