You have seen the headlines. You have heard the debates.
But do you actually understand how climate change works? Not the politics or the arguments. The actual physical process, step by step, from sunlight entering the atmosphere to temperatures rising around the world.
Most people have a rough sense that carbon dioxide is involved. Fewer can explain what it actually does and why it matters so much. Almost no one can explain why a 1.2-degree rise in average temperature is considered serious, or what feedback means in this context.
This article walks through the full mechanism, clearly and simply.
Quick Answer: Climate change works through a chain of physical processes. The Sun sends energy to Earth. Earth absorbs it and radiates heat back outward. Greenhouse gases in the atmosphere absorb that outgoing heat and re-emit it in all directions, including back toward Earth. As greenhouse gas concentrations rise, more heat is retained, and the planet warms. Feedback processes then amplify the initial warming further. The result is a long-term rise in average global temperature that disrupts the climate systems human civilization has depended on for thousands of years.
Step One: Energy In, Energy Out
To understand how climate change works, start with the most basic fact about the Earth’s temperature.
Earth receives energy from the Sun, mostly in the form of visible light. It absorbs that energy and warms up. As it warms, it radiates energy back outward in the form of infrared radiation, which is heat.
When the energy arriving from the Sun equals the energy leaving the planet, Earth is in thermal equilibrium, and its temperature stays stable. This balance has held, with natural fluctuations, for billions of years.
Climate change begins when something disrupts that balance.
Step Two: What Greenhouse Gases Actually Do
The major long-lived greenhouse gases include carbon dioxide, methane, and nitrous oxide. Carbon dioxide is the largest contributor to current human-caused warming.
Here is what they do.
As infrared radiation travels upward from Earth’s surface toward space, greenhouse gas molecules absorb it. They do not let it pass through cleanly. Instead, they absorb the heat and re-emit it in all directions, including back down toward Earth’s surface.
This slows the rate at which heat escapes the planet. More heat stays in the system. The planet warms.
Without any greenhouse gases, Earth’s average surface temperature would be approximately minus 18 degrees Celsius, roughly 32 degrees colder than today. Human civilization as we know it would not exist. A moderate greenhouse effect is not a problem. It is essential.
The problem is that greenhouse gas concentrations are rising rapidly, and the warming effect is intensifying as a result.
Carbon dioxide is now present at well over 420 parts per million, compared with about 280 parts per million before the Industrial Revolution. In the late 1950s, when geophysicist Charles Keeling began tracking CO2 concentrations atop Mauna Loa in Hawaii, the level was about 315 parts per million. The rise since then has been continuous, measurable, and directly linked to the burning of fossil fuels.
Step Three: The Energy Imbalance
In Why Don’t Spinning Tops Fall? by Charles DeLisi, Caroline works through the numbers with Barry, a geophysicist who becomes part of her extended family.
Barry explains that Earth absorbs an average of approximately 240 watts of solar energy per square meter across the planet. The current best estimate of the energy imbalance, the difference between what arrives and what escapes, is about 0.9 watts per square meter.
Caroline points out that this sounds small. Less than one percent of the incoming solar energy.
Barry’s response reframes everything.
When that seemingly tiny imbalance is multiplied across Earth’s entire surface, it represents an enormous amount of heat accumulating in the climate system every day.
The oceans absorb about 90 percent of this excess heat, which is why the warming of the surface has been gradual rather than immediate. But the heat is accumulating, and the oceans are warming too, which opens up a separate set of consequences.
Step Four: Feedback Loops Amplify the Warming
Here is where climate change becomes more complex and more serious than the basic greenhouse effect alone.
When the planet warms due to increased greenhouse gas concentrations, the warming triggers other processes that produce additional warming. These are called feedback loops.
The first major feedback is water vapor. Warmer air holds more water vapor. Water vapor is itself a greenhouse gas. So as temperatures rise, more water vapor enters the atmosphere, which traps more heat, which raises temperatures further, which adds more water vapor. The feedback is self-reinforcing.
The second major feedback is ice albedo. Ice is highly reflective. It bounces sunlight back into space rather than absorbing it. As temperatures rise, ice melts. The dark ocean or land surface underneath absorbs more sunlight than the ice did. The planet warms faster as a result.
When scientists account for these and other feedback effects, the expected long-term temperature increase from doubling carbon dioxide concentrations rises from roughly 1 degree Celsius to approximately 3 degrees Celsius, with significant uncertainty in either direction.
Step Five: The 1.2 Degrees That Feels Small but Is Not
Caroline raises the question directly in the book.
“1.2 degrees does not sound like much. It is much smaller than the difference between day and night, or between temperatures in different parts of the world.”
Barry’s answer is precise.
The 1.2-degree rise is a global average. It is layered on top of all the normal daily and seasonal variation that already exists. Think of it as a rising tide beneath all the waves. The waves still go up and down as they always did. But the baseline they ride on is higher than it used to be.
The situation is not static. As long as net carbon dioxide emissions continue, cumulative emissions continue to add to human-caused warming. Bringing net CO2 emissions to zero is necessary to stabilize CO2-induced warming.
Global carbon dioxide emissions remain extremely high, making the transition to net zero an urgent part of limiting further warming.
