Science
2024 Brought the World to a Dangerous Warming Threshold. Now What?
Source: Copernicus/ECMWF
Note: Temperature anomalies relative to 1850-1900 averages.
At the stroke of midnight on Dec. 31, Earth finished up its hottest year in recorded history, scientists said on Friday. The previous hottest year was 2023. And the next one will be upon us before long: By continuing to burn huge amounts of coal, oil and gas, humankind has all but guaranteed it.
The planet’s record-high average temperature last year reflected the weekslong, 104-degree-Fahrenheit spring heat waves that shuttered schools in Bangladesh and India. It reflected the effects of the bathtub-warm ocean waters that supercharged hurricanes in the Gulf of Mexico and cyclones in the Philippines. And it reflected the roasting summer and fall conditions that primed Los Angeles this week for the most destructive wildfires in its history.
“We are facing a very new climate and new challenges, challenges that our society is not prepared for,” said Carlo Buontempo, director of the Copernicus Climate Change Service, the European Union monitoring agency.
But even within this progression of warmer years and ever-intensifying risks to homes, communities and the environment, 2024 stood out in another unwelcome way. According to Copernicus, it was the first year in which global temperatures averaged more than 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, above those the planet experienced at the start of the industrial age.
For the past decade, the world has sought to avoid crossing this dangerous threshold. Nations enshrined the goal in the 2015 Paris agreement to fight climate change. “Keep 1.5 alive” was the mantra at United Nations summits.
Yet here we are. Global temperatures will fluctuate somewhat, as they always do, which is why scientists often look at warming averaged over longer periods, not just a single year.
But even by that standard, staying below 1.5 degrees looks increasingly unattainable, according to researchers who have run the numbers. Globally, despite hundreds of billions of dollars invested in clean-energy technologies, carbon dioxide emissions hit a record in 2024 and show no signs of dropping.
One recent study published in the journal Nature concluded that the absolute best humanity can now hope for is around 1.6 degrees of warming. To achieve it, nations would need to start slashing emissions at a pace that would strain political, social and economic feasibility.
But what if we’d started earlier?
By spewing heat-trapping gases into the atmosphere, humankind has lifted global temperatures to record highs.
If nations had started reducing emissions in 2005, they could have made gradual cuts to limit warming to 1.5 degrees.
Starting in 2015, when the Paris agreement was adopted, would have required steeper cuts.
Starting today would require cuts so drastic as to appear essentially impossible.
“It was guaranteed we’d get to this point where the gap between reality and the trajectory we needed for 1.5 degrees was so big it was ridiculous,” said David Victor, a professor of public policy at the University of California, San Diego.
The question now is what, if anything, should replace 1.5 as a lodestar for nations’ climate aspirations.
“These top-level goals are at best a compass,” Dr. Victor said. “They’re a reminder that if we don’t do more, we’re in for significant climate impacts.”
The 1.5-degree threshold was never the difference between safety and ruin, between hope and despair. It was a number negotiated by governments trying to answer a big question: What’s the highest global temperature increase — and the associated level of dangers, whether heat waves or wildfires or melting glaciers — that our societies should strive to avoid?
The result, as codified in the Paris agreement, was that nations would aspire to hold warming to “well below” 2 degrees Celsius while “pursuing efforts” to limit it to 1.5 degrees.
Even at the time, some experts called the latter goal unrealistic, because it required such deep and rapid emissions cuts. Still, the United States, the European Union and other governments adopted it as a guidepost for climate policy.
Christoph Bertram, an associate research professor at the University of Maryland’s Center for Global Sustainability, said the urgency of the 1.5 target spurred companies of all kinds — automakers, cement manufacturers, electric utilities — to start thinking hard about what it would mean to zero out their emissions by midcentury. “I do think that has led to some serious action,” Dr. Bertram said.
But the high aspiration of the 1.5 target also exposed deep fault lines among nations.
