Winters warmer, spring earlier, University of California study finds

Jane Kay in the San Francisco Chronicle: Earth's coldest days of the year are getting warmer, and scientists have seen winter temperatures rising at a much faster pace than summer temperatures. Now UC Berkeley researchers have figured out exactly how much.

Outside of the tropics, summer temperatures have risen 1.7 degrees over the last 50 years compared with winters, which have jumped by 3.2 degrees, according to a study published Wednesday in the journal Nature.

The researchers have also identified a shift in the seasons: The hottest day of the year is occurring nearly two days earlier than it was a half-century ago. "The highest temperature is hotter, and the lowest temperature is also hotter. But you're getting to both temperatures earlier in the year," said lead author Alexander Stine, a graduate student in UC Berkeley's Department of Earth and Planetary Science.

The changes reported in the study might seem small, "but they have huge economic and other societal implications," said climate expert Gretchen Daily, director of the Center for Conservation Biology at Stanford University. "In California, the changes are likely to reduce snowpack and water storage and supply, increase wildfires and lengthen and intensify heat waves," Daily said.

For 100 years, the arrival of spring showed up within the bounds of natural variability. But as global temperatures have risen in the last 50 years, researchers saw the advance of an earlier spring. When looking at temperatures over time, they found that summer tended to remain stable while winter temperatures jump up and down from year to year. "You have to see a lot of winters before you see a slow, steady signal," said Stine….

Black-and-white Ruffed Lemur sunning position itself; taken at the Santa Barbara Zoo by Visionholder, Wikimedia Commons, under the Creative Commons Attribution 3.0 Unported License