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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.