Science

This Scientist Has a Risky Plan to Cool Earth. There’s Growing Interest.

Published

1 year ago

August 1, 2024

This Scientist Has a Risky Plan to Cool Earth. There’s Growing Interest.

David Keith was a graduate student in 1991 when a volcano erupted in the Philippines, sending a cloud of ash toward the edge of space.

Seventeen million tons of sulfur dioxide released from Mount Pinatubo spread across the stratosphere, reflecting some of the sun’s energy away from Earth. The result was a drop in average temperatures in the Northern Hemisphere by roughly one degree Fahrenheit in the year that followed.

Today, Dr. Keith cites that event as validation of an idea that has become his life’s work: He believes that by intentionally releasing sulfur dioxide into the stratosphere, it would be possible to lower temperatures worldwide, blunting global warming.

Such radical interventions are increasingly being taken seriously as the effects of climate change grow more intense. Global temperatures have hit record highs for 13 months in a row, unleashing violent weather, deadly heat waves and raising sea levels. Scientists expect the heat to keep climbing for decades. The main driver of the warming, the burning of fossil fuels, continues more or less unabated.

Against this backdrop, there is growing interest in efforts to intentionally alter the Earth’s climate, a field known as geoengineering.

Already, major corporations are operating enormous facilities to vacuum up the carbon dioxide that’s heating up the atmosphere and bury it underground. Some scientists are performing experiments designed to brighten clouds, another way to bounce some solar radiation back to space. Others are working on efforts to make oceans and plants absorb more carbon dioxide.

But of all these ideas, it is stratospheric solar geoengineering that elicits the greatest hope and the greatest fear.

Proponents see it as a relatively cheap and fast way to reduce temperatures well before the world has stopped burning fossil fuels. Harvard University has a solar geoengineering program that has received grants from the Microsoft co-founder Bill Gates, the Alfred P. Sloan Foundation and the William and Flora Hewlett Foundation. It’s being studied by the Environmental Defense Fund along with the World Climate Research Program, an international scientific effort. The European Union last year called for a thorough analysis of the risks of geoengineering and said countries should discuss how to regulate an eventual deployment of the technology.

But many scientists and environmentalists fear that it could result in unpredictable calamities.

Because it would be used in the stratosphere and not limited to a particular area, solar geoengineering could affect the whole world, possibly scrambling natural systems, like creating rain in one arid region while drying out the monsoon season elsewhere. Opponents worry it would distract from the urgent work of transitioning away from fossil fuels. They object to intentionally releasing sulfur dioxide, a pollutant that would eventually move from the stratosphere to ground level, where it can irritate the skin, eyes, nose and throat and can cause respiratory problems. And they fear that once begun, a solar geoengineering program would be difficult to stop.

“The whole notion of spraying sulfur compounds to reflect sunlight is arrogant and simplistic,” the Canadian environmentalist David Suzuki said. “There are unintended consequences of powerful technologies like these, and we have no idea what they will be.”

Raymond Pierrehumbert, an atmospheric physicist at the University of Oxford, said he considered solar geoengineering a grave threat to human civilization.

“It’s not only a bad idea in terms of something that would never be safe to deploy,” he said. “But even doing research on it is not just a waste of money, but actively dangerous.”

Shuchi Talati, the founder of a nonprofit organization called the Alliance for Just Deliberation on Solar Geoengineering, called the technology “a double-edged sword.”

“It could be a way to limit human suffering,” she said. “At the same time, I think it can also exacerbate suffering if used in a bad way.”

In a series of interviews, Dr. Keith, a professor in the University of Chicago’s department of geophysical sciences, countered that the risks posed by solar geoengineering are well understood, not as severe as portrayed by critics and dwarfed by the potential benefits.

If the technique slowed the warming of the planet by even just one degree Celsius, or 1.8 degrees Fahrenheit, over the next century, Dr. Keith said, it could help prevent millions of heat-related deaths each decade.

A planet transformed by solar geoengineering would not be noticeably dimmer during the daytime, according to his calculations. But it could produce a different kind of twilight, one with an orange hue.

He agrees that nations should stop burning coal, oil and gas, period. But Dr. Keith believes in going further.

