Researchers admit inconvenient finding: CO2 is helping giant redwoods grow

Anthony Watts Meteorologist and Climate Blogger
Font Size:

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.

But just in case you think this is just another argument among friends over a few tree rings, I’ll remind readers of this story:

Surprise: Earths’ Biosphere is Booming, Satellite Data Suggests CO2 the Cause

The results surprised Steven Running of the University of Montana and Ramakrishna Nemani of NASA, scientists involved in analyzing the NASA satellite data. They found that over a period of almost two decades, the Earth as a whole became more bountiful by a whopping 6.2%. About 25% of the Earth’s vegetated landmass — almost 110 million square kilometers — enjoyed significant increases and only 7% showed significant declines. When the satellite data zooms in, it finds that each square meter of land, on average, now produces almost 500 grams of greenery per year.

Yeah, damned inconvenient these findings.

Now that California voters have reaffirmed their commitment to CARB’s favorite AB32 law reducing CO2 emissions, I’m waiting for the inevitable lawsuit from the Sierra Club which will argue that reducing CO2 will hurt the giant redwoods. It is, after all, what the Sierra Club does.

Mr. Watts operates the most visited blog on climate science in the world, www.wattsupwiththat.com now with over 61 million visits. He has spent 30 years on air in radio and television as a weather forecaster, and still does daily radio broadcasts. In 2007, he founded the surfacestations.org project, which with the help of volunteers nationwide found that only 1 in 10 of the weather stations used for monitoring climate in the USA met the government’s own standards for station siting quality. He also operates a weather technology business, embraces energy efficiency with solar power on his home and drives an electric car.