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- The Ends of the Earth

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CLIMATE SCIENCE | VIEW ON WEBSITE

The Ends of the Earth

By Yasemin Saplakoglu

September 15, 2025

Building an accurate model of Earth’s climate requires a lot of data. Photography reveals the extreme efforts scientists have undertaken to measure gases, glaciers, clouds and more.

Mark Belan/Quanta Magazine

CLIMATE SCIENCE

The Ends of the Earth

By Yasemin Saplakoglu

September 15, 2025

Building an accurate model of Earth’s climate requires a lot of data. Photography reveals the extreme efforts scientists have undertaken to measure gases, glaciers, clouds and more.

Introduction

Nearly 170 years ago, a scientist named Eunice Foote discovered a fundamental truth about the gases that surround us. In her home laboratory in New York, she filled one glass cylinder with carbon dioxide and another with regular air, placed a thermometer in each and left them out in the sun. Less than 20 minutes later, the carbon dioxide–filled cylinder was much warmer — and much harder to cool down — than the other one. Foote concluded that carbon dioxide traps heat and theorized that “an atmosphere of that gas would give to our earth a high temperature.” Several years later, the Irish physicist John Tyndall independently confirmed her results, and found that ozone and water vapor also trap heat. These early experiments were the overture to what would become the most monumental — and most frustrating — scientific undertaking ever: understanding, characterizing and modeling Earth’s climate system.

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What started as a simple chemistry experiment has grown to include geologists, physicists, computer scientists, mathematicians, biologists, meteorologists, archaeologists — and eventually climate scientists, a new kind of researcher. They work at desks or in the field, measuring, gathering and computing the astronomical amounts of information needed to understand how Earth’s land, sea, ice, atmosphere and life interact on local, regional and global scales. They’re extracting sediment from the seafloor to uncover ancient climate patterns, diving to track coral survival after heat waves, and flying drones into clouds and volcanoes. Workers at remote stations around the world are continuously tracking temperatures and air composition. Volunteers are documenting changes in bird populations and archaeological sites.

All this data on minerals, molecules, temperatures, ice, currents and more is woven into models, projections and reports. “Climate science has always required, by its very nature, collaboration,” said Andrew Weaver, a climate scientist at the University of Victoria in Canada. “If you sit in your silo, that’s not going to solve anything.”

Together, these efforts have shown us wondrous, surprising, harrowing things. They reveal that we are living in a rare temperate, stable climate period from which human civilization emerged. This window nurtured human creativity, ingenuity and industry, all of which are now driving an unprecedentedly rapid change to Earth’s atmosphere and all it supports. Climate science is also driving new ideas and strategies to compensate for our self-inflicted wounds.

None of this has been easy. Climate scientists have faced not only extreme working conditions, but also antagonistic political movements that reject their findings and attempt to defund their work entirely. Still, the desire to understand the planet compels them to keep putting on their snowsuits, their wet suits, their business suits. It motivates them to climb to the top of tall observatories or live on a piece of floating ice for months at a time. They show up so that polar bears, corals, birds and even the policymakers who resist their discoveries will continue to have a stable climate to live in.

And when they have a second to breathe, surrounded by a lush green forest or white ice as far as the eye can see, they admire the beauty of a planet that they don’t fully understand. Through the haze of doom that shrouds climate science shines the passion behind the quest to understand and solve one of the greatest challenges humanity has faced.

Using his radiant heat apparatus (left), the physicist John Tyndall (right) studied the effect of heat on gases.

Public Domain

“I used to be very pessimistic … but now I am more and more optimistic,” said Billur Bektaş, a plant ecologist at the Swiss Federal Institute of Technology Zurich (ETH Zurich), who is part of an international, interdisciplinary initiative to predict changes to biodiversity in ever-shifting ecosystems. “The collaborative environment of this network has been the hope for me. … I see how people really work toward this aim.”

Quanta has compiled a photographic record of climate science that captures the incalculable labor, dedication and ingenuity needed to acquire and utilize data on Earth’s climate. The effort to build climate science, spanning scientific disciplines and national borders, must surely be the most significant scientific collaboration in human history.

Climbing Into the Canopy

Deep in the remote Amazon rainforest, three lofty towers jut out of the canopy. Collectively known as the Amazon Tall Tower Observatory, they hold devices that take continuous measurements of atmospheric aerosols and greenhouse gases to help scientists understand energy and water cycles in the Amazon and beyond.

Researchers on top of the Amazon Tall Tower Observatory look out over the rainforest.

Phillip Papastefanou/Courtesy of ATTO

Getting to the observatory is no easy feat; it takes half a day’s travel from Manaus, Brazil, across rivers and roads built for this purpose. To reach the top of the tallest tower, 1,000 feet in the air, scientists climb more than 1,500 steps. About a third of the way up, there’s a moment where you feel like you lose contact with the surface below, said Jürgen Kesselmeier, a chemist at the Max Planck Institute for Chemistry and one of the scientists who set up the observatory. At that moment, he said, he feels “not fear, but respect.”

Drilling for Ancient Ice

Buried deep in glaciers and ice sheets lies information about our planet’s ancient climate. In Antarctica, snowfall accumulates in layers that compact into densely-packed snow, known as firn, and then ice. Year after year, these layers trap air bubbles as well as other materials such as volcanic ash or microscopic phytoplankton. Scientists can analyze these ancient samples to infer ocean temperature, sea ice cover or levels of atmospheric gases at different moments across thousands of years.

Or occasionally millions of years. In early 2025, researchers with the Beyond EPICA project in Antarctica extracted a 1.2-million-year-old ice core, the oldest continuous record to date. About a million years ago, during the mid-Pleistocene transition, Earth’s climate changed suddenly. “If we can understand how those kind of rapid changes happened in the past, when it was occurring for natural reasons, we can use that to improve our models predicting what’s going to happen soon here with our human-induced climate change,” said James Veale, an ice core drilling engineer with the British Antarctic Survey.

Scientists temporarily store ice cores in a frozen cave.

©PNRA_IPEV

The drilling site Concordia station in East Antarctica has ice dating back over 800,000 years.

©PNRA_IPEV

Ice cores contain trapped air bubbles that reveal information about ancient climates.

©PNRA_IPEV

Scientists extracted a 1.2-million-year-old ice core, the oldest continuous record to date, from Little Dome C in Antarctica.

©PNRA_IPEV

Drilling in Antarctica is both thrilling and difficult. “The rest of your life just goes on hold. … If something happens at home, there’s nothing you can do to help,” Veale said. “I hesitate to say adventure, because it makes us sound like we’re like the polar explorers of the olden days. It’s not like that anymore. We might be sleeping in tents and it might be very cold, but we have the internet. And when you’re on a project like Beyond EPICA with a bunch of French and Italians around, the food’s actually quite good.”

Conceiving of Clouds

In 2024, a research vessel traveled from the Cape Verde islands off the west coast of Africa, across the tropical Atlantic to Barbados to better understand clouds. Daniel Klocke, a meteorologist at the Max Planck Institute for Meteorology in Germany, and his team with the international Orcestra campaign spent two months collecting data, including surface wind speeds, sea surface temperature and precipitation levels, to unpack how air, seawater and waves work together to transfer heat in a process known as convection, which can generate clouds.

Researchers lower a CTD, or “conductivity, temperature and depth” instrument, to collect water samples.

Joelle Habib/Courtesy of ORCESTRA

Underwater gliders sample ocean conditions such as temperature and shear, which drives turbulence.

Philipp Henning/Courtesy of ORCESTRA

On the boat, “everyone’s focused on the same thing,” Klocke said. “You’re detached from the rest of the world. You’re working and enjoying life in the same place.” But even out in the middle of the Atlantic Ocean, they weren’t alone. Every couple of days, research planes from Germany, France and Romania flew over them. A Japanese-European satellite gazed down from above, and drones frequently zipped by. By taking measurements of clouds using these different modalities, the Orcestra researchers aim to collect data needed to refine our understanding of one of the great uncertainties in current climate models.

Constantly Catching Molecules

The Integrated Carbon Observation System, or ICOS, is a web of nearly 180 measurement stations scattered across 16 European countries. Some are remote — at sea, on mountaintops, out on the tundra — and some are near or in cities. They constantly collect data on greenhouse gases and the flow of carbon across the atmosphere, surfaces and oceans. This kind of continuous monitoring is critical for developing and maintaining climate models.

ICOS station Pallas Sammaltunturi, in the Arctic tundra of Lapland, measures air from the Norwegian Barents Sea and the North Atlantic.

