Five thousand miles west of Los Angeles and 500 miles north of the equator, on a far-flung spit of white coral sand in the central Pacific, a massive, aging and weathered concrete dome bobs up and down with the tide. Here in the Marshall Islands, Runit Dome holds more than 3.1 million cubic feet — or 35 Olympic-sized swimming pools — of U.S.-produced radioactive soil and debris, including lethal amounts of plutonium. Nowhere else has the United States saddled another country with so much of its nuclear waste, a product of its Cold War atomic testing program. Between 1946 and 1958, the United States detonated 67 nuclear bombs on, in and above the Marshall Islands — vaporizing whole islands, carving craters into its shallow lagoons and exiling hundreds of people from their homes. U.S. authorities later cleaned up contaminated soil on Enewetak Atoll, where the United States not only detonated the bulk of its weapons tests but, as The Times has learned, also conducted a dozen biological weapons tests and dumped 130 tons of soil from an irradiated Nevada testing site. It then deposited the atoll’s most lethal debris and soil into the dome. Now the concrete coffin, which locals call “the Tomb,” is at risk of collapsing from rising seas and other effects of climate change. Tides are creeping up its sides, advancing higher every year as distant glaciers melt and ocean waters rise. Officials in the Marshall Islands have lobbied the U.S. government for help, but American officials have declined, saying the dome is on Marshallese land and therefore the responsibility of the Marshallese government. “I’m like, how can it [the dome] be ours?” Hilda Heine, the president of the Republic of the Marshall Islands, said in an interview in her presidential office in September. “We don’t want it. We didn’t build it. The garbage inside is not ours. It’s theirs.” To many in the Republic of the Marshall Islands, Runit Dome is the most visible manifestation of the United States’ nuclear legacy, a symbol of the sacrifices the Marshallese made for U.S. security, and the broken promises they received in return. They blame the United States and other industrialized countries for global climate change and sea level rise, which threaten to submerge vast swaths of this island nation’s 29 low-lying atolls. “More than any other place, the Marshall Islands is a victim of the two greatest threats facing humanity — nuclear weapons and climate change,” said Michael Gerrard, a legal scholar at Columbia University’s law school. “The United States is entirely responsible for the nuclear testing there, and its emissions have contributed more to climate change than those from any other country.” Over the last 15 months, a reporting team from the Los Angeles Times and Columbia University’s Graduate School of Journalism made five trips to the Marshall Islands, where they documented extensive coral bleaching, fish kills and algae blooms — as well as major disease outbreaks, including the nation’s largest recorded epidemic of dengue fever. They interviewed folk singers who lost their voices to thyroid cancers and spent time in Arkansas, Washington and Oregon, where tens of thousands of Marshallese have migrated to escape poverty and an uncertain future. Marshallese leaders acknowledge that America doesn’t bear full responsibility for their nation’s distress. But they say the United States has failed to take ownership of the environmental catastrophe it left behind, and they claim U.S. authorities have repeatedly deceived them about the magnitude and extent of that devastation. A Times review of thousands of documents, and interviews with U.S. and Marshallese officials, found that the American government withheld key pieces of information about the dome’s contents and its weapons testing program before the two countries signed a compact in 1986 releasing the U.S. government from further liability. One example: The United States did not tell the Marshallese that in 1958, it shipped 130 tons of soil from its atomic testing grounds in Nevada to the Marshall Islands. U.S. authorities also didn’t inform people in Enewetak, where the waste site is located, that they’d conducted a dozen biological weapons tests in the atoll, including experiments with an aerosolized bacteria designed to kill enemy troops. U.S. Department