A roundup of some of the most popular but completely untrue stories and visuals of the week. None of these are legit, even though they were shared widely on social media. The Associated Press checked them out. Here are the facts:
CLAIM: Climate, weather or meteorological events that we would classify as "extreme" have declined in severity over the last 20 or 30 years.
THE FACTS: While the impacts of climate change vary across the globe, scientists agree that overall, human-caused warming is supercharging events such as extreme precipitation, droughts and forest fires. But a podcast clip shared on Instagram falsely claims that extreme climate, weather and meteorological events are actually declining in severity.
"We could look at accumulated cyclonic energy -- typhoons in the Pacific, hurricanes in the Atlantic -- and it's actually declined over the last 20 or 30 years," the speaker says in the video, which amassed thousands of likes. "We could look at forest fires, they've declined. We could look at droughts. By any measure that we care to look at, we can see that actually things have kind of calmed down a bit."
Scientists who study climate patterns say these kinds of extremes are aggravated by climate change -- and are becoming more severe, not less.
"Heat extremes are getting more frequent, more severe; precipitation extremes are getting more frequent, more severe," said Kai Kornhuber, a lecturer and research scientist at Columbia University. "Fire weather, which is linked to wildfires, is getting more frequent, more severe, more areas that didn't see these conditions before."
Kornhuber and other scientists reached by the AP pointed to rigorous studies and National Oceanic and Atmospheric Association data that show how many types of extreme weather and disasters, including those noted in the podcast clip, have become more intense as a result of climate change. For example, climate change has created warmer and drier conditions in the western United States, leading to fire seasons that last longer and burn more area in recent decades, according to NOAA.
Droughts are complicated because "there are big regional and temporal variations," according to Andrew Dessler, the director of the Texas Center for Climate Studies and a professor at Texas A&M University. "But you cannot say things are 'calming down.'"
A study published earlier this month used satellite data to show that the intensity of extreme drought and rainfall has "sharply" increased across the globe over the past 20 years. The researchers said the data confirms that both the frequency and intensity of rainfall and droughts are increasing due to burning fossil fuels and other human activity that releases greenhouse gases.
The AP has previously debunked false claims that U.S. hurricane landfall data disproves climate change. Studies show the intensity of tropical cyclones has been increasing globally.
The clip also ignores "some of the most certain ways climate change makes extreme weather more extreme," including increasing the chances of heat waves, extreme precipitation, and extreme sea level events, according to Dessler. A United Nations climate report published in 2022 also cited evidence that climate change is making it more likely for humans to die from extreme weather.
Today's children who may still be alive in the year 2100 will experience four times more climate extremes than they do now, even with just a few more tenths of a degree of warming, the U.N. Intergovernmental Panel on Climate Change said in the report.
CLAIM: 100 million humans in the same place would emit enough radiation to be deadly.
THE FACTS: Radiation experts confirm the human body contains trace amounts of radiation, but the levels aren't nearly enough to be lethal, even if 100 million people were somehow packed into a single place.
Social media users are sharing a post with the headline "Humans are Radioactive" along with the statement: "If 100 million average humans kept in an isolated place for eight hours, they will admit enough radiation to kill each one of them within 20 days."
While it's true that humans, like other living organisms, contain radioactive material, the levels are "extremely low" -- thousands of times smaller than an x-ray, according to Melissa Sullivan, a spokesperson for the U.S. Environmental Protection Agency. The radiation also can't be easily transmitted to others, experts say. To reach a dangerous level, the radiation would somehow have to be gathered from millions of people and then distilled into an extremely confined space.
"If you concentrated the radioactive material from many millions of people into a very small space, the result could be a radioactive source that would need to be handled with care to avoid being dangerous," Christopher Clement, CEO of the International Commission on Radiological Protection, a Canada-based group of scientists that advocates for radiation safety, wrote in an email. "But not as harmful as squeezing a hundred million people into a phone booth."
The social media claims also show a misunderstanding of the kind of radiation found in our bodies, said George Chabot, a physics professor at the University of Massachusetts, Lowell. Human radiation largely comes from eating foods that contain potassium -- a tiny fraction of which is radioactive potassium-40, he explained in an email.
"What may confuse people is that most of the dose to an individual from eating potassium-40 comes from the beta radiation emitted during the decay of the radioactive atoms," Chabot wrote. "This beta radiation is not very penetrating so that practically all of the energy emitted remains within the individual and cannot irradiate anyone else."
Michael Short, a nuclear science professor at the Massachusetts Institute of Technology, agreed, arguing that the radiation produced by 100 million people still wouldn't be deadly, despite what social media users claim.
"100,000,000 people would take up a tremendous amount of space, spreading out their radiation dose over that space. The dose one gets from being near a source of radiation decreases quickly with distance away from that dose," he said.
What's more, the human body acts as a sort of buffer, absorbing much of its own radiation and mitigating its wider impacts, added Christopher Baird, a physics professor at West Texas A&M University.
"If one human absorbs a bit of ionizing radiation, then this bit of radiation is no longer available to affect another human," he wrote in an email. "A hundred million humans will be emitting a hundred-million worth of human background radiation, but there will be a hundred million people absorbing this radiation."
CLAIM: Dental products containing fluoride are unsafe because the substance has been directly linked to dementia and Alzheimer's.
THE FACTS: While consuming high levels of fluoride can pose some health risks, experts say there is no research showing that topical products containing fluorides -- such as toothpaste and mouthwash -- cause dementia or Alzheimer's.
Still, an Instagram user is cautioning against going to dentists because of fluoride, calling dentists "one of the biggest scams I've ever seen."
"They don't know that fluoride is a neurotoxin that's been directly linked to dementia and Alzheimer's," the user claims in a video.
But experts say there is no research proving that topical fluoride products -- in other words, products not intended for digestion, such as toothpaste and mouthwash -- cause dementia or Alzheimer's.
Christine Till, a neuropsychologist and professor at York University in Canada who has researched fluoride, said she was not aware of studies linking topical fluoride use to those conditions. And the Centers for Disease Control and Prevention's Division of Oral Health told the AP in a statement that the agency "is not aware of any study that purports to link use of topical fluoride products, when used appropriately, to any systemic health risk."
Fluoride is a naturally occurring mineral that's found in water and used in toothpaste and dental products to strengthen teeth; it can also be found in foods and beverages. For decades it has been added to many public water supplies as an oral health measure, the CDC explains. But excessive levels of consumption can present health risks such as brittle bones.
The U.S. in 2015 lowered the recommended amount of fluoride in drinking water because some kids were getting too much, causing white splotches on their teeth.
Fluoride consumption has continued to stir controversy, and scientists say there is evidence that consuming fluoride in high levels may pose further risks, particularly for young children.
"I'm quite convinced that in utero or infantile exposure to fluoride ingestion is not a good thing for the developing brain of children," said Linda Birnbaum, a former director of the National Institute of Environmental Health Sciences, part of the National Institutes of Health, and of the National Toxicology Program. The National Toxicology Program has been continuing to evaluate the issue.
Jennifer Sass, a senior scientist at Natural Resources Defense Council, said the legitimate concerns in the scientific community about fluoride consumption don't justify avoiding the dentist because of topical fluoride use. The CDC advises that children less than age 2 only use toothpaste with fluoride if recommended by a dentist or doctor.