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Tuesday, May 18, 2021

Sea level

From Wikipedia, the free encyclopedia

This marker indicating sea level is situated between Jerusalem and the Dead Sea.

Mean sea level (MSL) (often shortened to sea level) is an average level of the surface of one or more of Earth's bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A common and relatively straightforward mean sea-level standard is instead the midpoint between a mean low and mean high tide at a particular location.

Sea levels can be affected by many factors and are known to have varied greatly over geological time scales. However, 20th century and current millennium sea level rise is presumed to be caused by climate change, and careful measurement of variations in MSL can offer insights into ongoing climate change.

The term above sea level generally refers to above mean sea level (AMSL). The term APSL means Above Present Sea Level, comparing sea levels in the past with the level today.

Measurement

Sea level measurements from 23 long tide gauge records in geologically stable environments show a rise of around 200 millimetres (7.9 in) during the 20th century (2 mm/year).

Precise determination of a "mean sea level" is difficult because of the many factors that affect sea level. Instantaneous sea level varies quite a lot on several scales of time and space. This is because the sea is in constant motion, affected by the tides, wind, atmospheric pressure, local gravitational differences, temperature, salinity and so forth. The easiest way this may be calculated is by selecting a location and calculating the mean sea level at that point and use it as a datum. For example, a period of 19 years of hourly level observations may be averaged and used to determine the mean sea level at some measurement point.

Still-water level or still-water sea level (SWL) is the level of the sea with motions such as wind waves averaged out. Then MSL implies the SWL further averaged over a period of time such that changes due to, e.g., the tides, also have zero mean. Global MSL refers to a spatial average over the entire ocean.

One often measures the values of MSL in respect to the land; hence a change in relative MSL can result from a real change in sea level, or from a change in the height of the land on which the tide gauge operates. In the UK, the Ordnance Datum (the 0 metres height on UK maps) is the mean sea level measured at Newlyn in Cornwall between 1915 and 1921. Before 1921, the vertical datum was MSL at the Victoria Dock, Liverpool. Since the times of the Russian Empire, in Russia and its other former parts, now independent states, the sea level is measured from the zero level of Kronstadt Sea-Gauge. In Hong Kong, "mPD" is a surveying term meaning "metres above Principal Datum" and refers to height of 1.230m below the average sea level. In France, the Marégraphe in Marseilles measures continuously the sea level since 1883 and offers the longest collated data about the sea level. It is used for a part of continental Europe and the main part of Africa as the official sea level. As for Spain, the reference to measure heights below or above sea level is placed in Alicante. Elsewhere in Europe vertical elevation references (European Vertical Reference System) are made to the Amsterdam Peil elevation, which dates back to the 1690s.

Satellite altimeters have been making precise measurements of sea level since the launch of TOPEX/Poseidon in 1992. A joint mission of NASA and CNES, TOPEX/Poseidon was followed by Jason-1 in 2001 and the Ocean Surface Topography Mission on the Jason-2 satellite in 2008.

Height above mean sea level

Height above mean sea level (AMSL) is the elevation (on the ground) or altitude (in the air) of an object, relative to the average sea level datum. It is also used in aviation, where some heights are recorded and reported with respect to mean sea level (MSL) (contrast with flight level), and in the atmospheric sciences, and land surveying. An alternative is to base height measurements on an ellipsoid of the entire Earth, which is what systems such as GPS do. In aviation, the ellipsoid known as World Geodetic System 84 is increasingly used to define heights; however, differences up to 100 metres (328 feet) exist between this ellipsoid height and mean tidal height. The alternative is to use a geoid-based vertical datum such as NAVD88 and the global EGM96 (part of WGS84).

When referring to geographic features such as mountains on a topographic map, variations in elevation are shown by contour lines. The elevation of a mountain denotes the highest point or summit and is typically illustrated as a small circle on a topographic map with the AMSL height shown in metres, feet or both.

In the rare case that a location is below sea level, the elevation AMSL is negative. For one such case, see Amsterdam Airport Schiphol.

Difficulties in use

To extend this definition far from the sea means comparing the local height of the mean sea surface with a "level" reference surface, or geodetic datum, called the geoid. In a state of rest or absence of external forces, the mean sea level would coincide with this geoid surface, being an equipotential surface of the Earth's gravitational field which, in itself, does not conform to a simple sphere or ellipsoid and exhibits measurable variations such as those measured by NASA's GRACE satellites to determine mass changes in ice-sheets and aquifers. In reality, this ideal does not occur due to ocean currents, air pressure variations, temperature and salinity variations, etc., not even as a long-term average. The location-dependent, but persistent in time, separation between mean sea level and the geoid is referred to as (mean) ocean surface topography. It varies globally in a range of ± 2 m.

Dry land

Sea level sign seen on cliff (circled in red) at Badwater Basin, Death Valley National Park

Several terms are used to describe the changing relationships between sea level and dry land. When the term "relative" is used, it means change relative to a fixed point in the sediment pile. The term "eustatic" refers to global changes in sea level relative to a fixed point, such as the centre of the earth, for example as a result of melting ice-caps. The term "steric" refers to global changes in sea level due to thermal expansion and salinity variations. The term "isostatic" refers to changes in the level of the land relative to a fixed point in the earth, possibly due to thermal buoyancy or tectonic effects; it implies no change in the volume of water in the oceans. The melting of glaciers at the end of ice ages is one example of eustatic sea level rise. The subsidence of land due to the withdrawal of groundwater is an isostatic cause of relative sea level rise. Paleoclimatologists can track sea level by examining the rocks deposited along coasts that are very tectonically stable, like the east coast of North America. Areas like volcanic islands are experiencing relative sea level rise as a result of isostatic cooling of the rock which causes the land to sink.

On other planets that lack a liquid ocean, planetologists can calculate a "mean altitude" by averaging the heights of all points on the surface. This altitude, sometimes referred to as a "sea level" or zero-level elevation, serves equivalently as a reference for the height of planetary features.

Change

Local and eustatic

Water cycles between ocean, atmosphere and glaciers

Local mean sea level (LMSL) is defined as the height of the sea with respect to a land benchmark, averaged over a period of time (such as a month or a year) long enough that fluctuations caused by waves and tides are smoothed out. One must adjust perceived changes in LMSL to account for vertical movements of the land, which can be of the same order (mm/yr) as sea level changes. Some land movements occur because of isostatic adjustment of the mantle to the melting of ice sheets at the end of the last ice age. The weight of the ice sheet depresses the underlying land, and when the ice melts away the land slowly rebounds. Changes in ground-based ice volume also affect local and regional sea levels by the readjustment of the geoid and true polar wander. Atmospheric pressure, ocean currents and local ocean temperature changes can affect LMSL as well.

Eustatic sea level change (as opposed to local change) results in an alteration to the global sea levels due to changes in either the volume of water in the world's oceans or net changes in the volume of the oceanic basins.

Short-term and periodic changes

Melting glaciers are causing a change in sea level

There are many factors which can produce short-term (a few minutes to 14 months) changes in sea level. Two major mechanisms are causing sea level to rise. First, shrinking land ice, such as mountain glaciers and polar ice sheets, is releasing water into the oceans. Second, as ocean temperatures rise, the warmer water expands.

Periodic sea level changes
Diurnal and semidiurnal astronomical tides 12–24 h P 0.2–10+ m
Long-period tides    
Rotational variations (Chandler wobble) 14-month P
Meteorological and oceanographic fluctuations
Atmospheric pressure Hours to months −0.7 to 1.3 m
Winds (storm surges) 1–5 days Up to 5 m
Evaporation and precipitation (may also follow long-term pattern) Days to weeks  
Ocean surface topography (changes in water density and currents) Days to weeks Up to 1 m
El Niño/southern oscillation 6 mo every 5–10 yr Up to 0.6 m
Seasonal variations
Seasonal water balance among oceans (Atlantic, Pacific, Indian)    
Seasonal variations in slope of water surface    
River runoff/floods 2 months 1 m
Seasonal water density changes (temperature and salinity) 6 months 0.2 m
Seiches
Seiches (standing waves) Minutes to hours Up to 2 m
Earthquakes
Tsunamis (generate catastrophic long-period waves) Hours Up to 10 m
Abrupt change in land level Minutes Up to 10 m

Recent changes

For at least the last 100 years, sea level has been rising at an average rate of about 1.8 mm (0.07 in) per year. Most of this rise can be attributed to the increase in temperature of the sea and the resulting slight thermal expansion of the upper 500 metres (1,640 feet) of sea water. Additional contributions, as much as one-quarter of the total, come from water sources on land, such as melting snow and glaciers and extraction of groundwater for irrigation and other agricultural and human uses.

