In The News
Seasons change -- earlier than before, study says
The hottest and coldest days of the year come roughly two days sooner than they did 50 years ago, according to a study published in Nature. The change coincides with the rise in global temperatures....
Catherine Ho
January 21, 2009
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 Cañada Flintridge.
"When you see a shift like this, or what appears to be the beginning of a shift,
it's yet another red flag about the potential implications of humans fiddling
with the climate," he said.
An earlier spring could lengthen wildfire season in Western states and affect
the availability of water resources, said Stephanie McAfee, a PhD student at the
University of Arizona who studies the effect of climate change on ecosystems.
"We rely on water that falls as snow in the mountains that melts and delivers
water to our reservoirs," she said. "The earlier that snow starts to melt, the
less of a buffer we have."
Stine worked with Peter Huybers, assistant professor of earth and planetary
sciences at Harvard, and Inez Fung, professor of atmospheric science at UC
Berkeley. They studied global surface temperature measurements from 1850 through
1953, and 1954 through 2007. In the first period, land temperatures in the
Northern Hemisphere peaked around July 21; in the later period, they peaked 1.7
days earlier.