Greenhouse Gas Emissions
What is a greenhouse gas?
A greenhouse gas is a gas that causes the greenhouse effect - where the temperature of the earth's surface is higher than what it would be without. This happens because a greenhouse gas in the atmosphere absorbs and emits energy, some of it towards the surface thus warming it. Greenhouse gases are responsible for keeping the earth at an average temperature of 15°C. Without this, the earth's surface would have been about -18°C.
Greenhouse Gas data is collected and tracked by the United Nations Framework Convention on Climate Change.
What are the main greenhouse gases?
The following are the main greenhouse gases in the atmosphere.
- Water vapor (H2O) (including clouds) is the most significant greenhouse gas in the atmosphere, and accounts for about 50% of the greenhouse effect.
- Carbon Dioxide (CO2) is the next most significant greenhouse gas due to the quantity produced. CO2 accounts for about 20% of the greehouse effect. Since the industrial revolution human-generated emission of this gas has rapidly increased contributing to global warming.
- Methane (CH4) is a naturally occuring gas (Natural Gas) that is used as a fuel. Methane accounts for about 4-9% of the greenhouse effect. Its Global Warming Potential (GWP) is 84, which means it traps 84 times as much heat as the same quantity of Carbon Dioxide (whose GWP is 1).
- Nitrous Oxide (N2O) is an oxide of nitrogen which has considerable usage in medical applications. It is produced naturally by bacteria and fungi in soil and oceans. It is also produced as a result of human activity. Its GWP is 264.
- Sulphur Hexafluoride (SF6) is an extremely potent greenhouse gas (with a GWP of 17500). About 80% of this gas is used in the electrical industry.
- ChloroFluoroCarbon (CFC) is a colorless gas sold under the brand name Freon-12 (Dichlorodifluoromethane (R-12)), and is used as a refrigerant and aerosol spray propellant. Complying with the Montreal Protocol, its manufacture was banned in developed countries (non-article 5 countries) in 1996, and developing countries (article 5 countries) in 2010 due to concerns about its damaging effect on the ozone layer. Its only allowed usage is as fire retardant in submarines and aircraft.
- Hydrofluorocarbons (HFCs) is used as a propellant and refrigerant, though its usage is being phased out in developed countries. Its GWP is 5280.
- Perfluorocarbons (PFCs), also known as Fluorocarbons, are used in a variety of medical and industrial applications. GWP ranges from 4880 to 8210. Examples of perfluorocarbons are: PFC-116 also known as Hexaflouroethane, and PFC-14 also known as Tetraflouromethane.
- Nitrogen Trifluoride (NF3) is used in microelectronics. It is a very potent greenhouse gas with a GWP of 12800.
What is the worst greenhouse gas?
Carbon Dioxide is the gas causing the most damage via the greenhouse effect. This is inspite of the fact that:
- Watervapor (also a greenhouse gas) is more prevalent in the atmosphere, but resides in the atmosphere for about 9 days. Compare this to Carbon Dioxide which has a lifetime of between 30 and 95 years. Also, human activity does not directly affect water vapor presence except at local scales.
- Even though other gases are much more potent than Carbon Dioxide, they are produced in much smaller quantities, and hence the effect is quite low. See the accompanying chart which shows the net effect of each greenhouse gas taking into account the potency (in the form of the global warming potential (GWP).
What is the largest contributor to greenhouse gases?
The biggest contribution to CO2 emissions from human activity are due to burning of fossil fuels and industry. The various component of this activity include:
- Burning of coal as fuel - 40%.
- Liquid fuels including gasoline, fuel oil, etc account for - 35%.
- Natural gas used as fuel accounts for - 20%.
- Emission from production of cement amounts to - 4%.
- Total of gas flaring industrially and at wells include - 1%.
What percentage of carbon dioxide is man made?
Comparing the levels of various greenhouse gases in recent years to levels in 1750 (before the industrial revolution), it is possible to determine the percentage of carbon dioxide, methane and nitrous oxide due to man-made causes. Upto 45% of carbon dioxide in the atmosphere today can be attributed to human activity.
|Name||1750 level||2015 level||Change (%)|
How much does farming contribute to global warming?
According to CAIT, Agriculture accounts for about 5246 million tons of carbon dioxide in 2014 which amounts to 6.11% of the total carbon dioxide emissions. Energy and electricy/heat are the largest sources of carbon dioxide production.
|Sector||CO2 contribution (%)|
|Other Fuel Combustion||4.8|
|Land-Use Change and Forestry||3.7|
Who are the biggest carbon emitters?
China is the biggest carbon dioxide emitter in the world with about 11 billion tonnes of emissions from fossil fuels in 2017. United States is next with a carbon footprint of about 5 billion tonnes, followed by EU (28 countries) at 3.5 billion tonnes and India at about 2.5 billion tonnes. The following 10 countries are the biggest carbon dioxide emitters.
|Country||CO2 emission in million tonnes|
Who are the biggest carbon emitters per capita?
This chart shows carbon dioxide and greenhouse gas emissions per capita for 2012. In addition to looking at the total emissions per country (above), it is sometimes more useful to compare the emissions per capita to estimate how much each person in that country is responsible for carbon dioxide and greenhouse gas emissions.
|Country||CO2 emissions (tonnes)||GHG emissions (tonnes)|
|Trinidad and Tobago||28.66||38.86|
|Israel and Palestine, State of||10.11||10.43|
|Bosnia and Herzegovina||6.37||8.04|
|Serbia and Montenegro||6.03||7.86|
|Spain and Andorra||6.08||7.3|
|France and Monaco||5.49||7.27|
|Switzerland and Liechtenstein||5.44||6.9|
|Antigua and Barbuda||6.36||4.66|
|Saint Kitts and Nevis||4.68||3.84|
|Saint Helena, Ascension and Tristan da Cunha||2.96||3.46|
|Saint Vincent and the Grenadines||1.7||3.39|
|Saint Pierre and Miquelon||9.78||1.76|
|Papua New Guinea||0.67||1.32|
What foods cause the most carbon dioxide emissions?
Meat fromt ruminant animals (cattle, sheep and goats) is the most expensive in terms of carbon emissions per kCal with 5.6 grams per kCal. This chart shows the most common foods sorted by carbon emissions produced per kCal.
- Catfish, Salmon, Sea-bass, Shrimp, Tilapia, Trout
- Cheese, Milk, Yogurt
- Alfonsino, Cod, Flat fish, Herring, Lumpfish, Mackerel, Mussels, Pollock, Pout, Rock fish, Snapper, Sea-bass, Swordfish, Turbo
- Prespa bean Soybean
- Oil crops
- Canola, Palm
- Other cereals
- Barley, oats
- Recirculating Aquaculture
- Char, Trout, Turbot
- Cassava, Potatoes
- Ruminant meat
- Beef, Goat, Mutton, Lamb
- Temperate fruits
- Apple, Blueberry, Chinese pear, Grape, Peach, Raspberry, Strawberry
- Tropical fruits
- Andean blackberry, Avocado, Golden berry, Kiwi, Lemon, Lulo, Mango, Orange, Passionfruit, Tree tomato
- Asparagus, Leek, Mushroom, Onion, Lettuce, Tomato