China and India never backed the goal, since it required them to curb their use of coal, gas and oil at a pace they said would hamstring their development. Rich countries that were struggling to cut their own emissions began choking off funding in the developing world for fossil-fuel projects that were economically beneficial. Some low-income countries felt it was deeply unfair to ask them to sacrifice for the climate given that it was wealthy nations — and not them — that had produced most of the greenhouse gases now warming the world.
“The 1.5-degree target has created a lot of tension between rich and poor countries,” said Vijaya Ramachandran, director for energy and development at the Breakthrough Institute, an environmental research organization.
Costa Samaras, an environmental-engineering professor at Carnegie Mellon University, compared the warming goals to health officials’ guidelines on, say, cholesterol. “We don’t set health targets on what’s realistic or what’s possible,” Dr. Samaras said. “We say, ‘This is what’s good for you. This is how you’re going to not get sick.’”
“If we were going to say, ‘Well, 1.5 is likely out of the question, let’s put it to 1.75,’ it gives people a false sense of assurance that 1.5 was not that important,” said Dr. Samaras, who helped shape U.S. climate policy from 2021 to 2024 in the White House Office of Science and Technology Policy. “It’s hugely important.”
Scientists convened by the United Nations have concluded that restricting warming to 1.5 degrees instead of 2 would spare tens of millions of people from being exposed to life-threatening heat waves, water shortages and coastal flooding. It might mean the difference between a world that has coral reefs and Arctic sea ice in the summer, and one that doesn’t.
Each tiny increment of additional warming, whether it’s 1.6 degrees versus 1.5, or 1.7 versus 1.6, increases the risks. “Even if the world overshoots 1.5 degrees, and the chances of this happening are increasing every day, we must keep striving” to bring emissions to zero as soon as possible, said Inger Anderson, the executive director of the United Nations Environment Program.
Officially, the sun has not yet set on the 1.5 target. The Paris agreement remains in force, even as President-elect Donald J. Trump vows to withdraw the United States from it for a second time. At U.N. climate negotiations, talk of 1.5 has become more muted compared with years past. But it has hardly gone away.
“With appropriate measures, 1.5 Celsius is still achievable,” Cedric Schuster, the minister of natural resources and environment for the Pacific island nation of Samoa, said at last year’s summit in Azerbaijan. Countries should “rise to the occasion with new, highly ambitious” policies, he said.
To Dr. Victor of U.C. San Diego, it is strange but all too predictable that governments keep speaking this way about what appears to be an unachievable aim. “No major political leader who wants to be taken seriously on climate wants to stick their neck out and say, ‘1.5 degrees isn’t feasible. Let’s talk about more realistic goals,’” he said.
Still, the world will eventually need to have that discussion, Dr. Victor said. And it’s unclear how it will go.
“It could be constructive, where we start asking, ‘How much warming are we really in for? And how do we deal with that?’” he said. “Or it could look very toxic, with a bunch of political finger pointing.”
Methodology
The second chart shows pathways for reducing carbon emissions that would have a 66 percent chance of limiting global warming this century to 1.5 degrees Celsius above the preindustrial average.
The Los Angeles County Department of Public Health is investigating a confirmed measles case in a resident who recently traveled internationally, the agency said in a release Saturday.
This is the fifth measles case identified by the county this year as outbreaks increase across the U.S. and globally.
The infected resident arrived at the Los Angeles International Airport on Thursday on Alaska Airlines Flight 1354. Other travelers at Tom Bradley International Terminal B that day between 6 a.m. and 8 a.m. may have been exposed to the virus, officials said.
Public health officials are advising residents to check their immunization status and watch for symptoms if exposed. The measles-mumps-rubella vaccine is the most effective protection from measles, according to the public health department.
“As measles cases increase, it is important that residents take steps to make sure they are fully protected,” L.A. County Health Officer Muntu Davis said in a statement. “The MMR vaccine is the safest and most reliable way to prevent measles and protect yourself, your family, and your community.”
In coordination with the federal Centers for Disease Control and Prevention, L.A. County Public Health will notify travelers seated near the infected person on the flight.