of Energy experts are encouraging the Marshallese to move back to other parts of Enewetak, where 650 now live, after being relocated during the U.S. nuclear tests during the Cold War. But many Marshallese leaders no longer trust U.S. assurances of safety. “We didn’t know the Runit Dome waste dump would crack and leak…. We didn’t know about climate change,” said Jack Ading, a Marshallese senator from Enewetak Atoll. “We weren’t nuclear scientists who could independently verify what the U.S. was telling us. We were just island people who desperately wanted to return home.” Adding to the alarm is a study published this year by a team of Columbia University scientists showing levels of radiation in some spots in Enewetak and other parts of the Marshall Islands that rival those found near Chernobyl and Fukushima. Such discoveries could give Marshallese leaders fresh ammunition to challenge the 1986 compact, which is up for renegotiation in 2023, and also to press the United States to honor property and health claims ordered by an international tribunal. The tribunal, established by the two countries in 1988, concluded the United States should pay $2.3 billion in claims, but Congress and U.S courts have refused. Documents show the U.S. paid just $4 million. The U.S. position is that it has already paid more than $600 million for the resettlement, rehabilitation and radiation-related healthcare costs of communities affected by the nuclear testing, said Karen Stewart, the U.S. ambassador to the Republic of the Marshall Islands. She said inflation brings the number closer to $1 billion. “The United States recognizes the effects of its testing and has accepted and acted on its responsibility to the people of the Republic of the Marshall Islands,” Stewart said in a statement. In September, the Marshallese parliament, the Nitijela, approved a national nuclear strategy, which calls for a risk analysis and environmental survey of Runit Dome, an assessment of legal options for its cleanup and a new attempt to secure the $2.3 billion ordered by the tribunal. Last month, Marshall Islands lawmakers called on the international community to reduce greenhouse gases causing what they declared to be a “national climate crisis.” China is taking an increasing interest in the Marshall Islands and other Pacific island nations, in part because of their strategic location and Beijing’s interest in reducing U.S. influence in the region. Those inroads by China have alarmed U.S. leaders, forcing them to pay more attention to the grievances of Marshallese leaders such as Heine. “This heightened interest,” Heine said, “should bode well for us.”

A shipwreck rests in the harbor off Majuro, where children play in the water.

From the U.S. mainland, it takes more than a day to fly to the Marshall Islands, and only one commercial airline makes the trip. The “Island Hopper,” United Airlines Flight 154, starts at Honolulu, making stops in the Marshall Islands at Majuro and Kwajalein before heading west toward the Micronesian islands of Kosrae, Pohnpei and Chuuk, and finally terminating in Guam. The next day, it doubles back. As it approaches Majuro, the blue-scape of the ocean is broken by an oblong necklace of white-coral-beached islands, dotted with coconut, pandanus and breadfruit trees. The Marshall Islands’ atolls are the remnants of ancient volcanoes that once protruded from these cerulean seas. They were settled 3,000 years ago by the ancestors of present-day Marshallese who crossed the ocean on boats from Asia and Polynesia. For American officials in the mid-1940s, this 750,000-square-mile expanse of ocean, nearly five times larger than the state of California, must have seemed like a near-perfect spot to test their growing atomic arsenal. “The Marshall Islands were selected as ground zero for nuclear testing precisely because colonial narratives portrayed the islands as small, remote and unimportant,” said Autumn Bordner, a former researcher at Columbia University’s K=1 Project, which has focused on the legacy of nuclear testing in the Marshall Islands, and now a research fellow in ocean law and policy at UC Berkeley’s Center for Law, Energy & the Environment. Nerje Joseph, 72, was a witness to the largest thermonuclear bomb tested by the United States: the Castle Bravo detonation. She