Causes
Earth's climate is constantly changing on it's own, but various activities by humans have caused increases in greenhouse gases in the atmosphere. These greenhouse gases are excellent at absorbing and retaining heat. The main greenhouse gases are:
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Water vapor provides an easily measurable feedback system because as water vapor increases, temperatures rise, and there is more clouds and precipitation. Since temperatures rise, even more water vapor can be contained within the atmosphere. It is usually not included in discussions on climate change, but it should be noted.
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Carbon dioxide does not constitute a large percentage of the gases in the atmosphere, but it is a large contributor to climate change especially with the multiple different ways it can enter the atmosphere.
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How it enters the atmosphere: respiration, volcanic eruptions, deforestation, and burning of fossil fuels
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Methane is able to trap way more heat than carbon dioxide, but is far less abundant in the atmosphere.
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How it enters the atmosphere: production and transport of coal, natural gas, and oil; decay in landfills, agriculture practices, and manure management from livestock
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Nitrous oxide makes up far less of the atmosphere, but contributes to acid rain.
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How it enters the atmosphere: fertilizers, and burning of fossil and biomass fuels
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Chlorofluorocarbons (CFCs) are entirely produced by industrial means and have, for most part, been banned globally due to their role in the destruction of the ozone layer.
Sources:
Environmental Protection agency. (n.d.). Greenhouse gas emissions: Overview of greenhouse gases. https://www.epa.gov/ghgemissions/overview-greenhouse-gases
National Aerospace and Aviation Association. (n.d.). Facts: Causes of climate change. Global Climate Change: Vital Signs of the Planet. https://climate.nasa.gov/causes/