What Causes Climate Change? An Interactive Explainer

What causes climate change? The short answer

Climate change today is caused mainly by humans adding greenhouse gases to the air, above all carbon dioxide (CO₂) from burning coal, oil and gas.¹¹² These gases act like a blanket around Earth: sunlight gets in easily, but part of the heat Earth gives off is caught and sent back down.² Add more gas and the blanket gets thicker, so the planet warms.

Before the industrial era, CO₂ was about 280 parts per million (ppm). It is now over 420 ppm, higher than at any time in at least two million years.⁹¹² Over the same time, Earth's average temperature has risen by about 1.2 °C since the late 1800s.¹⁰¹² The world's climate scientists, in the IPCC, call it "unequivocal" that human influence has warmed the atmosphere, ocean and land.¹²

What is climate change? Weather vs climate

Weather is what the atmosphere is doing over minutes to weeks: a snowstorm, a hot afternoon, a windy week. Climate is the weather averaged over several decades.³ So "climate change" means a long-term shift in those averages, and today it mostly means global warming plus everything warming does to rain, ice, oceans and living things.⁵

That is why a cold day, or even a cold winter where you live, doesn't disprove warming. One day is weather. The trend over many decades, measured all over the planet, is climate. In the player above, try averaging the same noisy data over one month, then over thirty years: the bumps smooth out and the trend appears.

How the greenhouse effect works

To understand what changes the climate, follow the energy:

Sunlight comes in. About 29% is reflected straight back to space by clouds, tiny particles, ice and snow. The other 71% is absorbed and warms the air, land and ocean.⁷
Earth glows with heat. A warm planet gives off energy of its own as invisible infrared light.¹
Greenhouse gases catch it. Gases such as carbon dioxide, methane, nitrous oxide and water vapour absorb most of that outgoing heat and re-release it in all directions, including back toward the surface.¹⁹

This natural greenhouse effect is a good thing. It keeps Earth's average temperature around 15 °C. Without it, the surface would be about 33 °C colder, and much of the planet would be frozen.²⁹ The problem isn't the blanket. It's that we keep making it thicker.

Scientists have known that CO₂ and water vapour trap heat since the 1850s and 1860s, when Eunice Foote and John Tyndall showed it in experiments. In 1896 Svante Arrhenius calculated that more CO₂ would warm the planet.⁴

The causes of climate change: where the extra gases come from

The IPCC groups global greenhouse gas emissions (2019) by sector:¹⁴

Sector	Share of emissions	Main sources
Energy supply	34%	Burning coal, oil and gas for electricity and heat
Industry	24%	Steel, cement, chemicals
Farming, forests and land use	22%	Deforestation, livestock, rice, fertilizer
Transport	15%	Cars, trucks, ships, planes
Buildings	6%	Heating and cooking with fuels

Fossil fuels are the biggest cause. Coal, oil and gas are the remains of ancient plants and sea life. The carbon in them was pulled out of the air by photosynthesis over millions of years (see how the carbon cycle works), and we are putting it back in a few hundred.⁹ Other gases add to the blanket too. Methane comes from livestock, rice farming, landfills and leaks from oil and gas systems (natural gas is 70–90% methane). Nitrous oxide comes mostly from fertilizer.¹

How does deforestation contribute to climate change?

Trees are made largely of carbon they took from the air. When forests are cleared and burned, or left to rot, that carbon goes back into the atmosphere as CO₂. And fewer trees are left to soak it up again. About half of the emissions from farming and land use are CO₂ from land-use change, mainly deforestation.¹⁴ Protecting and restoring forests is one of the ways to slow warming.

The climate change graph: the Keeling curve

In March 1958, scientist Charles David Keeling began measuring CO₂ at the Mauna Loa Observatory, 3,400 metres up a volcano in Hawaii. It is the longest direct record of CO₂ in the air.¹¹ It started at about 315 ppm.⁹ The line zigzags every year: in the northern spring, growing plants pull CO₂ out of the air, and in autumn, rotting leaves release it.⁸ But under the zigzag, the curve keeps climbing, and faster over time: about 0.8 ppm per year in the 1960s, and about 2.6 ppm per year in 2015–2024.⁹ The yearly average at Mauna Loa was 424.6 ppm in 2024.¹¹

Is climate change real? How we know humans are causing it

Yes. Scientists have checked the other suspects:

The Sun? Since 1750, the Sun's energy reaching Earth has stayed roughly the same or dropped slightly. And while the lower atmosphere warms, the upper atmosphere is cooling. If the Sun were the cause, both layers would warm. A thicker heat-trapping blanket explains the pattern.¹
Natural cycles? The IPCC estimates that natural factors (the Sun and volcanoes) changed global temperature by only about −0.1 to +0.1 °C between 1850–1900 and 2010–2019. Human activity accounts for about 1.07 °C.¹²
The CO₂ is ours. CO₂ has risen by nearly 50% since 1750. During the ice-age cycles of the past, it never went above 300 ppm.¹⁹

When the blanket thickens, Earth briefly takes in more energy than it gives off. It keeps warming until the two balance again.⁷¹⁰ The warming toy in the player uses a simple rule of thumb: about 3 °C of long-run warming for every doubling of CO₂, which is the IPCC's best estimate.¹²

