query: In fact, human emit 26 gigatonnes of CO2 per year while CO2 in the atmosphere is rising by only 15 gigatonnes per year - much of human CO2 emissions is being absorbed by natural sinks.

positive: Carbon sink A carbon sink is a natural or artificial reservoir that accumulates and stores some carbon-containing chemical compound for an indefinite period . The process by which carbon sinks remove carbon dioxide from the atmosphere is known as carbon sequestration . Public awareness of the significance of CO2 sinks has grown since passage of the Kyoto Protocol , which promotes their use as a form of carbon offset . There are also different strategies used to enhance this process .

positive: Carbon dioxide Carbon dioxide ( chemical formula ) is a colorless gas with a density about 60 % higher than that of air ( 1.225 g/L ) that is odorless at normally encountered concentrations . Carbon dioxide consists of a carbon atom covalently double bonded to two oxygen atoms . It occurs naturally in Earth 's atmosphere as a trace gas at a concentration of about 0.04 percent ( 400 ppm ) by volume . Natural sources include volcanoes , hot springs and geysers , and it is freed from carbonate rocks by dissolution in water and acids . Because carbon dioxide is soluble in water , it occurs naturally in groundwater , rivers and lakes , ice caps , glaciers and seawater . It is present in deposits of petroleum and natural gas .   As the source of available carbon in the carbon cycle , atmospheric carbon dioxide is the primary carbon source for life on Earth and its concentration in Earth 's pre-industrial atmosphere since late in the Precambrian has been regulated by photosynthetic organisms and geological phenomena . Plants , algae and cyanobacteria use light energy to photosynthesize carbohydrate from carbon dioxide and water , with oxygen produced as a waste product .   Carbon dioxide is produced by all aerobic organisms when they metabolize carbohydrates and lipids to produce energy by respiration . It is returned to water via the gills of fish and to the air via the lungs of air-breathing land animals , including humans . Carbon dioxide is produced during the processes of decay of organic materials and the fermentation of sugars in bread , beer and winemaking . It is produced by combustion of wood and other organic materials and fossil fuels such as coal , peat , petroleum and natural gas .   It is a versatile industrial material , used , for example , as an inert gas in welding and fire extinguishers , as a pressurizing gas in air guns and oil recovery , as a chemical feedstock and in liquid form as a solvent in decaffeination of coffee and supercritical drying . It is added to drinking water and carbonated beverages including beer and sparkling wine to add effervescence . The frozen solid form of , known as `` dry ice '' is used as a refrigerant and as an abrasive in dry-ice blasting .   Carbon dioxide is the most significant long-lived greenhouse gas in Earth 's atmosphere . Since the Industrial Revolution anthropogenic emissions - primarily from use of fossil fuels and deforestation - have rapidly increased its concentration in the atmosphere , leading to global warming . Carbon dioxide also causes ocean acidification because it dissolves in water to form carbonic acid .

positive: Greenhouse gas 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 .

negative: Carbon diet A carbon diet refers to reducing the impact on climate change by reducing greenhouse gas production specifically , CO2 production . In today 's society , we produce CO2 in every day activities such as driving , heating , deforestation and the burning of fossil fuels such as coal , oil and gas . It has been found that carbon dioxide from the burning of coal , natural gas , and oil for electricity and heat is the largest single source of global greenhouse gas emissions . For years , governments and corporations have been attempting to balance out their emissions by participating in carbon-offsetting -- the practice in which they invest in renewable energy to compensate for the global-warming pollution that they produce . Despite these efforts the results are still far off and we continue to see growth in CO2 concentration . Now , a growing number of individuals are trying to make a reduction in the amount of CO2 that is being produced by participating in low carbon dieting . This small adjustment in household CO2 production has the potential to reduce emissions much more quickly than other kinds of changes and it deserves explicit consideration as part of climate policy . It can potentially help avoid `` overshoot '' of greenhouse gas concentration targets ; provide a demonstration effect ; reduce emissions at low cost ; and buy time to develop new technologies , policies , and institutions to reach long-term greenhouse gas emission targets and to develop adaptation strategies .