Aviation

Pilots can estimate height above sea level with an altimeter set to a defined barometric pressure. Generally, the pressure used to set the altimeter is the barometric pressure that would exist at MSL in the region being flown over. This pressure is referred to as either QNH or "altimeter" and is transmitted to the pilot by radio from air traffic control (ATC) or an automatic terminal information service (ATIS). Since the terrain elevation is also referenced to MSL, the pilot can estimate height above ground by subtracting the terrain altitude from the altimeter reading. Aviation charts are divided into boxes and the maximum terrain altitude from MSL in each box is clearly indicated. Once above the transition altitude, the altimeter is set to the international standard atmosphere (ISA) pressure at MSL which is 1013.25 hPa or 29.92 in Hg.

Carbon dioxide removal

From Wikipedia, the free encyclopedia

Planting trees is a means of carbon dioxide removal.

Carbon dioxide removal (CDR), also known as greenhouse gas removal, is a process in which carbon dioxide gas (CO
2
) is removed from the atmosphere and sequestered for long periods of time – in the context of net zero greenhouse gas emissions targets, CDR is increasingly integrated into climate policy. CDR methods are also known as negative emissions technologies, and may be cheaper than preventing some agricultural greenhouse gas emissions.

CDR methods include afforestation, agricultural practices that sequester carbon in soils, bio-energy with carbon capture and storage, ocean fertilization, enhanced weathering, and direct air capture when combined with storage. To assess whether net negative emissions are achieved by a particular process, comprehensive life cycle analysis of the process must be performed.

The IPCC's analysis of climate change mitigation pathways that are consistent with limiting global warming to 1.5 °C found that all assessed pathways include the use of CDR to offset emissions. A 2019 consensus report by the US National Academies of Sciences, Engineering, and Medicine concluded that using existing CDR methods at scales that can be safely and economically deployed, there is potential to remove and sequester up to 10 gigatons of carbon dioxide per year. This would offset greenhouse gas emissions at about a fifth of the rate at which they are being produced.

Definitions

The Intergovernmental Panel on Climate Change defines CDR as:

Anthropogenic activities removing CO
2
from the atmosphere and durably storing it in geological, terrestrial, or ocean reservoirs, or in products. It includes existing and potential anthropogenic enhancement of biological or geochemical sinks and direct air capture and storage, but excludes natural CO
2
uptake not directly caused by human activities.

The U.S.-based National Academies of Sciences, Engineering, and Medicine (NASEM) uses the term "negative emissions technology" with a similar definition.

The concept of deliberately reducing the amount of CO
2
in the atmosphere is often mistakenly classified with solar radiation management as a form of climate engineering and assumed to be intrinsically risky. In fact, CDR addresses the root cause of climate change and is part of strategies to reduce net emissions.

Concepts using similar terminology

CDR can be confused with carbon capture and storage (CCS), a process in which carbon dioxide is collected from point-sources such as gas-fired power plants, whose smokestacks emit CO
2
in a concentrated stream. The CO
2
is then compressed and sequestered or utilized. When used to sequester the carbon from a gas-fired power plant, CCS reduces emissions from continued use of the point source, but does not reduce the amount of carbon dioxide already in the atmosphere.

Potential for climate change mitigation

Using CDR in parallel with other efforts to reduce greenhouse gas emissions, such as deploying renewable energy, is likely to be less expensive and disruptive than using other efforts alone. A 2019 consensus study report by NASEM assessed the potential of all forms of CDR other than ocean fertilization that could be deployed safely and economically using current technologies, and estimated that they could remove up to 10 gigatons of CO
2
per year if fully deployed worldwide. This is one-fifth of the 50 gigatons of CO
2
emitted per year by human activities. In the IPCC's 2018 analysis of ways to limit climate change, all analyzed mitigation pathways that would prevent more than 1.5 °C of warming included CDR measures.

Some mitigation pathways propose achieving higher rates of CDR through massive deployment of one technology, however these pathways assume that hundreds of millions of hectares of cropland are converted to growing biofuel crops. Further research in the areas of direct air capture, geologic sequestration of carbon dioxide, and carbon mineralization could potentially yield technological advancements that make higher rates of CDR economically feasible.

The IPCC's 2018 report said that reliance on large-scale deployment of CDR would be a "major risk" to achieving the goal of less than 1.5 °C of warming, given the uncertainties in how quickly CDR can be deployed at scale. Strategies for mitigating climate change that rely less on CDR and more on sustainable use of energy carry less of this risk. The possibility of large-scale future CDR deployment has been described as a moral hazard, as it could lead to a reduction in near-term efforts to mitigate climate change. The 2019 NASEM report concludes:

Any argument to delay mitigation efforts because NETs will provide a backstop drastically misrepresents their current capacities and the likely pace of research progress.

Carbon sequestration

Forests, kelp beds, and other forms of plant life absorb carbon dioxide from the air as they grow, and bind it into biomass. As the use of plants as carbon sinks can be undone by events such as wildfires, the long-term reliability of these approaches has been questioned.

Carbon dioxide that has been removed from the atmosphere can also be stored in the Earth's crust by injecting it into the subsurface, or in the form of insoluble carbonate salts (mineral sequestration). This is because they are removing carbon from the atmosphere and sequestering it indefinitely and presumably for a considerable duration (thousands to millions of years).

Methods

Afforestation, reforestation, and forestry management

According to the International Union for Conservation of Nature: "Halting the loss and degradation of natural systems and promoting their restoration have the potential to contribute over one-third of the total climate change mitigation scientists say is required by 2030."

Biosequestration

Biosequestration is the capture and storage of the atmospheric greenhouse gas carbon dioxide by continual or enhanced biological processes. This form of carbon sequestration occurs through increased rates of photosynthesis via land-use practices such as reforestation, sustainable forest management, and genetic engineering. The SALK Harnessing Plants Initiative led by Joanne Chory is an example of an enhanced photosynthesis initiative Carbon sequestration through biological processes affects the global carbon cycle.

Agricultural practices


Measuring soil respiration on agricultural land.
 
Carbon farming is a name for a variety of agricultural methods aimed at sequestering atmospheric carbon into the soil and in crop roots, wood and leaves. The aim of carbon farming is to increase the rate at which carbon is sequestered into soil and plant material with the goal of creating a net loss of carbon from the atmosphere. Increasing a soil's organic matter content can aid plant growth, increase total carbon content, improve soil water retention capacity and reduce fertilizer use. As of 2016, variants of carbon farming reached hundreds of millions of hectares globally, of the nearly 5 billion hectares (1.2×1010 acres) of world farmland. In addition to agricultural activities, forests management is also a tool that is used in Carbon farming.  The practice of carbon farming is often done by individual land owners who are given incentive to use and to integrate methods that will sequester carbon through policies created by governments.  Carbon farming methods will typically have a cost, meaning farmers and land-owners typically need a way in which they can profit from the use of carbon farming and different governments will have different programs. Potential sequestration alternatives to carbon farming include scrubbing CO2 from the air with machines (direct air capture); fertilizing the oceans to prompt algal blooms that after death carry carbon to the sea bottom; storing the carbon dioxide emitted by electricity generation; and crushing and spreading types of rock such as basalt that absorb atmospheric carbon. Land management techniques that can be combined with farming include planting/restoring forests, burying biochar produced by anaerobically converted biomass and restoring wetlands. (Coal beds are the remains of marshes and peatlands.)

Wetland restoration

Estimates of the economic value of blue carbon ecosystems per hectare. Based on 2009 data from UNEP/GRID-Arendal.

Blue carbon refers to carbon dioxide removed from the atmosphere by the world's ocean ecosystems, mostly algae, mangroves, salt marshes, seagrasses and macroalgae, through plant growth and the accumulation and burial of organic matter in the soil.

Historically the ocean, atmosphere, soil, and terrestrial forest ecosystems have been the largest natural carbon (C) sinks. "Blue carbon" designates carbon that is fixed via the largest ocean ecosystems, rather than traditional land ecosystems, like forests. Oceans cover 70% of the planet, consequently ocean ecosystem restoration has the greatest blue carbon development potential. Mangroves, salt marshes and seagrasses make up the majority of the ocean's vegetated habitats but only equal 0.05% of the plant biomass on land. Despite their small footprint, they can store a comparable amount of carbon per year and are highly efficient carbon sinks. Seagrasses, mangroves and salt marshes can capture carbon dioxide (CO
2
) from the atmosphere by sequestering the C in their underlying sediments, in underground and below-ground biomass, and in dead biomass.

