Greenhouse gas ( GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning such as coal, petroleum, 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 Big Oil. 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 . Emissions in the 2010s averaged 56 billion tons a year, higher than any decade before. Total cumulative emissions from 1870 to 2022 were 703 (2575 ), of which 484±20 (1773±73 ) from and industry, and 219±60 (802±220 ) 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.
Electricity generation, heat and transport are major emitters; overall energy is responsible for around 73% of emissions. Deforestation and other changes in land use also emit carbon dioxide and methane. The largest source of anthropogenic methane emissions is agriculture, closely followed by gas venting and fugitive emissions from the fossil-fuel industry. The largest agricultural methane source is livestock. Agricultural soils emit nitrous oxide partly due to . Similarly, fluorinated gases from play an outsized role in total human emissions.
The current -equivalent emission rates averaging 6.6 tonnes per person per year, are well over twice the estimated rate 2.3 tons
required to stay within the 2030 Paris Agreement increase of 1.5 °C (2.7 °F) over pre-industrial levels. Annual per capita emissions in the industrialized countries are typically as much as ten times the average in developing countries.The carbon footprint (or greenhouse gas footprint) serves as an indicator to compare the amount of greenhouse gases emitted over the entire life cycle from the production of a good or service along the supply chain to its final consumption.IPCC, 2022: Annex I: Glossary van. In IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change P.R.. Cambridge University Press, Cambridge, UK and New York, NY, USA. doi: 10.1017/9781009157926.020 Carbon accounting (or greenhouse gas accounting) is a framework of methods to measure and track how much greenhouse gas an organization emits.
Although CFCs are greenhouse gases, they are regulated by the Montreal Protocol which was motivated by CFCs' contribution to ozone depletion rather than by their contribution to global warming. Ozone depletion has only a minor role in greenhouse warming, though the two processes are sometimes confused in the media. In 2016, negotiators from over 170 nations meeting at the summit of the United Nations Environment Programme reached a legally binding accord to phase out hydrofluorocarbons (HFCs) in the Kigali Amendment to the Montreal Protocol. The use of CFC-12 (except some essential uses) has been phased out due to its Ozone depletion properties. The phasing-out of less active Haloalkane will be completed in 2030.Montreal Protocol
The main sources of greenhouse gases due to human activity (also called carbon sources) are:
The current -equivalent emission rates averaging 6.6 tonnes per person per year, are well over twice the estimated rate 2.3 tons required to stay within the 2030 Paris Agreement increase of 1.5 °C (2.7 °F) over pre-industrial levels.
While cities are sometimes considered to be disproportionate contributors to emissions, per-capita emissions tend to be lower for cities than the averages in their countries.
A 2017 survey of corporations responsible for global emissions found that 100 companies were responsible for 71% of global direct and indirect emissions, and that state-owned companies were responsible for 59% of their emissions.
China is, by a significant margin, Asia's and the world's largest emitter: it emits nearly 10 billion tonnes each year, more than one-quarter of global emissions. Other countries with fast growing emissions are South Korea, Iran, and Australia (which apart from the oil rich Persian Gulf states, now has the highest per capita emission rate in the world). On the other hand, annual per capita emissions of the EU-15 and the US are gradually decreasing over time. Emissions in Russia and Ukraine have decreased fastest since 1990 due to economic restructuring in these countries.
2015 was the first year to see both total global economic growth and a reduction of carbon emissions.
Africa and South America are both fairly small emitters, accounting for 3-4% of global emissions each. Both have emissions almost equal to international aviation and shipping.
These measures are sometimes used by countries to assert various policy/ethical positions on climate change.
Emissions may also be measured across shorter time periods. Emissions changes may, for example, be measured against the base year of 1990. 1990 was used in the United Nations Framework Convention on Climate Change (UNFCCC) as the base year for emissions, and is also used in the Kyoto Protocol (some gases are also measured from the year 1995).
A country's emissions may also be reported as a proportion of global emissions for a particular year.
Another measurement is of per capita emissions. This divides a country's total annual emissions by its mid-year population.
For example, in the main international treaty on climate change (the UNFCCC), countries report on emissions produced within their borders, e.g., the emissions produced from burning fossil fuels.