Lean and athletic at 60, with glacier-blue eyes, Dr. Keith has spent his life outside the lab rock climbing, sea kayaking and skiing in the Arctic. He is deeply troubled by the myriad ways climate change is disrupting the natural world.

By lowering global temperatures, solar geoengineering could help restore the planet to its preindustrial state, recreating conditions that existed before enormous amounts of carbon dioxide were pumped into the atmosphere and began to cook the Earth, he said.

If there were a global referendum tomorrow on whether to begin solar geoengineering, he said he would vote in favor.

“There certainly are risks, and there certainly are uncertainties,” he said. “But there’s really a lot of evidence that the risks are quantitatively small compared to the benefits, and the uncertainties just aren’t that big.”

The only thing more dangerous than his solution, he suggested, may be not using it at all.

∴

To understand just how contentious Dr. Keith’s work can be, consider what happened when he tried to perform an initial test in preparation for a solar geoengineering experiment known as Scopex.

Then a professor at Harvard, Dr. Keith wanted to release a few pounds of mineral dust at an altitude of roughly 20 kilometers and track how the dust behaved as it floated across the sky.

A test was planned in 2018, possibly over Arizona, but Dr. Keith couldn’t find a partner to launch a high-altitude balloon. When details of that plan became public, a group of Indigenous people objected and issued a manifesto against geoengineering.

Three years later, Harvard hired the Swedish space corporation to launch a balloon that would carry the equipment for the test. But before it took place, local groups once again rose up in protest.

The Saami Council, an organization representing Indigenous peoples, said it viewed solar geoengineering “to be the direct opposite of the respect we as Indigenous Peoples are taught to treat nature with.”

Greta Thunberg, the Swedish climate activist, joined the chorus. “Nature is doing everything it can,” she said. “It’s screaming at us to back off, to stop — and we are doing the exact opposite.”

Within months, the experiment was called off.

“A lesson I’ve learned from this is that if we do this again, we won’t be open in the same way,” Dr. Keith said.

Behind the scenes, the Harvard team and its advisory committee became mired in finger pointing over who was to blame for the collapse of the project. Dr. Talati, a member of the Scopex advisory board, said it was “the moment of peak chaos.”

It didn’t help that there were personality conflicts. Several committee members said Dr. Keith could be ornery and headstrong, correcting colleagues in casual conversation and belittling those with whom he disagreed.

“I can be abrasive and difficult,” Dr. Keith acknowledged. “I am sometimes inappropriately forceful in making my point. I’m intense.”

∴

Opponents of solar geoengineering cite several main risks.

They say it could create a “moral hazard,” mistakenly giving people the impression that it is not necessary to rapidly reduce fossil fuel emissions.

“The fundamental problem is that we think we’re so smart that we don’t have to pay attention to nature’s boundaries,” Dr. Suzuki said. “But we haven’t dealt with the root cause of the problem, which is us.”

The second main concern has to do with unintended consequences.

“This is a really dangerous path to go down,” said Beatrice Rindevall, the chairwoman of the Swedish Society for Nature Conservation, which opposed the experiment. “It could shock the climate system, could alter hydrological cycles and could exacerbate extreme weather and climate instability.”

And once solar geoengineering began to cool the planet, stopping the effort abruptly could result in a sudden rise in temperatures, a phenomenon known as “termination shock.” The planet could experience “potentially massive temperature rise in an unprepared world over a matter of five to 10 years, hitting the Earth’s climate with something that it probably hasn’t seen since the dinosaur-killing impactor,” Dr. Pierrehumbert said.

On top of all this, there are fears about rogue actors using solar geoengineering and concerns that the technology could be weaponized. Not to mention the fact that sulfur dioxide can harm human health.

Dr. Keith is adamant that those fears are overblown. And while there would be some additional air pollution, he claims the risk is negligible compared to the benefits.

“There’s plenty of uncertainty about climate responses,” he said. “But it’s pretty hard to imagine if you do a limited amount of hemispherically balanced solar geo that you don’t reduce temperatures everywhere.”

Last year, after the failure to launch the Scopex experiment in Sweden, Dr. Keith made a move that stunned his colleagues. He announced he was closing the door on 13 years at Harvard and taking his ambitions to the University of Chicago, where he would build a new program around climate interventions, including solar geoengineering.