In plant biomass such as leaves, stems, branches or roots, blue carbon can be sequestered for years to decades, and for thousands to millions of years in underlying plant sediments. Current estimates of long-term blue carbon C burial capacity are variable, and research is ongoing. Although vegetated coastal ecosystems cover less area and have less aboveground biomass than terrestrial plants they have the potential to impact longterm C sequestration, particularly in sediment sinks. One of the main concerns with Blue Carbon is the rate of loss of these important marine ecosystems is much higher than any other ecosystem on the planet, even compared to rainforests. Current estimates suggest a loss of 2-7% per year, which is not only lost carbon sequestration, but also lost habitat that is important for managing climate, coastal protection, and health.

Bioenergy with carbon capture & storage

Bioenergy with carbon capture and storage (BECCS) is the process of extracting bioenergy from biomass and capturing and storing the carbon, thereby removing it from the atmosphere. The carbon in the biomass comes from the greenhouse gas carbon dioxide (CO2) which is extracted from the atmosphere by the biomass when it grows. Energy is extracted in useful forms (electricity, heat, biofuels, etc.) as the biomass is utilized through combustion, fermentation, pyrolysis or other conversion methods. Some of the carbon in the biomass is converted to CO2 or biochar which can then be stored by geologic sequestration or land application, respectively, enabling carbon dioxide removal and making BECCS a negative emissions technology.

The IPCC Fifth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), suggests a potential range of negative emissions from BECCS of 0 to 22 gigatonnes per year. As of 2019, five facilities around the world were actively using BECCS technologies and were capturing approximately 1.5 million tonnes per year of CO2. Wide deployment of BECCS is constrained by cost and availability of biomass.

Biochar

Biochar is created by the pyrolysis of biomass, and is under investigation as a method of carbon sequestration. Biochar is a charcoal that is used for agricultural purposes which also aids in carbon sequestration, the capture or hold of carbon. It is created using a process called pyrolysis, which is basically the act of high temperature heating biomass in an environment with low oxygen levels. What remains is a material known as char, similar to charcoal but is made through a sustainable process, thus the use of biomass. Biomass is organic matter produced by living organisms or recently living organisms, most commonly plants or plant based material. A study done by the UK Biochar Research Center has stated that, on a conservative level, biochar can store 1 gigaton of carbon per year. With greater effort in marketing and acceptance of biochar, the benefit could be the storage of 5–9 gigatons per year of carbon in biochar soils.

Enhanced weathering

Enhanced weathering is a chemical approach to remove carbon dioxide involving land- or ocean-based techniques. One example of a land-based enhanced weathering technique is in-situ carbonation of silicates. Ultramafic rock, for example, has the potential to store from hundreds to thousands of years' worth of CO2 emissions, according to estimates. Ocean-based techniques involve alkalinity enhancement, such as grinding, dispersing, and dissolving olivine, limestone, silicates, or calcium hydroxide to address ocean acidification and CO2 sequestration. One example of a research project on the feasibility of enhanced weathering is the CarbFix project in Iceland.

Direct air capture

Direct air capture (DAC) is the use of chemical or physical processes to extract CO
2
directly from the ambient air. If the extracted CO
2
is then sequestered in safe long-term storage, the overall process will achieve carbon dioxide removal. Several companies such as Zurich startup Climeworks and California based Prometheus Fuels are now working on this approach.

DAC relying on amine-based absorption demands significant water input. It was estimated, that to capture 3.3 Gigatonnes of CO
2
a year would require 300 km3 of water, or 4% of the water used for irrigation. On the other hand, using sodium hydroxide needs far less water, but the substance itself is highly caustic and dangerous.

DAC energy requirements are very different between liquid solvent and solid sorbent systems, as solid sorbent systems can use waste heat, for example from geothermal power plants.

Ocean fertilization

A visualization of bloom populations in the North Atlantic and North Pacific oceans from March 2003 to October 2006. The blue areas are nutrient deficient. Green to yellow show blooms fed by dust blown from nearby landmasses.
 
Ocean fertilization or ocean nourishment is a type of climate engineering based on the purposeful introduction of nutrients to the upper ocean to increase marine food production and to remove carbon dioxide from the atmosphere. A number of techniques, including fertilization by iron, urea and phosphorus have been proposed.

Economic issues

A crucial issue for CDR is the cost, which differs substantially among the different methods: some of these are not sufficiently developed to perform cost assessments. In 2021 DAC cost from $250 to $600 per tonne, compared to less than $50 for most reforestation. In early 2021 the EU carbon price was slightly over $50. However the value of BECCS and CDR generally in integrated assessment models in the long term is highly dependant on the discount rate.

On 21 January 2021, Elon Musk announced he was donating $100m for a prize for best carbon capture technology.

Removal of other greenhouse gases

Although some researchers have suggested methods for removing methane, others say that nitrous oxide would be a better subject for research due to its longer lifetime in the atmosphere.

Carbon tax

From Wikipedia, the free encyclopedia
 
Carbon taxes and emission trading worldwide
Emission trading and carbon taxes around the world (2019)
  Carbon emission trading implemented or scheduled
  Carbon tax implemented or scheduled
  Carbon emission trading or carbon tax under consideration

A coal-fired power plant in Luchegorsk, Russia. A carbon tax would tax the CO
2
emitted from the power station.

A carbon tax is a tax levied on the carbon emissions required to produce goods and services. Carbon taxes are intended to make visible the "hidden" social costs of carbon emissions, which are otherwise felt only in indirect ways like more severe weather events. In this way, they are designed to reduce carbon dioxide (CO
2
) emissions
by increasing prices. This both decreases demand for such goods and services and incentivizes efforts to make them less carbon-intensive. In its simplest form, a carbon tax covers only CO2 emissions; however, they can also cover other greenhouse gases, such as methane or nitrous oxide, by calculating their global warming potential relative to CO2.

When a hydrocarbon fuel such as coal, petroleum, or natural gas is burnt, its carbon is converted to CO
2
and other carbon compounds/allotropes. Greenhouse gases cause global warming, which damages the environment and human health. This negative externality can be reduced by taxing carbon content at any point in the product cycle. Carbon taxes are thus a type of Pigovian tax. Research shows that carbon taxes effectively reduce emissions. Many economists argue that carbon taxes are the most efficient (lowest cost) way to curb climate change. Seventy-seven countries and over 100 cities have committed to achieving net zero emissions by 2050. As of 2019, carbon taxes have been implemented or scheduled for implementation in 25 countries, while 46 countries put some form of price on carbon, either through carbon taxes or emissions trading schemes.

On their own, carbon taxes are usually regressive, since lower-income households tend to spend a greater proportion of their income on emissions-heavy goods and services like transportation than higher-income households. To make them more progressive, policymakers usually try to redistribute the revenue generated from carbon taxes to low-income groups by lowering income taxes or offering rebates.

Background

Carbon dioxide is one of several heat-trapping greenhouse gases (others include methane and water vapor) emitted as a result of human activities. The scientific consensus is that human-induced greenhouse gas emissions are the primary cause of global warming, and that carbon dioxide is the most important of the anthropogenic greenhouse gases. Worldwide, 27 billion tonnes of carbon dioxide are produced by human activity annually. The physical effect of CO
2
in the atmosphere can be measured as a change in the Earth-atmosphere system's energy balance – the radiative forcing of CO
2
.

David Gordon Wilson first proposed a carbon tax in 1973. A series of treaties and other agreements have focused attention on climate change. In the 2015 Paris Agreement, countries committed to reducing their greenhouse gas emissions over the ensuing decades.

Different greenhouse gases have different physical properties: the global warming potential is an internationally accepted scale of equivalence for other greenhouse gases in units of tonnes of carbon dioxide equivalent.

Economic theory

Economists like to argue, about climate change as much as anything else. [...] But on the biggest issue of all, they nod in agreement, whatever their political persuasion. The best way to tackle climate change, they insist, is through a global carbon tax.

— The Economist, 28 November 2015

A carbon tax is a form of pollution tax. Unlike classic command and control regulations, which explicitly limit or prohibit emissions by each individual polluter, a carbon tax aims to allow market forces to determine the most efficient way to reduce pollution. A carbon tax is an indirect tax—a tax on a transaction—as opposed to a direct tax, which taxes income. Carbon taxes are price instruments since they set a price rather than an emission limit. In addition to creating incentives for energy conservation, a carbon tax puts renewable energy such as wind, solar and geothermal on a more competitive footing.

In economic theory, pollution is considered a negative externality, a negative effect on a third party not directly involved in a transaction, and is a type of market failure. To confront the issue, economist Arthur Pigou proposed taxing the goods (in this case hydrocarbon fuels), that were the source of the externality (CO
2
) so as to accurately reflect the cost of the goods to society, thereby internalizing the production costs. A tax on a negative externality is called a Pigovian tax, which should equal the cost.