Under a production-based accounting of emissions, embedded emissions on imported goods are attributed to the exporting, rather than the importing, country. Under a consumption-based accounting of emissions, embedded emissions on imported goods are attributed to the importing country, rather than the exporting, country.
A substantial proportion of emissions is traded internationally. The net effect of trade was to export emissions from China and other emerging markets to consumers in the US, Japan, and Western Europe.
When these numbers are calculated per capita cumulative emissions based on then-current population the situation is shown even more clearly. The ratio in per capita emissions between industrialized countries and developing countries was estimated at more than 10 to 1.
Non-OECD countries accounted for 42% of cumulative energy-related emissions between 1890 and 2007. Over this time period, the US accounted for 28% of emissions; the EU, 23%; Japan, 4%; other OECD countries 5%; Russia, 11%; China, 9%; India, 3%; and the rest of the world, 18%.The European Commission adopted a set of legislative proposals targeting a reduction of the emissions by 55% by 2030.
Overall, developed countries accounted for 83.8% of industrial emissions over this time period, and 67.8% of total emissions. Developing countries accounted for industrial emissions of 16.2% over this time period, and 32.2% of total emissions.
However, what becomes clear when we look at emissions across the world today is that the countries with the highest emissions over history are not always the biggest emitters today. For example, in 2017, the UK accounted for just 1% of global emissions.
In comparison, humans have emitted more greenhouse gases than the Chicxulub crater which caused the extinction of the dinosaurs.
Transport, together with electricity generation, is the major source of greenhouse gas emissions in the European Union. Greenhouse gas emissions from the transportation sector continue to rise, in contrast to power generation and nearly all other sectors. Since 1990, transportation emissions have increased by 30%. The transportation sector accounts for around 70% of these emissions. The majority of these emissions are caused by passenger and vans. Road travel is the first major source of greenhouse gas emissions from transportation, followed by aircraft and maritime. Waterborne transportation is still the least carbon-intensive mode of transportation on average, and it is an essential link in Sustainability Supply chain.
Buildings, like industry, are directly responsible for around one-fifth of greenhouse gas emissions, primarily from Space heater and hot water consumption. When combined with power consumption within buildings, this figure climbs to more than one-third.
Within the EU, the agricultural sector presently accounts for roughly 10% of total greenhouse gas emissions, with methane from livestock accounting for slightly more than half of 10%.
Estimates of total emissions do include biotic carbon emissions, mainly from deforestation. Including biotic emissions brings about the same controversy mentioned earlier regarding carbon sinks and land-use change. The actual calculation of net emissions is very complex, and is affected by how carbon sinks are allocated between regions and the dynamics of the climate system.
Using different base years for measuring emissions has an effect on estimates of national contributions to global warming.The cited paper uses the term "start date" instead of "base year". This can be calculated by dividing a country's highest contribution to global warming starting from a particular base year, by that country's minimum contribution to global warming starting from a particular base year. Choosing between base years of 1750, 1900, 1950, and 1990 has a significant effect for most countries.
Greenhouse gas emissions are measured in equivalents determined by their global warming potential (GWP), which depends on their lifetime in the atmosphere. Estimations largely depend on the ability of oceans and land sinks to absorb these gases. Short-lived climate pollutants (SLCPs) including methane, hydrofluorocarbons (HFCs), tropospheric ozone and black carbon persist in the atmosphere for a period ranging from days to 15 years; whereas carbon dioxide can remain in the atmosphere for millennia. Reducing SLCP emissions can cut the ongoing rate of global warming by almost half and reduce the projected Arctic warming by two-thirds.
Greenhouse gas emissions in 2019 were estimated at 57.4 Gte, while emissions alone made up 42.5 Gt including land-use change (LUC).using 100 year global warming potential from IPCC-AR4
While mitigation measures for decarbonization are essential on the longer term, they could result in weak near-term warming because sources of carbon emissions often also co-emit air pollution. Hence, pairing measures that target carbon dioxide with measures targeting non- pollutants – short-lived climate pollutants, which have faster effects on the climate, is essential for climate goals.
Most emissions (56%) of nitrous oxide comes from agriculture, especially meat production: cattle (droppings on pasture), fertilizers, animal manure.Further contributions come from combustion of fossil fuels (18%) and as well as industrial production of adipic acid and nitric acid.