negative: Fossil fuel Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms , containing energy originating in ancient photosynthesis . The age of the organisms and their resulting fossil fuels is typically millions of years , and sometimes exceeds 650 million years . Fossil fuels contain high percentages of carbon and include petroleum , coal , and natural gas . Other commonly used derivatives include kerosene and propane . Fossil fuels range from volatile materials with low carbon to hydrogen ratios like methane , to liquids like petroleum , to nonvolatile materials composed of almost pure carbon , like anthracite coal . Methane can be found in hydrocarbon fields either alone , associated with oil , or in the form of methane clathrates .   The theory that fossil fuels formed from the fossilized remains of dead plants by exposure to heat and pressure in the Earth 's crust over millions of years was first introduced by Georgius Agricola in 1556 and later by Mikhail Lomonosov in the 18th century .   The Energy Information Administration estimates that in 2007 the primary sources of energy consisted of petroleum 36.0 % , coal 27.4 % , natural gas 23.0 % , amounting to an 86.4 % share for fossil fuels in primary energy consumption in the world . Non-fossil sources in 2006 included nuclear 8.5 % , hydroelectric 6.3 % , and others ( geothermal , solar , tidal , wind , wood , waste ) amounting to 0.9 % . World energy consumption was growing about 2.3 % per year .   Although fossil fuels are continually being formed via natural processes , they are generally considered to be non-renewable resources because they take millions of years to form and the known viable reserves are being depleted much faster than new ones are being made .   The use of fossil fuels raises serious environmental concerns . The burning of fossil fuels produces around 21.3 billion tonnes ( 21.3 gigatonnes ) of carbon dioxide ( CO2 ) per year . It is estimated that natural processes can only absorb about half of that amount , so there is a net increase of 10.65 billion tonnes of atmospheric carbon dioxide per year . Carbon dioxide is a greenhouse gas that increases radiative forcing and contributes to global warming . A global movement towards the generation of renewable energy is underway to help reduce global greenhouse gas emissions .

negative: Low-carbon emission The main components of automobile exhaust are carbon dioxide ( CO2 ) and water vapor ( H2O ) . Carbon dioxide is the most important anthropogenic greenhouse gas ( GHG ) and the most significant Greenhouse Gas emitted in the U.S. ( with 82-84 % of all U.S. emissions ) . Increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change .   The CO2 emission standards can be referred to the fuel or to the vehicle :   The European Union is moving towards fuel mandatory CO2 standards and USA has reflected it in the Greenhouse Gas Score .  There are information , but no mandatory , standards for CO2 limits in vehicle ( engine ) emissions , excepting some state regulations ( i.e. California ) . See hybrid vehicles .   CO2 mass emission in vehicles is measured in g/km ( g/mi * 0.621371192 = g/km ) .

negative: Bio-energy with carbon capture and storage Bio-energy with carbon capture and storage ( BECCS ) is a future greenhouse gas mitigation technology which produces negative carbon dioxide emissions by combining bioenergy ( energy from biomass ) use with geologic carbon capture and storage . The concept of BECCS is drawn from the integration of trees and crops , which extract carbon dioxide ( CO2 ) from the atmosphere as they grow , the use of this biomass in processing industries or power plants , and the application of carbon capture and storage via CO2 injection into geological formations . There are other non-BECCS forms of carbon dioxide removal and storage that include technologies such as biochar , carbon dioxide air capture and biomass burial .   According to a recent Biorecro report , there is 550 000 tonnes CO2/year in total BECCS capacity currently operating , divided between three different facilities ( as of January 2012 ) .   In the IPCC Fourth Assessment Report by the Intergovernmental Panel on Climate Change ( IPCC ) , BECCS was indicated as a key technology for reaching low carbon dioxide atmospheric concentration targets . The negative emissions that can be produced by BECCS has been estimated by the Royal Society to be equivalent to a 50 to 150 ppm decrease in global atmospheric carbon dioxide concentrations and according to the International Energy Agency , the BLUE map climate change mitigation scenario calls for more than 2 gigatonnes of negative CO2 emissions per year with BECCS in 2050 . According to Stanford University , 10 gigatonnes is achievable by this date .   The Imperial College London , the UK Met Office Hadley Centre for Climate Prediction and Research , the Tyndall Centre for Climate Change Research , the Walker Institute for Climate System Research , and the Grantham Institute for Climate Change issued a joint report on carbon dioxide removal technologies as part of the AVOID : Avoiding dangerous climate change research program , stating that `` Overall , of the technologies studied in this report , BECCS has the greatest maturity and there are no major practical barriers to its introduction into today 's energy system . The presence of a primary product will support early deployment . ''   According to the OECD , `` Achieving lower concentration targets ( 450 ppm ) depends significantly on the use of BECCS '' .

