Science
Carbon Dioxide Levels Have Passed a New Milestone
Source: National Oceanic and Atmospheric Administration’s Global Monitoring Laboratory
The chart shows monthly numbers of carbon dioxide molecules per million molecules of dry air. Because of seasonal differences, levels are higher in May than in August.
Carbon dioxide acts like Earth’s thermostat: The more of it in the air, the more the planet warms.
In 2023, global levels of the greenhouse gas rose to 419 parts per million, around 50 percent more than before the Industrial Revolution. That means there are roughly 50 percent more carbon dioxide molecules in the air than there were in 1750.
As carbon dioxide builds up in the atmosphere, it traps heat and warms the planet.
Source: NOAA (carbon dioxide); NASA (temperature)
The chart shows the change in global surface temperature relative to 1951–1980, versus global carbon dioxide levels. The dotted line shows the trend line.
More carbon dioxide, warmer temperatures
Every additional amount of carbon dioxide in the atmosphere contributes to more warming, which is why climate scientists stress the need to get to zero emissions.
Currently, carbon dioxide levels are rising at near-record rates.
According to data released by the National Oceanic and Atmospheric Administration’s Global Monitoring Laboratory earlier this month, last year had the fourth-highest annual rise in global carbon dioxide levels.
Source: NOAA’s Global Monitoring Laboratory The chart shows the increase in global carbon dioxide levels over the course of each year. In 2023, they grew by around 2.8 parts per million.
Annual change in carbon dioxide levels
The long-term rise in carbon dioxide levels is caused by burning fossil fuels, as well as other human activities such as deforestation and concrete production.
But there is also a lot of variation from year to year, which you can see in the chart above.
How much carbon dioxide levels rise in a given year depends on two factors: the amount of fossil fuels burned globally, and the share of these emissions that are absorbed by the land and the ocean.
Consider the first factor: While it’s true that clean energy production is rising globally, so is the demand for energy.
Fossil fuels have made up the difference. This is why global fossil fuel emissions are still at record-high values (with a brief dip during the pandemic). And they stayed high in 2023, according to a projection by the Global Carbon Budget.
Not all of these emissions end up in the air. The ocean and land absorb roughly half of the carbon dioxide that humans emit, while the rest stays in the air, said Glen Peters, a senior researcher at the CICERO Center for International Climate Research.
Source: Global Carbon Budget The chart shows the net amounts of carbon dioxide emissions absorbed by the atmosphere, land and ocean. The emissions are produced by burning fossil fuels, deforestation and other human activities. Data does not include 2023.
Where do carbon dioxide emissions go?
That one-half figure is an approximation. It varies from year to year depending on weather conditions and other environmental factors, resulting in the jagged lines you see in the chart above. For example, in a warm and dry year with many wildfires, the land may absorb less carbon dioxide than usual.
As the Earth warms further, climate scientists expect the land and the ocean to absorb a smaller share of carbon dioxide emissions, causing a larger share to end up in the air, said Doug McNeall, who studies these effects at Britain’s Met Office.
Xin Lan, the lead scientist responsible for NOAA’s global carbon dioxide measurements, referred to the natural absorption as a “carbon discount.”
“We pay attention to it because we don’t know at which point that this discount is gone,” she said.
In addition to carbon dioxide, the levels of other potent greenhouse gases like methane and nitrous oxide are also on the rise, which further contribute to warming.
An exceptional year
2023 was unusually hot, both on land and in the ocean. (The oceans absorb over 90 percent of the excess heat caused by global warming.) It was the hottest year in over 170 years of record keeping, even exceeding scientists’ predictions.
One contributing factor to 2023’s extreme heat was El Niño, a climate pattern that tends to raise global temperatures. During El Niño, warm ocean currents in the Pacific Ocean cause warmer and drier weather in the tropics. This can lead to droughts that slow the growth of trees and increase the risk of wildfires.
When this happens, the land tends to absorb less carbon dioxide, and more of it ends up in the air. Several climate scientists said this may be why last year’s rise in carbon dioxide levels was substantially higher than in the years preceding it.
Getting to zero
The current high emissions levels make the climate goal of limiting global warming to 1.5 degrees Celsius increasingly difficult to reach.