Greenhouse gas emissions can be divided into those that arise from the combustion of fuels to produce energy, and those generated by other processes. Around two thirds of greenhouse gas emissions arise from the combustion of fuels.
Energy may be produced at the point of consumption, or by a generator for consumption by others. Thus emissions arising from energy production may be categorized according to where they are emitted, or where the resulting energy is consumed. If emissions are attributed at the point of production, then electricity generators contribute about 25% of global greenhouse gas emissions.IEA, Emissions from Fuel Combustion 2018: Highlights (Paris: International Energy Agency, 2018) p.98 If these emissions are attributed to the final consumer then 24% of total emissions arise from manufacturing and construction, 17% from transportation, 11% from domestic consumers, and 7% from commercial consumers.IEA, Emissions from Fuel Combustion 2018: Highlights (Paris: International Energy Agency, 2018) p.101 Around 4% of emissions arise from the energy consumed by the energy and fuel industry itself.
The remaining third of emissions arise from processes other than energy production. 12% of total emissions arise from agriculture, 7% from land use change and forestry, 6% from industrial processes, and 3% from waste.
In March 2024, the International Energy Agency (IEA) reported that in 2023, global emissions from energy sources increased by 1.1%, rising by 410 million tonnes to a record 37.4 billion tonnes, primarily due to coal. Drought-related decreases in hydropower contributed to a 170 million tonne rise in emissions, which would have otherwise led to a decrease in the electricity sector's emissions. The implementation of clean energy technologies like Solar power, Wind power, nuclear, , and since 2019 has significantly tempered emissions growth, which would have been threefold without these technologies.
There are substantial uncertainties in the measurement of net carbon emissions.
In 1997, human-caused Indonesian peat fires were estimated to have released between 13% and 40% of the average annual global carbon emissions caused by the burning of fossil fuels.
Maritime transport accounts for 3.5% to 4% of all greenhouse gas emissions, primarily carbon dioxide.
In 2020, approximately 3.5% of the overall human impacts on climate are from the aviation sector. The impact of the sector on climate in the last 20 years had doubled, but the part of the contribution of the sector in comparison to other sectors did not change because other sectors grew as well.
Some representative figures for average direct emissions (not accounting for high-altitude radiative effects) of airliners expressed as and equivalent per passenger kilometer:
The construction industry has seen marked advances in building performance and energy efficiency over recent decades. Green building that avoid emissions or capture the carbon already present in the environment, allow for reduced footprint of the construction industry, for example, use of hempcrete, cellulose fiber insulation, and landscaping.
In 2019, the building sector was responsible for 12 Gt-eq emissions. More than 95% of these emissions were carbon, and the remaining 5% were , , and halocarbon.
The largest contributor to building sector emissions (49% of total) is the production of electricity for use in buildings.
Of global building sector GHG emissions, 28% are produced during the manufacturing process of building materials such as Steel frame, cement (a key component of concrete), and glass. The conventional process inherently related to the production of steel and cement results in large amounts of CO2 emitted. For example, the production of steel in 2018 was responsible for 7 to 9% of the global CO2 emissions.
The remaining 23% of global building sector GHG emissions are produced directly on site during building operations.
GHG emissions which are produced during the mining, processing, manufacturing, transportation and installation of building materials are referred to as the embodied carbon of a material. The embodied carbon of a construction project can be reduced by using low-carbon materials for building structures and finishes, reducing demolition, and reusing buildings and construction materials whenever possible.
[[Secunda CTL]] is the world's largest single emitter, at 56.5 million tonnes a year.
The World Bank estimates that 134 billion cubic meters of natural gas are flared or vented annually (2010 datum), an amount equivalent to the combined annual gas consumption of Germany and France or enough to supply the entire world with gas for 16 days. This flaring is highly concentrated: 10 countries account for 70% of emissions, and twenty for 85%.
More recent estimates suggest that global steel production emitted around 2,280 million tons of CO₂ in 2017, indicating the scale has increased significantly. A 2022 study found that across bulk material sectors—steel, aluminum, cement, and paper—total emissions reached approximately 8.4 billion tons of CO₂ equivalent.