was 7 years old at the time, living with her family in Rongelap Atoll, 100 miles east of Bikini Atoll — a tropical lagoon commandeered for nuclear testing. On March 1, 1954, Joseph recalls waking up and seeing two suns rising over Rongelap. First there was the usual sun, topping the horizon in the east and bringing light and warmth to the tropical lagoon near her home. Then there was another sun, rising from the western sky. It lighted up the horizon, shining orange at first, then turning pink, then disappearing as if it had never been there at all. Joseph and the 63 others on Rongelap had no idea what they had just witnessed. Hours later, the fallout from Castle Bravo rained down like snow on their homes, contaminating their skin, water and food. According to Joseph and government documents, U.S. authorities came to evacuate the Rongelapese two days later. By that time, some islanders were beginning to suffer from acute radiation poisoning — their hair fell out in clumps, their skin was burned, and they were vomiting. Nerje Joseph, 72, was 7 years old when the United States detonated its largest nuclear bomb. The Castle Bravo test sent a mushroom cloud into the sky and unexpectedly irradiated parts of the northern Marshall Islands that she and her family called home. The Castle Bravo test and others in the Marshall Islands helped the U.S. establish the credibility of its nuclear arsenal as it raced against its Cold War adversary, the Soviet Union, to develop new atomic weapons. But the testing came at a horrible price; Joseph and other Marshallese ended up becoming human guinea pigs for U.S. radiation research. Three years after Castle Bravo, U.S. authorities encouraged Joseph, her family and her neighbors to return to Rongelap. U.S. government documents from the time show that officials weighed the potential hazards of radiation exposure against “the current low morale of the natives” and a “risk of an onset of indolence.” Ultimately they decided to go forward with the resettlement so researchers could study the effects of lingering radiation on human beings. “Data of this type has never been available,” Merrill Eisenbud, a U.S official with the Atomic Energy Commission, said at a January 1956 meeting of the agency’s Biology and Medicine Committee. “While it is true that these people do not live the way that Westerners do, civilized people, it is nonetheless also true that they are more like us than the mice.” The resettlement proved catastrophic for the people of Rongelap. Cancer cases, miscarriages and deformities multiplied. Ten years later, in 1967, 17 of the 19 children who were younger than 10 and on the island the day Bravo exploded had developed thyroid disorders and growths. One child died of leukemia. In 1985, the people of Rongelap asked Greenpeace to evacuate them again after the United States refused to relocate them or to acknowledge their exposure, according to government documents and news reports from the time. Joseph, who had her thyroid removed because of her radiation exposure, has spent nearly seven decades taking daily thyroid medication, enabling her body to produce hormones it otherwise would not generate. A quiet, dignified woman with thick, wavy gray hair, Joseph lives in a cinder-block home in Majuro, the capital, a setting far different from the pristine atoll where she grew up. Composed of three low-lying islands connected by one flood-prone road, Majuro is long and narrow and home to roughly half the population of the Marshall Islands, about 28,000 people. Taxis crawl the length of this lone road, fitting as many riders into their vehicles as they can accommodate. Visitors opting to walk are encouraged to carry long sticks to beat away packs of feral dogs that roam the streets. Joseph says she misses her home, but she knows she may never go back. “We had a oneness when we lived on Rongelap,” she said of her childhood. “We worked together, we ate together, we played together. That has been lost.”

More than 40 years ago, U.S. authorities buried plutonium and other waste from nuclear testing in an unlined bomb crater on Runit Island and encapsulated it with concrete. The so-called Tomb, which is in Enewetak Atoll, now bobs with the tide, sucking in and flushing out radioactive water into nearby coral reefs, contaminating marine life.