Within Pigou's framework, the changes involved are marginal, and the size of the externality is assumed to be small enough not to distort the economy. Climate change is claimed to result in catastrophe (non-marginal) changes. "Non-marginal" means that the impact could significantly reduce the growth rate in income and welfare. The amount of resources that should be devoted to climate change mitigation is controversial. Policies designed to reduce carbon emissions could have a non-marginal impact, but are asserted to not be catastrophic.

Two common economic alternatives to carbon taxes are tradable permits/credits and subsidies.

Carbon leakage

Carbon leakage happens when the regulation of emissions in one country/sector pushes those emissions to other places that with less regulation. Leakage effects can be both negative (i.e., increasing the effectiveness of reducing overall emissions) and positive (reducing the effectiveness of reducing overall emissions). Negative leakages, which are desirable, can be referred to as "spill-over".

According to one study, short-term leakage effects need to be judged against long-term effects. A policy that, for example, establishes carbon taxes only in developed countries might leak emissions to developing countries. However, a desirable negative leakage could occur due to reduced demand for coal, oil, and gas in developed countries, lowering prices. This could allow developing countries to substitute oil or gas for coal, lowering emissions. In the long-run, however, if less polluting technologies are delayed, this substitution might have no long-term benefit.

Carbon leakage is central to climate policy, given the 2030 Energy and Climate Framework and the review of the European Union's third carbon leakage list.

Border adjustments, tariffs and bans

Policies have been suggested to address concerns over competitive losses experienced by countries that introduce a carbon tax versus countries that do not. Border tax adjustments, tariffs and trade bans have been proposed to encourage countries to introduce carbon taxes.

Border tax adjustments compensate for emissions attributable to imports from nations without a carbon price. An alternative would be trade bans or tariffs applied to such countries. Such approaches could be inadmissible at the World Trade Organization. Case law there has not provided specific rulings on climate-related taxes. The administrative aspects of border tax adjustments have been discussed.

Other types of taxes

Two related taxes are emissions taxes and energy taxes. An emissions tax on greenhouse gas emissions requires individual emitters to pay a fee, charge, or tax for every tonne of greenhouse gas, while an energy tax is applied to the fuels themselves.

In terms of climate change mitigation, a carbon tax is not a perfect substitute for an emissions tax. For example, a carbon tax encourages reduced fuel use, but it does not encourage emissions reduction such as carbon capture and storage.

Energy taxes increase the price of energy regardless of emissions. An ad valorem energy tax is levied according to the energy content of a fuel or the value of an energy product, which may or may not be consistent with the emitted greenhouse gas amounts and their respective global warming potentials. Studies indicate that to reduce emissions by a certain amount, ad valorem energy taxes would be more costly than carbon taxes. However, although greenhouse gas emissions are an externality, using energy services may result in other negative externalities, e.g., air pollution not covered by the carbon tax (such as ammonia or fine particles). A combined carbon-energy tax may therefore be better at reducing air pollution than a carbon tax alone.

Any of these taxes can be combined with a rebate, where the money collected by the tax is returned to qualifying parties, taxing heavy emitters and subsidizing those that emit less carbon.

Embodied carbon and architecture

Embodied carbon emissions, or upfront carbon emissions (UCE), are the result of creating and maintaining the materials that form a building. As of 2018, "Embodied carbon is responsible 11% of global greenhouse gas emissions and 28% of global building sector emissions ... Embodied carbon will be responsible for almost half of total new construction emissions between now and 2050."

Steve Webb, co-founder of Webb Yates Engineers, has suggested that buildings with "high carbon frames should be taxed like cigarettes," to create a presumption in favour of timber, stone, and other zero-carbon architectural design techniques."

Other reduction strategies

Carpooling

Fuel taxes and carbon taxes encourage carpooling. Carpools offer the added benefits of helping to reduce commute time, reduce car accident rates, increase personal savings, and improve quality of life. Drawbacks include the cost of enforcement, increased police stops, and political resistance from increased government involvement in daily life.

Petroleum (gasoline, diesel, jet fuel) taxes

Many countries tax fuel directly; for example, the UK imposes a hydrocarbon oil duty directly on vehicle hydrocarbon oils, including petrol and diesel fuel.

While a direct tax sends a clear signal to the consumer, its efficiency at influence consumers' fuel use has been challenged for reasons including:

  • Possible delays of a decade or more as inefficient vehicles are replaced by newer models and the older models filter through the fleet.
  • Political pressures that deter policymakers from increasing taxes.
  • Limited relationship between consumer decisions on fuel economy and fuel prices. Other efforts, such as fuel efficiency standards, or changing income tax rules on taxable benefits, may be more effective.
  • The historical use of fuel taxes as a source of general revenue, given fuel's low price elasticity, which allows higher rates without reducing fuel volumes. In these circumstances, the policy rational may be unclear.

Vehicle fuel taxes may reduce the "rebound effect" that occurs when vehicle efficiency improves. Consumers may make additional journeys or purchase heavier and more powerful vehicles, offsetting the efficiency gains.

Social cost of carbon

A carbon tax based on the social cost of carbon (SCC) varies by fuel source. CO
2
production per unit of mass or volume is multiplied by the SCC to compute the tax. Based on the mean peer-reviewed value ($43 per tonne coal or $12 per tonne CO
2
), the table below estimates the appropriate tax by fuel type:

Fuel CO
2
emissions
(mass of CO
2
produced)
Tax
(per fuel unit)
CO
2
emissions
(mass of CO
2
produced)
Tax per kWh of electricity
gasoline 2.35 kg/L (19.6 lb/US gal) $0.029/L ($0.11/US gal) n/a n/a
diesel 2.67 kg/L (22.3 lb/US gal) $0.032/L ($0.12/US gal) n/a n/a
avgas 2.65 kg/L (22.1 lb/US gal) $0.032/L ($0.12/US gal) n/a n/a
natural gas 1.93 kg/m3 (0.1206 lb/cu ft) $0.023/m3 ($0.00066/cu ft) 181 g/kWh (117 lb/million BTU) $0.0066
coal (lignite) 1.396 kg/kg (2,791 lb/short ton) n/a 333 g/kWh (215 lb/million BTU) $0.0121
coal (subbituminous) 1.858 kg/kg (3,715 lb/short ton) n/a 330 g/kWh (213 lb/million BTU) $0.0119
coal (bituminous) 2.466 kg/kg (4,931 lb/short ton) n/a 317 g/kWh (205 lb/million BTU) $0.0115
coal (anthracite) 2.843 kg/kg (5,685 lb/short ton) n/a 351 g/kWh (227 lb/million BTU) $0.0127

The tax per kWh of electricity depends on the thermal efficiency of the related power plant. The table follows the American Physical Society (APS) estimate of 3.0 Wh (10.3 BTU) input per output 1.0 Whe or 33%. The APS noted that "future plants, especially those based on gas turbine systems, often will have higher efficiency, in some cases exceeding 50%.The EDF powerplant in Bouchain, France achieved highest efficiency to date: 62%.

Impact

Research shows that carbon taxes effectively reduce greenhouse gas emissions. Most economists assert that carbon taxes are the most efficient and effective way to curb climate change, with the least adverse economic effects.

One study found that Sweden's carbon tax successfully reduced carbon dioxide emissions from transport by 11%. A 2015 British Columbia study found that the taxes reduced greenhouse gas emissions by 5–15% while having negligible overall economic effects. A 2017 British Columbia study found that industries on the whole benefited from the tax and "small but statistically significant 0.74 percent annual increases in employment" but that carbon-intensive and trade-sensitive industries were adversely affected. A 2020 study of carbon taxes in wealthy democracies showed that carbon taxes had not limited economic growth.

A number of studies have found that in the absence of an increase in social benefits and tax credits, a carbon tax would hit poor households harder than rich households. Gilbert E.Metcalf disputed that carbon taxes would be regressive in the US.

Implementation

Both energy and carbon taxes have been implemented in response to commitments under the United Nations Framework Convention on Climate Change. In most cases the tax is implemented in combination with exemptions.

Africa

South Africa

A tax on emissions was proposed for South Africa. Announced by Finance Minister Pravin Gordhan. The tax will be implemented starting 1 September 2015 on new motor vehicles. This tax was to apply at the time of sale, and related to the amount of CO
2
emitted by the vehicle. 75 South African Rand were to be added to the price for every gram of CO2 per kilometer the vehicle emits above 120 g/km. The tax applied to passenger cars first and eventually to commercial vehicles. Bakkies (pickup trucks) are to be taxed because of their use as passenger vehicles: this caused an uproar for fear of affecting industry.