negative: Gorgon Carbon Dioxide Injection Project The Gorgon Carbon Dioxide Injection Project is part of the Gorgon Project , the world 's largest natural gas project . The Gorgon Project , located on Barrow Island in Western Australia , includes a liquefied natural gas ( LNG ) plant , a domestic gas plant , and a Carbon Dioxide Injection Project .   The initial carbon dioxide injections are planned to take place by the end of 2017 . Once launched , the Gorgon Carbon Dioxide Injection Project will be the world 's largest CO2 injection plant , with an ability to store up to 4 million tons of CO2 per year -- approximately 120 million tons over the project 's lifetime , and 40 percent of total Gorgon Project emissions .

negative: Carbon price Carbon pricing -- the method favored by many economists for reducing global-warming emissions -- charges those who emit carbon dioxide ( CO2 ) for their emissions . That charge , called a carbon price , is the amount that must be paid for the right to emit one tonne of CO2 into the atmosphere . Carbon pricing usually takes the form either of a carbon tax or a requirement to purchase permits to emit , generally known as cap-and-trade , but also called `` allowances '' .   Carbon pricing solves the economic problem that , a known greenhouse gas , is what economics calls a negative externality -- a detrimental product that is not priced ( charged for ) by any market . As a consequence of not being priced , there is no market mechanism responsive to the costs of CO2 emitted . The standard economic solution to problems of this type , first proposed by Arthur Pigou in 1920 , is for the product - in this case , CO2 emissions - to be charged at a price equal to the monetary value of the damage caused by the emissions . This should result in the economically optimal ( efficient ) amount of CO2 emissions . Many practical concerns mar the theoretical simplicity of this picture : for example , the exact monetary damage caused by a tonne of CO2 is uncertain .   The economics of carbon pricing is much the same for taxes and cap-and-trade . Both prices are efficient ; they have the same social cost and the same effect on profits if permits are auctioned . However , some economists argue that caps prevent non-price policies , such as renewable energy subsidies , from reducing carbon emissions , while carbon taxes do not . Others argue that an enforced cap is the only way to guarantee that carbon emissions will actually be reduced ; a carbon tax will not prevent those who can afford to do so from continuing to generate emissions .   The choice of pricing approach , a tax or cap-and-trade , has been controversial . A carbon tax is generally favored on economic grounds for its simplicity and stability , while cap-and-trade is often favored on political grounds . Recently ( 2013 − 14 ) economic opinion has been shifting more heavily toward taxes as national policy measures , and toward a neutral carbon-price-commitment position for the purpose of international climate negotiations .

negative: Carbon rift Carbon rift is a theory attributing the input and output of carbon into the environment to human capitalistic systems . This is a derivative of Karl Marx 's concept of metabolic rift . In practical terms , increased commodity production demands that greater levels of carbon dioxide ( or CO2 ) be emitted into the biosphere via fossil fuel consumption . Carbon rift theory states that this ultimately disrupts the natural carbon cycle and that this `` rift '' has adverse effects on nearly every aspect of life . Many of the specifics regarding how this metabolic carbon rift interacts with capitalism are proposed by Brett Clark and Richard York in a 2005 article titled `` Carbon Metabolism : Global capitalism , climate change , and the biospheric rift '' in the journal Theory and Society . Researchers such as Jean P. Sapinski of the University of Oregon claim that , despite increased interest in closing the carbon rift , it is projected that as long as capitalism continues , there is little hope of reducing the rift .   Both deforestation and the emission of greenhouse gases have been linked to increased atmospheric CO2 levels . Carbon rift theory states that these are the result of human production through capitalistic systems . There are proposed solutions to climate change such as geoengineering proposed in the December 2015 Paris Agreement . However , some argue that the capitalist mode of production is at fault for the emission of greenhouse gas and that solutions must be found to this issue before climate change itself can be addressed .   Carbon rift theory , while rarely criticized directly , often indirectly receives criticism regarding the underlying causes of climate change and attributing the stated effects to alternative explanations for climate change , instead of as a result of human activity . Such explanations include the Chaotic Solar System Theory and that increased water vapor is responsible for climate change .

