What is causing climate change?
The main cause, the other causes, and the natural ones that have been ruled out.
The Met Office says the evidence is clear: the main cause of climate change is burning fossil fuels such as oil, gas and coal. Met Office: Causes of climate change
Burning fossil fuels
The Met Office dates the start of the problem to the mid-1800s, when people began burning coal, oil and gas for fuel on a large scale. Met Office: What is climate change? Burning fossil fuels releases greenhouse gases such as carbon dioxide, methane and nitrous oxide. Met Office: What is climate change?
Yearly carbon dioxide emissions from fossil fuels rose from about 11 billion tons in the 1960s to an estimated 37.4 billion tons in 2024. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
The IPCC’s Sixth Assessment Report found 64% of human-made greenhouse gas emissions come from fossil fuels and industry, and 11% from land use and forestry. Met Office: What is climate change?
Aeroplanes and cement-making add carbon dioxide too. Met Office: What is climate change? Making cement causes 2% of all carbon dioxide emissions. Met Office: Causes of climate change
Forests and farms
Forests take in and store carbon dioxide, so cutting them down lets it build up faster, and burning the trees releases the carbon they stored. Met Office: Causes of climate change
The Met Office says methane from farm animals is 30 times more powerful than carbon dioxide as a greenhouse gas, and nitrous oxide nearly 300 times. Met Office: Causes of climate change
Where the carbon dioxide goes
Plants and the ocean soak up about half the carbon dioxide people release from fossil fuels. The rest stays in the air. NOAA Climate.gov (archived June 2025): Atmospheric carbon dioxide
The shape of the curve shows that about 57% of carbon dioxide emissions stay in the atmosphere from year to year. Encyclopaedia Britannica: Keeling Curve
The oceans also take up around 25% of the carbon dioxide people release, which makes the water more acidic. Met Office: Effects of climate change
More than for 2 million years
There is more carbon dioxide in the air today than at any time in at least the past 2 million years. Met Office: Causes of climate change During the 20th and 21st centuries the level of carbon dioxide rose by 40%. Met Office: Causes of climate change
Natural causes, and why they don’t explain it
Earth’s climate has been changing since the planet formed 4.5 billion years ago. Until recently, natural factors drove those changes. Met Office: Causes of climate change Over the past million years, cold glacials and warmer interglacials have come round roughly every 100,000 years, driven by changes in Earth’s orbit. Met Office: Causes of climate change
- Milankovitch cycles, small changes in Earth’s path and tilt, alter how much sunlight reaches us, but they work over tens or hundreds of thousands of years. Met Office: Causes of climate change
- El Niño years warm the globe and La Niña years cool it, but only for months or years. They can’t explain the steady warming. Met Office: Causes of climate change
- If extra energy from the Sun were the cause, the whole atmosphere would warm, but only the bottom layer is warming. Met Office: Causes of climate change
- Volcanoes give out 50 times less carbon dioxide than people do, and their main effect is actually cooling. Met Office: Causes of climate change
- Scientists have ruled out natural causes such as volcanoes, changes in the Sun and natural sources of carbon dioxide as the main driver. Met Office: What is climate change?
Next: the evidence →