Affected travelers are at risk of developing measles from seven to 21 days after exposure to the virus. Symptoms include rash, fever, cough and red, watery eyes.
Measles can lead to complications including pneumonia, brain swelling and even death. Those with symptoms should notify their healthcare facility before visiting, officials said.
So far this year, 1,814 measles cases have been confirmed nationwide, including 48 in California.
In January, health officials recorded the most amount of cases since the U.S. achieved elimination of the virus in 2000.
Archaeologists working in Egypt have discovered a remarkable combination of Homeric epic and Egyptian ritual: a 2,000-year-old mummy with a papyrus fragment of the “Iliad” sealed in a clay packet outside its wrappings.
It is the first time a literary work has been found playing a functional, spiritual role in the mummification process. And it suggests that for a Roman-era Egyptian, the “Iliad” — specifically some lines from Book 2’s “Catalogue of Ships” — was perhaps as crucial for navigating the afterlife as a magical spell.
“The find is incredibly significant, primarily for the discovery of such a papyrus with Greek literary text in its original context,” said Foy Scalf, an Egyptologist at the University of Chicago. “We have evidence that such Greek literary texts could be used as magical amulets and that Homer was frequently cited in such amulets, as well as in the large handbooks now known as ‘The Greco-Egyptian Formularies.’ The new find directly supports that indirect knowledge.”
The mummy, a nonroyal male, was unearthed by the Mission of the University of Barcelona at a burial site known as Oxyrhynchus, as part of a project directed by Ignasi-Xavier Adiego of the university’s Institute of Ancient Near East. Leah Mascia, a specialist in the written and material culture of Greco-Roman and Late Antique Egypt at the Free University of Berlin, coordinated the collaborative breakthrough that finally brought the damaged text to light.
Recognizing that the heavily degraded papyrus required careful analysis, Dr. Mascia worked with a conservator, Margalida Munar, to stabilize the artifact, and Dr. Adiego, an authority on the Carian language, to study the text. Together, their combined expertise in preservation and linguistics allowed them to identify and read the document.
After six years of painstakingly reconstructing tomb fragments, Dr. Mascia uncovered a rare moment of cultural alchemy: Roman Egypt, where foreign and local customs merged. Her analysis, which identified embalmer seals and folding patterns of the papyrus packet, suggests that classical Greek epics were not merely read but physically repurposed.
Traditionally, mummified bodies were buried with sepulchral texts like the “Book of the Dead” and “The Book of Breathing,” formulaic manuals intended to protect and guide the deceased through the underworld. Yet, by the early Roman period, a major shift emerged: the introduction of sealed papyrus packets placed upon the dead.
These new packets contained a surprising mix of texts, including Greco-Egyptian magic, documentary records and even literary works like the “Iliad,” indicating a personalized, alternative funerary practice.
Out of the dumps
The Oxyrhynchus necropolis, located near the modern village of El-Bahnasa about 120 miles south of Cairo, is not just a burial site but an archaeological mother lode. Located on the banks of the Bahr Yussef canal, the area is speckled with ancient garbage dumps that managed to preserve everything from wedding invitations and tax records to horoscopes and early Christian gospels.
The ruins of Oxyrhynchus were initially documented by Vivant Denon, a scholar during Napoleon’s 1798 Egyptian campaign. But they held a secret that remained buried for an additional century, until 1896, when British archaeologists dug up more than 400,000 fragments of papyri from the ancient trash heaps. The discoveries ultimately included lost masterworks by poets and playwrights like Sappho and Euripides, transforming millenniums-old refuse into a cornerstone of classical literature.
In the 1990s, the Mission of the University of Barcelona and the University of Cairo began a joint project largely funded by the Spanish Ministry of Culture and the Egyptian Ministry of Tourism and Antiquities. This ongoing mission, directed by Maite Mascort i Roca and Esther Pons Mellado and staffed by archaeologists, epigraphists and papyrologists, focuses on various sectors of the necropolis, including No. 22, where experts are reconstructing the elaborate social and religious life of residents during the transition from the Ptolemaic to the Roman era.