David Powels of the National Association of Automobile Manufacturers of South Africa (NAAMSA), opposes this taxation on light commercial vehicles. The tax could increase the cost of new vehicles by 2.5% and decrease sales: Powels also questioned the ability to accurately predict CO2 emissions based on engine capacity. NAAMSA acknowledged the ability of carbon taxes to change consumer behavior for the betterment of the environment, but argued that this tax is not transparent enough because the taxation occurs at the time of automobile production. Powels says the tax is discriminatory because it targets new vehicles, and that the government should focus on introducing "green fuel" to South Africa.

Zimbabwe

Carbon tax is payable in foreign currency at the rate of US$0.03 (3 cents) per litre of petroleum and diesel products or 5% of the cost, insurance, and freight value (as defined in the Customs and Excise Act [Chapter 23:02]), whichever is greater.

Asia

China

The Chinese Ministry of Finance proposed to introduce a carbon tax in 2012 or 2013. The tax might affect the internal market, as well as many other laws and regulations. Given the size of the Chinese economy also contribute importantly to the mitigation of climate change. In 2017, China announced an emissions trading scheme.

India

On 1 July 2010, India introduced a carbon tax of 50 rupees per tonne ($1.07/t) of coal both produced and imported into India. In 2014, the tax increased the price to ₹100 per tonne ( $1.60/t at $60.5 conversion)Coal powers more than half of the country's electricity generation.

India's total coal production was estimated to reach 571.87  million tons in the year ending March 2010 and was expected to import around 100 million tons. The carbon tax expects to raise ₹25 billion ($535 million) for the financial year 2010–2011. The clean energy tax was promised to finance a National Clean Energy Fund (NCEF). Industry bodies did not support the levy.

Under Narendra Modi, the carbon tax was increased form ₹100 per tonne to ₹200 per tonne in the Budget 2015–16. It later rose to ₹400 per tonne.

Japan

In October 2012, Japan introduced a carbon tax to finance renewable energy and energy conservation projects.

In December 2009, nine industry groupings opposed a carbon tax at the opening day of the COP-15 Copenhagen climate conference stating, "Japan should not consider a carbon tax as it would damage the economy which is already among the world's most energy-efficient." The industry groupings represented the oil, cement, paper, chemical, gas, electric power, auto manufacturing and electronics, and information technology sectors. The sectors stated that "the government has neither studied nor explained thoroughly enough why such a carbon tax is needed, how effective and fair it is and how the payments are to be used."

In 2005, an environmental tax proposed by Japanese authorities was delayed due to major opposition from the Petroleum Association of Japan (PAJ), other industries, and consumers.

Singapore

On 20 February 2017, Singapore proposed a carbon tax. The proposal was refined to tax large emitters at S$5 per tonne of greenhouse gas emissions. The Carbon Pricing Act or CPA, was passed on 20 March 2018 and came into operation on 1 January 2019.

Taiwan

In October 2009, vice finance minister Chang Sheng-ho announced that Taiwan was planning to adopt a carbon tax in 2011. However, Premier Wu Den-yih and legislators stated that carbon taxes would increase public suffering from the recession and that the government should not levy the new taxes until Taiwan's economy had recovered, opposing the tax. However, Chung-Hua Institution for Economic Research (CIER), the think-tank that was commissioned by the government to advise on its plan to overhaul the nation's taxes, had recommended a levy of NT$2,000 (US$61.8, £37.6) on each tonne of CO2 emissions. CIER estimated that Taiwan could raise NT$164.7bn (US$5.1bn, £3.1bn) from the energy tax and a further NT$239bn (US$7.3bn, £4.4bn) from the carbon levy on an annual basis by 2021. The government planned to subsidize low income families and public transportation with the revenues.

Oceania

Australia

On 1 July 2012, the Australian Federal government introduced a carbon price of AUD$23 per tonne on selected fossil fuels consumed by major industrial emitters and government bodies such as councils. To offset the tax, the government reduced income tax (by increasing the tax-free threshold) and increased pensions and welfare payments slightly, while introducing compensation for some affected industries. On 17 July 2014, a report by the Australian National University estimated that the Australian scheme had cut carbon emissions by as much as 17 million tonnes. The tax notably helped reduce pollution from the electricity sector.

On 17 July 2014, the Abbott Government passed repeal legislation through the Senate, and Australia became the first nation to abolish a carbon tax. In its place, the government set up the Emission Reduction Fund.

New Zealand

In 2005, the Fifth Labour Government proposed a carbon tax to meet obligations under the Kyoto Protocol. The proposal would have set an emissions price of NZ$15 per tonne of CO2-equivalent. The planned tax was scheduled to take effect from April 2007 and apply across most economic sectors though with an exemption for methane emissions from farming and provisions for special exemptions from carbon-intensive businesses if they adopted best-practice standards.

After the 2005 election, some of the minor parties supporting the Fifth Labour Government (NZ First and United Future) opposed the proposed tax, and it was abandoned in December 2005.[89] In 2008, the New Zealand Emissions Trading Scheme was enacted via the Climate Change Response (Emissions Trading) Amendment Act 2008.

Europe

In Europe, many countries have imposed energy taxes or energy taxes based partly on carbon content. These include Denmark, Finland, Germany, Ireland, Italy, the Netherlands, Norway, Slovenia, Sweden, Switzerland, and the UK. None of these countries has been able to introduce a uniform carbon tax for fuels in all sectors.

European Union

During the 1990s, a carbon/energy tax was proposed at the EU level but failed due to industrial lobbying. In 2010, the European Commission considered implementing a pan-European minimum tax on pollution permits purchased under the European Union Greenhouse Gas Emissions Trading Scheme (EU ETS) in which the proposed new tax would be calculated in terms of carbon content. The suggested rate of €4 to €30 per tonne of CO2.

Denmark

As of 2002, the standard carbon tax rate since 1996 amounted to 100 DKK per tonne of CO
2
, equivalent to approximately €13 or US$18. The rate varies between 402 DKK per tonne of oil to 5.6 DKK per tonne of natural gas and 0 for non-combustible renewables. The rate for electricity is 1164 DKK per tonne or 10 øre per kWh, equivalent to .013 Euros or .017 US dollars per kWh. The tax applies to all energy users. Industrial companies can be taxed differently according to the process the energy is used for, and whether or not the company has entered into a voluntary agreement to apply energy efficiency measures.

In 1992, Denmark issued a carbon tax, charging about $14 for business and $7 for households, per ton of CO
2
. However, Denmark offers a tax refund for energy efficient changes. Most of the money collected would be put into research for alternative energy resources.

Finland

Finland was the first country in the 1990s to introduce a CO2 tax, initially with exemptions for specific fuels or sectors. Energy taxation was changed many times. These changes were related to the opening of the Nordic electricity market. Other Nordic countries exempted energy-intensive industries, and Finnish industries felt disadvantaged by this. Finland placed a border tax on imported electricity, but this was found to be out of line with EU single market legislation. Changes were then made to the carbon tax to partially exclude energy-intensive firms. This had the effect of increasing the costs of reducing CO2 emissions.

Vourc'h and Jimenez proposed that arguments based on competitive losses be viewed with caution. For example, they suggested that carbon tax revenues could be used to reduce labour taxes, which would favour non-energy-intensive industries.

France

In 2009, France detailed a carbon tax with a levy on oil, gas, and coal consumption by households and businesses that was supposed to come into effect on 1 January 2010. The tax would affect households and businesses, which would have raised the cost of a litre of unleaded fuel by about four euro cents (25 US cents per gallon). The total estimated income from the carbon tax would have been between €3–4.5 billion annually, with 55 percent from households and 45 percent from businesses. The tax would not have applied to electricity, which in France comes mostly from nuclear power.

On 30 December 2009, the bill was blocked by the French Constitutional Council, which said it included too many exceptions. Among those exceptions, certain industries were excluded that would have made the taxes unequal and inefficient. They included exemptions for agriculture, fishing, trucking, and farming. French President Nicolas Sarkozy, although he vowed to "lead the fight to save the human race from global warming", was forced to back down after mass social protests led to strikes. He wanted support from the rest of the European Union before proceeding.

In 2014, a carbon tax was implemented. Prime Minister Jean-Marc Ayrault announced the new Climate Energy Contribution (CEC) on 21 September 2013. The tax would apply at a rate of €7/tonne CO
2
in 2014, €14.50 in 2015 and rising to €22 in 2016. As of 2018, the carbon tax was at €44.60/tonne. and was due to increase every year to reach €65.40/tonne in 2020 and €86.20/tonne in 2022.

After weeks of protests by the "Gilets Jaunes" (yellow vests) against the rise of gas prices, French President Emmanuel Macron announced on 4 December 2018, the tax would not be increased in 2019 as planned.

