What Is Carbon Pricing? Core Concepts and Mechanisms

Theoretical Foundations: Pigouvian Taxation and the Coasean Alternative

The intellectual roots of carbon pricing lie in welfare economics' analysis of externalities. Pigou (1920) demonstrated that activities imposing costs on third parties not party to market transactions -- negative externalities -- can be internalised through a corrective tax that closes the gap between marginal social cost and marginal private cost. Greenhouse gas emissions constitute a paradigmatic negative externality within this framework: the private cost of fossil fuel combustion does not reflect the climate damages caused by atmospheric accumulation -- losses in agricultural productivity, increased frequency and severity of extreme weather events, sea-level rise, and ecosystem degradation. The Pigouvian solution is the imposition of a tax per unit of emissions equivalent to the marginal damage cost.

Coase (1960) offered an alternative perspective on the externality problem. According to the Coase theorem, when property rights are clearly defined and transaction costs are negligible, parties can reach an efficient allocation of resources through negotiation, rendering corrective taxation unnecessary. In the context of greenhouse gas emissions, the operational counterpart of the Coasean approach is the emissions trading system, which enables the definition and trading of emission rights. The setting of an emissions cap corresponds to the creation of property rights; the trading of allowances corresponds to the channelling of abatement effort to the point of lowest cost.

Goulder and Schein (2013) demonstrated that the two approaches can produce identical distributional and environmental outcomes under specific conditions -- particularly in scenarios where allowances are entirely auctioned and revenue use is equivalent. However, the authors emphasise that practical design parameters -- scope, price stability mechanisms, revenue recycling method, and carbon leakage provisions -- can significantly differentiate the performance of the two instruments. This analytical framework reveals that instrument choice in carbon pricing policy is a technical engineering problem; asserting the general superiority of one instrument over the other in the abstract is difficult.

Carbon Tax: Design Parameters and Empirical Evidence

A carbon tax is a price-based instrument that establishes a direct price per unit of greenhouse gas emissions. Instrument design rests on three fundamental parameters: the tax rate, the tax base, and the point of regulation.

The tax rate is the primary variable determining the environmental effectiveness of the policy. In theory, the optimal rate equals the marginal social damage cost of emissions; however, estimates of this cost span wide uncertainty ranges. The U.S. Interagency Working Group's social cost of carbon estimates vary from USD 51 to USD 190 per tonne depending on the discount rate applied (IWG, 2021). In practice, tax rates are determined as a resultant of political feasibility, competitiveness concerns, and emissions reduction targets.

The tax base defines which greenhouse gases and sectors the tax covers. A broad-based carbon tax can achieve greater emissions reductions at a lower rate; a narrow-based tax produces no behavioural change in uncovered sectors. The point of regulation -- the stage of the value chain at which the tax is applied -- determines administrative efficiency: upstream regulation (at the producer or importer level) covers fewer entities and lowers administrative costs; downstream regulation (at the point of final emission) generates more targeted signals but increases administrative burden.

The Swedish carbon tax constitutes an empirical reference point demonstrating that phased rate escalation can deliver long-term emissions reductions. Introduced in 1991 at approximately EUR 26 per tonne, the tax reached approximately EUR 120 per tonne by 2024 through systematic increases. Over this period, Sweden reduced its greenhouse gas emissions by more than 30 percent below 1990 levels while GDP grew by over 80 percent (Andersson, 2019). This decoupling -- the simultaneity of declining emissions and economic growth -- provides strong evidence that carbon taxation can be compatible with growth, though structural factors such as the high share of hydroelectric and nuclear power in Sweden's energy mix should not be overlooked in interpreting this result.

British Columbia's carbon tax, introduced in 2008, offers a distinctive model through its revenue-neutral design: tax revenues are returned to taxpayers through reductions in personal and corporate income taxes. Murray and Rivers (2015) found that this design substantially mitigated the public acceptance challenge and strengthened the political sustainability of the tax. The British Columbia experience demonstrates that the revenue recycling mechanism is a decisive variable in the political economy of carbon taxation.