Copyright of ICOS ERIC and Konsta Punkka/Photo by Konsta Punkka

The ICOS Simon Stevin research vessel measures greenhouse gases in the North Sea.

Copyright of ICOS ERIC and Konsta Punkka/Photo by Konsta Punkka

Norway’s Zeppelin Observatory measures gases 1,000 kilometers south of the North Pole.

Copyright of ICOS ERIC and Konsta Punkka/Photo by Konsta Punkka

Researchers recently installed equipment to measure the Earth’s surface temperature at the Abisko-Stordalen Palsa Bog, Sweden.

Copyright of ICOS ERIC and Pekka Pelkonen/Photo by Pekka Pelkonen

Marine chemist Michele Giani catches a buoy at the Miramare station to monitor ocean processes in the Adriatic Sea.

Copyright of ICOS ERIC and Pekka Pelkonen/Photo by Pekka Pelkonen

Moving Mountains

A helicopter lifts a huge chunk of vegetation extracted from a mountainside and flies it downslope. “We’ve been doing these crazy experiments that require us to transplant tons and tons of soils and communities,” said Bektaş, the ETH Zurich plant ecologist.

More than 20 research groups around the world have conducted more than 40 experiments in this style, where they uproot a square meter of soil with all its vegetation — what Bektaş calls a “natural laboratory” — and replant it at a lower elevation. Over many years, they’ve been tracking these natural laboratories, complete with microbes, plants and fungi, to see how they adjust to warmer conditions.

In 2016, a helicopter transported land from higher to lower altitudes in the French Alps.

Tamara Münkemüller

The researchers are already finding that the communities respond in unexpected ways. For example, plants and fungi acclimate to the new environment at different rates, suggesting a potentially problematic asynchrony that could disrupt ecological communities as warmer temperatures creep up mountainsides.

Crunching Numbers

Scientists often simulate one part of the climate story at a time, focusing on the atmosphere, the ocean, the land, or even just a sliver of one of those areas, said Klocke of Max Planck. But such simulations can be coarse or fuzzy, which makes it hard to draw strong conclusions about extreme climate scenarios from them in isolation.

Enter supercomputers. Jupiter, based at Forschungszentrum Jülich in Germany, is one of the fastest in the world, capable of performing 1 quintillion calculations per second. This speed lets researchers simulate many interacting components of the Earth system in high resolution, while preserving the ability to zoom in on smaller units, such as an accurately modeled coastline.

The Jupiter supercomputer yields high-resolution climate simulations.

©Forschungszentrum Jülich / Sascha Kreklau

“The information content just becomes much larger, and one will be able to make more refined statements about climate change,” Klocke said. He hopes such models will help us understand the local impacts of climate change, which are what “really matter to people,” he said. “Nobody has a sensor for global mean temperature. … What does it mean for New York if the sea level rises? What does it mean for agriculture in Spain?”

Eyeing Earth From Orbit

In 1969, the first accurate atmospheric temperature readings came from NASA’s Nimbus 3 satellite. In the decades since, satellites have surveyed the world’s forests, oceans, deserts and ice. They gather data about atmospheric gases, weather, temperature, sea level changes, ice changes and coastline changes. By stitching satellite readings to data collected from ground and aerial surveys, researchers can gain a highly accurate picture of how our planet is changing.

The Ili River Delta, Kazakhstan

NASA/Joshua Stevens/USGS/Landsat

Mount Taranaki, New Zealand

NASA/Wanmei Liang/USGS/Landsat

An oceanfront in the Bahamas.

NASA/USGS/Landsat

Namib-Naukluft National Park in Namibia’s Namib Desert

NASA/Wanmei Liang/USGS/Landsat

The European Space Agency’s Biomass satellite uses a long-wavelength radar system to see through forest canopies, such as Bolivia’s forests (pictured here), to gauge their carbon storage.

ESA

Measuring the Planet’s Breath

About 11,135 feet above sea level, on the flank of the largest active volcano on the planet, the Mauna Loa Observatory is the site of the longest continuous measurement of atmospheric carbon dioxide. In 1958, the geochemist Charles Keeling implemented his pioneering approach to measuring carbon dioxide there, which has since been implemented at other stations on land, at sea and in the air.

The Mauna Loa Observatory sits at around 11,000 feet on the volcano of the same name on the Big Island of Hawaiʻi.

NOAA/Forest Mims III

From the measurements at Mauna Loa emerged the famous Keeling Curve, a graph that shows the steady increase in carbon dioxide deposited into the atmosphere by human activity. A 2022 volcanic eruption temporarily halted the readings; thanks to a backup station, the disruption was minimized. Now the observatory’s biggest threat is not from molten earth but from the Trump administration, whose proposed 2026 budget would shut it down, halting the research that has gathered some of the most important and conclusive evidence for carbon dioxide–driven climate change to date.

Traversing the White Continent

Above us, satellites are constantly taking stock of the Earth. But how can scientists be sure that the data is accurate? Sometimes they have to ground-truth it — even deep in Antarctica. At 88-degrees south, the orbits of NASA’s Ice, Cloud and Land Elevation Satellite-2 (Icesat-2) converge, giving this location a high density of data. So that’s where researchers had to journey to confirm its findings.

For three years in a row, researchers embarked on a two-week traverse of Antarctica. They drove 470 miles in PistenBully snowcats, which are usually used to groom ski trails. The vehicles pulled sleds with everything the researchers needed to survive for weeks in remote Antarctica, including tents and GPS instruments, as they took ground measurements of ice sheet elevation to check Icesat-2’s accuracy.

In December 2017, using snow machines called PistenBullys, NASA scientists traversed a 470-mile arc on the 88-degree south latitude line in Antarctica.

Courtesy of NASA/GSFC

Conditions were frigid, with wind chills of minus 50 degrees Celsius. “Cold, dry air fills your nose and lungs. Your eyes blink, trying in vain to bat away the overwhelming brilliance of sunlight reflecting off the snow,” wrote the researchers Adam Greeley and Kelly Brunt in field notes describing their arrival on the continent in 2018. The scientists had their fun, however. For Christmas in 2020, they cooked up a nice dinner and the next day hosted a “race around the world” — a 2-mile race across every longitude line. Two winners were awarded 10-minute showers (rather than the allotted two minutes).

Recording Damage

Climate science is not limited to professionals. Volunteers around the world are documenting changes in their communities, such as effects on bird populations or cultural sites. In Florida, the Heritage Monitoring Scouts visit archaeological sites, including cemeteries, forts and mills, to record any impacts after extreme weather events. Hurricanes, for instance, send storm surges and strong winds inland, causing erosion and other damage. “The health of the archaeological sites can also speak to the health of the environment,” said Sarah Miller, a regional director for the Florida Public Archaeology Network in St. Augustine.

Heritage Monitoring Scouts assess a flooded moat at Fort Center, an archaeological site in Glades County, Florida, after Hurricane Irma struck in September 2017.

Sara Ayers-Rigsby/Florida Public Archaeology Network

Flying Over Changing Landscapes

Between 2009 and 2019, aircraft with NASA’s Operation IceBridge took to the skies with lasers, radar, optical and infrared cameras, gravimeters, and magnetometers to precisely survey changes in the planet’s polar ice. Across more than 1,000 flights, the aerial surveys collected sea ice and glacier measurements, including height, depth, thickness and ice flow. This data helped map changes on the surface of the ice and also in the invisible parts — the glacial bottoms, the bedrock of Greenland and the inside of the ice itself — to track and model melt dynamics.

In November 2013, a U.S. Air Force C-17 aircraft dropped scientists off at McMurdo Station in Antarctica.

NASA/Jefferson Beck

Bush pilot Paul Claus flies scientists in a single-engine de Havilland Otter to collect data on mountain glaciers.

NASA/Maria-José Viñas

In August 2018, Operation IceBridge flew over Sheridan Glacier in Alaska.

NASA/UAF/Martin Truffer

Drifting With the Ice

In subzero temperatures, under the dark of polar night, nearly 100 people drifted on a piece of ice for close to a year. Their eyelashes often froze. They worked in near-complete darkness, illuminated only by moonlight, headlamps and the light from their ship. Occasionally a curious polar bear meandered near camp, which was always changing as the ice floe buckled and drifted across the Arctic Ocean.

The dedicated researchers worked through these harsh conditions to study a place exceptionally vulnerable to climate change — the Arctic is warming faster than anywhere else on Earth — and its influence on the rest of the world. Models for how climate change will affect the Arctic are largely based on data collected in the 1980s, said Marcel Nicolaus, a sea ice physicist who coordinated the sea ice program for Mosaic (Multidisciplinary Drifting Observatory for the Study of Arctic Climate), a scientific expedition that took place between September 2019 and October 2020. By taking simultaneous measurements from ice, ocean and atmosphere, Nicolaus and his colleagues hoped to update their understanding of how these different parts of the ecosystem interact and to improve their models and predictions.

