Fog in Redwood Groves Has Declined by 33 Percent Since 1901

The coastal fog that has nurtured the growth of northern California’s giant redwood trees has decreased by a third over the past century, according to a detailed study of data from 114 weather stations. One major reason for the decline in foggy days is that the temperature gradient between northern
Big Basin
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Sunlight cuts through redwoods
California’s cool coastal areas and warmer inland areas — a key factor in creating fog in the areas where redwoods flourish — has declined significantly since 1901. At the beginning of the 20th century, the daytime temperature difference between the two climatic zones was 17 degrees Fahrenheit. Today, the difference is 11 degrees F, according to the study, published online in the journal Proceedings of the National Academy of Sciences. The study, conducted by scientists at the University of California, Berkeley, said over the past century the presence of fog along the coast in summer has dropped from 56 percent to 42 percent, a loss of about three hours per day. Co-author Todd Dawson said that the study showed “coast redwood and other ecosystems along the U.S. west coast may be increasingly drought-stressed.” The study said it is unclear whether the decline in foggy days is the result of natural weather cycles or human-caused climate change.