Känzig (2023) provides causal evidence on the macroeconomic effects of carbon taxes, showing that European carbon tax increases generate a moderate short-term output contraction while triggering a structural decline in energy intensity. These findings suggest that the transition costs of carbon taxation are real but manageable, and that long-term efficiency gains have the potential to compensate for these costs.

According to IMF (2023) modeling, achieving net zero through carbon pricing alone would require a price of $280 per ton by 2050, a level that is politically infeasible in many countries. Alternatively, combining a $75 per ton carbon price with substantial green public investment can achieve the net-zero target but would increase the debt-to-GDP ratio by 45 percentage points by 2050. A moderate expenditure increase alone would achieve only approximately 40 percent emission reduction by 2050. These findings underscore that carbon pricing alone is insufficient, yet it remains indispensable as a revenue-generating policy instrument for fiscal sustainability (IMF, 2023).

Emissions Trading System: Cap-and-Trade Architecture

An emissions trading system (ETS) is a quantity-based instrument that caps total emissions and channels abatement effort to the point of lowest cost through market mechanisms. The fundamental architecture of an ETS comprises five components: cap-setting, allowance allocation, monitoring-reporting-verification (MRV), the compliance mechanism, and the trading platform.

Cap-setting is the primary design parameter determining the environmental integrity of the system. The cap represents the total allowable emissions from covered sectors and is reduced through an annual linear reduction factor consistent with climate targets. In Phase 4 of the EU ETS, the annual linear reduction factor was raised from 2.2 percent to 4.3 percent under the "Fit for 55" package (European Commission, 2021).

The allowance allocation method constitutes one of the most contested dimensions of ETS design. Three basic approaches exist: free allocation based on historical emissions (grandfathering), free allocation based on sectoral benchmark values (benchmarking), and sale by auction (auctioning). Grandfathering has been criticised for rewarding existing high emission levels and penalising firms that reduce emissions early. Benchmarking preserves efficiency incentives by referencing best-in-class performance while managing carbon leakage risk. Auctioning is the method most consistent with the "polluter pays" principle and generates public revenue; however, it may raise competitiveness concerns in sectors exposed to carbon leakage (Ellerman, Convery, and de Perthuis, 2010).

The institutional evolution of the EU ETS illustrates that ETS design is an iterative learning process. In Phase 1 (2005-2007), over-allocation through member states' national allocation plans caused prices to collapse to near zero (Ellerman and Buchner, 2007). In Phase 2 (2008-2012), the emissions decline triggered by the global financial crisis deepened the surplus problem. In Phase 3 (2013-2020), the system transitioned to a single EU-wide cap, the auction share was increased, and the Market Stability Reserve (MSR) was introduced to absorb the accumulated allowance surplus. In Phase 4 (2021-2030), targets were strengthened under the "Fit for 55" package, maritime transport was included, and a separate ETS for buildings and road transport (ETS 2) was established.

Price discovery is a core economic function of the ETS. When the allowance supply is fixed by the cap, the carbon price forms at the intersection of the marginal abatement cost curve and the total allowance quantity. Firms with high marginal abatement costs purchase allowances on the market, while firms that can abate at low cost sell their surplus allowances. This mechanism produces a cost-effective allocation that minimises total abatement costs -- the fundamental advantage of an ETS over command-and-control regulation (Montgomery, 1972).

Hybrid Instruments and Price Stability Mechanisms

The structural weaknesses of both pure price-based (carbon tax) and pure quantity-based (ETS) instruments have led most jurisdictions in practice to adopt hybrid designs. Hybrid instruments aim to soften the trade-off between price certainty and emission certainty.

Price floor and ceiling mechanisms are the primary instruments used to constrain price volatility in emissions trading systems. A price floor prevents the carbon price from falling below a specified level, preserving investment signals; it provides a minimum price guarantee even during periods of low demand, thereby supporting the return calculations of low-carbon technology investments. A price ceiling limits compliance costs when prices rise excessively and mitigates competitiveness impacts on regulated sectors. The United Kingdom ETS adopted a price floor mechanism following its departure from the EU ETS; regional ETS programmes in North America (RGGI, California) employ "price corridor" designs in which floor and ceiling operate jointly.