“I don’t know whether that stuff will ever get used,” said Mr. Gates, a major investor in climate technology. “I do believe that doing the research and understanding it makes sense.”

∴

Dr. Keith’s career can be traced to his father, Tony Keith, a wildlife biologist who attended the first global gathering to address threats to nature, the 1972 United Nations Conference on the Human Environment in Stockholm.

Dyslexia prevented him from learning to read until late in 4th grade, but when he was finally able to make sense of written words, he became a voracious reader. He also loved camping and, at 17, hiked a stretch of the Appalachian Trail solo.

After graduating from the University of Toronto, he spent months rock climbing. Looking for a way to get paid to live in the wilderness, he got a job studying walruses in the Canadian Arctic.

Dr. Keith eventually enrolled in a doctoral program at the Massachusetts Institute of Technology to study experimental physics.

In 1992, he published an academic paper, “A Serious Look at Geoengineering,” that raised the questions that would shape his career: Who should authorize the use of these technologies? Who is liable if something goes wrong?

His academic career took him from Carnegie Mellon University to the University of Calgary, where he began investigating ways to capture and store carbon dioxide. The next stop was Harvard, where he got serious about solar geoengineering.

In 2006, a mutual acquaintance introduced him to Mr. Gates, who wanted to learn more about technologies that might help fight global warming. The two men discussed climate and technology in a series of meetings over the next 10 years.

Then in 2009, Dr. Keith founded Carbon Engineering, a company that developed a process for pulling carbon dioxide from the atmosphere. Investors included Mr. Gates, Chevron and N. Murray Edwards, who made billions pumping oil from the Canadian oil sands.

Last year Carbon Engineering was acquired by Occidental Petroleum, a major oil and gas producer based in Texas, for $1.1 billion. Dr. Keith owned about 4 percent of the company at the time of the sale, delivering him a personal windfall of about $72 million.

Occidental is now building a series of enormous carbon capture plants. It plans to sell carbon credits to big companies like Amazon and AT&T that want to offset their emissions. Critics say that will only delay the phaseout of fossil fuels while allowing an oil company to profit.

“Of course I’m uncomfortable about it being sold to an oil company, no question,” Dr. Keith said, adding that he plans to give away most of his profits from the sale of Carbon Engineering, perhaps to a conservation group.

∴

On a summer Monday in Cambridge, Mass., the Harvard campus was mostly quiet. But inside one classroom, a standing-room-only crowd listened as experts discussed the merits and risks of solar geoengineering.

Among those featured was Frank Keutsch, Dr. Keith’s former collaborator on the Scopex experiment.

Dr. Keutsch is less sanguine than Dr. Keith when considering its potential risks.

“I compare stratospheric solar geoengineering with opiates,” he said on the panel. “They only treat the symptom and not the actual cause. You can get addicted to it if you don’t actually address the cause. In addition, like any painkiller, you’re going to have side effects. And then there are withdrawal symptoms, and that’s termination shock.”

Dr. Keutsch is now investigating whether calcium carbonate or diamond dust might be a better material than sulfur, and pondering issues around how a deployment might one day be governed. There are no current plans for a field experiment.

Academic energy in the field has followed Dr. Keith to the University of Chicago, which is allowing him to hire 10 full-time faculty members and build a new program focused on various types of geoengineering. The total cost could reach as much as $100 million.

The move has puzzled some. Dr. Pierrehumbert, who recently departed the University of Chicago for Oxford, said he was “flabbergasted” and contended that those research dollars could be better spent investigating ways to reduce the use of fossil fuels.

To celebrate his 60th birthday in October, Dr. Keith went hiking in the Canadian Rockies and came across a glacier that had shrunk dramatically in recent years. It was a visual reminder that global warming is upending the natural world, and it confirmed his central, controversial belief: Humans have already altered the planet, heating the climate with greenhouse gases. To repair the climate and return it to a more pristine state, we may need to take even more drastic action and engineer the stratosphere.

“I’m more motivated even now to push on solar geo because the rationalist case for it is looking stronger,” Dr. Keith said. “While there are still lots of strong individual voices of opposition, there are a lot of people in serious policy positions that are taking it seriously, and that’s really exciting.”

