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In all of California, there is no greater shrine to nature than the giant redwoods of Northern California. Readers may remember this news article from last year which talks about a threat to giant redwoods, due to a supposed global warming-induced lack of coastal fog, which these trees need as part of their life cycle: “One more thing to worry about — fog shortage.”

From the University of California, Berkeley, via Eurekalert:

Fog has declined in past century along California’s redwood coast

An analysis of hourly airport cloud cover reports leads to this surprising finding: California’s coastal fog has decreased significantly over the past 100 years, potentially endangering coast redwood trees dependent on cool, humid summers, according to a new study by University of California, Berkeley, scientists.

The fog research conclusion was soon shown to be false. Last summer the San Francisco Chronicle carried a story about research on fog and climate with a different conclusion:

The Bay Area just had its foggiest May in 50 years. And thanks to global warming, it’s about to get even foggier. That’s the conclusion of several state researchers, whose soon-to-be-published study predicts that even with average temperatures on the rise, the mercury won’t be soaring everywhere.

Well, now the same scientist that published the fog decline research has spawned another story in the San Francisco Chronicle that flies in the face of his earlier study.

Here are some excerpts from the story:

The $2.5 million Redwoods and Climate Change Initiative has allowed Sillett and other specialists from Humboldt State and UC Berkeley to set up shop in some of California’s last remaining old-growth redwood groves. The researchers are climbing, poking, prodding, measuring and testing everything, including molecules of coast redwood and giant sequoia trees on 16 research plots throughout the ancient trees’ geographic range.

The plan is to chart the health of the trees over time and use laboratory analysis of carbon and oxygen isotopes to figure out how the trees have reacted in the past to climate and weather conditions.

“Embedded in this tree ring is a remarkable record of climate,” said Todd Dawson, the director of the Center for Stable Isotope Biogeochemistry at UC Berkeley, as he held up a core sample from a Montgomery Woods redwood. “Based on what has happened in the past, we can really project what will happen in the future.”

This was interesting:

Laboratory testing of tree-ring data is now so advanced that scientists can determine things like whether tree growth in a certain year was the result of fog or precipitation. Scientists intend to plot biological changes in redwood tree rings dating back 1,000 to 2,000 years, with particular emphasis on effects that might have been caused by the industrial revolution.

I assume, then, that they have fog and precipitation measurement records spanning 1,000-2,000 years that allow them to verify this.

Here’s where the older fog research and the newer tree ring studies collide with our current climate, bold emphasis mine:

Redwood studies thus far have come up with some confounding results. Redwood trees are known to thrive on summer fog, and it was believed that they grew more slowly as they aged, but studies by Sillett and others show redwood growth increasing, in some cases doubling, over the past century. That’s despite a 33 percent decrease in the amount of fog along the Northern California coast since the early 20th century, according to a study by Dawson.

Anthony Ambrose, a postdoctoral research fellow at the UC Berkeley department of integrative biology, said the growth spurt could be the result of more sunlight and more carbon dioxide in the atmosphere, which generally increases plant growth.

“Maybe it is because there is a CO2 increase while there is still enough moisture,” Ambrose said.