Jürgen Gräser and Sandro Dahlke prepare a weather balloon named “Miss Piggy” to collect atmospheric data from a few thousand feet above the ice.

Alfred-Wegener-Institut / rbb / UFA Show & Factual

The icebreaker RV Polarstern was intentionally lodged in sea ice and drifted for nearly a year.

Esther Horvath

Roberta Pirazzini prepares a drone to study Earth’s energy budget, or how energy is exchanged between the planet and space.

Alfred-Wegener-Institut / Jan Rohde

In August 2020, RV Polarstern navigated over the North Pole, breaking ice along the way.

Alfred-Wegener-Institut / Steffen Graupner

Allison Fong saws an ice block to launch a FishCam into the water to capture images of sea life.

Esther Horvath

Stefan Hendricks, Gunnar Spreen and Oguz Demir return to the ship during a storm.

Esther Horvath

To “go with the flow” of drifting ice and currents, Nicolaus said, researchers lodged their ship, the RV Polarstern, in a floe and stayed with it for 300 days until the ice cracked apart. First, “we had to build our little Mosaic city,” he said — a series of encampments on the ice beyond the ship that let physicists, biologists, oceanographers and others take measurements safely and consistently. It took about a week to construct the Mosaic city, but the work to maintain it never ended. The ice was constantly shifting, building new pressure ridges and destroying parts of instruments and sites. “We had so much ice dynamics,” he said. “It was always something in transition, continuously changing.”

Whether the researchers were stabilizing their little city or taking measurements, the cold, dark days could be rough. But for the most part spirits stayed high. “There’s a type of person that likes to do these things,” Nicolaus said on a video call from a different ship while on another Arctic expedition (with impressive Wi-Fi). “In the end, there’s one out of 50 [researchers] that would say, ‘OK, I’ve been here; I don’t need to do that again.’ But the other 49, they catch the Arctic virus and they want to come back.”

COMPLEXITY | VIEW ON WEBSITE

The Climate Change Paradox

By Joseph Howlett

September 15, 2025

Earth’s climate is chaotic and volatile. Climate change is simple and predictable. How can both be true?

Mark Belan/Quanta Magazine

COMPLEXITY

The Climate Change Paradox

By Joseph Howlett

September 15, 2025

Earth’s climate is chaotic and volatile. Climate change is simple and predictable. How can both be true?

Introduction

The Earth’s atmosphere is nothing but freely roaming molecules. Left alone, they would drift and collide, and eventually even out into a mixture that’s dynamic, yet stable and broadly unchanging.

The sun’s rays complicate things. Energy enters the Earth system in daily cycles, the bulk of it going to whichever half of the planet is tilted toward the sun (and experiencing summer). The molecules in that half acquire more energy than others, which sets the global atmosphere steadily swirling. Depending on the season and location, molecules in our atmosphere might traverse warm land, then cold seas. They might encounter a mountain range that forces them to high altitudes, where the air pressure is low and water condenses. Then they might become part of large-scale phenomena, such as currents, atmospheric rivers, turbulent jet streams and continental fronts.

These phenomena are erratic. They interact at every scale and manifest as weather, from clear sunny days to blustery blizzards and the anomalous events — from hurricanes and polar vortices to hailstorms and tornadoes — that are happening with increasing intensity. Any thought of stability is illusory; no patch of molecules dances in isolation.

The result, from seemingly simple inputs of molecules and energy, is emergent, incalculable chaos. Some individual molecule in the room you are sitting in is careening about blindly and colliding with its immediate neighbors. Zoom out — block to city, field to landscape, region to continent — and patterns appear and intermix. Complexity abounds and compounds. Nothing in the atmosphere is untethered from the rest of the global picture.

We live with this unpredictable mess of an atmosphere every day. We tote around unopened umbrellas, or refresh weather apps and watch our weekend plans dissolve. Anticipating conditions any further out than a week or two is a fool’s errand. The Earth is a complex dynamical system — an interwoven mass of moving parts, each of which requires a different branch of science to understand. Even with advanced knowledge, sophisticated algorithms and modern instruments, it defies and eludes us.

Yet this engine of chaos is now under our influence. It is incontrovertible fact that we are changing the Earth’s temperature by adding more carbon dioxide to the atmosphere. We know exactly how we are changing it — that when we double the proportion of carbon dioxide in the thin layer that rests over the surface of the Earth, the planet will become 2 to 4 degrees Celsius warmer, overall, than it is today. This conclusion has remained essentially unchanged since 1896, when the Swedish scientist Svante Arrhenius arrived at an estimate of 2 to 5 degrees. (Using an extraordinarily simplified picture of Earth, he made a number of mistakes that, in the end, balanced out.) Some details may remain uncertain, some chaos untamable, but the basic conclusion is a matter of unwavering scientific agreement — 97% is a rare degree of consensus on almost any subject. We are nearly as sure of this as we are of the causes of infectious disease, or how stars form, or the fact that life evolves through natural selection.

Huilo-Huilo Falls, Chile

Alexis Gonzalez/iStock

Both things are true: The climate system is vastly complex, and we’re certain about what we are doing to it. How can we be so confident in a hundred-year projection when we can’t predict the weather with any reliability more than a week out?

“How can it be that both are true?” said Nadir Jeevanjee, an atmospheric physicist at NOAA’s Geophysical Fluid Dynamics Laboratory, a leading institution for cutting-edge simulations of the atmosphere. “It’s a huge tension that’s lurking behind the whole conversation.”

It turns out that complexity can be a veil concealing more basic truths. An enormously complicated system can yield simple answers. You just have to ask a simple enough question.

Complexity Rises

In 1961, Edward Lorenz, a meteorologist at Massachusetts Institute of Technology, was running and rerunning his computer simulation of an atmosphere when something surprised him. What seemed like minute differences in the simulation’s initial states ballooned, until the weather outcomes of different runs bore zero resemblance to one another. In subsequent years, he formulated what would become gospel truth in the Earth modeling community: No matter how much weather prediction advances, it has little value beyond two weeks.

Floodwaters, Oder River, Wrocław, Poland

Mindea/iStock

“You need to get the initial conditions right, then you need to get your model right to propagate them forward in time, and very quickly you run into chaos,” said Isla Simpson, an atmospheric scientist at the National Center for Atmospheric Research.

Weather prediction takes a snapshot of the atmosphere today and projects its motion forward, through the theoretical universe of all possible forecasts. Imagine dropping a rubber duck into a raging river. You can have a sense of where it might go, but it’s increasingly impossible to predict precisely where the duck will be the farther downriver it travels. Even if you had flawless equations to describe how the river is moving, you’d never get an exact answer. Turbulent waters vary so dramatically that a slight shift in the duck’s initial position, or a slight error in our knowledge of the starting conditions, would lead to a totally different outcome. As the duck progresses downstream, any tiny deviation will multiply.

An enormously complicated system can yield simple answers. You just have to ask a simple enough question.

The same is true of Earth’s atmosphere. Even with 21st-century technology, no snapshot can perfectly capture the locations and paths of all the gas molecules. Those starting errors — the proverbial flaps of a butterfly’s wings, a metaphor that emerged from Lorenz’s work — grow over time, as will the difference between prediction and reality.

But the trajectory of a river is not defined by the turbulence of the water in it. The river’s bends are driven by larger-scale, longer-term phenomena — the shifting of tectonic plates, the erosion of the riverbank by plant roots, the volume of water flowing through the atmosphere and landscape, and more. A meteorologist is concerned with predicting where the duck will go; a climatologist is concerned with predicting where the river will go.

“We’re not asking what will the weather be on July 7 of 2047 in San Francisco,” said one of those climatologists, Daniel Swain at University of California Agriculture and Natural Resources. “We’re describing the envelope of those variations, not which specific path we’ll take.”

In other words, we can’t possibly know where the duck will end up. But from here, we can clearly see that the river’s course is changing. “We’re giving the system such an enormous and sudden kick — that is actually what gives us the predictability,” Swain added. “Two to four degrees centigrade is like a quarter to half of an ice age, but in the opposite direction.”

Braided glacial rivers, Iceland

Extreme-Photographer/iStock

Simplicity Emerges

Syukuro Manabe was already intimately familiar with the perils of weather forecasting when, in 1965, as a scientist at the Geophysical Fluid Dynamics Laboratory, he was tasked with building a mathematical model of the Earth’s climate. He had trained as a meteorologist in Japan, but instead of making local forecasts, his new job was to sketch out the universe of possible weather, given the atmosphere’s content and interactions. He was not following the duck, but rather working on a basic simulation of the river.