negative: Carbon sequestration Carbon sequestration is the process involved in carbon capture and the long-term storage of atmospheric carbon dioxide . Carbon sequestration involves long-term storage of carbon dioxide or other forms of carbon to mitigate or defer global warming . It has been proposed as a way to slow the atmospheric and marine accumulation of greenhouse gases , which are released by burning fossil fuels .   Carbon dioxide is naturally captured from the atmosphere through biological , chemical , and physical processes . Artificial processes have been devised to produce similar effects , including large-scale , artificial capture and sequestration of industrially produced using subsurface saline aquifers , reservoirs , ocean water , aging oil fields , or other carbon sinks .

negative: Atmospheric carbon cycle The atmosphere is one of the Earth 's major carbon reservoirs and an important component of the global carbon cycle , holding approximately 720 gigatons of carbon . Atmospheric carbon plays an important role in the greenhouse effect . The most important carbon compound in this respect is the gas carbon dioxide . Although it is a small percentage of the atmosphere ( approximately 0.04 % on a molar basis ) , it plays a vital role in retaining heat in the atmosphere and thus in the greenhouse effect . Other gases with effects on the climate containing carbon in the atmosphere are methane and chlorofluorocarbons ( the latter is entirely anthropogenic ) . Emissions by humans in the past 200 years have almost doubled the amount carbon dioxide in the atmosphere .

negative: Carbon profiling Carbon profiling is a mathematical process that calculates how much carbon dioxide is put into the atmosphere per m2 of space in a building over one year .   The analysis is in two parts which are then added together to produce an overall figure which is termed the ` Carbon Profile ' :  operational carbon emissions  embodied carbon emissions .   Embodied carbon emissions relate to the amount of carbon dioxide emitted into the atmosphere from creating and maintaining the materials that form the building e.g. the carbon dioxide released from the baking of bricks or smelting or iron . In the Carbon Profiling Model these emissions are measured as Embodied Carbon Efficiency ( ECE ) , measured as kg of CO2/m2/year .   Occupational Carbon Emissions relate to the amount of Carbon Dioxide emitted into the atmosphere from the direct use of energy to run the building e.g. the heating or electricity used by the building over the year . In the Carbon Profiling Model these emissions are measured in BER 's ( Building Emission Rate ) in kg of / m2/year .   The BER is a United Kingdom government accepted unit of measurement that comes from an approved calculation process called sBEM ( Simplified Building Emission Model )   The purpose of Carbon Profiling is to provide a method of analyzing and comparing both operational and embodied carbon emissions at the same time . With this information it is then possible to allocate a projects resources in such a way to minimize the total amount of Carbon Dioxide emitted into the atmosphere through the use of a given piece of space .   A secondary benefit is that having quantified the Carbon Profiling of different buildings it is then possible to make comparisons and rank buildings in term of their performance . This allows investors and occupiers to identify which building are good and bad carbon investments .   Simon Sturgis and Gareth Roberts of Sturgis Associates in the United Kingdom originally developed ` Carbon Profiling ' in December 2007 .

negative: North American Carbon Program The North American Carbon Program ( NACP ) is one of the major elements of the Strategic Plan for the U.S. Climate Change Science Program .  The central objective of NACP is to measure and understand carbon stocks and sources and sinks of carbon dioxide ( CO2 ) , methane ( CH4 ) , and carbon monoxide ( CO ) in North America and adjacent ocean regions .   The specific program goals are as followed :   Develop quantitative scientific knowledge , robust observations , and models to determine the emissions and uptake of CO2 , CH4 , and CO , changes in carbon stocks , and the factors regulating these processes for North America and adjacent ocean basins .   Develop the scientific basis to implement full carbon accounting on regional and continental scales . This is the knowledge base needed to design monitoring programs for natural and managed CO2 sinks and emissions of CH4 .   Support long-term quantitative measurements of fluxes , sources , and sinks of atmospheric CO2 and CH4 , and develop forecasts for future trends .   The North American Carbon Program was designed to help with the process of providing data needed to model the synthesis activities .