To limit warming to this threshold, experts say countries need to slam the brakes on global emissions and bring them down to near-zero in about a decade. And some are even considering more extreme technological solutions to help bridge the gap.
Even if global emissions were brought down to half of their current value, we would still continue to add carbon dioxide to the air, causing further warming.
“You need to bring them essentially down to zero in order to stop warming,” Mr. McNeall said.
How much more warming will occur depends on how long it takes for this to happen.
On one hand, clean energy investments are booming, and renewable energy production is rising globally. But energy demand is also projected to rise, coal power plants are still being built, and some sectors of the economy — like construction and manufacturing — are harder to decarbonize, making the task ahead a steep challenge.
Even if the world exceeds the 1.5-degree threshold, “every fraction of a degree matters,” Mr. McNeall said.
“The closer that you can get to that threshold, the better.”
About the data
NOAA’s annual global carbon dioxide measurements are an average of thousands of measurements made near sea level at about 30 locations around the world. To account for local differences in humidity, measurements are made using dry air.
Science
What’s in a Name? For These Snails, Legal Protection
The sun had barely risen over the Pacific Ocean when a small motorboat carrying a team of Indigenous artisans and Mexican biologists dropped anchor in a rocky cove near Bahías de Huatulco.
Mauro Habacuc Avendaño Luis, one of the craftsmen, was the first to wade to shore. With an agility belying his age, he struck out over the boulders exposed by low tide. Crouching on a slippery ledge pounded by surf, he reached inside a crevice between two rocks. There, lodged among the urchins, was a snail with a knobby gray shell the size of a walnut. The sight might not dazzle tourists who travel here to see humpback whales, but for Mr. Avendaño, 85, these drab little mollusks represent a way of life.
Marine snails in the genus Plicopurpura are sacred to the Mixtec people of Pinotepa de Don Luis, a small town in southwestern Oaxaca. Men like Mr. Avendaño have been sustainably “milking” them for radiant purple dye for at least 1,500 years. The color suffuses Mixtec textiles and spiritual beliefs. Called tixinda, it symbolizes fertility and death, as well as mythic ties between lunar cycles, women and the sea.
The future of these traditions — and the fate of the snails — are uncertain. The mollusks are subject to intense poaching pressure despite federal protections intended to protect them. Fishermen break them (and the other mollusks they eat) open and sell the meat to local restaurants. Tourists who comb the beaches pluck snails off the rocks and toss them aside.
A severe earthquake in 2020 thrust formerly submerged parts of their habitat above sea level, fatally tossing other mollusks in the snail’s food web to the air, and making once inaccessible places more available to poachers.
Decades ago, dense clusters of snails the size of doorknobs were easy to find, according to Mr. Avendaño. “Full of snails,” he said, sweeping a calloused, violet-stained hand across the coves. Now, most of the snails he finds are small, just over an inch, and yield only a few milliliters of dye.
Science
Video: This Parrot Has No Beak, But Is at the Top of the Pecking Order
new video loaded: This Parrot Has No Beak, But Is at the Top of the Pecking Order
By Meg Felling and Carl Zimmer
April 20, 2026
Science
Contributor: Focus on the real causes of the shortage in hormone treatments
For months now, menopausal women across the U.S. have been unable to fill prescriptions for the estradiol patch, a long-established and safe hormone treatment. The news media has whipped up a frenzy over this scarcity, warning of a long-lasting nationwide shortage. The problem is real — but the explanations in the media coverage miss the mark. Real solutions depend on an accurate understanding of the causes.
Reporters, pharmaceutical companies and even some doctors have blamed women for causing the shortage, saying they were inspired by a “menopause moment” that has driven unprecedented demand. Such framing does a dangerous disservice to essential health advocacy.
In this narrative, there has been unprecedented demand, and it is explained in part by the Food and Drug Administration’s recent removal of the “black-box warning” from estradiol patches’ packaging. That inaccurate (and, quite frankly, terrifying) label had been required since a 2002 announcement overstated the link between certain menopause hormone treatments and breast cancer. Right-sizing and rewording the warning was long overdue. But the trouble with this narrative is that even after the black-box warning was removed, there has not been unprecedented demand.