Decades of indifference had followed Arrhenius’ initial calculation of warming due to carbon dioxide. More than half a century later, Manabe thought his model could help bring some rigor to the idea of a “greenhouse effect.” He used it to simulate the atmosphere at a single location on Earth. He started in equilibrium, with the same amount of energy entering from the sun and escaping to space.

Anthropogenic carbon dioxide has shifted the course of the river, the envelope of uncertainties that constrain our chaotic weather patterns.

Most radiation from the sun cruises right through the atmosphere to warm Earth’s surface. But the return route of that energy — Earth’s radiation back to space — takes the form of infrared light. Infrared light has longer wavelengths and, crucially, can interact with some gas molecules. So instead of escaping straight to space, it gets absorbed and released many times on its path up through the atmosphere.

Manabe’s model held information about the gas of the atmosphere, including its water content and equilibrium temperature, at various altitudes. Manabe then doubled the amount of carbon dioxide in his artificial atmosphere. Carbon dioxide, one of the gases that absorbs infrared light, is called a “greenhouse gas” for its heat-absorbing effect. More carbon dioxide molecules means more chances for that light to be absorbed and released before it exits to space, lengthening its time within our atmosphere.

Over time, Manabe’s simulated Earth system settled into a new equilibrium. The same amount of the sun’s energy was coming in, and the same total was escaping to space. But more infrared light stayed in residence in the atmosphere — flying around at every height and being exchanged between gas molecules. This made the temperature at every altitude just a little bit hotter, all the way down to the Earth’s surface.

Krimmler Ache River, Salzburg, Austria

rusm/iStock

His simulation was no ambiguous, unreliable weather forecast. It was the greenhouse effect, clear as the air after a summer rain.

“The fundamental physics is very well established,” said Joanna Haigh, an emeritus atmospheric physicist at Imperial College London. “We can say without any shadow of doubt that more greenhouse gases means higher surface temperature.”

In Manabe’s simple simulation, the complexities of weather didn’t matter to the long-term outcome. The state in which those complexities played out — the course of the metaphorical river — had shifted.

The question is, are clouds going to make things worse by a small amount or a lot?

Robin Wordsworth, Harvard University.

The model also told Manabe something new: Water vapor is a much larger component of Earth’s atmosphere than carbon dioxide (up to 4% versus 0.04%), and traps more heat per molecule. The model made it clear that a warmer atmosphere can hold more water, which in turn doubles the total warming and therefore draws even more water molecules into the air. This was the first and most significant calculation of a climatic “feedback loop,” or an additional, indirect impact of carbon dioxide on temperature.

In the decades since Manabe’s groundbreaking work, study after study has stacked evidence to confirm the startling accuracy of his prediction. His model is playing out on Earth’s surface right now, escaping from simulations into the realm of human experience. Today, the global mean temperature has risen at least 1.2 degrees Celsius from preindustrial levels, according to the World Meteorological Organization — almost exactly as much as Manabe’s simple model predicted for the amount of carbon dioxide we’ve pumped into the air. Anthropogenic carbon dioxide has shifted the course of the river, the envelope of uncertainties that constrain our chaotic weather patterns.

Chaos Lingers

Manabe’s model has been confirmed by vast reams of data from a wide range of sources. But it was hardly complete. Changing the temperature changes lots about the Earth, from the reflectivity of sea ice to the stability of permafrost. The oceans are their own swirling mess, deeply interwoven with climate and weather alike. We’ve since begun to understand how these downstream, often chaotic forces may further shape the river. As scientists decipher them, there’s one particular feedback loop that has come to dominate the conversation.

Taklamakan Desert, Tibet

c1a1p1c1o1m1/iStock

“Clouds are certainly the greatest current source of uncertainty,” said Kerry Emanuel, an emeritus atmospheric scientist at the Massachusetts Institute of Technology. “We’re flying almost blind on clouds.” These familiar, turbulent morasses of swirling droplets continue to stymie scientists. Water vapor is a greenhouse gas, and the liquid droplets and ice in clouds can also trap heat. But at the same time they reflect some of the sun’s ultraviolet and visible light back to space. The cloud droplets form around natural and human-made aerosol particulates in the air according to microscopic physics that are not fully understood.

“We’re pretty sure we have a good sense what the baseline is,” said Robin Wordsworth, a climate scientist at Harvard University. “The question is, are clouds going to make things worse by a small amount or a lot?”

We know the planet will keep getting hotter, but by exactly how much will be determined by these subtle factors scientists are still trying to understand.

Clouds are chaos’s revenge. In the decades since Manabe’s work, the uncertainty present in climate models due to clouds has barely improved, and remains consequential. “Clouds will make the difference between climate change being kind of tolerable for humanity and catastrophic for humanity,” said Timothy Palmer, a climate physicist at the University of Oxford.

Chaos complicates the picture in other ways, too. The atmosphere’s “memory” of its beginning state (that is, today) is a matter of weeks. After that, today’s conditions cease to matter, which is why weather prediction has a hard limit. But as models have improved to include more feedback loops, researchers have started to incorporate the longer “memories” of other parts of the climate system. The upper ocean takes a few years to “forget” its initial conditions; the deep ocean takes centuries. Ice sheets can “remember” for millennia. In 2100, the state of these systems will depend intricately on their state today, and will partly determine the global climate of that increasingly less distant time. We know the planet will keep getting hotter, but by exactly how much will be determined by these subtle factors scientists are still trying to understand.

Tamul Waterfall, San Luis Potosí, Mexico

ferrantraite/iStock

Subtle, but consequential. Several distinct measurements have recently suggested that more energy is entering the Earth system than leaving it — more than our best climate change models predicted. “It’s quite worrying. We really need to figure out exactly why this happened,” Emanuel said. The answer could be clouds, or aerosols, or possibly an unknown ocean cycle that will dissipate in 10 years and put us back on the predicted track. But something significant is clearly missing from our picture of the system.

The simple question — What happens when you double atmospheric carbon dioxide? — has indeed yielded a relatively simple answer: The Earth will get a few degrees hotter. From that baseline, we can now ask, if not answer, ever more specific questions in the space between weather and climate. The answers to these questions have less to do with the fate of the climate than with how we are going to deal with it.

“If you’re building a bridge in North Carolina, you need to know what’s the maximum rainfall in the year 2100,” said R. Saravanan, an atmospheric scientist at Texas A&M University. “The global average temperature is not very useful for that.”

So much sophistication has already been layered upon the simple models of Arrhenius, Lorenz and Manabe. Day by day, we are recharting the river of our climate and all its possible futures. We study the loops and update our map, hoping it will help us navigate the torrent. And we’re doing it from the perspective of the duck, trying to make that critical guess where we will be in 100 years when we can hardly tell where we will be tomorrow.

EXPLAINERS | VIEW ON WEBSITE

The Quantum Mechanics of Greenhouse Gases

By Joseph Howlett +1 authors

Mark Belan

September 15, 2025

Earth’s radiation can send some molecules spinning or vibrating, which is what makes them greenhouse gases. This infographic explains how relatively few heat-trapping molecules can have a planetary effect.

Mark Belan/Quanta Magazine

EXPLAINERS

The Quantum Mechanics of Greenhouse Gases

By Joseph Howlett +1 authors

Mark Belan

September 15, 2025

Earth’s radiation can send some molecules spinning or vibrating, which is what makes them greenhouse gases. This infographic explains how relatively few heat-trapping molecules can have a planetary effect.

Introduction

There’s a simple story of the greenhouse effect: A blanket of carbon dioxide envelops the planet, letting sunlight in but trapping its heat. As a result, Earth warms.

But how does this actually work? Carbon dioxide amounts to only a tiny smattering of gas molecules — 0.042%, or roughly 420 parts per million — in our thick atmosphere. And yet, we know that doubling carbon dioxide levels can change the character of life on Earth.

The answer is quantum mechanics, which determines whether a molecule can interact with the right type of radiation.

Part 1: Maintaining Energy Balance

But first, we need a basic understanding of how radiation, such as sunlight, interacts with objects, such as planets.

Everything in the universe radiates, pumping out heat. A light bulb radiates heat; so does a rock sitting on the ground. Same with your phone, your body and Earth itself.

The radiation given off by an object takes the form of light, or electromagnetic waves. These magnetic and electric fields undulate as they move through space, carrying energy with them.