Effects of climate change: how it affects the environment

A degree or so sounds small, but warming a whole planet takes an enormous amount of energy, and the effects add up:

Oceans: the ocean has absorbed about 90% of the extra heat.⁴ It also absorbs CO₂, which has made seawater about 30% more acidic since the Industrial Revolution (pH 8.21 → 8.10). That makes it harder for corals and shellfish to build their shells.⁹
Ice: glaciers are retreating almost everywhere. Between 1993 and 2019, Greenland lost about 279 billion tonnes of ice per year and Antarctica about 148 billion tonnes.⁴
Sea level: it rose about 20 cm (8 inches) in the last century, from melting land ice and from seawater expanding as it warms. The rate in the last two decades is nearly double that of the last century.⁴
Extreme weather: heat waves are getting more intense and more frequent, and heavy downpours heavier. Every extra half-degree of warming makes these extremes clearly worse.⁵¹²

How does climate change affect biodiversity and animals?

Plants and animals are on the move. About half of the species scientists have assessed have shifted toward the poles or to higher ground as their homes warm.¹³ Coral reefs are bleaching, and coral reefs and Arctic ecosystems face a high risk of losing species.¹³

How does climate change affect humans? Why it matters

Climate change is important because people depend on steady weather, water, crops and coastlines. The IPCC estimates that 3.3 to 3.6 billion people live in places that are highly vulnerable to climate change.¹³ How much worse it gets depends on our choices. By 2081–2100, the IPCC projects about 1.0–1.8 °C of warming if emissions fall very fast, and 3.3–5.7 °C if they keep rising steeply.¹² That gap is why this matters.

Climate change solutions: how to stop climate change

Here's the hopeful part: because we know the cause, we know the fix. To stop the warming, the world must reach at least net zero CO₂, putting no more into the air than is taken out.¹² NASA notes that if we stopped adding greenhouse gases, global temperature would level off within a few years.⁶ And the tools keep getting cheaper. From 2010 to 2019, the cost of solar power fell by about 85%, wind by 55% and lithium-ion batteries by 85%.¹⁴

Scientists talk about two kinds of action: mitigation, which means cutting emissions (clean electricity, electric transport, efficient buildings, protecting forests), and adaptation, which means preparing for the changes already happening.⁶ Every bit of warming we avoid makes a difference.

Common misconceptions

"It's cold today, so there's no global warming." That's weather. Climate is the average over decades, measured across the whole planet.³

"The greenhouse effect is bad." Without it, Earth would be about 33 °C colder. The problem is the extra gases we add.²

"It's just the Sun." The Sun's energy has been flat or slightly lower since 1750, and the upper atmosphere is cooling.¹

"One degree is nothing." For a whole planet it is a huge amount of heat, and it's already raising seas and intensifying heat waves.⁴⁵

"It's too late to do anything." Scientists expect warming to level off within a few years once net CO₂ emissions stop (reach net zero), and every fraction of a degree avoided reduces the harm.⁶¹²

FAQ

What are the main causes of climate change?

The main cause is burning coal, oil and gas, which adds carbon dioxide to the air. Cutting down forests, farming (which releases methane and nitrous oxide) and some industrial processes add more. These extra greenhouse gases trap more heat, so Earth warms.

How do we know climate change is caused by humans?

Carbon dioxide has risen from about 280 to over 420 parts per million, matching the fossil fuels we burn. The Sun's energy hasn't increased since the 1750s, and natural factors changed global temperature by only about 0.1 °C either way. The IPCC concludes it is unequivocal that human influence has warmed the planet.

What is the difference between weather and climate?

Weather is what the atmosphere is doing over minutes to weeks: rain, snow, sun and wind. Climate is the weather averaged over several decades. One cold day doesn't disprove a warming climate.

Is the greenhouse effect bad?

No, the natural greenhouse effect keeps Earth livable. Without it, the planet would be about 33 °C colder. The problem is the extra greenhouse gas we add, which thickens the blanket and warms Earth further.

How does deforestation contribute to climate change?

Trees store carbon in their wood and roots. When forests are cut down and burned or left to rot, that carbon goes into the air as carbon dioxide, and fewer trees remain to take it back out. Land-use change, mostly deforestation, is a major source of CO2.

How does climate change affect animals and biodiversity?

About half of the species scientists have studied have shifted toward the poles or to higher ground as their homes warm. Warmer oceans are bleaching coral reefs (and more acidic water makes it harder for corals to build their skeletons), and Arctic species are losing sea ice.

Is it too late to stop climate change?

No. NASA notes that if we stopped adding greenhouse gases, global temperatures would level off within a few years. Some warming is locked in, but every bit of warming we avoid reduces the harm.

What causes climate change?

Run the climate yourself

Play with Earth's blanket!

Weather or climate?

Averaging window

Switch off the blanket

The greenhouse effect

Earth's blanket

Read the Keeling curve

The Mauna Loa record

Thicken the blanket

Energy balance

A thicker blanket

What is changing?

Observed effects

A warmer world

Switch to clean

Cutting emissions (a toy)

We can help