Around 40% of menopausal women were prescribed hormone treatments in some form before the 2002 announcement. Use plummeted in its aftermath, dipping to less than 5% in 2020 and just 1.8% in 2024. According to the most recent data, the number has now settled back at the 5% mark. Unprecedented? Hardly. Modest at best.
Nor is estradiol a new or complex drug; the patch formulation has existed for decades, and generic versions are widely manufactured. There is no exotic ingredient, no rare supply chain dependency, no fluke that explains why women are suddenly being told their pharmacy is out of stock month after month.
The story is far more an indictment of the broken insurance industry: market concentration, perverse incentives and the consequences of allowing insurance companies to own the pharmacy benefit managers that effectively control drug access for the majority of users. Three companies — CVS Caremark, Express Scripts and OptumRx — manage 79% of all prescription drug claims in the United States. Those companies are wholly owned subsidiaries of three insurance behemoths: CVS Health, Cigna and UnitedHealth Group, respectively. This means that the same corporation that sells you your insurance plan also decides which drugs get covered, at what price, and whether your pharmacy can stock them. This is called vertical integration. In another era, we might have called it a cartel. The resulting problems are not unique to hormone treatments; they have affected widely used medications including blood thinners, inhalers and antibiotics. When a low-cost generic such as estradiol — a medication with no blockbuster profit margins and no patent protection — runs into friction in this system, the friction is not random. It is structural. Every decision in that chain is filtered through the same corporate profit motive. And when the drug in question is an off-patent estradiol patch that has negligible profit margins because of generic competition but requires logistical investment to keep consistently in stock? The math on “how much does this company care about ensuring access” is not complicated.
Unfortunately, there is little financial incentive to ensure smooth, consistent access. There is, however, significant financial incentive to steer patients toward branded alternatives, or simply to let supply tighten — because the companies aren’t losing much profit if sales of that product dwindle. This is not a conspiracy theory: The Federal Trade Commission noted this dynamic in a report that documented how pharmacy benefit managers’ practices inflate costs, reduce competition and harm patient access, particularly for independent pharmacies and for generic drugs.
Any claim that the estradiol patch shortage is meaningfully caused by more women now demanding hormone treatments is a distraction. It is also misogyny, pure and simple, to imply that the solution to the shortage is for women’s health advocates to dial it down and for women to temper their expectations. The scarcity of estradiol patches is the outcome of a broken system refusing to provide adequate supply.
Meanwhile, there are a few strategies to cope.
- Ask your prescriber about alternatives. Estradiol is available in multiple formulations, including gel, spray, cream, oral tablet, vaginal ring and weekly transdermal patch, which is a different product from the twice-weekly patch and may be more consistently available depending on manufacturer and region.
- Consider an online pharmacy. Many are doing a good job locating and filling these prescriptions from outside the pharmacy benefit manager system.
- Call ahead. Patch shortages are inconsistent across regions and distributors. A call to pharmacies in your area, or a broader geographic radius if you’re able, can locate stock that your regular pharmacy doesn’t have.
- Consider a compounding pharmacy. These sources can sometimes meet needs when commercially manufactured products are inaccessible. The hormones used are the same FDA-regulated bulk ingredients.
Beyond those Band-Aid solutions, more Americans need to fight for systemic change. The FTC report exists because Congress asked for it and committed to legislation that will address at least some of the problems. The FDA took action to change the labeling on estrogen in the face of citizen and medical experts’ pressure; it should do more now to demand transparency from patch manufacturers.
Most importantly, it is on all of us to call out the cracks in the current system. Instead of repeating “there’s a patch shortage” or a “surge in demand,” say that a shockingly small minority of menopausal women still even get hormonal treatments prescribed at all, and three drug companies control the vast majority of claims in this country. Those are the real problems that need real solutions.
Jennifer Weiss-Wolf, the executive director of the Birnbaum Women’s Leadership Center at New York University School of Law, is the author of the forthcoming book “When in Menopause: A User’s Manual & Citizen’s Guide.” Suzanne Gilberg, an obstetrician and gynecologist in Los Angeles, is the author of “Menopause Bootcamp.”
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