Hotter objects give off more heat; their waves are more energetic, oscillating with a shorter wavelength. Objects on Earth tend to be cool (generally under 30 degrees Celsius) and radiate light with relatively long wavelengths, known as infrared radiation. The sun is much hotter, about 5,000 degrees Celsius, so it radiates visible radiation with shorter wavelengths.

A radiating object will cool off unless there’s a source of heat replenishing it. For example, Earth releases heat, but it doesn’t cool down. That’s because all the heat that it loses gets replenished by the sun’s radiation. As long as Earth absorbs the same amount of heat from the sun as the amount it gives off, it will stay the same temperature — in equilibrium.

Imagine Earth with no atmosphere. Its surface butts up right against the cold vacuum of space, with no barrier in between. Even if the Earth’s surface was extremely cold, about minus 18 degrees Celsius, it would be warm enough to radiate all the heat it’s taking in. At that low temperature, the Earth and sun would already be in a happy equilibrium.

Now add an atmosphere — a thicket of gas molecules bound to the Earth by its gravitational pull. Say some of these molecules are greenhouse gases that interact with the outgoing radiation. Some of Earth’s radiation is now redirected back to its surface. Instantly, the amount of heat escaping the planet drops. But the same amount of heat is entering from the sun as before. We are out of equilibrium.

With more heat entering than leaving, the planet’s temperature begins to rise. But remember, the hotter an object, the more it radiates. So as Earth warms up, it begins pumping out more heat. This trend continues until the same amount of heat is escaping as is entering. Balance is restored at this new, hotter equilibrium.

Add an Atmosphere

Add an Atmosphere

Now, we can answer the deeper question: What makes a molecule trap heat in the atmosphere?

Part 2: The Quantum States

To interact with Earth’s radiation, a molecule’s electric charge needs to be off balance.

Take carbon monoxide: one carbon atom bonded to one oxygen atom. Oxygen attracts electrons more strongly than carbon does; as a result, the molecule’s electrons tend to skew towards the oxygen side, making the duo permanently off balance.

On the other hand, diatomic nitrogen, or N_2, which makes up 78% of our atmosphere, is totally balanced.

Earth’s radiation produces electric and magnetic fields in the atmosphere that change over time. These shifting fields can cause an unbalanced molecule to dance. When the electric field is positive (when the wave in the figure below rises above a central horizontal axis), positive charges are pushed upward and negative charges are pulled downward. When it’s negative, the reverse happens.

An unbalanced molecule, such as carbon monoxide, acts like a positive and negative charge bonded together. The electric field makes the molecule stretch and contract. This motion — called “vibration” — requires energy. And the molecule absorbs that energy from the passing wave.

But an unbalanced molecule can’t absorb energy from just any radiation. The passing wave needs to have exactly the right wavelength to match one of the quantum states of the specific molecule. Otherwise, the wave will sail right by. (This is also why the sun’s visible light doesn’t interact with unbalanced molecules: It’s the wrong wavelength.) Because molecules have multiple quantum states, they can absorb multiple wavelengths of light. Each wavelength generates a different excited state.

Start

The excited state lasts a few seconds at most. Then the radiation is released, beaming in a random direction. That could be along its initial trajectory toward space, or one back down toward Earth, or anywhere in between.

The molecule can also rotate around its axis. Rotations are similarly “quantized”: The light’s wavelength has to line up precisely with the molecule’s quantum state, which is determined by the molecule’s structure. To absorb energy from radiation, the wavelength has to align exactly with any of these states’ energies.

This is the definition of a greenhouse gas: any atmospheric molecule whose quantum states precisely match the wavelengths of Earth’s radiation.

Part 3: The Cast of Molecules

Most of the atmosphere is nitrogen. Nitrogen and other balanced molecules, including diatomic oxygen (O_2) and lone noble gas atoms, together make up more than 99.5% of the air. None of them interact with Earth’s radiation; they are not greenhouse gases.

When it comes to the climate, the tiny remaining sliver of atmospheric molecules is where the action is.

Carbon monoxide is the simplest unbalanced molecule in air, but it makes up only 0.00001% and isn’t a big player in the greenhouse game.

Water vapor is the most important greenhouse gas; without it, the planet’s surface would be only a few degrees above freezing. Like other greenhouse gases, it is an imbalanced molecule: Its electrons prefer to congregate around the oxygen atom.

Most of Earth’s radiation isn’t energetic enough to excite water molecules into a vibrational quantum states. But it can set water spinning around the rotational excited state of one of its three axes.

Ozone and nitrous oxide also have an intrinsic charge imbalance: Earth’s radiation aligns with their quantum states that mix rotation and vibration. They are important greenhouse gases as well.

The most famous greenhouse gas is different from the rest. Carbon dioxide is not intrinsically imbalanced. Usually, its electrons are spread evenly along its length.

But its shape allows for special vibrational states: Carbon dioxide can bend, creating a temporary imbalance.

That imbalance lines up precisely with one of the wavelengths of Earth’s radiation. Carbon dioxide can interact with light by simultaneously bending and rotating. The bending temporarily creates the requisite imbalance, enabling the radiation to force it into rotation.

This uncanny coincidence — that the Earth’s radiation lines up with the energies of carbon dioxide’s mixed vibrational/rotational quantum state — is how this tiny trace of molecules, mere flecks in the air, completely dominates our climate.

Methane is nearly symmetric, too: Its four hydrogen atoms form a pyramid with the carbon atom at the center. But it can similarly bend into a temporarily unbalanced shape and rotate. Some of these rotations match up with Earth’s radiation.

Each of these gases has its own unique quirks, but they all lead to the same outcome: absorbing and redirecting some of Earth’s outgoing infrared radiation.

Part 4: Back to Earth’s Energy Balance

A redirected packet of radiation is usually reabsorbed by a nearby molecule. That means that any single packet of radiation can escape to space only after a long, random trudge through the atmosphere.

When more greenhouse gases join the party, that walk becomes longer. Even less energy escapes.

That longer walk means that the amount of heat escaping Earth declines, just as it did when the planet first gained an atmosphere. Equilibrium is again disrupted: More energy is entering than can leave. With a denser morass of radiation changing hands, the atmosphere begins to warm, all the way down to Earth’s surface.

Add More Greenhouse Gases

Add More Greenhouse Gases

Earth will eventually settle into a new, hotter equilibrium, but only if its atmosphere stops changing. As long as we keep adding more greenhouse gases, the planet will keep getting hotter, chasing an equilibrium it can never reach.

CLIMATE MODELS | VIEW ON WEBSITE

How Climate Scientists Saw the Future Before It Arrived

By Zack Savitsky

September 15, 2025

Over the past 60 years, scientists have largely succeeded in building a computer model of Earth to see what the future holds. One of the most ambitious projects humankind has ever undertaken has now reached a critical moment.

Mark Belan/Quanta Magazine

CLIMATE MODELS

How Climate Scientists Saw the Future Before It Arrived

By Zack Savitsky

September 15, 2025

Over the past 60 years, scientists have largely succeeded in building a computer model of Earth to see what the future holds. One of the most ambitious projects humankind has ever undertaken has now reached a critical moment.

Introduction

A gust of wind strikes the Sahara Desert, launching a speck of dust into the air. For a week, the grain rides atmospheric currents halfway around the globe, reflecting sparkles of sunlight back to space along its journey. Other dust particles floating in the same breeze catch drafts up to Greenland, where they pepper glaciers and accelerate their melting, and down to the Amazon, where they fertilize the rainforest soil. But this particular speck hovers in the sky off the east coast of Florida, serving as a seed for water vapor to condense around and form a cloud. The dust then falls to Earth inside a raindrop, plopping down in the Atlantic Ocean, where it feeds iron to phytoplankton. The floating creatures bloom in fluorescent green swirls that soak up carbon dioxide emitted by factories and power plants all over the world.

In this way, a dust grain’s path traces the interwoven processes linking all parts of Earth across distances and scales. “It shows how the world is really connected,” said Martina Klose, an aerosol scientist at the Karlsruhe Institute of Technology in Germany. “It just demonstrates the beautiful complexity that we’re located in.”

For centuries, humans have sought to understand the intricate workings of our planet. As vulnerable critters, we crave some control over nature, or at least a handle on coming shifts in the weather and climate. But Earth is a chaotic beast, sensitive to innumerable tiny details; we can’t possibly keep track of every speck of dust. Therein lies the challenge of climate modeling: building a computer model of Earth’s surface and atmosphere that captures the gist of its behavior simply but effectively. “The goal of climate modeling is really to build a fake version of the Earth,” said Isla Simpson, an atmospheric scientist at the National Center for Atmospheric Research — a coarse-grained copy of the planet that’s stripped down to “the processes we think are relevant.”

