Writing in the Dec. 6 issue of the journal Nature, Sagarin focuses his attention on recent climate studies documenting the early arrival of spring an important indicator of global warming. He points out that, by ignoring leap year, climate experts have inadvertently allowed statistical bias to creep into their analyses, resulting in false estimates of springs actual arrival.
"A number of international studies have shown that spring is coming significantly earlier each year. The question is how much earlier," notes Sagarin, a postdoctoral fellow in biological sciences at Stanfords Hopkins Marine Station in Pacific Grove, Calif.
Sagarin, who began studying climate change as a Stanford undergraduate in the mid-1990s, has become immersed in the field of phenology, which uses historical records of annual bird migrations, ice melts and other natural events to establish trends in global warming.
In October, he co-authored a study in the journal Science documenting the early arrival of spring in Alaska based on the Nenana Ice Classic a popular betting contest that awards cash prizes for predicting the exact time of the annual ice breakup on the Tanana River. After examining Ice Classic archives dating back 84 years, Sagarin concluded that, on average, Alaskas springtime thaw is occuring 5.5 days sooner than it did in 1917.
"While I was researching the Science study, I realized that a lot of these phenological surveys of spring events were based on the calendar date rather than on their timing relative to the vernal equinox," Sagarin says.