negative: Carbon footprint A carbon footprint is historically defined as the total set of greenhouse gas emissions caused by an individual , event , organisation , or product , expressed as carbon dioxide equivalent .   In most cases , the total carbon footprint can not be exactly calculated because of inadequate knowledge of and data about the complex interactions between contributing processes , especially which including the influence on natural processes storing or releasing carbon dioxide . For this reason , Wright , Kemp , and Williams , have suggested to define the carbon footprint as :   A measure of the total amount of carbon dioxide ( CO2 ) and methane ( CH4 ) emissions of a defined population , system or activity , considering all relevant sources , sinks and storage within the spatial and temporal boundary of the population , system or activity of interest . Calculated as carbon dioxide equivalent using the relevant 100-year global warming potential ( GWP100 ) .   Greenhouse gases ( GHGs ) can be emitted through land clearance and the production and consumption of food , fuels , manufactured goods , materials , wood , roads , buildings , transportation and other services . For simplicity of reporting , it is often expressed in terms of the amount of carbon dioxide , or its equivalent of other GHGs , emitted .   Most of the carbon footprint emissions for the average U.S. household come from `` indirect '' sources , i.e. fuel burned to produce goods far away from the final consumer . These are distinguished from emissions which come from burning fuel directly in one 's car or stove , commonly referred to as `` direct '' sources of the consumer 's carbon footprint .   The concept name of the carbon footprint originates from ecological footprint , discussion , which was developed by Rees and Wackernagel in the 1990s which estimates the number of `` earths '' that would theoretically be required if everyone on the planet consumed resources at the same level as the person calculating their ecological footprint . However , given that ecological footprints are a measure of failure , Anindita Mitra ( CREA , Seattle ) chose the more easily calculated `` carbon footprint '' to easily measure use of carbon , as an indicator of unsustainable energy use . In 2007 , carbon footprint was used as a measure of carbon emissions to develop the energy plan for City of Lynnwood , Washington . Carbon footprints are much more specific than ecological footprints since they measure direct emissions of gases that cause climate change into the atmosphere .   Carbon footprint is one of a family of footprint indicators , which also includes water footprint and land footprint .

negative: Greenhouse effect The greenhouse effect is the process by which radiation from a planet 's atmosphere warms the planet 's surface to a temperature above what it would be without its atmosphere .   If a planet 's atmosphere contains radiatively active gases ( i.e. , greenhouse gases ) the atmosphere will radiate energy in all directions . Part of this radiation is directed towards the surface , warming it . The downward component of this radiation -- that is , the strength of the greenhouse effect -- will depend on the atmosphere 's temperature and on the amount of greenhouse gases that the atmosphere contains .   On Earth , the atmosphere is warmed by absorption of infrared thermal radiation from the underlying surface ( heated by the sun ) , absorption of shorter wavelength radiant energy from the sun , and convective heat fluxes from the surface . Greenhouse gases in the atmosphere radiate energy , some of which is directed to the surface and lower atmosphere . The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect .   Earth 's natural greenhouse effect is critical to supporting life . Human activities , primarily the burning of fossil fuels and clearing of forests , have intensified the natural greenhouse effect , causing global warming .   The mechanism is named after a faulty analogy with the effect of solar radiation passing through glass and warming a greenhouse . The way a greenhouse retains heat is fundamentally different , as a greenhouse works by reducing airflow and retaining warm air inside the structure .

negative: Estuarine acidification Estuarine acidification is a decrease in the pH of coastal marine ecosystems , specifically those of estuaries . pH change in estuaries is more complicated than in the open ocean due to direct impacts from land run-off and coastal current dynamics . Ocean acidification is the ongoing decrease in the pH of the Earth 's oceans , caused by the absorption of carbon dioxide ( CO2 ) from the atmosphere ( 0.1 units over the last century ) . The ocean absorbs 30-40 % of all CO2 emitted to the atmosphere ; this increase in aqueous carbon dioxide causes a decline in the pH of the ocean surface . As carbon dioxide combines with water , it releases protons ( hydrogen ions ) , based on the following equation :   CO2 + H2O ↔ H2CO3 ↔ HCO3 + H + ↔ CO3 + 2 H +

negative: Climate system Earth's climate arises from the interaction of five major climate system components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things). Climate is the average weather, typically over a period of 30 years, and is determined by a combination of processes in the climate system, such as ocean currents and wind patterns. Circulation in the atmosphere and oceans is primarily driven by solar radiation and transports heat from the tropical regions to regions that receive less energy from the Sun. The water cycle also moves energy throughout the climate system. In addition, different chemical elements, necessary for life, are constantly recycled between the different components. The climate system can change due to internal variability and external forcings. These external forcings can be natural, such as variations in solar intensity and volcanic eruptions, or caused by humans. Accumulation of heat-trapping greenhouse gases, mainly being emitted by people burning fossil fuels, is causing global warming. Human activity also releases cooling aerosols, but their net effect is far less than that of greenhouse gases. Changes can be amplified by feedback processes in the different climate system components.