Germany

The German ecological tax reform was adopted in 1999. After that, the law was amended in 2000 and in 2003. The law grew taxes on fuel and fossil fuels and laid the foundation for the tax for energy. In December 2019, the German Government agreed on a carbon tax of 25 Euros per tonne of CO
2
on oil and gas companies. The law will come into effect in January 2021. The tax will be grow to 55 Euros per tonne by 2025.

Netherlands

The Netherlands initiated a carbon tax in 1990. However, in 1992, it was replaced with a 50/50 carbon/energy tax called the Environmental Tax on Fuels. The taxes are assessed partly on carbon content and partly on energy content. The charge was transformed into a tax and became part of general tax revenues. The general fuel tax is collected on all hydrocarbon fuels. Fuels used as raw materials are not subject to the tax.

In 1996, the Regulatory Tax on Energy, another 50/50 carbon/energy tax, was implemented. The environmental tax and the regulatory tax are 5.16 Dutch guilder, or NLG, (~$3.13) or per tonne of CO2 and 27.00 NLG (~$16.40) per tonne CO2 respectively. Under the general fuel tax, electricity is not taxed, though fuels used to produce electricity are taxable. Energy-intensive industries initially benefited from preferential rates under this tax, but the benefit was canceled in January 1997. Since 1997, nuclear power has been taxed under the general fuel tax at the rate of NLG 31.95 per gram of uranium-235.38.

In 2007, the Netherlands introduced a Waste Fund that is funded by a carbon-based packaging tax. This tax was both used to finance government spending and to finance activities to help reach the goals of recycling 65% of used packaging by 2012. The organization Nedvang (Nederland van afval naar grondstof or The Netherlands from waste to value) was set up in 2005. It supports producers and importers of packaged goods. This decree was signed in 2005 and states that producers and importers of packaged goods are responsible for the collection and recycling of related waste and that at least 65% of that waste has to be recycled. Producers and importers can choose to reach the goals on an individual basis or by joining an organization like Nedvang.

The Carbon-Based Tax on Packaging was found to be ineffective by the Ministry of Infrastructure and the Environment. It was therefore abolished. Producer responsibility activities for packaging are now financed based on legally binding contracts.

Norway

Norway introduced a CO2 tax on fuels in 1991. The tax started at a rate of US$51 per tonne of CO2 on gasoline, with an average tax of US$21 per tonne. The tax applied to diesel, mineral oil, oil and gas used in North Sea extraction activities. The International Energy Agency's (IEA) in 2001 stated that "since 1991 a carbon dioxide tax has applied in addition to excise taxes on fuel." It is among the highest rates in OECD. The applies to offshore oil and gas production. IEA estimates for revenue generated by the tax in 2004 were 7,808 million NOK (about US$1.3 billion in 2010 dollars).

According to IEA's 2005 Review, Norway's CO2 tax is its most important climate policy instrument, and covers about 64% of Norwegian CO2 emissions and 52% of total greenhouse gas emissions. Some industry sectors were exempted to preserve their competitive position. Various studies in the 1990s, and an economic analysis by Statistics Norway, estimated the effect to be a reduction of 2.5–11% of Norwegian emissions compared to (untaxed) business-as-usual. However, Norway's per capita emissions still rose by 15% as of 2008.

In attempt to reduce CO
2
emissions by a larger amount, Norway implemented an Emissions Trading Scheme in 2005 and joined the European Union Emissions Trading Scheme (EU ETS) in 2008. As of 2013, roughly 55% of CO
2
emissions in Norway were taxed and exempt emissions are included in the EU ETS. Certain CO
2
taxes are applied to emissions that result from petroleum activities on the continental shelf. This tax is charged per liter of oil and natural gas liquids produced, as well as per standard cubic meter of gas flared or otherwise emitted. However, this carbon tax is a tax deductible operating cost for petroleum production. In 2013, carbon tax rates were doubled to 0.96 NOK per liter/standard cubic meter of mineral oil and natural gas. As of 2016, the rate increased to 1,02 NOK. The Norwegian Ministry of the Environment described CO
2
taxes as the most important tool for reducing emissions.

Republic of Ireland

In 2004, following a policy review, the Irish Government rejected a carbon tax option. In 2007 a Fianna Fáil-Green Party coalition government was formed, and promised to reconsider the matter. In 2010 the country's carbon tax was introduced at €15 per tonne of CO2 emissions (approx. US$20 per tonne).

The tax applies to kerosene, marked gas oil, liquid petroleum gas, fuel oil, and natural gas. The tax does not apply to electricity because the cost of electricity is already included in pricing under the Single Electricity Market (SEM). Similarly, natural gas users are exempt if they can prove they are using the gas to "generate electricity, for chemical reduction, or for electrolytic or metallurgical processes". Partial relief is granted for natural gas covered by a greenhouse gas emissions permit issued by the Environmental Protection Agency. Such gas will be taxed at the minimum rate specified in the EU Energy Tax Directive, which is €0.54 per megawatt-hour at gross calorific value." Pure biofuels are also exempt. The Economic and Social Research Institute (ESRI) estimated costs between €2 and €3 a week per household: a survey from the Central Statistics Office reports that Ireland's average disposable income was almost €48,000 in 2007.

Activist group Active Retirement Ireland proposed a pensioner's allowance of €4 per week for the 30 weeks currently covered by the fuel allowance and that home heating oil be covered under the Household Benefit Package.

The tax is paid by companies. Payment for the first accounting period was due in July 2010. Fraudulent violation is punishable by jail or a fine.

The NGO Irish Rural Link noted that according to ESRI a carbon tax would weigh more heavily on rural households. They claim that other countries have shown that carbon taxation succeeds only if it is part of a comprehensive package that includes reducing other taxes.

Carbon Tax was introduced in Ireland in the 2010 budget by the Green Party/Fianna Fáil coalition government at a rate of €15/tonne CO
2
. It was applied to motor gasoline and diesel and to home heating oil (diesel).

In 2011, the coalition government of Fine Gael and Labour raised the tax to €20/tonne. Farmers were granted tax relief.

Sweden

In January 1991, Sweden enacted a CO2 tax of SEK 250 per 1000 kg ($40 at the time, or EUR 27 at current rates) on the use of oil, coal, natural gas, liquefied petroleum gas, petrol, and aviation fuel used in domestic travel. Industrial users paid half the rate (between 1993 and 1997, 25%), and preferred industries such as commercial horticulture, mining, manufacturing, and pulp and paper were exempted entirely. As a result, the tax only covers around 40% of Sweden's carbon emissions. The rate was raised to SEK 365 ($60) in 1997 and SEK 930 in 2007.

According to a 2019 study, the tax was instrumental in substantially reducing Sweden's carbon dioxide emissions. The tax is also credited by Swedish Society for Nature Conservation climate change expert Emma Lindberg and University of Lund Professor Thomas Johansson with spurring a significant move from hydrocarbon fuels to biomass. Lindberg said, "It was the one major reason that steered society towards climate-friendly solutions. It made polluting more expensive and focused people on finding energy-efficient solutions."

Switzerland

In January 2008, Switzerland implemented a CO
2
incentive tax on all hydrocarbon fuels, unless are used for energy Gasoline and diesel fuels are not affected. It is an incentive tax because it is designed to promote the economic use of hydrocarbon fuels. The tax amounts to CHF 12 per tonne CO
2
, the equivalent of CHF 0.03 per litre of heating oil (US$0.108 per gallon) and CHF 0.025 per m3 of natural gas (US$0.024 per m3). Switzerland prefers to rely on voluntary actions and measures to reduce emissions. The law mandated a CO2 tax if voluntary measures proved to be insufficient. In 2005, the federal government decided that additional measures were needed to meet Kyoto Protocol commitments of an 8% reduction in emissions below 1990 levels between 2008 and 2012. In 2007, the CO
2
tax was approved by the Swiss Federal Council, coming into effect in 2008. In 2010, the highest tax rate was to be CHF 36 per tonne of CO
2
(US$34.20 per tonne CO
2
).

Companies are allowed to escape the tax by participating in emissions trading where they voluntarily commit to legally binding reduction targets. Emission allowances are given to companies for free, and each year emission allowances equal to the amount of CO2 emitted must be surrendered by the company. Companies are allowed to sell or trade excess permits. However, a company that fails to surrender sufficient allowances must pay the tax retroactively for each tonne emitted since the exemption was granted. As of 2009 some 400 companies operated under this program. In 2008 and 2009 the companies returned enough credits to the Swiss government to cover their CO2 emissions. The companies emitted about 2.6 million tonnes, well below the limit of 3.1 million tonnes. Switzerland issued so many allowances that few emissions permits were traded.

