If we want to understand climate change honestly, we have to start with a simple fact: Earth’s climate system is extraordinarily complex. It doesn’t lend itself to easy answers or single causes. Yet much of the public conversation has narrowed to one idea—rising carbon dioxide levels from human activity. That may contain truth, but it’s not the whole story.
Greenhouse gases influence climate. The greenhouse effect is well understood: gases like carbon dioxide, methane, and water vapor absorb and re-emit infrared radiation, warming the atmosphere near Earth’s surface. Without it, the planet would be too cold to sustain life.
But understanding the greenhouse effect is not the same as understanding climate change. The real question isn’t whether greenhouse gases matter—they do. The question is how much they matter compared to everything else that shapes climate, and how confidently we can isolate their role in such a tangled, dynamic system.
To explore that, scientists use climate models—mathematical tools that simulate how energy moves through the atmosphere, oceans, and land. These models are useful, but they’re not direct evidence. They rely on estimates, assumptions, and simplifications. Core processes like cloud formation, ocean mixing, and soil moisture can’t be directly resolved and must be approximated. Many variables are tuned to make the models reproduce past temperature trends. That doesn’t make the models useless—but it does mean their projections can’t be treated as independent evidence of causation. You can’t fit a model to observed warming and then cite its output as proof of what caused it.
Outside the models, we have real-world observations. Global surface temperatures have risen by about 1.1°C since the late 19th century. During that time, atmospheric CO₂ rose from roughly 280 to over 420 parts per million. The correlation is clear. But in a system driven by many overlapping factors, correlation isn’t causation.
So what else drives climate?
Start with the sun—the source of nearly all climate energy. Though total output has stayed roughly stable in recent decades, solar activity varies over multiple timescales. Researchers have explored links between solar cycles, magnetic fields, cosmic rays, and cloud formation. While not well represented in most models, these interactions could influence clouds, radiation, or circulation in subtle but significant ways. The science remains unsettled—but it is serious enough to warrant far more study.
Land use is another major factor. Human activities like deforestation, agriculture, irrigation, and urban development change how energy and moisture move through the system. Cities trap heat, croplands shift evaporation, and forest removal changes how sunlight is reflected or absorbed. These changes reshape local and regional climates—sometimes dramatically—without requiring changes in atmospheric greenhouse gases.
Then there are aerosols—tiny particles released by both nature and industry. Sulfates from burning coal reflect sunlight and cool the atmosphere. Black carbon, by contrast, absorbs heat. Volcanic eruptions can inject aerosols high into the stratosphere, cooling the planet for years. Mount Pinatubo’s 1991 eruption, for example, dropped global temperatures by about half a degree Celsius. Aerosols also affect cloud formation and rainfall. Those interactions are complex and remain one of the least constrained areas in climate science. Models struggle to account for them accurately.
The system also contains its own internal variability. Cycles like El Niño and La Niña shift global weather patterns every few years. Others, like the Pacific Decadal Oscillation or the Atlantic Multidecadal Oscillation, operate over decades. These patterns emerge from within the climate system—no outside trigger required. They can mask or amplify broader trends, sometimes for decades at a time.
Looking further back, we see that Earth’s climate has always changed. The Medieval Warm Period, the Little Ice Age, the end of the last glacial period—all occurred before modern industry. These shifts were driven by solar variation, ocean circulation, volcanic activity, orbital cycles, and forces we still don’t fully understand. If we can’t precisely explain past changes, we should be cautious about overconfidence in explaining the present.
Then there are feedbacks—where one change leads to others. Warming increases water vapor, which traps more heat. Melting sea ice reduces reflectivity, pulling in more solar energy. Some feedbacks amplify change, others dampen it, and many remain poorly quantified—and poorly understood. These dynamics are already observable in places like the Arctic, and when feedbacks dominate, even small uncertainties in inputs can lead to wide differences in outcome.
Step back far enough, and a deeper truth emerges: this isn’t just a physics problem. It’s a complex, dynamic system with multiple interacting parts—some measurable, some not, many still misunderstood. Yet the public narrative has largely narrowed to a single explanation: fossil fuel emissions. That may serve messaging goals or policy agendas—but it doesn’t serve scientific understanding.
This is not a call for denial or delay. Climate change is real, and the risks of ignoring it are serious. But the forces behind it are many, and our understanding of them is still evolving. If we oversimplify the causes, we’ll oversimplify the responses too. Reducing the problem to a single variable may simplify headlines—but it oversimplifies the science.
So what drives climate change?
The most honest answer is: many things, in many ways, often interacting in ways we don't fully understand. Greenhouse gases matter. So do aerosols, solar cycles, land use, ocean patterns, and feedbacks that push in both directions. There is no single driver—and no single solution.
What matters most now is how we interpret what we see. That means asking harder questions, tolerating uncertainty, and resisting answers that sound too simple to be true.
Truth, in this domain, is rarely tidy. But if we want to respond wisely, we have to start by telling it plainly.