negative: Energy policy of China The energy policy of China is a policy decided on by the Central Government with regard to energy and energy resources . Ensuring adequate energy supply to sustain economic growth has been a core concern of the Chinese government since 1949 . The country is currently the world 's largest emitter of greenhouse gases according to a Dutch research agency . However , China 's per capita emissions are still far behind the developed countries . In addition , China is the world 's leading renewable energy producer .   From 2010 to 2015 China reduced energy consumption per unit of GDP by 18 % , and CO2 emissions per unit of GDP by 20 % .   Primary energy use in China was 26,250 TWh and 20 TWh per million persons in 2009 . According to IEA the primary energy use grew 40 % and electricity use 70 % from 2004 to 2009 . The energy import was three times bigger in 2009 compared to 2004 . The share of energy import of the primary energy use was 12 % in 2009 . The CO2 emissions growth in five years ( 2004-2009 ) was 44 % .

negative: List of countries by carbon dioxide emissions -RSB-   This is a list of sovereign states and territories by carbon dioxide emissions due to certain forms of human activity , based on the EDGAR database created by European Commission and Netherlands Environmental Assessment Agency released in 2015 . The following table lists the 2015 annual emissions estimates ( in thousands of tonnes ) along with a list of emissions per capita ( in tonnes of per year ) from same source . The data only considers carbon dioxide emissions from the burning of fossil fuels and cement manufacture , but not emissions from land use , land-use change and forestry . Emissions from international shipping or bunker fuels are also not included in national figures , which can make a huge difference for small countries with important ports .  The top 10 largest emitter countries account for 67.6 % of the world total . Other powerful , more potent greenhouse gases , including methane , are not included in this data .

negative: Global dimming Global dimming is the gradual reduction in the amount of global direct irradiance at the Earth 's surface that was observed for several decades after the start of systematic measurements in the 1950s . The effect varies by location , but worldwide it has been estimated to be of the order of a 4 % reduction over the three decades from 1960 -- 1990 . However , after discounting an anomaly caused by the eruption of Mount Pinatubo in 1991 , a very slight reversal in the overall trend has been observed .   Global dimming is thought to have been caused by an increase in particulates such as sulfate aerosols in the atmosphere due to human action .   It has interfered with the hydrological cycle by reducing evaporation and may have reduced rainfall in some areas . Global dimming also creates a cooling effect that may have partially counteracted the effect of greenhouse gases on global warming .

negative: 350.org 350 . org is an international environmental organization encouraging citizens to action with the belief that publicizing the increasing levels of carbon dioxide will pressure world leaders to address climate change and to reduce levels from 400 parts per million to 350 parts per million . It was founded by author Bill McKibben with the goal of building a global grassroots movement to raise awareness about human-driven climate change , to confront climate change denial , and to cut emissions of carbon dioxide in order to slow the rate of global warming . 350 . org takes its name from the research of Goddard Institute for Space Studies scientist James E. Hansen , who posited in a 2007 paper that 350 parts-per-million ( ppm ) of CO2 in the atmosphere is a safe upper limit to avoid a climate tipping point .

negative: Carbon respiration Carbon respiration ( also called carbon emissions and carbon releases ) is used in combination with carbon fixation to gauge carbon flux ( as CO2 ) between atmospheric carbon and the global carbon cycle .

negative: Quest Carbon Capture and Storage Project The Quest Carbon Capture and Storage Project captures and stores underground one million tonnes of CO2 emissions per year . The capture unit is located at the Scotford Upgrader in Alberta , Canada , where hydrogen is produced to upgrade bitumen from oil sands into synthetic crude oil .

negative: Nitrogen cycle The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into various chemical forms as it circulates among the atmosphere and terrestrial and marine ecosystems . The conversion of nitrogen can be carried out through both biological and physical processes . Important processes in the nitrogen cycle include fixation , ammonification , nitrification , and denitrification . The majority of Earth 's atmosphere ( 78 % ) is nitrogen , making it the largest source of nitrogen . However , atmospheric nitrogen has limited availability for biological use , leading to a scarcity of usable nitrogen in many types of ecosystems . The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes , including primary production and decomposition . Human activities such as fossil fuel combustion , use of artificial nitrogen fertilizers , and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle .

negative: Revelle factor The Revelle factor ( buffer factor ) is the ratio of instantaneous change in carbon dioxide to the change in total dissolved inorganic carbon ( DIC ) , and is a measure of the resistance to atmospheric CO2 being absorbed by the ocean surface layer . The buffer factor is used to examine the distribution of CO2 between the atmosphere and the ocean , and measures the amount of CO2 that can be dissolved in the mixed surface layer . It is named after the oceanographer Roger Revelle , who was one of the first scientists to study global warming .   Revelle factor = / ( Δ -LSB- DIC -RSB- / -LSB- DIC -RSB- ) where DIC is dissolved inorganic carbon . Δ -LSB- -RSB- / -LSB- -RSB- is the instantaneous change in p and Δ -LSB- DIC -RSB- / -LSB- DIC -RSB- is the instantaneous change in DIC .

negative: Anthropogenic metabolism Anthropogenic metabolism , also referred to as ` metabolism of the anthroposphere ' , is a term used in industrial ecology , material flow analysis , and waste management to describe the material and energy turnover of human society . It emerges from the application of systems thinking to the industrial and other man-made activities and it is a central concept of sustainable development . In modern societies , the bulk of anthropogenic ( man-made ) material flows is related to one of the following activities : sanitation , transportation , habitation , and communication , which were `` of little metabolic significance in prehistoric times '' . Global man-made stocks of steel in buildings , infrastructure , and vehicles , for example , amount to about 25 Gigatonnes ( more than three tonnes per person ) , a figure that is surpassed only by construction materials such as concrete .  Sustainable development is closely linked to the design of a sustainable anthropogenic metabolism , which will entail substantial changes in the energy and material turnover of the different human activities . Anthropogenic metabolism can be seen as synonymous to social or socioeconomic metabolism . It comprises both industrial metabolism and urban metabolism .

negative: Project Vulcan Project Vulcan is a NASA/DOE funded effort under the North American Carbon Program ( NACP ) to quantify North American fossil fuel carbon dioxide ( CO2 ) emissions at space/time scales much finer than has been achieved in the past . The initial purpose of the Vulcan Project was to aid in quantification of the North American carbon budget , to support inverse estimation of carbon sources and sinks , and to support the demands posed by higher resolution CO2 observations . The detail and scope of the Vulcan CO2 inventory has now made it a valuable tool for policymakers , demographers , social scientists and the public at large .   Project Vulcan has achieved U.S. fossil fuel CO2 emissions at < 10 km spatial scales and an hourly time scale , based on datasets such as air quality emissions reporting , census data , highway statistics , energy statistics , and econometric data . Furthermore , Vulcan includes significant process-level detail , dividing the emissions into economic sectors and sub-sectors in addition to 23 fuel types . It has been produced for the year 2002 , and an annual product spanning 1980-2006 will be available by late-2009 .   The first Vulcan inventory ( v1 .0 ) was released to the public in early April 2008 . Version 1.1 was released in February 2009 and Version 1.2 is due out in early August 2009 . In addition to the data release , establishment of the Vulcan website and a press release , a video of various aspects of atmospheric transport was released on Purdue University 's YouTube website and portions of the Vulcan inventory are available on Google Earth . As of 2015 , version 2.2 has been published on a site hosted by Arizona State University .

negative: Regional Greenhouse Gas Initiative ` The Regional Greenhouse Gas Initiative ( RGGI , pronounced `` Reggie '' ) is the first mandatory market based program in the United States to reduce greenhouse gas emissions . RGGI is a cooperative effort among the states of Connecticut , Delaware , Maine , Maryland , Massachusetts , New Hampshire , New York , Rhode Island , and Vermont to cap and reduce CO2 emissions from the power sector . RGGI compliance obligations apply to fossil-fueled power plants 25MW and larger within the nine-state region .   RGGI establishes a regional cap on the amount of CO2 pollution that power plants can emit by issuing a limited number of tradable CO2 allowances . Each allowance represents an authorization for a regulated power plant to emit one short ton of CO2 . Individual CO2 budget trading programs in each RGGI state together create a regional market for CO2 allowances .   The RGGI states distribute over 90 percent of allowances through quarterly auctions . These allowance auctions generate proceeds , which participating states are able to invest in strategic energy and consumer benefit programs . Programs funded through RGGI have included energy efficiency , clean and renewable energy , greenhouse gas abatement , and direct bill assistance .   An initial milestone program 's development occurred in 2005 , when seven states signed a Memorandum of Understanding ( MOU ) announcing an agreement to implement RGGI . The RGGI states then established individual CO2 budget trading programs , based on the RGGI Model Rule . The first pre-compliance RGGI auction took place in September 2008 , and the program became effective on January 1 , 2009 . The RGGI program is currently in its third three-year compliance period , which began January 1 , 2015 .

