Main causes are: Burning of hydrocarbons followed by deforestation.
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Globalisation, as each country becomes more popular with the country on the other side of the planet in terms or immigration, trade etc. it drastically increases the percentage of population growth without drastically increasing the cost of living resulting in more births than deaths each year, considering each family in modern times own a car and will go on holiday every so often, ask for items to be exported/imported, throws away any surplus they might have and will require more food the total amount of carbon emissions increases along with each countries carbon footprint.
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Burning hydrocarbon fuels, more cattle to feed the larger human population, deforestation.