Douglas Hardy usually thinks in increments of a century. The climate scientist at the University of Massachusetts Amherst has for 13 years been trekking to the top of Mount Kilimanjaro to take measurements that will help him understand the record of environmental change embedded in 11,000-year-old cylinders of ice drilled out of glaciers.

Lately, though, he has been obsessing about the weather on an hourly basis, thinking about the fluctuations in wind speed over a single day.