The legacy of the testing program is most evident at Enewetak, an atoll that took the brunt of the United States’ late-stage nuclear detonations before an international ban on atmospheric testing in 1963. A string of 40 islands to the west of Bikini, Enewetak was once a postcard-perfect ring of coral reefs, white-sand beaches and coconut trees, where roughly 450 dri-Enewetak and dri-Enjebi — the two clans that lived in the atoll — gathered breadfruit and pandanus, and harvested fish and clams from the lagoon. Between 1948 and 1958, the U.S. military detonated 43 atomic bombs here. After agreeing to a 1958 temporary moratorium on nuclear testing with the United Kingdom and the Soviet Union, the U.S. began using the atoll as a conventional and bioweapons testing ground. For the next 18 years, the U.S. shot ballistic missiles at it from California, tested virulent forms of bacteria on its islands and detonated a series of other large, conventional bombs in the lagoon. In 1972, after the U.S had nearly exhausted its military interest in the region, it invited the leaders of Enewetak back to see the atoll for the first time since 1946. According to a Department of Energy report of the event, the Enewetak leaders “were deeply gratified to be able to visit their ancestral homeland, but they were mortified by what they saw.” The islands were completely denuded. Photos show an apocalyptic scene of windswept, deforested islands, with only the occasional coconut tree jutting up from the ground. Elsewhere, crumbling concrete structures, warped tarmac roads and abandoned construction and military equipment dotted the barren landscape. The damage they saw on that visit was the result of nearly three decades of U.S. military testing. The United States had detonated 35 bombs in the Marshall Islands in 112 days in 1958. Nine of these were on Enewetak’s Runit Island. With names such as Butternut, Holly and Magnolia, the bombs were detonated in the sky, underwater and on top of islands. From 1946-51, the U.S. began the first of 67 nuclear tests on Bikini and Enewetak atolls, forcing hundreds of islanders to evacuate. Nine bombs were detonated, ranging in size from 23 to 225 kilotons. In 1952, the government shifted to testing larger weapons. Over the next four years, 25 bombs were detonated, including Castle Bravo, then the largest artificial explosion ever. Its radioactive fallout spread hundreds of miles and contaminated both Rongelap and Utirik atolls. In 1958, U.S. authorities grew concerned about a possible ban on above-ground nuclear experiments and accelerated testing. A final 33 bombs were detonated between April 28 and Aug. 18. One test shot, Quince, misfired Aug. 6, 1958, and sprayed plutonium fuel across Runit Island. The Department of Defense and the Lawrence Livermore National Laboratory, which was sponsoring the test, ordered soldiers into the contaminated ground zero to prepare the site for the next bomb, 12 days later. Soldiers swarmed in with bulldozers and earthmoving equipment, pushing the radioactive soil into big debris piles that they shoved into the lagoon, the ocean or possibly left alone; government reports differ on these details. What is clear, and which has never been reported before, is that 130 tons of soil transported 5,300 miles from an atomic test site in Nevada was dumped into a 30-foot-wide, 8-foot-deep “conical plug” where the next bomb, Fig, was detonated. Archived documents suggest the soil was used as part of an experiment, to help scientists understand how soil types contribute to different blast impacts and crater sizes. Terry Hamilton, a researcher at the Lawrence Livermore National Laboratory and today the Department of Energy’s point person on the Marshall Islands’ nuclear issues, said the soil was clean and taken from Area 10 at the Nevada Test Site. That area of the Nevada site had been the site of two nuclear blasts in 1951 and 1955, according to government records. “It is appalling that the Marshallese people, and in particular the people of Enewetak, are just learning about this for the first time,” said Sen. Ading, the Marshallese minister of justice, immigration and labor. A decade later, in 1968, teams from the Department of Defense set up a new experiment. This time, they were testing biological weapons — bombs and missiles filled with bacteria designed to fell enemy troops. According to a 2002 military fact sheet and Ed Regis, the author of “The Biology of Doom,” U.S. government scientists came to Enewetak with “their boats and monkeys, space suits and jet fighter planes” and then sprayed clouds of biologically enhanced staphylococcal enterotoxin B, an incapacitating biological agent known to cause toxic shock and food poisoning and considered “one of the most potent bacterial superantigens.” The bacteria were sprayed over much of the atoll — with ground zero at Lojwa Island, where U.S. troops were stationed 10 years later for the cleanup of the atoll. According to military documents, the weapons testers concluded a single weapon could cover 926.5 square miles — roughly twice the size of modern-day Los Angeles — and produce a 30% casualty rate. Records of the test, including a two-volume, 244-page account of operation “Speckled Start,” as it was called, are still classified, according to the Defense Technical Information Center, a branch of the Department of Defense.