Over the past 60 years, this effort has come to fruition. Generations of scientists have dedicated their careers to sculpting increasingly sophisticated planetary replicas. Computer models of Earth have helped us reconstruct past epochs, forecast long-term weather trends and, above all, understand how human activities are changing the climate.

From the very first computer simulations, climate models have shown that carbon dioxide released by the burning of fossil fuels warms the planet considerably. In the decades since, more advanced simulations show how a warming planet could trigger all sorts of calamities, from heat waves and superstorms to desertification and ecosystem collapse. According to modeling results compiled by the United Nations, Earth is on track to warm between 2.6 and 3.1 degrees Celsius over the course of this century. The last time Earth was that warm was around 3 million years ago during the Pliocene era, when fires ravaged the Arctic and sea levels were some 50 feet higher than they are today.

A dust storm rolls across Erg Chebbi, a section of the Sahara Desert in Morocco. Several billion tons of dust are lofted into the atmosphere each year, affecting the climate in complicated ways.

Pavliha/iStock

As the frightening futures foretold grow nearer, the details are also growing more precise. Climate scientists have reached a pivotal moment in which their predictions are being borne out, allowing them to recalibrate and hone their models. “We were essentially predicting worlds we couldn’t see for a very long time,” said Tiffany Shaw, a climate dynamicist and geophysicist at the University of Chicago. Watching the ramifications of climate change play out in the real world has both validated the models and highlighted their shortcomings. Now, modelers are exploring new approaches that could usher in the next generation of fine-grained models that make better regional predictions.

As climate modeling enters this critical phase of refinement, the effort faces its greatest challenge yet. Since taking office, the Trump administration has taken siege to the U.S. research ecosystem, with a particular focus on undermining the quest to track Earth’s climate. Decades of work is on the line as the administration strips funding, guts agencies, scrubs resources and buries datasets. “It’s a whole-scale destruction and not something that will be undone,” said Bjorn Stevens, a climate scientist and the director of the Max Planck Institute for Meteorology in Germany. “It’s a completely existential threat.”

Humans have largely succeeded in digitally reconstructing the Earth in order to ask what the future holds. Now, not liking the answer, some are reaching to unplug the machine — while others fight to perfect it.

Prophesizing the Skies

For thousands of years, would-be weather forecasters struggled to pin down the relevant factors. The ancient Egyptians, for instance, meticulously tracked the star Sirius, believing it to be a widowed goddess whose tears caused the flooding of the Nile.

The British polymath Lewis Fry Richardson pioneered the science of weather forecasting in the 1910s and ’20s.

National Portrait Gallery, London

Eventually we came to understand the true drivers of natural phenomena. The British polymath Lewis Fry Richardson was the first to try his hand at using the laws of physics to model the weather system. During World War I, between shifts as an emergency ambulance driver in France, Richardson calculated how the local weather would evolve over six hours, starting with the atmospheric conditions provided by weather balloon observations on a particular morning in 1910. He spent weeks completing the pencil-and-paper calculations, complaining that the atmosphere resembled London, in that both have far more going on than anyone could properly attend to. His results were inaccurate due to the poor quality of the observations, but they got the ball rolling. Richardson expressed the hope that “perhaps someday in the dim future it will be possible to advance the calculations faster than the weather advances.”

That day came as a result of the next world war. With funding from the U.S. military, the mathematician John von Neumann helped develop the first general-purpose digital computer, called ENIAC. Among its first applications was weather forecasting. In 1950, von Neumann and collaborators built a simple model of the North American atmosphere that came to the brink of realizing Richardson’s dream: a 24-hour forecast that took 24 hours to calculate.

Norman Phillips, von Neumann’s colleague at the Institute for Advanced Study in Princeton, New Jersey, then took numerical weather prediction to the next level. Phillips had been inspired by recent “dishpan” experiments, in which scientists would heat the outer rim of a dishpan filled with liquid while cooling the pan’s center to simulate the temperature difference between Earth’s equator and poles. Remarkably, this simple experiment could effectively capture global wind patterns. “One is almost forced to the conclusion that at least the gross features of the general circulation of the atmosphere can be predicted without having to specify the heating and cooling in great detail,” Phillips wrote. He constructed a bare-bones computer model of a cylindrical atmosphere that similarly recreated realistic wind circulation patterns.

The Electronic Numerical Integrator and Computer, better known as ENIAC, is pictured in 1946, the year it was unveiled at the University of Pennsylvania. The machine was the world’s first electronic, general-purpose computer and could complete 5,000 additions per second. It was soon put to work on numerical weather simulations.

Wikimedia Commons

A colleague, Joseph Smagorinsky, went on to establish a federal institute, later known as the Geophysical Fluid Dynamics Laboratory (GFDL), dedicated to developing Phillips’ approach into a full-fledged global computer model of Earth’s atmosphere. Smagorinsky noticed the work of a graduate student at the University of Tokyo named Syukuro Manabe and recruited him to join his lab.

Manabe had a knack for simplifying Earth processes in ways that captured the essential ingredients. To start out, he simulated how radiation moves up and down along a column between the sun and Earth’s surface: The sun’s rays deliver energy to Earth, Earth radiates some heat back to space, and the leftover energy sets Earth’s atmosphere into motion. He focused on balancing this energy spreadsheet. “Manabe realized that this is the key for understanding the climate,” said Tapio Schneider, a climate scientist at the California Institute of Technology who as a graduate student overlapped with Manabe at GFDL. By 1965, Manabe had built this premise out into a 3D computer model of the atmosphere. The planet sitting below was dramatically oversimplified — just a smooth sphere with no geography or oceans. But if one squinted, the model behaved vaguely as our planet does, capturing, for instance, how warm air rises at the equator and creates the windless “doldrums” zones where sailors often get stranded.

Syukuro Manabe at the Geophysical Fluid Dynamics Laboratory in 1972.

GFDL NOAA

“Many people think you have to build a model that mimics nature as realistically as possible,” Manabe said decades later. But “the more complicated you make a model, the harder it is to find out why it malfunctions.”

His pioneering approach relied on a key assumption: that large-scale climate processes can be inferred without precise knowledge of all small-scale weather events. Following Phillips’ scheme, Manabe broke his computerized, 3D atmosphere into a coarse grid of boxes. Inside each box, he assigned a statistical estimate of properties such as temperature or pressure. He then used the equations governing fluid flow to calculate how fluids and energy migrate between boxes. The model could capture global properties remarkably well.

Manabe’s model offered a way to test the greenhouse effect — the century-old idea that certain gases trap heat that would otherwise be radiated from Earth back to space.

Varying the composition of his model atmosphere, Manabe noticed that the global temperature responded dramatically to carbon dioxide. “As it turned out, I changed the right variable and hit the jackpot,” he later recalled. In a landmark 1967 paper, he and Richard Wetherald calculated how much warmer Earth would become if the amount of carbon dioxide in the atmosphere doubled, an idea dating back almost a century to the Swedish physicist Svante Arrhenius. Carbon dioxide makes up only a minuscule fraction of the gas in the atmosphere, yet Manabe and Wetherald estimated that doubling its concentration would warm Earth by roughly 2.3 degrees Celsius. That’s impressively close to today’s estimates of around 3 degrees of expected warming, which scientists think could be reached by 2100. Manabe and Wetherald also predicted a telling sign of this CO_2-driven global warming: the lowest layer of the atmosphere (where greenhouse gases pile up) should get hotter, while the layer above it should cool.

Tapio Schneider is one of many climate scientists who are trying to improve the modeling of clouds and other processes below the grid scale. At the California Institute of Technology, he has developed a new climate model that automatically calibrates itself with real-world data much more efficiently.

Sabrina Pirzada

Manabe’s initial model ignored the ocean, which makes up about 70% of Earth’s surface, so he worked to marry his swirling skies to the churning ocean models of his colleague Kirk Bryan. In the summer of 1969 — weeks before the first humans walked on the moon — Manabe and Bryan recreated the Earth. On their simulated planet, clouds released rain that froze into icebergs that melted and flowed down rivers, soaking soil and evaporating to rejoin the atmosphere.

The model got a lot wrong about our planet, and the joint ocean-atmosphere system never settled into a steady equilibrium state. Nevertheless, “that’s the first time you can say you have something like a real climate model,” said David Randall, an atmospheric scientist at Colorado State University who led a review of the last century of efforts to model the Earth system. The simulation was a major milestone in one of the most ambitious projects humankind has ever undertaken, later earning Manabe a share of the 2021 Nobel Prize in Physics. “And then,” Randall said, it was “off to the races.”

