The seasons begin two days earlier than they did 50 years ago, a shift that may be related to human activity, according to researchers at UC Berkeley and Harvard University.
The season skewing means that the hottest and coldest days of the year come about two days sooner than they did 50 years ago, according to a study published in the Jan. 22 edition of the journal Nature. The study also found that the difference between average winter and summer temperatures shrank in the same 50-year span, indicating winters are heating up faster than summers.
The change coincides with the rise in global temperatures, which could suggest a link to human-induced global warming, said Alexander Stine, the study's first author and a graduate student at UC Berkeley's Department of Earth & Planetary Science.
"The pattern that we see suggests there's a relationship between global warming and the shifting of the seasons," Stine said.
Earlier seasons could affect farming, rainfall distribution, water supplies and the diversity of ecosystems, said Bill Patzert, a climatologist at NASA's Jet Propulsion Laboratory in La Canada Flintridge.