Where does all that carbon dioxide (CO2) come from? Who is mainly responsible for all that CO2 in our atmosphere? 

Different types of greenhouse gases

Carbon dioxide is considered the most common greenhouse gas (GHG), but it is not the only one. CO2 accounts for about 80 percent of greenhouse gases. It is followed by methane (CH4), nitrous oxide (N2O) and fluorinated gases.  

Here is an overview of the four largest greenhouse gases and their sources. More details can be found in the following graphic:  

Carbon Dioxide (CO2)  — Its sources are fossil fuel use, solid waste, deforestation, land clearing for agriculture, and degradation of soils. 

Methane (CH4) — Its sources are agricultural activities, waste management, energy use, and biomass. 

Nitrous Oxid (N2O) — Its sources are agricultural activities (fertilizer use), industrial activities, combustion of fossil fuels, and solid waste. 

Fluorinated Gases — Its sources are industrial processes, refrigeration, and use of consumer products. 

sources of green house gases

CO2 Emissions By Source 

Since CO2 accounts for the largest share of greenhouse gases (around 80%), it is worth taking a closer look at the sources of emissions. 

Around 84% of all anthropogenic (human-made) CO₂ emissions come from the areas of electricity and heat production, agriculture, industry and transport. Which of these produces the most CO2 on a global scale? The burning of fossil fuels (oil, gas and coal) is responsible for about 80% of the CO2 emissions. The rest comes from the conversion of land, mainly from forests to pastures and croplands. 

Energy production, industry and construction, transport, agriculture and private households are all sharing the CO2 emissions to a decreasing extent. 

Energy And Heat Supply  

The energy industry burns fossil fuels — such as lignite and hard coal, oil and gas — to generate electricity and fuels. Overall, coal consumption is declining, but oil and natural gas consumption is rising. About 40 percent of global carbon dioxide emissions are from coal consumption, 34 percent from oil, 20 percent from natural gas and the remaining 6 percent from cement production and other sources.   

Cement production also accounts for a notable eight percent of global greenhouse gas emissions. Cement is very energy-intensive to produce and additional CO2 is also produced through chemical processes in the production. 


Industry and construction are responsible for about one-fifth of CO2 emissions worldwide.

co2 emission air pollution


Around one-third of CO2 emissions are attributed to transportation, first and foremost to cars, commercial vehicles, airplanes, ships and, last but not least, trains.  

When we travel by air, we produce 214 grams of CO2 per kilometer, making air travel the most climate-damaging mode of transport of all. At 38 grams per kilometer, rail is much more climate-friendly. Global air traffic is responsible for around two percent of global CO2 emissions, which corresponds to around 12% of transport emissions. When flying, not only the kerosene combustion but also the condensation trails produced in the process contribute to global warming.  

Flying increases the individual CO2 footprint particularly strongly. For example, a long-haul flight causes as much CO2 as the average European consumes in a year. 

co2 emission by planes

Private Households  

Electricity is the biggest CO2 guzzler. It is therefore all the more important to save electricity. This can be done with small steps, such as switching off the lights or unplugging appliances that are not constantly used, for example, the toaster or the hair dryer. Switching to electricity from renewable energy sources also helps to save CO2. 

Did you know that the CO2 emissions of the entire Internet are now as great as those of global air travel (before the coronavirus). Streaming a 30-minute video releases about as much CO2 as a six-kilometer car ride.  

A European electricity provider published a study showing that video streaming consumed as much electricity worldwide in 2018 as Poland, Italy, and Germany combined in the same year. 

co2 emissions by video streaming

Forecasters expect an increase in electricity consumption in industrialized nations of over 20% in the next few years due to digitization.  

Unfortunately, the use of renewable energies such as hydro, wind and solar power is only helping to counteract this to a limited extent. 


Another quarter is caused by agriculture and forestry. Here, it is primarily methane that is produced during milk and meat production. 

Land Use and Forestry (11.6 percent of 2018 greenhouse gas emissions) — Land areas can act as a sink (absorbing CO2 from the atmosphere) or a source of greenhouse gas emissions. 

If you want to know how the green house effect works click here .

If you need more background information on the greenhouse gas see also the Global Carbon Project  or the United States Environmental Protection Agency, EPA

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