The tax is revenue-neutral because revenues are redistributed to companies and to the Swiss population. For example, if the population bears 60% of the tax burden, it receives 60% of the rebate. Revenues are redistributed to all payers, except those who exempt themselves from the tax through the cap-and-trade program. The revenue is given to companies in proportion to payroll. Tax revenues that were paid by the population are redistributed equally to all residents. In June 2009, the Swiss Parliament allocated about one-third of the carbon tax revenue to a 10-year construction initiative. This program promotes building renovations, renewable energies, waste heat reruse, and building engineering.

Tax revenue from 2008-2010 were distributed in 2010. In 2008, the tax raised around CHF 220 million (US$209 million) in revenue. As of 16 June 2010, a total of around CHF 360 million (US$342 million) had become available for distribution. The 2010 revenue was about CHF 630 million (US$598 million). CHF 200 million (US$190 million) was to be allocated for the building program, while the remaining CHF 430 million (US$409 million) was to be redistributed to the population. IEA commended Switzerland's tax for its design and that tax revenues would be recycled as "sound fiscal practice".

Since 2005, transport fuels in Switzerland have been subjected to the Climate Cent Initiative surcharge—a surcharge of CHF 0.015 per liter on gasoline and diesel (US$0.038 per gallon). However, this surcharge was supplemented with a CO2 tax on transport fuels if emissions reductions are not satisfactory. In their 2007 review, IEA recommended that Switzerland implement a CO2 tax on transport fuels or increase the Climate Cent surcharge to better balance the costs of meeting emissions reductions targets across sectors.

United Kingdom

The United Kingdom currently does not have a carbon tax. Instead, various fuel taxes and energy taxes have been implemented over the years, such as the fuel duty escalator (1993) and the Climate Change Levy (2001). The UK was also a member of the European Union Emission Trading Scheme until it left the EU. It has since implemented its own carbon trading scheme.

Central America

Costa Rica

In 1997, Costa Rica imposed a 3.5 percent carbon tax on hydrocarbon fuels. A portion of the proceeds go to the "Payment for Environmental Services" (PSA) program which gives incentives to property owners to practice sustainable development and forest conservation. Approximately 11% of Costa Rica's national territory is protected by the plan. The program now pays out roughly $15 million a year to around 8,000 property owners.

North America

Canada

In the 2008 Canadian federal election, a carbon tax proposed by Liberal Party leader Stéphane Dion, known as the Green Shift, became a central issue. It would have been revenue-neutral, balancing increased taxation on carbon with rebates. However, it proved to be unpopular and contributed to the Liberal Party's defeat, earning the lowest vote share since Confederation. The Conservative party won the election by promising to "develop and implement a North American-wide cap-and-trade system for greenhouse gases and air pollution, with implementation to occur between 2012 and 2015".

In 2018, Canada enacted a revenue-neutral carbon levy starting in 2019, fulfilling Prime Minister Justin Trudeau's campaign pledge. The Greenhouse Gas Pollution Pricing Act applies only to provinces without provincial adequate carbon pricing.

As of September 2020, seven of thirteen Canadian provinces and territories use the federal carbon tax while three have developed their own carbon tax programs.

Quebec

Quebec became the first province to introduce a carbon tax. The tax was to be imposed on energy producers starting 1 October 2007, with revenue collected used for energy-efficiency programs. The tax rate for gasoline is $CDN0.008 per liter, or about $3.50 per tonne of CO
2
equivalent.

British Columbia

On 19 February 2008, British Columbia announced its intention to implement a carbon tax of $10 per tonne of Carbon dioxide equivalent (CO2e) emissions (2.41 cents per litre on gasoline) beginning 1 July 2008, the first North American jurisdiction to implement such a tax. The tax was to increase until 2012, reaching a final price of $30 per tonne (7.2 cents per litre at the pumps). The tax was to be revenue neutral by reducing corporate and income taxes accordingly. The government was to reduce other taxes by $481 million over three years. In January 2010, the carbon tax was applied to biodiesel. Before the tax went into effect, the government of British Columbia sent out "rebate cheques" from expected revenues to all residents. In January 2013, the tax was collecting about $1 billion/year, which was rebated.

The tax was based on the following principles:

  • All revenue is recycled through tax reductions – The government was required to demonstrate how all carbon tax revenue was to be returned to taxpayers through tax reductions..
  • The tax rate increased gradually – to give individuals and businesses time to make adjustments and respect decisions made prior to the announcement of the tax.
  • Protect Low-income individuals and families – A refundable Low Income Climate Action Tax Credit helps offset the tax paid by low-income individuals and families.
  • Broad base – Virtually all emissions from fuel combustion are taxed, with no exemptions except those required for integration with other climate actions.
  • The tax would not, on its own, meet B.C.'s emission-reduction targets.

Many Canadians concluded that the carbon tax generally benefitted the British Columbian economy, in large part because its revenue neutral feature reduced personal income taxes. However some industries complained loudly that the tax had harmed them, notably cement manufacturers and farmers. Nevertheless, the tax attracted attention in the United States and elsewhere from those seeking an economically efficient way of reducing the emission of greenhouse gases without hurting economic growth.

Alberta

In July 2007, Alberta enacted the Specified Gas Emitters Regulation, Alta. Reg. 139/2007, (SGER). This tax exacts a $15/tonne contribution by companies that emit more than 100,000 tonnes of greenhouse gas annually that do not reduce their CO2 emissions per barrel by 12 percent, or buy an offset. In January 2016, the contribution required by large emitters increased to $20/tonne. The tax fell heavily on oil companies and coal-fired electricity plants. It was intended to encourage companies to lower emissions while fostering new technology. The plan only covered the largest emitters, who produced 70% of Alberta's emissions. Critics charged that the smallest energy producers are often the most casual about emissions and pollution. The carbon tax is currently $20 per tonne. Because Alberta's economy is dependent on oil extraction, the majority of Albertans opposed a nationwide carbon tax. Alberta also opposed a national cap and trade system. The local tax retains the proceeds within Alberta.

On 23 November 2015, the Alberta government announced a carbon tax scheme similar to British Columbia's in that it would apply to the entire economy. All businesses and residents paid tax based upon equivalent emissions, including the burning of wood and biofuels. The tax came into force in 2017 at $20 per tonne.

On 4 June 2019 a carbon tax repeal bill was enacted.

United States

Estimated effect of a carbon tax on sources of United States electrical generation (US Energy Information Administration)

A national carbon tax has been repeatedly proposed, but never enacted. On 23 July 2018 Representative Carlos Curbelo (R-FL) introduced H.R. 6463, the "Modernizing America with Rebuilding to Kick-start the Economy of the Twenty-first Century with a Historic Infrastructure-Centered Expansion (MARKET CHOICE) Act." The Citizens' Climate Lobby (CCL) attempted to create support for a tax. Americans for Carbon Dividends supports the Baker-Shultz Carbon Dividends Plan, and is supported by companies including Microsoft, First Solar, American Wind Energy Association, Exxon Mobil, BP, Royal Dutch Shell, and Total SA.

Internal price on carbon

Many corporations calculate an "internal price on carbon". Companies use this internal price to assess the risk of future projects into their investment decisions. Companies usually assess a higher internal price when the company a) emits large amounts of CO
2
, and b) projects further into the future. Oil company have assets (factories, refineries) with a long lifespan that can be affected by future energy policies.

Internal carbon prices for various US companies
Company Internal carbon price (US$) CO2 emitted in 2013 (million tonnes)
Exxon Mobil 60 127
BP 40 60
Shell 40 72
Total 34 47
Ameren 30 56
Xcel Energy 20 54
Google 13 .04
Disney 10–20 .9
ConocoPhillips 8–46 24
Microsoft 6 .05
Colorado

In November 2006, voters in Boulder, Colorado passed what is said to be the first municipal carbon tax. It covers electricity consumption with deductions for using electricity from renewable sources (primarily Xcel's WindSource program). The goal is to reduce their emissions by 7% below 1990 levels by 2012. Tax revenues are collected by Xcel Energy and are directed to the city's Office of Environmental Affairs to fund programs to reduce emissions.

Boulder's Climate Action Plan (CAP) tax was expected to raise $1.6 million in 2010. The tax was increased to a maximum allowable rate by voters in 2009 to meet CAP goals. As of 2017 the tax was set at $0.0049 /kWh for residential users (avg. $21 per year), $0.0009 /kWh for commercial (avg. $94 per year), and $0.0003 /kWh for industrial (avg. $9,600 per year). Tax revenues were expected to decrease over time as conservation and renewable energy expand. The tax was renewed by voters on 6 November 2012.