Researchers exploring the multichambered burial site have exhumed a remarkable trove of treasures, among them mummies adorned with golden tongues — gold foil placed over the mouth — and at least one with copper, ritualistic additions that may have ensured that the dead could confidently speak their case to Osiris, the god of death and resurrection, before judgment.
A separate, distinct area of the necropolis — Sector 42 — has yielded large jars containing cremated remains. One vessel held the bones of an adult, an infant and a feline, along with fabric fragments. While these individuals most likely date to a slightly different period from the “Iliad” mummy, the immense complexity of these rites implies a wealthy, status-conscious class, providing fresh insight into the spiritual anxieties of the Roman-era community.
A cultural passport
Recovered in December from Tomb 65, the fragmentary papyrus packet contains a passage from the 2,800-year-old “Iliad” that functions as a detailed inventory of the Achaean army’s naval strength and regional origins, describing the forces arrayed against Troy to retrieve Helen. The text mentions specific commanders, such as Guneus, who arrived with “two and twenty ships from Cyphus,” and Tlepolemus, a “son of Hercules” who brought nine ships from Rhodes.
Dr. Mascia’s findings reveal a deliberate, intimate act: a document prepared in a mummification workshop and placed directly upon the body of the deceased. “These sealed papyrus packets may have been regarded as part of an alternative funerary procedure,” she said, adding that further studies were essential to prove this hypothesis.
This spiritual first-aid follows a long tradition. Dr. Scalf noted that “The Greco-Egyptian Formularies” even suggests the “Iliad” doubled as a literal medical kit. For a bed-bound patient shivering with malaria, the prescription was simple: Brace your head against a papyrus scroll of Book 4 to break the fever.
For residents navigating the complex, vibrant crossroads of Roman Egypt, Greek literary papyri may have functioned as a crucial cultural passport, said Anna Dolganov, a historian at the Austrian Archaeological Institute. In Egypt, being Hellenic connoted an exclusive social status and financial privilege — and had to be meticulously documented through genealogies going back across several centuries.
Buried with the dead, the “Iliad” perhaps served as a cheat code for a more comfortable afterlife. Dr. Dolganov wonders if carrying the epic poem was a deliberate strategy to secure entry into the Greek underworld, effectively sidestepping the torturous trials of Egyptian mythology. For these individuals, a Hellenic identity wasn’t just for this world — it was an eternal upgrade, offering a smoother path and higher status in the great beyond.
Science
Ten times worse than benzene — California updates its science on two chemicals in everyday air
Two toxic contaminants present in California’s ambient air appear to be much stronger carcinogens than previously known, state environmental health officials announced Thursday.
The draft finding from the state’s Office of Environmental Health Hazard Assessment finds that acrolein and ethylene oxide may pose an estimated cancer risk more than 10 times higher than benzene, a serious carcinogen linked to leukemia and other cancers.
It is the first step in a review process before final risk values are adopted, and it arrives at a time federal air-quality regulations are being reined in.
“If the early air monitoring results bear out, and if the draft cancer values developed are close to what eventually becomes final, then each air contaminant poses an unacceptable cancer risk,” said Kris Thayer, OEHHA’s director.
The update reflects the state’s evolving understanding of its most dangerous pollutants, which has shifted over the decades from visible pollutants, such as smog, to more invisible ones that cause cancer, heart disease and other health harms.
It comes only two months after the Trump administration’s Environmental Protection Agency moved to roll back standards on ethylene oxide, or EtO, in an effort to save millions of dollars in compliance costs for facilities that use the chemical for medical sterilization. The administration said it acted to “safeguard the supply of essential medical equipment,” but experts said the move will also expose more people to health risks.
It also follows a new national report from the American Lung Assn. that found 82% of Californians live in counties with unhealthful air, nearly double the national average.