negative: GHG footprint The GHG footprint , or greenhouse gas footprint , refers to the amount of GHG that are emitted during the creation of products or services . It is more comprehensive than the commonly used carbon footprint , which measures only carbon dioxide , one of many greenhouse gases .   The GHG footprint differs from the ecological footprint in that the former is expressed in units of GHG warming potential ( GGWP ) and is generated by products or services , whereas the latter is expressed in units of land area and is generated by whole societies .

negative: Mitigation of aviation's environmental impact Aviation affects the environment due to aircraft engines emitting noise , particulates , and gases which contribute to climate change and global dimming . Despite emission reductions from automobiles and more fuel-efficient ( and therefore less polluting ) turbofan and turboprop engines , the rapid growth of air travel in recent years contributes to an increase in total pollution attributable to aviation . In the EU , greenhouse gas emissions from aviation increased by 87 % between 1990 and 2006 .   At present aviation accounts for 2.5 % of global CO2 emissions . Due to projected growth in air travel , in the most technologically radical scenarios for having a better than 50 % chance of keeping global warming below 2 degrees Celsius , in 2050 aviation will make up 15 % of global CO2 emissions . In more conventional scenarios its emissions will exceed the entire global carbon budget before then . This presents governments and the operators of aircraft with a responsibility to reduce the aviation industry 's emissions .

negative: Soil respiration Soil respiration refers to the production of carbon dioxide when soil organisms respire . This includes respiration of plant roots , the rhizosphere , microbes and fauna .   Soil respiration is a key ecosystem process that releases carbon from the soil in the form of CO2 . CO2 is acquired from the atmosphere and converted into organic compounds in the process of photosynthesis . Plants use these organic compounds to build structural components or respire them to release energy . When plant respiration occurs below-ground in the roots , it adds to soil respiration . Over time , plant structural components are consumed by heterotrophs . This heterotrophic consumption releases CO2 and when this CO2 is released by below-ground organisms , it is considered soil respiration .   The amount of soil respiration that occurs in an ecosystem is controlled by several factors . The temperature , moisture , nutrient content and level of oxygen in the soil can produce extremely disparate rates of respiration . These rates of respiration can be measured in a variety of methods . Other methods can be used to separate the source components , in this case the type of photosynthetic pathway ( C3/C4 ) , of the respired plant structures .   Soil respiration rates can be largely affected by human activity . This is because humans have the ability to and have been changing the various controlling factors of soil respiration for numerous years . Global climate change is composed of numerous changing factors including rising atmospheric CO2 , increasing temperature and shifting precipitation patterns . All of these factors can affect the rate of global soil respiration . Increased nitrogen fertilization by humans also has the potential to effect rates over the entire Earth .   Soil respiration and its rate across ecosystems is extremely important to understand . This is because soil respiration plays a large role in global carbon cycling as well as other nutrient cycles . The respiration of plant structures releases not only CO2 but also other nutrients in those structures , such as nitrogen . Soil respiration is also associated with positive feedbacks with global climate change . Positive feedbacks are when a change in a system produces response in the same direction of the change . Therefore , soil respiration rates can be effected by climate change and then respond by enhancing climate change .

negative: Exhaust gas Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas , gasoline , petrol , biodiesel blends , diesel fuel , fuel oil , or coal . According to the type of engine , it is discharged into the atmosphere through an exhaust pipe , flue gas stack , or propelling nozzle . It often disperses downwind in a pattern called an exhaust plume .   It is a major component of motor vehicle emissions ( and from stationary internal combustion engines ) , which can also include :  Crankcase blow-by  Evaporation of unused gasoline   Motor vehicle emissions contribute to air pollution and are a major ingredient in the creation of smog in some large cities . A 2013 study by MIT indicates that 53,000 early deaths occur per year in the United States alone because of vehicle emissions . According to another study from the same university , traffic fumes alone cause the death of 5,000 people every year just in the United Kingdom .