Due to the lightness of plastic versus glass or metal, plastic may reduce energy consumption. For example, packaging beverages in PET plastic rather than glass or metal is estimated to save 52% in transportation energy, if the glass or metal package is single-use, of course.
In 2019 a new report "Plastic and Climate" was published. According to the report, the production and incineration of plastics will contribute in the equivalent of 850 million tonnes of carbon dioxide () to the atmosphere in 2019. With the current trend, annual life cycle greenhouse gas emissions of plastics will grow to 1.34 billion tonnes by 2030. By 2050, the life cycle emissions of plastics could reach 56 billion tonnes, as much as 14 percent of the Earth's remaining Emissions budget. The report says that only solutions which involve a reduction in consumption can solve the problem, while others like biodegradable plastic, ocean cleanup, using renewable energy in plastic industry can do little, and in some cases may even worsen it.
Mining for proof-of-work Cryptocurrency requires enormous amounts of electricity and consequently comes with a large carbon footprint. Proof-of-work blockchains such as Bitcoin, Ethereum, Litecoin, and Monero were estimated to have added between 3 million and 15 million tonnes of carbon dioxide () to the atmosphere in the period from 1 January 2016 to 30 June 2017. By the end of 2021, Bitcoin was estimated to produce 65.4 million tonnes of , as much as Greece, and consume between 91 and 177 terawatt-hours annually. Bitcoin is the least energy-efficient cryptocurrency, using 707.6 kilowatt-hours of electricity per transaction.
A study in 2015 investigated the global electricity usage that can be ascribed to Communication Technology (CT) between 2010 and 2030. Electricity usage from CT was divided into four principle categories: (i) consumer devices, including personal computers, mobile phones, TVs and home entertainment systems; (ii) network infrastructure; (iii) data center computation and storage; and lastly (iv) production of the above categories. The study estimated for the worst-case scenario, that CT electricity usage could contribute up to 23% of the globally released greenhouse gas emissions in 2030. Text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License
Based on the 2013 life cycle emissions in the health care sector, it is estimated that the GHG emissions associated with US health care activities may cause an additional 123,000 to 381,000 DALYs annually.
Recent studies show that tourism produces around 1 kg of CO₂ per dollar spent—about 25% higher than the global economic average—highlighting its substantial carbon intensity.
The Net-Zero Banking Alliance has created guidelines for climate target setting for banks, while the Partnership for Carbon Accounting Financials is developing a harmonized approach to assess and disclose the greenhouse gas emissions associated with financial institutions' loans and investments.
Studies find that the most affluent citizens of the world are responsible for most environmental impacts, and robust action by them is necessary for prospects of moving towards safer environmental conditions.
According to a 2020 report by Oxfam and the Stockholm Environment Institute, the richest 1% of the global population have caused twice as much carbon emissions as the poorest 50% over the 25 years from 1990 to 2015. This was, respectively, during that period, 15% of cumulative emissions compared to 7%. The bottom half of the population is directly responsible for less than 20% of energy footprints and consume less than the top 5% in terms of trade-corrected energy. The largest disproportionality was identified to be in the domain of transport, where e.g. the top 10% consume 56% of vehicle fuel and conduct 70% of vehicle purchases. However, wealthy individuals are also often and typically have more influence and, especially in the case of , may also direct lobbying efforts, direct financial decisions, and/or control companies.
Based on a study in 32 developed countries, researchers found that "seniors in the United States and Australia have the highest per capita footprint, twice the Western average. The trend is mainly due to changes in expenditure patterns of seniors".
Policies implemented by governments include for example national and regional targets to reduce emissions, promoting energy efficiency, and support for an energy transition.
Informally describes as a "narrative" and tagged IEO2023.
Landing page.
YouTube. Duration: 00:57:12. Includes interview with [[Joseph DeCarolis]].Unlike many integrated systems modeling in this field, emissions are allowed to float rather than be pinned to netzero in 2050. Asensitivity analysis varied key parameters, primarily future GDP growth (2.6%per annum as reference, variously 1.8% and 3.4%) and secondarily technological learning rates, future Brent Crude, and similar exogeny. The model results are far from encouraging. In no case did aggregate energy-related carbon emissions ever dip below 2022 levels (see figure3 plot). The IEO2023 exploration provides a benchmark and suggests that far stronger action is needed.
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