The Runit Dome shows signs of aging and weathering. Trapezoidal sections of the concrete cap are cracked; vines and foliage snake up its sides. At its base, pools of brown brackish water are filled with chunks of concrete that have chipped off over the years.

Today, 40 years after it was constructed, the Tomb resembles an aged, neglected and slightly diminutive cousin of the Houston Astrodome. Spiderweb cracks whipsaw across its cap and chunks of missing concrete pock its facade. Pools of brown, brackish water surround its base, and vines and foliage snake up its sides. The Tomb, which was built atop an unlined crater created by a U.S. nuclear bomb, was designed to encapsulate the most radioactive and toxic land-based waste of the U.S. testing programs in Enewetak Atoll. This included irradiated military and construction equipment, contaminated soil and plutonium-laced chunks of metal pulverized by the 43 bombs detonated in this 2.26-square-mile lagoon, according to U.S. government documents. It took 4,000 U.S. servicemen three years to scoop up 33 Olympic-sized swimming pools’ worth of irradiated soil and two Olympic swimming pools’ worth of contaminated debris from islands across the atoll and dump it into the crater on Runit Island. Much of it was mixed in a slurry of concrete and poured into the pit, which was eventually capped with a concrete dome. Six men died during the cleanup; hundreds of others developed radiation-induced cancers and maladies that the U.S. government has refused to acknowledge, according to news reports. Rising seas could unseal a toxic tomb More than 3.1 million cubic feet of radioactive material lie within a bomb crater that was capped with an 18-inch-thick cover on Runit Island. What is underneath the dome Contaminated debris and soil left behind by 43 nuclear bombs detonated in Enewetak Atoll were cemented and enclosed in a crater from one of the nuclear tests. The dome, constructed in the late ’70s, is showing signs of decay. If it crumbles, its radioactive contents will be released into the lagoon and ocean. Department of Defense, Lawrence Livermore National Laboratory “It’s like they say in the Army,” said Bob Retmier, a retired Huntington Beach-based electrician who did two six-month tours of duty at the dome in 1977 and 1978. “They treat us like mushrooms: They feed us crap and keep us in the dark.” Retmier, who was in Enewetak with Company C, 84th Engineer Battalion out of Schofield Barracks, Hawaii, said he didn’t know he had been working in a radioactive landscape until he read about the dome in The Times this year. “They had us mixing that soil into cement,” he said. “There were no masks, or respirators, or bug suits, for that matter. My uniform was a pair of combat boots, shorts and a hat. That was it. No shirt. No glasses. It was too hot and humid to wear anything else.” According to unclassified military documents, the completion of the dome fulfilled “a moral obligation incurred by the United States.” Marshallese officials say they were never told that U.S. authorities had doubts about the long-term integrity of the dome to safely store waste. According to a 1981 military document chronicling the construction of the dome, U.S. government officials met Feb. 25, 1975, to discuss various cleanup options — including ocean dumping and transporting the waste back to the U.S. mainland. Many “of those present seemed to realize that radioactive material was leaking out of the crater even then and would continue to do so,” the document reported. But because the other options were so expensive, they settled on the dome and relied on military personnel to do the cleaning instead of contractors. At that meeting, a top Pentagon official was asked what would happen if the dome failed and who would be responsible. “It would be the responsibility of the United States,” said Lt. Gen. Warren D. Johnson of the U.S. Air Force, who was directing the cleanup process through the Defense Nuclear Agency. Documents show that as construction teams were finishing the dome by capping it with an 18-inch concrete cover, new, highly contaminated debris was discovered. In the process of adding that material to the waste site, parts of the concrete top were embedded with contaminated metallic debris. “It was sloppy,” said Paul Griego, who worked as a contract radiochemist for Eberline Instruments in Enewetak while the military built the dome. The authors of the report noted that because the dome was “designed to contain material and prevent erosion rather than act as a radiation shield,” the radioactive material in the dome cover was no cause for concern. Today, U.S. officials maintain that the dome has served its “intended purpose” — to hold garbage, not necessarily to be a radiation shield. That distinction, though, is not well understood in the Marshall Islands, where many assumed the United States built the dome to protect them. “My understanding from day one is that the dome was to shield the radiation from leaking out,” Ading said. Soon after the dome was completed, the winter tides washed more than 120 cubic yards of radioactive debris onto Runit’s shores, prompting U.S. authorities to build a small antechamber adjacent to the dome to hold the new “red-level” debris. When more debris washed up, they built a second, smaller antechamber. Then they left.

