Nitrous oxide in the context of "Flammability"

Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (CO₂), from burning fossil fuels such as coal, oil, and natural gas, is the main cause of climate change. The largest annual emissions are from China followed by the United States. The United States has higher emissions per capita. The main producers fueling the emissions globally are large oil and gas companies. Emissions from human activities have increased atmospheric carbon dioxide by about 50% over pre-industrial levels. The growing levels of emissions have varied, but have been consistent among all greenhouse gases. Emissions in the 2010s averaged 56 billion tons a year, higher than any decade before. Total cumulative emissions from 1870 to 2022 were 703 GtC (2575 GtCO₂), of which 484±20 GtC (1773±73 GtCO₂) from fossil fuels and industry, and 219±60 GtC (802±220 GtCO₂) from land use change. Land-use change, such as deforestation, caused about 31% of cumulative emissions over 1870–2022, coal 32%, oil 24%, and gas 10%.

Carbon dioxide is the main greenhouse gas resulting from human activities. It accounts for more than half of warming. Methane (CH₄) emissions have almost the same short-term impact. Nitrous oxide (N₂O) and fluorinated gases (F-gases) play a lesser role in comparison. Emissions of carbon dioxide, methane and nitrous oxide in 2023 were all higher than ever before.

Greenhouse gases (GHGs) are the gases in an atmosphere that trap heat, raising the surface temperature of astronomical bodies such as Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. The Earth is warmed by sunlight, causing its surface to radiate heat, which is then mostly absorbed by greenhouse gases. Without greenhouse gases in the atmosphere, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F). Human-induced warming has been increasing at a rate that is unprecedented in the instrumental record, reaching 0.27 [0.2–0.4] °C per decade over 2015–2024. This high rate of warming is caused by a combination of greenhouse gas emissions being at an all-time high of 53.6±5.2 Gt CO2e yr−1 over the last decade (2014–2023), as well as reductions in the strength of aerosol cooling.

The five most abundant greenhouse gases in Earth's atmosphere, listed in decreasing order of average global mole fraction, are: water vapor, carbon dioxide, methane, nitrous oxide, ozone. Other greenhouse gases of concern include chlorofluorocarbons (CFCs and HCFCs), hydrofluorocarbons (HFCs), perfluorocarbons, SF
₆, and NF
₃. Water vapor causes about half of the greenhouse effect, acting in response to other gases as a climate change feedback.

There is scientific consensus that the Earth has been consistently warming since the start of the Industrial Revolution, that the rate of recent warming is largely unprecedented, and that this warming is mainly the result of a rapid increase in atmospheric carbon dioxide (CO₂) caused by human activities. The human activities causing this warming include fossil fuel combustion, cement production, and land use changes such as deforestation, with a significant supporting role from the other greenhouse gases such as methane and nitrous oxide. This human role in climate change is considered "unequivocal" and "incontrovertible".

Nearly all actively publishing climate scientists say humans are causing climate change. Surveys of the scientific literature are another way to measure scientific consensus. A 2019 review of scientific papers found the consensus on the cause of climate change to be at 100%, and a 2021 study concluded that over 99% of scientific papers agree on the human cause of climate change. The small percentage of papers that disagreed with the consensus often contained errors or could not be replicated.

Greenhouse gas emissions from agriculture are large: the agriculture, forestry and land use sectors contribute between 13% and 21% of global greenhouse gas emissions. Direct greenhouse gas emissions include those from rice and livestock farming. Indirect emissions from the conversion of non-agricultural land such as forests into agricultural land are also very important. With regards to direct emissions, nitrous oxide and methane makeup over half of total greenhouse gas emissions from agriculture. A 2023 review emphasizes that emissions from agricultural soils are shaped by factors such as soil type, climate, and management practices. It also highlights several mitigation strategies, including conservation tillage, precision agriculture, improved water use, and the application of biochar, that can reduce emissions and enhance soil carbon storage.

Furthermore, there is also fossil fuel consumption for transport and fertilizer production. For example, the manufacture and use of nitrogen fertilizer contributes around 5% of all global greenhouse gas emissions. Livestock farming is a major source of greenhouse gas emissions.