“This is an important step to better understanding the harms of pollutants impacting Californians’ health,” said Will Barrett, assistant vice president for nationwide clean air policy at the American Lung Assn., who reviewed the state’s findings for The Times. “Following the latest available health science to determine risk is crucial to protecting health.”
Ethylene oxide is a colorless gas often used in the sterilization of medical devices, particularly those that can’t be cleaned using steam or radiation.
Acrolein can be formed when materials burn, such as cigarettes, e-cigarettes and vapes, wood, plastics and gasoline for cars, trucks, ships and aircraft. It can also be released by cooking fats and oils at high temperatures, and has been found in water produced by oil and gas operations and is an ingredient in some pesticides used in irrigation canals.
People can take steps to protect themselves from acrolein exposure in everyday life by avoiding smoking tobacco or using e-cigarettes and vaping products, avoiding smoke from fires or exhaust from diesel and gasoline vehicles and equipment — much of which can also help reduce exposure to ethylene oxide, officials said. When cooking with oils or fats, people should avoid very high temperatures and use a range hood fan when possible.
While both chemicals have been present in the state’s air for years, the new assessments from OEHHA are based on the latest science on health risks, officials said. Both acrolein and ethylene oxide were found to pose an estimated cancer risk exceeding 800 in 1 million — on par with the cancer risk that diesel exhaust was estimated to pose when it first emerged as a major public health concern in the 1990s, the agency said.
In response to the findings, Gov. Gavin Newsom’s May budget revision, released Thursday, includes $2.5 million in funding for the California Air Resources Board and OEHHA in support of research to help reduce people’s exposure to acrolein and ethylene oxide. The funding will help the state identify and track major sources of the chemicals and turn the findings into public health policy outcomes, officials said.
OEHHA’s assessment provides the first cancer risk value for acrolein since it was classified as probably cancer-causing to humans by the International Agency for Research on Cancer in 2020. Ethylene oxide was already identified as a carcinogen by the state, but the new assessment updates its risk levels based on the new research. The risk calculations are based on air monitoring data, which vary across the state depending on location, nearby sources and other factors.
Officials said the findings underscore the state’s efforts to strengthen environmental protection measures for residents at a moment when federal officials seek to loosen them.
“Especially in light of some of the national rollbacks we’re seeing on protections for public health, it really underscores how important the work that we’re doing here in California is,” said Courtney Smith, principal deputy executive officer with the Air Resources Board. “Not only for protecting the health of Californians, but also to ensure that there is rigorous, solid science available to other entities as well who may want to pursue additional protections.”
Short-term exposure to EtO by inhalation can cause headaches, dizziness, nausea, fatigue respiratory irritation and other adverse health effects, according to the federal Agency for Toxic Substances and Disease Registry. Longer-term exposure increases the risk of cancers of the white blood cells, such as non-Hodgkin’s lymphoma, as well as breast cancer.
Inhaling acrolein can cause nose and throat irritation and a decreased breathing rate. Chronic exposure, such as through cigarette smoke, has been linked to the development of asthma, chronic obstructive pulmonary disease and respiratory cancers.
The findings also come as California continues to receive poor grades on air quality. The American Lung Assn. annual State of the Air report found that the five U.S. counties with the worst smog pollution are all in California. Bakersfield was the metropolitan area with the worst level of year-round particle pollution for the seventh year in a row, while Los Angeles was the city with the worst ozone pollution, as it has been for 26 of the last 27 years.
“Californians face the most significant smog and soot challenges in the nation, but our air agencies have followed the science to build policies and programs to make real headway,” Barrett said. The state’s latest assessment “speaks to the need for ongoing local efforts while the federal government ignores the science and opens the door for more pollution. California must continue to invest in things like cleaning up truck fleets, broader public education and the underlying science to guide policies to protect health.”
Thursday’s announcement kicks off a 45-day public comment period, after which the draft assessments may be revised before undergoing additional public comment, peer review by the state’s Scientific Review Panel on Toxic Air Contaminants, and eventual adoption.
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