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What's actually causing global warming?
Almost all of the extra greenhouse gas behind today's warming comes from human activity since the 1800s — mainly the everyday business of making electricity, growing food, manufacturing things, and getting around.
Industrial emissions · via Wikimedia CommonsRanked by scale
The big sources, in order of how much they matter
This list is genuinely a ranking — it follows roughly how much each sector contributes to global human-caused greenhouse gas emissions, based on international energy and climate accounting.
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Burning fossil fuels for electricity & heat
Coal, oil and natural gas power plants are the single largest source. Every kilowatt-hour generated this way releases CO2 that took millions of years to lock underground.
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Transport
Petrol and diesel cars, motorcycles, trucks, ships and planes all burn fossil fuel directly. Road transport alone is a major and fast-growing slice of this.
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Industry & manufacturing
Making cement, steel, plastics and chemicals both burns fuel for heat and, in some processes (like cement), releases CO2 as a direct by-product of the chemistry itself.
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Agriculture & land use
Clearing forests removes carbon-storing trees and often releases the carbon stored in soil. Livestock farming adds methane; fertiliser use adds nitrous oxide — both far more potent than CO2 molecule-for-molecule.
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Waste
Organic waste rotting in landfills without oxygen produces methane. It's a smaller slice of the total, but one of the easiest to shrink quickly through better waste management and recycling.
It isn't only how much we emit — it's how fast. Natural processes (plants, oceans, rock weathering) absorb CO2 over centuries to millennia. Humans have added a comparable amount in a little over a century, which is why concentrations have climbed roughly 100 times faster than at the end of the last ice age.