Science

A retired teacher found some seahorses off Long Beach. Then he built a secret world for them

Published

2 days ago

December 14, 2025

Press Room

A retired teacher found some seahorses off Long Beach. Then he built a secret world for them

Rog Hanson emerges from the coastal waters, pulls a diving regulator out of his mouth and pushes a scuba mask down around his neck.

“Did you see her?” he says. “Did you see Bathsheba?”

On this quiet Wednesday morning, a paddle boarder glides silently through the surf off Long Beach. Two stick-legged whimbrels plunge their long curved beaks into the sand, hunting for crabs.

Classic stories from the Los Angeles Times’ 143-year archive

But Hanson, 68, is enchanted by what lies hidden beneath the water. Today he took a visitor on a tour of the secret world he built from palm fronds and pine branches at the bottom of the bay: his very own seahorse city.

The visitor confirms that she did see Bathsheba, an 11-inch-long orange Pacific seahorse, and a grin spreads across Hanson’s broad face.

“Isn’t she beautiful?” he says. “She’s our supermodel.”

If you get Hanson talking about his seahorses, he’ll tell you exactly how many times he’s seen them (997), who is dating whom, and describe their personalities with intimate familiarity. Bathsheba is stoic, Daphne a runner. Deep Blue is chill.

He will also tell you that getting to know these strange, almost mythical beings has profoundly affected his life.

“I swear, it has made me a better human being,” he says. “On land I’m very C-minus, but underwater, I’m Mensa.”

Hanson is a retired schoolteacher, not a scientist, but experts say he probably has spent more time with Pacific seahorses, also known as Hippocampus ingens, than anyone on Earth.

“To my knowledge, he is the only person tracking ingens directly,” says Amanda Vincent, a professor at the University of British Columbia and director of the marine conservation group Project Seahorse. “Many people love seahorses, but Roger’s absorption with them is definitely distinctive. There’s a degree of warm obsession there, perhaps.”

Rog Hanson posing in his gear on the beach.

Over the last three years, Hanson has made the two-hour trek from his home in Moreno Valley to the industrial shoreline of Long Beach to visit his “kids” about every five days. To avoid traffic, he often leaves at 2 a.m. and then sleeps in his car when he arrives.

He keeps three tanks of air and his scuba gear in the trunk of his 2009 Kia Rio. A toothbrush and a pair of pink leopard print reading glasses rest on the dash.

Hanson makes careful notes after all his dives in a colorful handmade log book he stores in a three-ring binder. On this Wednesday he dutifully records the water temperature (62 degrees), the length of the dive (58 minutes), the greatest depth (15 feet) and visibility (3 feet), as well as the precise location of each seahorse. His notes also include phase of the moon, the tidal currents and the strength of the UV rays.

“Scientists will tell you that sunlight is an important statistic to keep down,” he says.

He has given each of his four seahorses a unique logo that he draws with markers in his log book. Bathsheba’s is a purple star outlined in red, Daphne’s is a brown striped star in a yellow circle.

A detailed log of seahorse sightings written in a notebook with colorful inks.

He’s learned that the seahorses don’t like it when he hovers nearby for too long. Now he limits his interactions with them to 15 to 30 seconds at a time.

“At first I bugged them too much,” he says. “I was the paparazzi swimming around.”

Hanson traces the origins of his seahorse story back nearly two decades to the early morning of Dec. 30, 2000.

He was diving solo off Shaw’s Cove in Laguna Beach when a slow-moving giant emerged from the abyss. It was a gray whale whose 40-foot frame cast Hanson in shadow.

The whale could have killed him with a flick of its tail, Hanson says, but he felt no fear. The two made eye contact and, as Hanson tells it, he felt the whale’s gaze peering directly into his soul.

It was all over in 10 seconds, but Hanson was altered. He had always wanted to live at the beach, but after this encounter, he vowed to make it happen. It took years —15, in fact — but he finally got a job as a special education teacher in the Long Beach public school system. He bought a van and parked it on Ocean Boulevard. He lived at the beach and dived every day for 3½ months before moving to Moreno Valley.

To amuse himself while he lived at the beach, he built an underwater city he called Littleville out of discarded toys he found at the bottom of the bay.

