Scientific studies calculate climate change as health danger, while Trump calls it a 'scam'

The Trump administration on Thursday revoked a scientific finding that climate change is a danger to public health, an idea that President Donald Trump called “a scam.” But repeated scientific studies say it’s a documented and quantifiable harm.

Again and again, research has found increasing disease and deaths — thousands every year — in a warming world.

The Environmental Protection Agency finding in 2009, under the Obama administration, has been the legal underpinning of nearly all regulations fighting global warming.

“It boggles the mind that the administration is rescinding the endangerment finding; it’s akin to insisting that the world is flat or denying that gravity is a thing,” said Dr. Howard Frumkin, a physician and professor emeritus of public health at the University of Washington.

Thousands of scientific studies have looked at climate change and its effects on human health in the past five years and they predominantly show climate change is increasingly dangerous to people.

Many conclude that in the United States, thousands of people have died and even more were sickened because of climate change in the past few decades.

For example, a study on “Trends in heat-related deaths in the U.S., 1999-2023 ” in the prestigious JAMA journal shows the yearly heat-related death count and rate have more than doubled in the past quarter century from 1,069 in 1999 to a record high 2,325 in 2023.

A 2021 study in Nature Climate Change looked at 732 locations in 43 countries — including 210 in the United States — and determined that more than a third of heat deaths are due to human-caused climate change. That means more than 9,700 global deaths a year attributed to warming from the burning of coal, oil and natural gas.

A new study published this week found that 2.2% of summer deaths in Texas from 2010 to 2023 were heat related “as climate change brings more frequent and intense heat to Texas.”

In the more than 15 years, since the government first determined climate change to be a public health danger, there have been more than 29,000 peer-reviewed studies that looked at the intersection of climate and health, with more than 5,000 looking specifically at the United States, according to the National Library of Medicine's PubMed research database.

More than 60% of those studies have been published in the past five years.

“Study after study documents that climate change endangers health, for one simple reason: It’s true,” said Frumkin, a former director of the National Center for Environmental Health appointed by President George W. Bush.

In a Thursday event at the White House, Trump disagreed, saying: “It has nothing to do with public health. This is all a scam, a giant scam.”

Experts strongly disagree.

“Health risks are increasing because human-cause climate change is already upon us. Take the 2021 heat dome for example, that killed (more than) 600 people in the Northwest,'' said Dr. Jonathan Patz, a physician who directs the Center for Health, Energy and Environmental Research at the University of Wisconsin-Madison. "The new climate attribution studies show that event was made 150-fold more likely due to climate change.”

Patz and Frumkin both said the “vast majority” of peer-reviewed studies show health harms from climate change. Peer-reviewed studies are considered the gold standard of science because other experts pore over the data, evidence and methods, requiring changes, questioning techniques and conclusions.

The various studies look at different parts of health. Some looked at deaths that wouldn't have happened without climate change. Others looked at illnesses and injuries that didn't kill people. Because researchers used different time periods, calculation methods and specific aspects of health, the final numbers of their conclusions don't completely match.

Studies also examined disparities among different peoples and locations. A growing field in the research are attribution studies that calculate what proportion of deaths or illness can be blamed on human-caused climate change by comparing real-world mortality and illness to what computer simulations show would happen in a world without a spike in greenhouse gases.

Last year an international team of researchers looked at past studies to try to come up with a yearly health cost of climate change.

While many studies just look at heat deaths, this team tried to bring in a variety of types of climate change deaths — heat waves, extreme weather disasters such as 2017's Hurricane Harvey, wildfires, air pollution, diseases spread by mosquitos such as malaria — and found hundreds of thousands of climate change deaths globally.

They then used the EPA's own statistic that puts a dollar value on human life — $11.5 million in 2014 dollars — and calculated a global annual cost “on the order of at least $10 billion.”

Studies also connect climate change to waterborne infections that cause diarrhea, mental health issues and even nutrition problems, Frumkin said.

“Public health is not only about prevention of diseases, death and disability but also well-being. We are increasingly seeing people displaced by rising seas, intensifying storms and fires,” said Dr. Lynn Goldman, a physician and dean emeritus at the George Washington University School of Public Health.