Eyes on the Earth

By the time Manabe and Bryan ran their coupled model at GFDL in Princeton (where the laboratory moved from Washington, D.C. in 1968), similar efforts were popping up across the country. On the other coast, Yale Mintz at the University of California, Los Angeles, had recruited Akio Arakawa, another graduate student from Tokyo. While Manabe’s mind was up in the clouds, Arakawa’s was down in the dirt. He focused on developing sophisticated ways to deal with small-scale effects inside grid boxes — working so diligently that he once failed to notice his wastebasket had caught fire. At the time, many simulations would derail after running for a few weeks, as rounding errors at the grid points artificially amplified atmospheric waves. Arakawa managed to mathematically tame these instabilities, and his scheme remains a bedrock of modern models.

These parallel efforts allowed simulations to grow progressively more detailed — and in so doing, called attention to the holes that needed patching. “When the models started improving in resolution, they found they were becoming less realistic,” said Isaac Held, an atmospheric and oceanic scientist at Princeton University who worked under Manabe’s supervision at GFDL in graduate school. In one instance, at finer resolution, the jet stream — a fast current of air that circles the Earth — migrated to the wrong location in the simulation. Researchers helped to balance this effect by accounting for the roughness of Earth’s surface, correcting “an accidental cancellation of errors in the original models,” Held said.

The Trump administration’s proposed NOAA budget would shutter the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey.

GFDL NOAA

From around 1979, NASA began systematically observing Earth with satellites, offering “a big step change in our ability to look at the planet,” said Simpson, the NCAR scientist. Orbiting observatories provided real-time observations of Earth’s surface, oceans, ice caps and atmosphere that improved models. Scientists could monitor the motion of heat and moisture in the atmosphere and directly measure how much radiation Earth returned to space.

Not long after, climate modeling escaped the lab and entered the public arena. Since Manabe’s CO_2-doubling paper, scientists had gradually come to appreciate the extent to which the greenhouse effect would warm the planet and exacerbate weather fluctuations. (Because warm air holds more water, a hotter planet means both more droughts and more intense storms.) Meanwhile, researchers in Europe were learning to tease out warming signals from the random fluctuations of weather. Klaus Hasselmann, an oceanographer at the Max Planck Institute for Meteorology, developed a statistical method for separating the “fingerprints” of different climatic drivers, such as volcanic eruptions and the burning of fossil fuels — work for which he would eventually share the Nobel Prize with Manabe. The message was reinforced when observations reflected Manabe’s prediction that human-driven warming would cool the upper atmosphere.

In 1988, a catastrophic heat wave and drought plagued the United States, killing thousands of people and triggering over $80 billion in damage. Congress turned to scientists for answers. Manabe testified before a Senate committee, along with James Hansen, then the director of the NASA Goddard Institute for Space Studies. Hansen explained that 1988 was on track to be the warmest year on record and that he could say with 99% certainty that global warming, which spurred extreme weather events, was a reality. “The greenhouse effect has been detected, and it is changing our climate now,” Hansen said.

On June 23, 1988, James Hansen, then the director of NASA’s Goddard Institute for Space Studies, testified to Congress about the role of the greenhouse effect in causing what was then the warmest year on record. “Global Warming Has Begun, Expert Tells Senate,” ran the New York Times headline. This photo was taken when Hansen returned to Capitol Hill the following year.

Dennis Cook/Associated Press

Later that year, the United Nations established the Intergovernmental Panel on Climate Change (IPCC). Since then, climate scientists from around the world have regularly convened to compare models and to advise on global policy. The IPCC reinforced a push for modelers to collaborate and iterate. Researchers across institutions began contributing to community models that hundreds of other climate scientists could use to run experiments. Scientists worked to systematically probe and compare their predictions, running ensembles of many models together while slightly varying the input conditions or settings to assess the range of climate outcomes.

At the core of all these simulations sat Manabe’s paradigm. “We’ve gotten better at doing pretty much the same thing,” Randall said. Steadily, climate modelers shrank the grid boxes and incorporated more complex effects, such as those of atmospheric dust.

But as climate scientists came together to pool their efforts, and as their models grew increasingly detailed, a funny thing happened. These digital worlds began to diverge in subtle but important ways from the behavior of our actual planet.

Questioning the Oracle

Climate models have yielded solid predictions about broad properties of Earth’s climate, such as rates of Arctic warming and the rise in global mean temperatures. However, “very few people live in the Arctic, and nobody lives in the global mean,” as Gavin Schmidt, a climatologist and director of the NASA Goddard Institute for Space Studies, put it. “The impacts of climate change are becoming felt at the local level.” The current generation of climate models can answer specific questions about local or regional phenomena, but the problem is, many of those more detailed predictions are being proven wrong. “We’re seeing various things starting to be apparent in trends that are different from what the models are predicting,” Held said.

One of the most notable discrepancies takes place in the tropical Pacific Ocean, which stretches from Indonesia to Ecuador. Contrary to model predictions, ocean temperatures on the western side of this band have warmed relative to the eastern side. The slipup matters because this stretch of ocean generates atmospheric waves that have been connected to droughts from California to Africa. Models’ predictions in this region therefore affect climate policies worldwide.

Additionally, in sharp contrast to all climate simulations, scientists have lately seen humidity levels dropping unexpectedly in southern Africa and the southwestern United States. The jet stream is strengthening more than expected, and heat extremes in Western Europe are increasing faster than anticipated. Models also failed to predict just how much higher average global temperatures would climb in 2023 than ever before.

In a paper published this year, Shaw of the University of Chicago and Stevens of Max Planck argued that these discrepancies have culminated in “the other climate crisis”: a breakdown in the standard schema of modeling. “The normal way of doing it has sort of lost its explanatory power,” Stevens said.

All climate models to date have relied on Manabe’s assumption, which Shaw and Stevens refer to as “large-scale determinism”: the idea that fine-scale processes can be approximated to match large-scale climate features. But they and other researchers feel the time has come to revisit this fundamental principle of climate modeling. To answer the more detailed, local questions we’re now asking of models, “we need to rethink how we deal with processes below the grid scale,” Schneider said.

Stevens has been leading an effort to significantly decrease the size of grid boxes down to around one kilometer wide. (The current norm for global models is around 100 kilometers.) He thinks this scale represents a critical threshold that can resolve important “mesoscale” processes, from thunderclouds to ocean eddies, that were previously represented in terms of their average effect. And to capture the nuances of the Earth system, Stevens advocates cutting out as many estimations as possible and attempting to use physics all the way down. Recently, his group at Max Planck managed to run a one-kilometer model, one that included complex processes like carbon cycles and the effects of aerosols, that could simulate 90 days in 24 hours.

“Being able to resolve the mesoscale is transformational,” Randall said. “For 60 years, we haven’t been able to represent those things even though they’re among the most important weather systems out there.”

A high-resolution computer simulation of precipitating cumulus clouds, created by Tapio Schneider and colleagues at the California Institute of Technology.

Kyle Pressel

But researchers caution that ultra-high-resolution modeling is not a panacea. For one thing, we’re still “a long way off” from having the computational power to run such detailed models on the long timescales and large number of iterations needed, Simpson said. “This is a new frontier. I don’t think that’s the only path we should be following.”

One tool that appears poised to truly shift the mode of climate modeling is artificial intelligence. While AI has not yet transformed climate simulations the way it has weather forecasting, it is beginning to help make existing climate models more efficient by improving statistical representations and by automating model tunings. Some industry efforts, including one at the Allen Institute for Artificial Intelligence in Seattle, are now attempting to emulate the climate entirely with AI. “There’s nothing in there that is recognizably connected to the paradigm that we had,” Shaw said. But though these models seem to capture the atmosphere fairly well, she said, researchers have not yet managed to couple them to oceans or to outperform human-made models.

In the meantime, Shaw is concentrating her effort on understanding why current models are going wrong — even where they all agree with one another. “Model agreement became more of a gold standard than really understanding why the models agree,” she said. She’s focusing on hierarchical modeling, which involves blurring or turning off certain features in the models to reveal the essential processes underneath. “We need to be able to explain why we’re wrong just as equally well as why we’re right.”

The focus on addressing how models are formulated represents a fundamental shift in perspective within the field. “Climate scientists as a rule don’t like to talk about what they don’t know, because that’s so often been manipulated to cast doubt on what they do know,” Stevens said.

And the perfection of climate models matters less than the societal response to their central message, he argues. To that end, he helped found a European Union initiative called Destination Earth to bring climate models down from the ivory tower and into the hands of policymakers and the public. “A much higher-resolution model will not give you a much better climate policy decision,” said Wilco Hazeleger, a climate scientist at Utrecht University who also helped establish Destination Earth.