Off the island of Ebeye, children play on an old sunken ship, with the U.S. military base on Kwajalein Island in the background.

The U.S. scientific expert on Runit Dome is Hamilton, the Energy Department contractor. He began working on radiation issues nearly three decades ago and is widely respected among nuclear scientists and physicists. In 2012, Hamilton called the waste site a highly radioactive “point source” whose construction was “not consistent” with U.S. Nuclear Regulatory Commission regulations. He also suggested it could possibly release more plutonium into the surrounding environment. “Any increases in availability of plutonium will have an impact on food security reserves for the local population,” he wrote with two Lawrence Livermore National Laboratory coauthors, noting a “growing commercial export market” for sea cucumbers in the lagoon. In more recent years, Hamilton’s message has changed: The islands are safe, U.S. researchers are monitoring the situation, and no one should be concerned. At a May meeting in Majuro, he told an audience of Marshallese dignitaries, politicians and U.S. officials that the Tomb was bobbing with the tides, sucking in and flushing out radioactive water into the lagoon. Moreover, he said, its physical integrity is “vulnerable to leakage and the sustained impacts of storm surge and sea level rise.” But Hamilton went on to assure them such a scenario was not cause for alarm. Enewetak lagoon is already so contaminated, he said, that any added radiation introduced by a dome failure would be virtually undetectable — in the lagoon, or in the wider ocean waters. Hamilton has said that his assessment is based on a sampling of U.S. documents from the 1970s and 1980s suggesting that there is far more contamination in Enewetak lagoon than remains inside the dome. He contends the land is safe for habitation and will remain so, even if the dome crumbles and releases its contents into the contaminated lagoon. Plutonium is a risk to human health only when it is airborne or introduced via a cut in the skin, Hamilton said. The plutonium in the lagoon, he claims, is not a concern. “Under existing living conditions, there is no radiological basis why I or anyone else should be concerned about living on Enewetak,” Hamilton said in an email, reflecting a position that other experts find perplexing. “That’s crazy,” said Holly Barker, a University of Washington anthropologist who serves on the Marshall Islands nuclear commission. The whole point of building the Tomb, she said, was to clean up contamination left behind by the U.S. testing programs. “Does that mean they didn’t clean it up?” she asked. Asked about his contradictory messages, Hamilton wrote in an email that his earlier assessment was “put forward to help provide a scientific justification” for securing funding and time for a more thorough analysis of the dome. “People living on Enewetak do not show elevated levels of plutonium in their bodies,” he said, discounting concerns. “This is the ultimate test.” To many, Hamilton’s most recent position is just another case of the United States moving the goal posts in the Marshall Islands: It promised a thorough cleanup, only to backtrack in the face of new revelations or costs. Griego, the radiochemist and the New Mexico state commander of the National Assn. of Atomic Veterans, notes that when Hamilton wrote a report for the Department of Energy in 2013 stating that catastrophic failure of the dome would be inconsequential, the report included a mission statement that cast doubt on its scientific integrity. According to the document, the report’s purpose was to “address the concerns of the Enewetak community” and “help build public confidence in the maintenance of a safe and sustainable resettlement program on Enewetak Atoll.” Griego worked as a contractor in Enewetak in 1978. “I saw the water rising and falling as we filled that dome. I know that limestone is porous. And I know how sick people got,” Griego said. “That dome is dangerous. And if it fails, it’s a problem.”