“We have only begun to understand the full consequences of a changing climate in terms of health.”

The issue gets complicated when cold-related deaths are factored in. Those deaths are decreasing, yet in the United States there are still 13 times more deaths from cold exposure than heat exposure, studies show.

Another study concludes that until the world warms another 2.7 degrees (1.5 degrees Celsius) from now, the number of temperature-related deaths won't change much “due to offsetting decreases in cold-related mortality and increases in heat-related deaths.”

But that study said that after temperatures rise beyond that threshold, and if society doesn't adapt to the increased heat, “total mortality rises rapidly."

The Associated Press’ climate and environmental coverage receives financial support from multiple private foundations. AP is solely responsible for all content. Find AP’s standards for working with philanthropies, a list of supporters and funded coverage areas at AP.org.

FILE - Traffic moves along Interstate 76 ahead of the Memorial Day holiday weekend, in Philadelphia, May 22, 2025. (AP Photo/Matt Rourke, File)

FILE - The Shell Norco oil refinery operates in Norco, La., April 7, 2025. (AP Photo/Gerald Herbert, File)

FILE Joe Chyuwei, right, Addison Black, front center, James Black, front left, and back row from left, Helen Chyuwei, Jameson Black, Grace Chyuwei and Grayson Black watch the sunset in the heat at Zabriskie Point, Aug. 3, 2025, in Death Valley National Park, Calif. (AP Photo/John Locher, File)

FILE - A pumpjack is visible before sunrise Feb. 26, 2025, in Kermit, Texas. (AP Photo/Julio Cortez, File)

President Donald Trump speaks during an event with Environmental Protection Agency director Lee Zeldin to announce the EPA will no longer regulate greenhouse gases, in the Roosevelt Room of the White House, Thursday, Feb. 12, 2026, in Washington. (AP Photo/Evan Vucci)

FILE - The Gen. James Gavin Power Plant, a coal-fired power plant, operates April 14, 2025, in Cheshire, Ohio. (AP Photo/Joshua A. Bickel, File)

DUBAI, United Arab Emirates (AP) — Iran said it considers the Strait of Hormuz closed once again after a vessel using an ‘unauthorized route’ was struck by a warning shot in the critical waterway, further jeopardizing the already tenuous ceasefire agreement with the United States.

U.S. Central Command said a short time later that its forces began a third round of strikes against Iran.

“The United States is imposing a heavy cost by continuing to degrade Iran’s ability to attack civilian mariners and commercial ships freely transiting the strait,” the military said.

A Cyprus-flagged container ship struck by Iran suffered “significant engineroom damage” and a civilian crew member is missing, U.S. Central Command said.

Senior U.S. officials had previously said in Washington that negotiations to further cement last month's deal to end the war will be unable to progress without the strait being secure — and had even said they expected Iran to offer public statements to that effect.

Instead, the Revolutionary Guards Corps stated in an online post on Saturday that Iran launched warning shots at a “violating ship.” Iran further reported that the strait would now remain closed until further notice.

Those announcements followed Iran and Oman’s foreign ministers meeting on Saturday to discuss the strait that lies between them, after days of Iranian attacks on ships and U.S. retaliation that dealt a blow to the interim deal to end the war.

Iran’s new supreme leader, still unseen since the war began, also vowed in his first statement since the funeral of his father, Ayatollah Ali Khamenei that Iranians would avenge his killing in the war’s opening strikes on Feb. 28.

Such revenge “is the will of our nation and must certainly be carried out,” Supreme Leader Mojtaba Khamenei said in a statement carried on state television, hours after President Donald Trump threatened more missile attacks.

Oman said it and Iran agreed to keep talking about the Strait of Hormuz “at the technical and political levels,” a day after the United States called on Iran to publicly say the crucial waterway is open and ships won’t be attacked.

Iranian Foreign Minister Abbas Araghchi said he met with his counterpart in Oman to discuss “appropriate mechanisms for ensuring the safe passage of ships.”

The world for decades has considered the strait an international waterway. Iran has insisted that the strait now remain under its control and that it be allowed to charge ships moving through it, a stance it took after the war began. The U.S. urges mariners to transit on a southern route through Oman’s territorial waters.