As of 2015, the Boulder carbon tax was estimated to reduce carbon output by over 100,000 tons per year and provided $1.8 million in revenue. This revenue is invested in bike lanes, energy-efficient solutions, rebates, and community programs. The surcharge has been generally well-received.

California

In May 2008, the Bay Area Air Quality Management District, which covers nine counties in the San Francisco Bay Area, passed a carbon tax on businesses of 4.4 cents per ton of CO2.

In 2006, the state of California passed AB-32 (Global Warming Solutions Act of 2006), which requires California to reduce greenhouse gas emissions. To implement AB-32, the California Air Resources Board proposed a carbon tax but this was not enacted.

Maryland

In May 2010, Montgomery County, Maryland passed the nation's first county-level carbon tax. The legislation required payments of $5 per ton of CO2 emitted from any stationary source emitting more than a million tons of carbon dioxide per year. The only source of emissions fitting the criteria is an 850 megawatt coal-fired power plant then owned by Mirant Corporation. The tax was expected to raise between $10 million and $15 million for the county, which faced a nearly $1 billion budget gap. The law directed half of tax revenues toward low interest loans for county residents to invest in residential energy efficiency. The County's energy supplier buys its energy at auction, requiring the plant owner to sell its energy at market value, preventing any increase in energy costs. In June 2010, Mirant sued the county to stop the tax. In June 2011 the Federal Court of Appeals ruled that the tax was a fee imposed "for regulatory or punitive purposes" rather than a tax, and therefore could be challenged in court. The County Council repealed the fee in July 2012.

Support

Economists and climate scientists

Greg Mankiw, head of the Council of Economic Advisers under the George W. Bush administration, economic adviser to Mitt Romney for his 2012 presidential campaign and economics professor at Harvard University since 1985, has been advocating for increased carbon/oil taxation since at least 1999. In 2006, he founded the Pigou Club of economists advocating for Pigovian taxes, a carbon tax among them. The club's manifesto states "[h]igher gasoline taxes, perhaps as part of a broader carbon tax, would be the most direct and least invasive policy to address environmental concerns."

In 1979, economist Milton Friedman expressed support for the idea of a carbon tax in an interview on The Phil Donahue Show, saying "...the best way to [deal with pollution] is to impose a tax on the cost of the pollutants emitted by a car and make an incentive for car manufacturers and for consumers to keep down the amount of pollution."

In 2001, environmental scientist Lester Brown, founder of the Worldwatch Institute and founder and president of the Earth Policy Institute, outlined a detailed "tax shifting" structure that would not lead to an overall higher tax level: "It means reducing income taxes and offsetting them with taxes on environmentally destructive activities such as carbon emissions, the generation of toxic waste, the use of virgin raw materials, the use of non-refillable beverage containers, mercury emissions, the generation of garbage, the use of pesticides, and the use of throwaway products... activities that should be discouraged by taxing."

Former US Federal Reserve chairman Paul Volcker suggested (6 February 2007) that "it would be wiser to impose a tax on oil, for example, than wait for the market to drive up oil prices. A tax would give the government 'some leverage that you can use for other things.'", supporting a carbon tax.

NASA climatologist James E. Hansen has argued in support of a carbon tax.

Citizens' Climate Lobby advocates for carbon tax legislation (specifically a progressive fee and dividend model). The organization has about 165 chapters in the United States, Canada, and several other countries including Bangladesh and Sweden.

Monica Prasad, a Northwestern University sociologist, wrote about Denmark's carbon tax in The New York Times in 2008. Prasad argued that a critical component for Denmark's success was that the revenues subsidized firms to switch to renewable energy.

According to economist Laura D'Andrea Tyson, "The beauty of a carbon tax is its market-based simplicity. Economists since Adam Smith have insisted that prices are by far the most efficient way to guide the decisions of producers and consumers. Carbon emissions have an 'unpriced' societal cost in terms of their deleterious effects on the earth's climate. A tax on carbon would reflect these costs and send a powerful price signal that would discourage carbon emissions."

The American Enterprise Institute, Environmental economist Jack Pezzey, economist Jeffrey Sachs (director of the Earth Institute of Columbia University), Yale economist William Nordhaus support carbon taxes.

In January 2019, economists published a statement in the Wall Street Journal calling for a carbon tax, describing it as "the most cost-effective lever to reduce carbon emissions at the scale and speed that is necessary." In February 2019, the statement had been signed by more than 3,000 U.S. economists, including 27 Nobel Laureates.

Others

  • Carl Pope, former executive director of the Sierra Club, supports a carbon tax over cap-and-trade because employers will know exactly what their emissions cost, and because cap-and-trade (with grandfathered permits) rewards those who have the highest emissions.
  • In 2008, Rex Tillerson, then CEO of Exxonmobil, said a carbon tax is "a more direct, more transparent and more effective approach" than a cap and trade program, which he said, "inevitably introduces unnecessary cost and complexity." He said that he hoped that the revenues from a carbon tax would be used to lower other taxes.
  • In 2016 in Washington state, the Sierra Club, the Washington Environmental Council, Climate Solutions, and the Alliance for Jobs and Clean Energy opposed a proposed tax of $25 per tonne on fossil fuels arguing that the enactment would undermine state finances. In 2018, they instead supported a $15 per tonne tax in that state, along with many other environmental groups, in part because the proceeds would fund projects that would steer the state away from fossil fuels.
  • In 2015, BG Group, BP, Eni, Royal Dutch Shell, Statoil, and Total sent an open letter to the UNFCCC calling for carbon pricing and eventually link it into a global system.
  • A 2019 International Monetary Fund report stated that "a global tax of $75 per ton by the year 2030 could limit the planet's warming to 2 degrees Celsius."
  • CEOs supporting carbon taxes include Fred Smith (FedEx); James Owens (Caterpillar), Paul Anderson (Duke Energy), Elon Musk (Tesla and SpaceX).
  • Companies include Unilever and Nestlé

Alternatives

As of 2015, developing countries were responsible for 63% of carbon emissions. Various barriers stand in the way of developing countries from adopting plans to slow carbon emissions, including a carbon tax. Developing countries often prioritize economic growth over lower emissions. Nuclear power is under development in multiple countries as an emissions-free energy source.

Wind energy and solar energy are other alternatives to fossil fuels. Wind turbines are a sustainable and renewable source of power.

Emission trading

Cap and trade is another approach. Emission levels are limited and emission permits traded among emitters. The permits can be issued via government auctions or by offered without charge based on existing emissions (grandfathering). Auctions raise revenues that can be used to reduce other taxes or to fund government programs. Variations include setting price-floor and/or price-ceiling for permits. A carbon tax can combined with trading.

A cap with grandfathered permits can have an efficiency advantage since it applies to all industries. Cap and trade provides an equal incentive for all producers at the margin to reduce their emissions. This is an advantage over a tax that exempts or has reduced rates for certain sectors.

Both carbon taxes and trading systems aim to reduce emissions by creating a price for emitting CO
2
. In the absence of uncertainty both systems will result in the efficient market quantity and price of CO
2
. When the environmental damage and therefore the appropriate tax of each unit of CO
2
cannot be accurately calculated, a permit system may be more advantageous. In the case of uncertainty regarding the costs of CO
2
abatement for firms, a tax is preferable.

Permit systems regulate total emissions. In practice the limit has often been set so high that permit prices are not significant. In the first phase of the European Union Emissions Trading System, firms reduced their emissions to their allotted quantity without the purchase of any additional permits. This drove permit prices to nearly zero two years later, crashing the system and requiring reforms that would eventually appear in EUETS Phase 3.

The distinction between carbon taxes and permit systems can get blurred when hybrid systems are allowed. A hybrid sets limits on price movements, potentially softening the cap. When the price gets too high, the issuing authority issues additional permits at that price. A price floor may be breached when emissions are so low that noone needs to buy a permit. Economist Gilbert Metcalf has proposed such a system, the Emissions Assurance Mechanism, and the idea, in principle, has been adopted by the Climate Leadership Council.

Views

A 2018 survey of leading economists found that 58% of the surveyed economists agreed with the assertion, "Carbon taxes are a better way to implement climate policy than cap-and-trade," 31% stated that they had no opinion or that it was uncertain, but none of the respondents disagreed.

In a review study Fisher et al. concluded that the choice between an international quota (cap) system, or an international carbon tax, remained ambiguous. Lu et al. (2012) compared a carbon tax, emissions trading, and command-and-control regulation at the industry level, concluding that market-based mechanisms would perform better than emission standards in achieving emission targets without affecting industrial production.

James E. Hansen argued in Storms of My Grandchildren and in an open letter to then President Barack Obama that emissions trading would only make money for banks and hedge funds and allow 'business-as-usual' for the chief carbon-emitting industries.

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