Soil gases (soil atmosphere) are the gases found in the air space between soil components. The spaces between the solid soil particles, if they do not contain water, are filled with air. The primary soil gases are nitrogen, carbon dioxide and oxygen. Oxygen is critical because it allows for respiration of both plant roots and soil organisms. Other natural soil gases include nitric oxide, nitrous oxide, methane, and ammonia. Some environmental contaminants below ground produce gas which diffuses through the soil such as from landfill wastes, mining activities, and contamination by petroleum hydrocarbons which produce volatile organic compounds. The soil atmosphere is also made of a variety of volatile compounds emitted by soil organisms, as respiratory metabolites, allelopathic compounds or semiochemical signals used in within-species and between-species communication. Soil is a net emitter of greenhouse gases, in particular when and where permafrost is thawing and degassing under the influence of climate warming.

Gases fill soil pores in the soil structure as water drains or is removed from a soil pore by evaporation or root absorption. The network of pores within the soil aerates, or ventilates, the soil. This aeration network becomes blocked when water enters soil pores. Not only are both soil air and soil water very dynamic parts of soil, but both are often inversely related.

This article is a list of locations and entities by greenhouse gas emissions, i.e. the greenhouse gas emissions from companies, activities, and countries on Earth which cause climate change. The relevant greenhouse gases are mainly: carbon dioxide, methane, nitrous oxide and the fluorinated gases bromofluorocarbon, chlorofluorocarbon, hydrochlorofluorocarbon, hydrofluorocarbon, nitrogen trifluoride, perfluorocarbons and sulfur hexafluoride.

The extraction and subsequent use of fossil fuels coal, oil and natural gas, as a fuel source, is the largest contributor to global warming.

This is a list of sovereign states and territories by per capita greenhouse gas emissions due to certain forms of human activity, based on the EDGAR database created by European Commission. The following table lists the 1970, 1990, 2000, 2010, 2020, 2021, 2022 and 2023 annual per capita GHG emissions estimates (in metric tons of CO₂ equivalent per year). The data include carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) from all sources, including agriculture and land use change. They are measured in carbon dioxide-equivalents over a 100-year timescale.

The Intergovernmental Panel on Climate Change (IPCC) 6th assessment report finds that the "Agriculture, Forestry and Other Land Use (AFOLU)" sector on average, accounted for 13–21% of global total anthropogenic GHG emissions in the period 2010–2019. Land use change drivers net AFOLU CO₂ emission fluxes, with deforestation being responsible for 45% of total AFOLU emissions. In addition to being a net carbon sink and source of GHG emissions, land plays an important role in climate through albedo effects, evapotranspiration, and aerosol loading through emissions of volatile organic compounds. The IPCC report finds that the LULUCF sector offers significant near-term mitigation potential while providing food, wood and other renewable resources as well as biodiversity conservation. Mitigation measures in forests and other natural ecosystems provide the largest share of the LULUCF mitigation potential between 2020 and 2050. Among various LULUCF activities, reducing deforestation has the largest potential to reduce anthropogenic GHG emissions, followed by carbon sequestration in agriculture and ecosystem restoration including afforestation and reforestation. Land use change emissions can be negative.

Global warming potential (GWP) is a measure of how much heat a greenhouse gas traps in the atmosphere over a specific time period, relative to carbon dioxide (CO₂). It is expressed as a multiple of warming caused by the same mass of (CO₂). Therefore, by definition CO₂ has a GWP of 1. For other gases it depends on how strongly the gas absorbs thermal radiation, how quickly the gas leaves the atmosphere, and the time frame considered.

For example, methane has a GWP over 20 years (GWP-20) of 81.2 meaning that, a leak of a tonne of methane is equivalent to emitting 81.2 tonnes of carbon dioxide measured over 20 years. As methane has a much shorter atmospheric lifetime than carbon dioxide, its GWP is much less over longer time periods, with a GWP-100 of 27.9 and a GWP-500 of 7.95.