About a fifth of all traded oil and natural gas passed through the strait before the war began. Iran’s grip on it during the war led to a global energy crisis, though oil prices have sharply dropped since wartime highs of $120 a barrel.

Iran's top diplomat also accused the U.S. of violating the interim deal by ending waivers allowing Iran to sell crude oil on the open market in U.S. dollars. Washington ended them in response to the attacks on ships in the strait.

“Reality check: There can only be mutual compliance,” Araghchi wrote on X.

A thousand “missiles are Locked and Loaded and aimed at the Islamic Republic of Iran, with thousands more to immediately follow, should the Iranian Government act on its threat,” Trump wrote on social media overnight

He said he was responding to threats “to assassinate, or attempt to assassinate” him. During Khamenei's funeral, mourners held posters or banners calling for Trump to be killed along with Israeli Prime Minister Benjamin Netanyahu.

Trump has declared the ceasefire over but said the U.S. would continue negotiations.

U.S. officials, speaking Friday on condition of anonymity about the current situation with Iran, said the resumption of strikes in recent days came after what they described as a rogue faction of Iranian hard-liners tried to sabotage the ceasefire.

Iran has insisted its theocracy is unified under the new supreme leader.

After the U.S. wrapped up its latest strikes on Thursday, more attacks reportedly hit Iran, raising questions about who else may be targeting the Islamic Republic.

Israel didn't claim them, meaning the Gulf Arab states may have launched them, likely as a means to deter Iran from attacking them again. Iran on Thursday retaliated for U.S. strikes by targeting Bahrain, Jordan, Kuwait and Qatar.

The strikes in Iran over two days killed at least 17 people and wounded 115 others, Iranian Health Ministry spokesperson Hossein Kermanpour said.

Price and Weissert reported from Washington. Associated Press writer Sam Metz in Ramallah, West Bank, contributed to this report.

A pro-government demonstrator wears an Iranian flag as she waves a religious flag in a gathering commemorating the late Iranian Supreme Leader Ayatollah Ali Khamenei at a square in Tehran, Saturday, July 11, 2026. (AP Photo/Vahid Salemi)

A pro-government demonstrator holds an anti-Trump placard in a gathering commemorating the late Iranian Supreme Leader Ayatollah Ali Khamenei at a square in Tehran, Saturday, July 11, 2026. (AP Photo/Vahid Salemi)

A girl waves an Iranian flag in a pro-government gathering commemorating the late Iranian Supreme Leader Ayatollah Ali Khamenei at a square in Tehran, Saturday, July 11, 2026. (AP Photo/Vahid Salemi)

A man holds a poster of the late Iranian Supreme Leader Ayatollah Ali Khamenei in a gathering commemorating him at a square in Tehran, Saturday, July 11, 2026. (AP Photo/Vahid Salemi)

A cleric waves an Iranian flag while holding a child as a woman waves a religious flag in a pro-government gathering commemorating the late Iranian Supreme Leader Ayatollah Ali Khamenei at a square in Tehran, Saturday, July 11, 2026. (AP Photo/Vahid Salemi)

Mostafa Khamenei, center, brother of Iran's new Supreme Leader Mojtaba Khamenei, leads a prayer over the coffin of his late father, Iranian Supreme Leader Ayatollah Ali Khamenei before his burial at the Imam Reza Shrine in Mashhad, northeastern Iran, Thursday, July 9, 2026. (Office of the Iranian Supreme Leader via AP)

In this photo released by Iran's Supreme Leader's office, mourners chant and raise their fists during the final funeral ceremony for the late Iranian Supreme Leader Ayatollah Ali Khamenei at the Imam Reza Shrine before his burial in Mashhad, northeastern Iran, Thursday, July 9, 2026. (Office of the Iranian Supreme Leader via AP)

In this photo released by Iran's Supreme Leader's office, mourners carry the coffin of the late Iranian Supreme Leader Ayatollah Ali Khamenei above the crowd for the final prayer before his burial at the Imam Reza Shrine in Mashhad, northeastern Iran, Thursday, July 9, 2026. (Office of the Iranian Supreme Leader via AP)