Hanson saw his first seahorse in January 2016 while checking on Littleville. It was bright orange, just 4.5 inches long, and Hanson, who had logged over a thousand dives in the area, knew it didn’t belong there.

A red seahorse surrounded by sealife under water.

The range of the Pacific seahorse is generally thought to extend from Peru to as far north as San Diego. This seahorse ended up about 100 miles north of that.

Scientists said the seahorse and others that joined her had probably ridden an unusual pulse of warm water up the coast, along with other animals generally found in southern waters.

“We were getting a lot of weird sightings in the fall of 2015,” says Sandy Trautwein, vice president of husbandry at the Aquarium of the Pacific. “There was a yellow-bellied sea snake, bluefin tuna, marlin, whale sharks — a lot of animals associated with warm water.”

Most of these animals eventually left after ocean temperatures returned to normal, but Hanson’s seahorses stayed.

That may be because Hanson had built them a home.

It happened like this: In June 2016 he watched in horror as more than 100 high school football players splashed in the shallow waters, right where his seahorses usually hung out.

“I thought, I gotta do something, I gotta do something,” he says.

“On land I’m very C-minus, but underwater, I’m Mensa.”

— Rog Hanson

Then he remembered that, back in the Midwest where he grew up, he used to help the city park service make “fish cribs.” In early spring they would use brush and twigs to build what looked like a miniature log cabin with no roof on an ice-covered lake. When the ice melted, the cribs would fall to the bottom, creating a habitat for fish and other animals.

“So I said to myself, build them a city that’s deeper, where feet can’t get to it even at low tide,” Hanson says.

And he did.

By July 2016 two pairs of seahorses had moved into the new habitat. Daphne, the runner, was named after the nymph from Greek mythology who flees Apollo, Kenny’s name came from the proprietor of a local kayaking company. “Bathsheba” was inspired by a Bible story, and her mate, Deep Blue, named after a dive shop that has helped sponsor Hanson’s work since he launched his seahorse study.

He’s seen Kenny’s and Deep Blue’s bellies swell with pregnancy and noted how their partners check in on them daily, frequently standing sentinel nearby. He’s visited the fish at odd hours to see how their behavior changes from morning to night. And he mourned when Kenny disappeared in January. He still hasn’t come back. (A new member, CD Street, arrived June 29.)

“It feels like I’m reading a book, the book of their life, and I can’t put it down,” he says.

He’s also reached out to seahorse scientists across the globe to compare notes. “I won’t say I know the most about seahorses in the world, but I know the people who do,” he says.

Amanda Vincent, the director of Project Seahorse, says that seahorses spark an emotional reaction in almost everyone.

Daphne is one of the seahorses that Rog Hanson is studying in Alamitos Bay.

“Remember those books with three flaps where you can mix the head of a giraffe with the body of a snake and the tail of a monkey? That’s what we’ve got here,” she says. “They appeal to the sense of fancy and wonder in us.”

When Mark Showalter, a planetary astronomer at the SETI Institute, recently discovered a moon orbiting Neptune, he named it Hippocamp in part because of his love of seahorses.

“I’ve seen them in the wild and they are marvelously strange and interesting,” he says. “It’s a fish, but it doesn’t look anything like a fish.”

Pacific seahorses are among the largest members of the seahorse family. Males can grow up to 14 inches long, while females generally top out at about 11. They come in a variety of colors, including orange, maroon, brown and yellow. They are talented camouflagers that can alter the color of their exoskeleton to blend into their environment.

“I won’t say I know the most about seahorses in the world, but I know the people who do.”

But perhaps their most distinguishing characteristic is that they are the only known species in the animal kingdom to exhibit a true male pregnancy. Females deposit up to 1,500 eggs in the male’s pouch. The males incubate the eggs, providing nutrition and oxygen for the growing embryos. When the larval seahorses are ready to be released, he goes into labor — scientists call it “jackknifing” — pushing his trunk toward his tail.

After three years of observation, Hanson has collected new evidence about seahorse mating practices. His research suggests that although most seahorses are monogamous, a female will mate with two males if there are no other female seahorses around.

He also found that males, who are in an almost constant state of pregnancy, tend to stick to an area about the size of a king-size mattress, while the females roam up to 150 feet from their home during a typical day.