Josephine Noka walks with her son Jules, 6, from Ejit Island to Majuro during low tide. Bikini refugees and their descendants moved to Ejit after being forced to leave their islands because of nuclear testing conducted by the U.S. government. They are still unable to return home.

Climate scientists have been nearly unanimous about one thing: The waters around the Marshall Islands are rising — and growing warmer. On an August day a year ago, tens of thousands of dead fish washed up on the ocean side of Bikini Atoll. Dick Dieke Jr., one of seven temporary caretakers working for a Department of Energy contractor there, recalls the water being uncomfortable. “It didn’t feel good to put my feet in it,” he said. “It was too hot.” Earlier that day, the typically crystalline and azure waters of the Bikini lagoon, near Nam Island, were cloudy and brown. Sea turtles, reef fish and rays swam slowly through the murk, appearing suddenly out of the cloudy bloom only to disappear just as quickly. Dive computers showed 92-degree temperatures 30 feet below the surface in the lagoon, an area usually no warmer than 86 degrees in August. It is impossible to say exactly what caused that day’s massive algae bloom and fish kill, but scientists say such marine incidents will occur more frequently as oceans warm from climate change. “I’ve never seen or heard of a fish kill in Bikini,” Jack Niedenthal, the Marshall Islands’ secretary of health and human services, said in an interview last summer, just a week after the event. “That’s surprising and deeply upsetting.” Just a few years ago, the northern Marshall Islands were known for their pristine coral reefs, little disturbed by human contact, in part because many of these isles were radiation no-go zones. But during a visit last year, The Times saw vast expanses of bleached and dead coral around Bikini Atoll, a finding that surprised some familiar with the region. Thousands of dead fish — including black angelfish and a red snapper — mark the high-tide line of Bikini Island in August 2018 after record high temperatures. Healthy coral has subtle earthy tones. Brighter fluorescent tones indicate heat stress. The purple tips of this coral show signs of stress. Elora López, a Stanford University doctoral student, accompanied a PBS documentary film team in 2016 to Bikini Atoll to collect coral samples. The reefs — hundreds of miles from the nearest tourist — were healthy. But when she returned in 2018, using GPS coordinates to find the same location, all of the corals were dead. Since 1993, sea levels have risen about 0.3 inches a year in the Marshall Islands, far higher than the global average of 0.11 to 0.14 inches. Studies show sea levels are rising twice as fast in the western Pacific than elsewhere. Based on forecasts by the Intergovernmental Panel on Climate Change, sea levels could rise 4 to 5 feet by the end of the century, submerging most of the Marshall Islands. Even if seas rose just half that, said Curt Storlazzi, a geoengineer at the United States Geological Survey, the islands would be in trouble — damaging infrastructure and contaminating most groundwater reserves. “We have a lot of difficult choices to make,” James Matayoshi, the mayor of Rongelap Atoll, said in a September interview. “If the seas don’t stop rising, we’re going to lose some places. Assuming we can save some, we’ll have to decide which islands, which places, for which people. But who gets to do that?” The thought of abandoning their homeland is unthinkable for many Marshallese, the nation’s president said. “Many of our people … want to stay here,” Heine said. “For us, for these people, land is a critical part of our existence. Our culture is based on our land. It is part of us. We cannot think about abandoning the land.” Outbreaks of certain diseases in the Pacific also have been linked to climate change. The Republic of the Marshall Islands is fighting the largest outbreak of dengue fever in its recorded history — more than 1,000 people have been infected, with the outer atolls quarantined to prevent the spread of disease among people with no access to hospital care. “Most people talk about rising sea levels when it comes to climate change,” said Niedenthal, the health secretary. “Even more immediate and devastating is what has been happening with disease outbreaks. This is the worst outbreak in Pacific history.”

Job Atlaia works on building a sea wall on the northwest end of Majuro. The government project is designed to hold back flooding caused by king tides and sea level rise.