Why the Ice Core Evidence Matters
One of the most powerful pieces of evidence for understanding climate change comes from ice cores drilled from polar ice sheets.
As snow accumulates over thousands of years, air bubbles become trapped in the ice. Scientists can analyze those bubbles to reconstruct the composition of the atmosphere going back about 800,000 years, long before modern industrial civilization.
What the ice cores show is striking.
Over the past 800,000 years, atmospheric carbon dioxide generally fluctuated between roughly 170 and 300 parts per million as Earth moved through glacial and interglacial cycles. That range held steady for hundreds of thousands of years.
Then, over the last 150 years, carbon dioxide shot from 280 parts per million to well over 420 parts per million.
Caroline calculates that this spike occurred during a period that is one five-thousandth of the 800,000-year timeframe. The speed of the increase has no natural parallel in the ice core record.
How Do Scientists Know Humans Are Causing It?
The isotope evidence is one of the clearest lines of evidence.
Carbon from burning fossil fuels has a specific chemical fingerprint. Plants preferentially absorb the lighter isotope of carbon, carbon-12, over the heavier carbon-13. Fossil fuels are made from ancient plant material. When they are burned, the carbon dioxide they release has a lower ratio of carbon-13 to carbon-12 than naturally occurring carbon dioxide does.
Over the past 70 years, as atmospheric carbon dioxide has risen, the ratio of carbon-13 to carbon-12 in the atmosphere has decreased in exactly the pattern you would expect if the source were fossil fuel combustion.
This evidence is, in the words of Caroline’s father in the book, “essentially unchallengeable.”
What Can Be Done
Caroline asks the question that follows naturally from all of this.
“Is there any way to prevent the additional increase in temperature?”
The answer is yes, though not without difficulty.
Three broad approaches exist. The first is reducing emissions by transitioning from fossil fuels to clean energy sources. The second is carbon removal, drawing carbon dioxide out of the atmosphere through natural systems like forests or technological methods. The third is short-term interventions to limit warming while longer-term solutions scale up.
If this explanation made climate change easier to understand, Why Don’t Spinning Tops Fall? Takes the same clear, conversational approach to clean energy, wind power, solar energy, and the physics behind the solutions. Explore the full book here, or visit the Shop to get your copy.
Why Curious Teenagers Should Understand This
Caroline is a high school junior when this conversation takes place. She pushes back on every claim, calculates the numbers herself, and follows the answer wherever it leads, even when it takes her somewhere unexpected.
By the end of the conversation, she not only knows that climate change is real. She understands the mechanism well enough to evaluate what she reads, identify which claims are solid and which are exaggerated, and ask the right follow-up questions.
That kind of understanding is not reserved for scientists. It is available to anyone who is genuinely curious and willing to follow the reasoning step by step.
If you know a curious teenager, or you are an adult who wishes science had always been explained this way, Why Don’t Spinning Tops Fall? is designed to make complex ideas approachable without oversimplifying them.
Visit the Shop to get your copy, or order on Amazon.
Frequently Asked Questions
Q1: How does climate change work in simple terms?
Climate change works through the greenhouse effect. Greenhouse gases in the atmosphere absorb heat radiating from Earth’s surface and re-emit it in all directions, including back toward Earth. As greenhouse gas concentrations rise due to burning fossil fuels, more heat is retained, and the planet’s average temperature rises. Feedback processes involving water vapor and melting ice then amplify the initial warming.
Q2:What is the greenhouse effect, and is it bad?
The greenhouse effect is the process by which greenhouse gases trap heat in the atmosphere. Without it, Earth’s average surface temperature would be about minus 18 degrees Celsius and life as we know it would not exist. The problem is not the greenhouse effect itself but the rapid increase in greenhouse gas concentrations caused by human activity, which is intensifying the effect beyond the range to which current ecosystems and human systems are adapted to.
Q3: Why does a 1.2-degree rise in temperature matter?
The 1.2-degree rise is a global average layered on top of all existing temperature variation. It acts like a rising tide beneath all the normal waves of daily and seasonal change. Even this amount of warming is already causing measurable shifts in sea levels, storm intensity, ice coverage, and ecosystem behavior. And the warming is not finished. As long as net carbon dioxide emissions continue, cumulative emissions continue to add to human-caused warming. Bringing net CO2 emissions to zero is necessary to stabilize CO2-induced warming.
Q4: How do scientists know the warming is caused by humans?
Multiple independent lines of evidence point to human activity. Global surface temperature has increased faster since 1970 than during any other 50-year period in at least the past 2,000 years. The carbon dioxide in the atmosphere has a specific isotopic signature that identifies it as coming from fossil fuel combustion rather than natural sources. And the rise in atmospheric carbon dioxide directly tracks the rise in fossil fuel use since the Industrial Revolution.
Q5: What are feedback loops in climate science?
Feedback loops are processes that amplify or reduce an initial change. In climate science, the main positive feedbacks are water vapor feedback, where warmer air holds more water vapor, which is itself a greenhouse gas, and ice albedo feedback, where melting ice exposes darker surfaces that absorb more sunlight. This feedback means the total long-term warming from rising greenhouse gas concentrations is significantly larger than the direct warming from the gases alone.