Eventually, he may be able to help scientists answer another long-standing question: What is the lifespan of Pacific seahorses in the wild? Some researchers say about five years; others think it could be up to 12.

“It will be interesting to see what Roger finds out,” Vincent says.

In June 2017, about one year after Hanson began formally tracking the seahorses, he took on a partner: a young scuba instructor named Ashley Arnold.

Arnold, who has short red hair and a jocular vibe, is a former Army staff sergeant who served in Iraq and Afghanistan. She learned to dive as part of a program the Salt Lake City Veterans Affairs hospital offered to female veterans suffering from post-traumatic stress disorder and military sexual trauma. Arnold suffered from both. Diving became her salvation.

Dive instructor Ashley Arnold sitting at the bed of a truck.

“All the irritation on the surface disappears when you go under the water,” she says. “It’s like, ‘What was I concerned about?’ You forget about everything else. Nothing else matters.”

She used her GI Bill to pay for a scuba instructor course and to set up her own business. Now, she finds that if she dives at least twice a week and has a dog, she does not need to take medication.

“All the irritation on the surface disappears when you go under the water.”

— Ashley Arnold

“That’s a pretty big statement in my opinion,” she says.

Arnold and Hanson met in June 2016 on a dive trip to Catalina. Hanson mentioned his seahorses. Arnold was intrigued, but still lived in Salt Lake City.

One year later, Arnold moved to Huntington Beach and gave Hanson a call.

“I said, ‘Hey Roger, let’s chat. Any chance I could join you at the seahorses you talked about?’” she says. “And he decided I was acceptable.”

Now, Arnold and her boyfriend, Jake Fitzgerald, check in on the seahorses about once a week and help Roger rebuild the city he created for them.

Rog Hanson and Ashley Arnold posing in their gear on the beach.

“We call them our kids because we love them so much,” Arnold says.

Hanson and Arnold are very protective of their seahorse family. They tell visitors to remove GPS tags from their photos. They swear them to secrecy.

There is little chance anyone would find Hanson’s seahorses without a guide. Also, diving in these waters off Long Beach can be a challenge.

The water is shallow. It’s hard to get your buoyancy right. A misplaced flipper kick can stir up blinding sand and silt.

But if Hanson wants to show you his underwater world, nothing will stop him. He will hold you firmly by the hand and guide you down to the forest he built at the bottom of the bay.

Rog Hanson rinses off Ashley Arnold in her gear on the beach.

He will use a plastic tent stake, jabbing it into the bottom to propel himself — and you holding on — across the ocean floor. When he spots a seahorse he will use the stake as a pointer. Through the murky water you strain to see. Then it appears.

Orange and rigid. Thin snout. Bony plates. Stripes down the torso. Totally still.

And if you’ve never seen a seahorse in the wild before, you will feel honored and awed, as if you’ve just seen a unicorn beneath the sea.

Science

California’s summer COVID wave shows signs of waning. What are the numbers in your community?

Published

2 days ago

December 14, 2025

Press Room

California’s summer COVID wave shows signs of waning. What are the numbers in your community?

There are some encouraging signs that California’s summer COVID wave might be leveling off.

That’s not to say the seasonal spike is in the rearview mirror just yet, however. Coronavirus levels in California’s wastewater remain “very high,” according to the U.S. Centers for Disease Control and Prevention, as they are in much of the country.

But while some COVID indicators are rising in the Golden State, others are starting to fall — a hint that the summer wave may soon start to decline.

Statewide, the rate at which coronavirus lab tests are coming back positive was 11.72% for the week that ended Sept. 6, the highest so far this season, and up from 10.8% the prior week. Still, viral levels in wastewater are significantly lower than during last summer’s peak.

The latest COVID hospital admission rate was 3.9 hospitalizations for every 100,000 residents. That’s a slight decline from 4.14 the prior week. Overall, COVID hospitalizations remain low statewide, particularly compared with earlier surges.

The number of newly admitted COVID hospital patients has declined slightly in Los Angeles County and Santa Clara County, but ticked up slightly up in Orange County. In San Francisco, some doctors believe the summer COVID wave is cresting.

“There are a few more people in the hospitals, but I think it’s less than last summer,” said Dr. Peter Chin-Hong, a UC San Francisco infectious diseases expert. “I feel like we are at a plateau.”

