Query: ...Livestock are responsible for 18 per cent of the  greenhouse gases that cause global warming, more than cars, planes and  all other forms of transport put together.

Relevant passages:
Livestock <=SEP=> Livestock are domesticated animals raised in an agricultural setting to produce commodities such as food , fiber , and labor . The term is often used to refer solely to those raised for food , and sometimes only farmed ruminants , such as cattle and goats . In recent years , some organizations have also raised livestock to promote the survival of rare breeds . The breeding , maintenance , and slaughter of these animals , known as animal husbandry , is a component of modern agriculture that has been practiced in many cultures since humanity 's transition to farming from hunter-gatherer lifestyles .   Animal husbandry practices have varied widely across cultures and time periods . Originally , livestock were not confined by fences or enclosures , but these practices have largely shifted to intensive animal farming , sometimes referred to as `` factory farming '' . These practices increase yield of the various commercial outputs , but have led to increased concerns about animal welfare and environmental impact . Livestock production continues to play a major economic and cultural role in numerous rural communities .

Greenhouse gas <=SEP=> A greenhouse gas ( abbrev . GHG ) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range . This process is the fundamental cause of the greenhouse effect . The primary greenhouse gases in Earth 's atmosphere are water vapor , carbon dioxide , methane , nitrous oxide , and ozone . Without greenhouse gases , the average temperature of Earth 's surface would be about -18 ° C , rather than the present average of 15 ° C . In the Solar System , the atmospheres of Venus , Mars and Titan also contain gases that cause a greenhouse effect .   Human activities since the beginning of the Industrial Revolution ( taken as the year 1750 ) have produced a 40 % increase in the atmospheric concentration of carbon dioxide , from 280 ppm in 1750 to 406 ppm in early 2017 . This increase has occurred despite the uptake of a large portion of the emissions by various natural `` sinks '' involved in the carbon cycle . Anthropogenic carbon dioxide emissions ( i.e. , emissions produced by human activities ) come from combustion of fossil fuels , principally coal , oil , and natural gas , along with deforestation , soil erosion and animal agriculture .   It has been estimated that if greenhouse gas emissions continue at the present rate , Earth 's surface temperature could exceed historical values as early as 2047 , with potentially harmful effects on ecosystems , biodiversity and the livelihoods of people worldwide . Recent estimates suggest that on the current emissions trajectory the Earth could pass a threshold of 2 ° C global warming , which the United Nations ' IPCC designated as the upper limit to avoid `` dangerous '' global warming , by 2036 .

Agriculture <=SEP=> Agriculture or farming is the cultivation and breeding of animals , plants and fungi for food , fiber , biofuel , medicinal plants and other products used to sustain and enhance human life . Agriculture was the key development in the rise of sedentary human civilization , whereby farming of domesticated species created food surpluses that nurtured the development of civilization . The study of agriculture is known as agricultural science . The history of agriculture dates back thousands of years , and its development has been driven and defined by greatly different climates , cultures , and technologies . Industrial agriculture based on large-scale monoculture farming has become the dominant agricultural methodology .   Modern agronomy , plant breeding , agrochemicals such as pesticides and fertilizers , and technological developments have in many cases sharply increased yields from cultivation , but at the same time have caused widespread ecological damage and negative human health effects . Selective breeding and modern practices in animal husbandry have similarly increased the output of meat , but have raised concerns about animal welfare and the health effects of the antibiotics , growth hormones , and other chemicals commonly used in industrial meat production . Genetically modified organisms are an increasing component of agriculture , although they are banned in several countries . Agricultural food production and water management are increasingly becoming global issues that are fostering debate on a number of fronts . Significant degradation of land and water resources , including the depletion of aquifers , has been observed in recent decades , and the effects of global warming on agriculture and of agriculture on global warming are still not fully understood .   The major agricultural products can be broadly grouped into foods , fibers , fuels , and raw materials . Specific foods include cereals ( grains ) , vegetables , fruits , oils , meats and spices . Fibers include cotton , wool , hemp , silk and flax . Raw materials include lumber and bamboo . Other useful materials are also produced by plants , such as resins , dyes , drugs , perfumes , biofuels and ornamental products such as cut flowers and nursery plants . Over one third of the world 's workers are employed in agriculture , second only to the service sector , although the percentages of agricultural workers in developed countries has decreased significantly over the past several centuries .

Methane <=SEP=> Methane ( -LSB- ˈmɛθeɪn -RSB- or -LSB- ˈmiːθeɪn -RSB- ) is a chemical compound with the chemical formula ( one atom of carbon and four atoms of hydrogen ) . It is a group 14 hydride and the simplest alkane , and is the main constituent of natural gas . The relative abundance of methane on Earth makes it an attractive fuel , though capturing and storing it poses challenges due to its gaseous state under normal conditions for temperature and pressure .   Natural methane is found both below ground and under the sea floor . When it reaches the surface and the atmosphere , it is known as atmospheric methane . The Earth 's atmospheric methane concentration has increased by about 150 % since 1750 , and it accounts for 20 % of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases ( these gases do n't include water vapor which is by far the largest component of the greenhouse effect ) .