Hazeleger had grown frustrated by the slow pipeline for conveying climate model forecasts to government policymakers — a process that often takes more than a decade, he said. Destination Earth is developing a series of operational “digital twins” of the planet — global climate simulations with kilometer-scale resolution that downstream users, such as windfarm operators and city planners, can interact with directly and hopefully use to strategize.

Climate scientists have long been vexed by the disconnect between the dire warnings blared by their models and the restrained policies enacted by world leaders. After his 1988 testimony, Hansen was arrested multiple times while participating in climate protests. “The science of the situation is clear — it’s time for the politics to follow,” he wrote in a 2012 op-ed column criticizing the Obama administration for its hesitancy to curb carbon emissions. “We can’t wait any longer.” Today, three presidential terms later, the tension has escalated dramatically.

Unplugging the Machine

Clare Singer is the scion of a fabled academic family. She recently completed her Ph.D. at Caltech under Schneider, who studied under Held, who studied under Manabe. “My scientific upbringing was full of stories of the legends of GFDL,” she said. A year after finishing her Ph.D., she landed her dream job at the lab.

Clare Singer landed her dream job at the Geophysical Fluid Dynamics Laboratory last year and worked to improve simulations of clouds. Then in February, her employment was terminated as part of cost-cutting efforts by the Department of Government Efficiency.

Courtesy of Clare Singer

She was tasked with helping future models better simulate clouds, which remain one of their biggest sources of uncertainty. Clouds have a large impact on the climate. But the amounts of sunlight they reflect and precipitation they drop depend on tiny particles of pollen, salt, soot, microbes or Sahara Desert dust at the center of every droplet — something global models could never hope to capture. Singer is pioneering a new technique to incorporate small-scale simulations that can track individual particles to better ascertain the competing warming and cooling effects of clouds.

On February 27, just four months into her position at GFDL, Singer received an email terminating her employment. Several of her colleagues around the office were reading the same message. Across the National Oceanic and Atmospheric Administration (GFDL’s parent agency), nearly 800 employees were fired that day. “It was total chaos,” said Zachary Labe, a climate scientist who was among the lab’s fallen.

When Labe joined GFDL full time last year to help predict extreme weather events, “this was one of the most secure research positions that was possible in the entire ecosystem.” But the situation quickly changed when the Department of Government Efficiency, led at the time by Elon Musk, began its demolition in the name of reducing waste in federal bureaucracy. Dismissed NOAA researchers were temporarily reinstated in mid-March after a federal court issued a restraining order to halt the terminations — only to be re-fired weeks later when that order was repealed.

For researchers, the dismantling of the birthplace of climate modeling stings. “That lab I see as part of our world cultural heritage,” Stevens said. “What you see is a conscious effort to destroy institutions which are in some ways the foundation of modern society.” But GFDL is only a microcosm of the Trump administration’s larger assault on climate modeling — and science writ large. Since January, the administration has cancelled billions of dollars in research grants and fired thousands of federal scientists. It has axed two seminal climate reports, moved to repeal the Environmental Protection Agency’s finding that greenhouse gases endanger public health, and evicted Schmidt’s entire team at the NASA Goddard Institute for Space Studies from its office (even though the lease will likely still be paid out until 2031). “There’s nothing rational about what’s happening right now,” Held said. “I think it’s a tragedy.”

NASA merged observations of the atmosphere with advanced Earth system models to depict aerosols circulating in Earth’s atmosphere over a six-week period in 2024.

NASA’s Global Modeling and Assimilation Office and NASA’s Scientific Visualization Studio.

In May, the Trump administration released its fiscal 2026 budget request, which called for cutting National Science Foundation and NASA science budgets by more than half. The administration’s proposed NOAA budget, released a few weeks later, proposes eliminating the agency’s scientific research arm altogether, terminating over 1,000 additional employees and shuttering around a dozen institutes, including GFDL. It includes the line: “With this termination, NOAA will no longer support climate research grants.”

“The proposed budget is a disaster for science,” said one senior federal scientist who asked to remain anonymous out of fear of retaliation. “It’s existential for almost everything that any of the agencies are doing.” If scientists’ pleas fall short and the budget passes through Congress, the official warned, “The sky will go dark.”

Some climate researchers are pivoting to different fields, while others are seeking employment abroad. Efforts overseas will pick up some of the slack, but losing the continued observations and federal funding for the world’s leading climate research ecosystem would handicap the global collaborative effort to monitor the planet. “The United States has been very important in the past, and it’s just taking itself off the map,” Stevens said. “It’ll be a setback for everyone.” Even a course correction in the 2028 elections might not make up for the disruption of momentum. “It’s quicker to tear the building down than it is to build it up,” Randall said.

The biggest impacts will likely be felt by early-career researchers. The GFDL scientists dismissed in February re-entered the job market to find that many universities and federal labs had stopped hiring. “It’s a collapse of support for the next generation of scientists,” Labe said. Beyond the lack of employment opportunities, the blatant attack on climate science leaves some early-career researchers with “a deep existential crisis,” said one fired federal scientist who also requested anonymity. Modeling the climate “is an important thing that we do as a society,” the researcher added. “What does it mean if the country I live in no longer values that?”

In May, a handful of early-career meteorologists and climatologists organized a livestreamed virtual rally. For 100 consecutive hours, more than 200 scientists presented research and fielded questions from the public. Over those four days, viewers placed over 7,000 calls to their congressional representatives, urging them to prioritize funding for weather and climate science. The livestream closed with a message from one of the organizers, Jonah Bloch-Johnson, a climate scientist at Tufts University, who called the funding cuts “our own unnatural disaster in the making.” He encouraged listeners to continue marveling at the complexity of the Earth system — to appreciate how the clouds dance in the sky and how the waters ebb and flow. “This science belongs to you,” he said. “It’s the science of the world we all live in.”

The Dust Lingers

Martina Klose of the Karlsruhe Institute of Technology in Germany conducts field research on the properties of dust and other aerosols to unravel their effect on Earth’s atmosphere.

Courtesy of Martina Klose

In 2014, a gust of wind struck the Sahara, launching a dust cloud into the atmosphere. After a few days’ travel, some of the specks landed on a buoy floating in the North Atlantic off the coast of French Guyana. When scientists collected this sample and analyzed it in the lab, they noticed that some of the grains were huge — 15 times bigger than the largest particles they thought could be swept overseas.

“We were all wondering, how can it be possible that they actually stay suspended in the air for so long?” said Klose, the Karlsruhe Institute aerosol scientist. Over the last few years, she and her colleagues have realized that these extra-coarse grains account for around 85% of the total dust mass in the atmosphere.

While they’re still not sure how these giant grains travel so far, they’re confident that they represent an overlooked climate variable. Dust was thought to mainly reflect sunlight, but larger grains primarily absorb it. In a new paper now under review, Klose and colleagues report how current models are underestimating the impact of these particles on Earth’s energy balance by a factor of two, calling into question whether dust has an overall cooling effect on the climate, as previously suspected, or whether it’s actually amplifying warming. This uncertainty is critical, as over 5 billion tons of dust — around 1,000 times the weight of the Great Pyramid of Giza — are lofted into the atmosphere annually. And thanks to agriculture and other land-use changes, dust emission is only rising, having roughly doubled since the Industrial Revolution.

Related:

1. The Ends of the Earth

2. Forests Emerge as a Major Overlooked Climate Factor

3. The Quantum Mechanics of Greenhouse Gases

4. How Earth’s Climate Changes Naturally (and Why Things Are Different Now)

Scientists have been working to better track the journey of dust and more realistically simulate its climatic effects. NASA’s Earth Observing System operates three satellites that track properties of dust in the atmosphere. But in Trump’s proposed budget, all three are slated for cancellation.

Still, Klose is determined to keep an eye on the dust. Every few years, she brings tiny shovels and giant air-sucking machines to deserts across the world to collect samples. Then she transports those samples back to her lab in southern Germany and other labs, where her colleagues blow them inside a metal chamber to study how they stimulate cloud formation. Those results get fed directly into climate models to better represent how variations in tiny grains influence the nature of the entire planet.

“Obviously we can never, ever represent this in all its wonderful beauty in detail,” Klose said. Nevertheless, she said, she aims to learn as much as possible about the invisible intricacy of Earth before the dust settles. “We don’t have any plans to give up any time soon.”

Table of Contents

Quanta Magazine: 2025 Sep 15

All articles

The Ends of the Earth

The Climate Change Paradox

The Quantum Mechanics of Greenhouse Gases

How Climate Scientists Saw the Future Before It Arrived