Those who are being hospitalized tend to be older people who didn’t get immunized against COVID within the last year, Chin-Hong said, and some have a secondary infection known as superimposed bacterial pneumonia.

Los Angeles County

In L.A. County, there are hints that COVID activity is either peaking or starting to decline. Viral levels in local wastewater are still rising, but the test positivity rate is declining.

For the week that ended Sept. 6, 12.2% of wastewater samples tested for COVID in the county were positive, down from 15.9% the prior week.

“Many indicators of COVID-19 activity in L.A. County declined in this week’s data,” the L.A. County Department of Public Health told The Times on Friday. “While it’s too early to know if we have passed the summer peak of COVID-19 activity this season, this suggests community transmission is slowing.”

Orange County

In Orange County, “we appear to be in the middle of a wave right now,” said Dr. Christopher Zimmerman, deputy medical director of the county’s Communicable Disease Control Division.

The test positivity rate has plateaued in recent weeks — it was 15.3% for the week that ended Sept. 6, up from 12.9% the prior week, but down from 17.9% the week before that.

COVID is still prompting people to seek urgent medical care, however. Countywide, 2.9% of emergency room visits were for COVID-like illness for the week that ended Sept. 6, the highest level this year, and up from 2.6% for the week that ended Aug. 30.

San Diego County

For the week that ended Sept. 6, 14.1% of coronavirus lab tests in San Diego County were positive for infection. That’s down from 15.5% the prior week, and 16.1% for the week that ended Aug. 23.

Ventura County

COVID is also still sending people to the emergency room in Ventura County. Countywide, 1.73% of ER patients for the week that ended Sept. 12 were there to seek treatment for COVID, up from 1.46% the prior week.

San Francisco

In San Francisco, the test positivity rate was 7.5% for the week that ended Sept. 7, down from 8.4% for the week that ended Aug. 31.

“COVID-19 activity in San Francisco remains elevated, but not as high as the previous summer’s peaks,” the local Department of Public Health said.

Silicon Valley

In Santa Clara County, the coronavirus remains at a “high” level in the sewershed of San José and Palo Alto.

Roughly 1.3% of ER visits for the week that ended Sunday were attributed to COVID in Santa Clara County, down from the prior week’s figure of 2%.

Science

Early adopters of ‘zone zero’ fared better in L.A. County fires, insurance-backed investigation finds

Published

3 days ago

December 13, 2025

Press Room

Early adopters of ‘zone zero’ fared better in L.A. County fires, insurance-backed investigation finds

As the Eaton and Palisades fires rapidly jumped between tightly packed houses, the proactive steps some residents took to retrofit their homes with fire-resistant building materials and to clear flammable brush became a significant indicator of a home’s fate.

Early adopters who cleared vegetation and flammable materials within the first five feet of their houses’ walls — in line with draft rules for the state’s hotly debated “zone zero” regulations — fared better than those who didn’t, an on-the-ground investigation from the Insurance Institute for Business and Home Safety published Wednesday found.

Over a week in January, while the fires were still burning, the insurance team inspected more than 250 damaged, destroyed and unscathed homes in Altadena and Pacific Palisades.

On properties where the majority of zone zero land was covered in vegetation and flammable materials, the fires destroyed 27% of homes; On properties with less than a quarter of zone zero covered, only 9% were destroyed.

The Insurance Institute for Business and Home Safety, an independent research nonprofit funded by the insurance industry, performed similar investigations for Colorado’s 2012 Waldo Canyon fire, Hawaii’s 2023 Lahaina fire and California’s Tubbs, Camp and Woolsey fires of 2017 and 2018.

While a handful of recent studies have found homes with sparse vegetation in zone zero were more likely to survive fires, skeptics say it does not yet amount to a scientific consensus.

Travis Longcore, senior associate director and an adjunct professor at the UCLA Institute of the Environment and Sustainability, cautioned that the insurance nonprofit’s results are only exploratory: The team did not analyze whether other factors, such as the age of the homes, were influencing their zone zero analysis, and how the nonprofit characterizes zone zero for its report, he noted, does not exactly mirror California’s draft regulations.

Meanwhile, Michael Gollner, an associate professor of mechanical engineering at UC Berkeley who studies how wildfires destroy and damage homes, noted that the nonprofit’s sample does not perfectly represent the entire burn areas, since the group focused specifically on damaged properties and were constrained by the active firefight.

Nonetheless, the nonprofit’s findings help tie together growing evidence of zone zero’s effectiveness from tests in the lab — aimed at identifying the pathways fire can use to enter a home — with the real-world analyses of which measures protected homes in wildfires, Gollner said.

A recent study from Gollner looking at more than 47,000 structures in five major California fires (which did not include the Eaton and Palisades fires) found that of the properties that removed vegetation from zone zero, 37% survived, compared with 20% that did not.

Once a fire spills from the wildlands into an urban area, homes become the primary fuel. When a home catches fire, it increases the chance nearby homes burn, too. That is especially true when homes are tightly packed.

When looking at California Department of Forestry and Fire Protection data for the entirety of the two fires, the insurance team found that “hardened” homes in Altadena and the Palisades that had noncombustable roofs, fire-resistant siding, double-pane windows and closed eaves survived undamaged at least 66% of the time, if they were at least 20 feet away from other structures.

But when the distance was less than 10 feet, only 45% of the hardened homes escaped with no damage.

“The spacing between structures, it’s the most definitive way to differentiate what survives and what doesn’t,” said Roy Wright, president and chief executive of the Insurance Institute for Business and Home Safety. At the same time, said Wright, “it’s not feasible to change that.”

Looking at steps that residents are more likely to be able to take, the insurance nonprofit found that the best approach is for homeowners to apply however many home hardening and defensible space measures that they can. Each one can shave a few percentage points off the risk of a home burning, and combined, the effect can be significant.

As for zone zero, the insurance team found a number of examples of how vegetation and flammable materials near a home could aid the destruction of a property.

At one home, embers appeared to have ignited some hedges a few feet away from the structure. That heat was enough to shatter a single pane window, creating the perfect opportunity for embers to enter and burn the house from the inside out. It miraculously survived.

At others, embers from the blazes landed on trash and recycling bins close to the houses, sometimes burning holes through the plastic lids and igniting the material inside. In one instance, the fire in the bin spread to a nearby garage door, but the house was spared.

Wooden decks and fences were also common accomplices that helped embers ignite a structure.

California’s current zone zero draft regulations take some of those risks into account. They prohibit wooden fences within the first five feet of a home; the state’s zone zero committee is also considering whether to prohibit virtually all vegetation in the zone or to just limit it (regardless, well-maintained trees are allowed).

On the other hand, the draft regulations do not prohibit keeping trash bins in the zone, which the committee determined would be difficult to enforce. They also do not mandate homeowners replace wooden decks.

The controversy around the draft regulations center around the proposal to remove virtually all healthy vegetation, including shrubs and grasses, from the zone.

Critics argue that, given the financial burden zone zero would place on homeowners, the state should instead focus on measures with lower costs and a significant proven benefit.

“A focus on vegetation is misguided,” said David Lefkowith, president of the Mandeville Canyon Assn.

At its most recent zone zero meeting, the Board of Forestry and Fire Protection directed staff to further research the draft regulations’ affordability.

“As the Board and subcommittee consider which set of options best balance safety, urgency, and public feasibility, we are also shifting our focus to implementation and looking to state leaders to identify resources for delivering on this first-in-the-nation regulation,” Tony Andersen, executive officer of the board, said in a statement. “The need is urgent, but we also want to invest the time necessary to get this right.”

Home hardening and defensible space are just two of many strategies used to protect lives and property. The insurance team suspects that many of the close calls they studied in the field — homes that almost burned but didn’t — ultimately survived thanks to firefighters who stepped in. Wildfire experts also recommend programs to prevent ignitions in the first place and to manage wildlands to prevent intense spread of a fire that does ignite.

For Wright, the report is a reminder of the importance of community. The fate of any individual home is tied to that of those nearby — it takes a whole neighborhood hardening their homes and maintaining their lawns to reach herd immunity protection against fire’s contagious spread.

“When there is collective action, it changes the outcomes,” Wright said. “Wildfire is insidious. It doesn’t stop at the fence line.”