The Market Stability Reserve (MSR), introduced into the EU ETS in 2019, is a structural mechanism that dynamically manages the allowance supply-demand balance. When the total number of allowances in circulation exceeds specified threshold values, the MSR withdraws allowances from the auction volume into the reserve; when it falls below, the reserve releases allowances to the market. This mechanism aims to provide a structural solution to the problem of allowance accumulation arising from economic cycles.

Revenue recycling typology is a critical design dimension that determines the distributional effects and political sustainability of carbon pricing policy. Four basic categories of revenue use can be identified: lump-sum transfer, recycling through tax cuts, green investment allocation, and public debt reduction. The lump-sum approach -- implemented in Canada's federal carbon pricing system as the "Climate Action Incentive" -- has the potential to offset regressive distributional effects. Recycling through tax cuts -- the British Columbia model -- tests the "double dividend" hypothesis, investigating whether improvements in environmental quality and economic efficiency gains can be obtained simultaneously (Goulder, 1995). Green investment allocation encompasses the channelling of revenues toward low-carbon technology research and development, infrastructure modernisation, and climate adaptation.

The Choice between Price and Quantity: The Weitzman Framework

The instrument choice between a carbon tax and an ETS constitutes one of the fundamental debates in the environmental economics literature. Weitzman's (1974) analysis of the relative superiority of price and quantity instruments provides the analytical framework for this debate. Weitzman showed that under conditions of uncertainty, the optimal instrument choice depends on the relative slopes of the marginal benefit and marginal cost curves.

When the marginal damage curve is relatively flat -- that is, when the marginal damage of an additional unit of emissions does not vary greatly with the emissions level -- the price instrument (carbon tax) is preferred, because price certainty limits the transformation of uncertainty in abatement costs into social welfare losses. Conversely, when the marginal damage curve is steep -- that is, when exceeding a certain threshold could cause catastrophic damage -- the quantity instrument (ETS) is preferred, because the certainty of the emissions cap is critical for preventing irreversible environmental damage.

The implications of this framework in the context of climate change are contested. In the short to medium term -- while the atmospheric accumulation of greenhouse gases remains distant from tipping points -- it can be argued that the marginal damage curve is relatively flat and that price instruments hold a relative advantage. However, in the long term, as the risk of crossing critical climate thresholds increases, the argument for the priority of quantity certainty strengthens (Pizer, 2002). In practical policy design, this dilemma is managed through hybrid instruments -- ETS programmes with price floors and ceilings, or carbon taxes with adaptive rate mechanisms.

The Global Carbon Pricing Landscape

According to the World Bank's annual carbon pricing report, as of 2024, more than 75 carbon pricing instruments are in force or scheduled for implementation worldwide; these instruments collectively cover approximately 23 percent of global greenhouse gas emissions (World Bank, 2024). According to OECD (2024) data, only 27 percent of greenhouse gas emissions across 79 countries are covered by explicit carbon pricing, with substantial pricing gaps persisting; achieving climate targets requires raising the effective carbon rate to EUR 60-120/tCO₂e by 2030. Carbon pricing revenues exceeded USD 100 billion globally in 2023; these revenues are being channelled in increasing proportion toward the financing of climate action.

In terms of regional distribution, Europe occupies the most mature position in carbon pricing implementation. The EU ETS produced prices in the range of EUR 50-100 per tonne during 2023-2024, reaching levels considered sufficient to trigger decarbonisation investments. The United Kingdom ETS has strengthened as an independent system following its departure from the EU ETS, generating GBP 17.2 billion in total revenue, lowering the net-zero cap from 156 to 50 MtCO₂e by 2030, and announcing a UK CBAM effective January 2027; the system covers 27 percent of national emissions (ICAP, 2024d). In the Asia-Pacific region, rapid development is under way: China's national ETS covers 8 billion tCO₂, encompassing over 60 percent of the country's CO₂ emissions across more than 3,500 companies, with an average secondary market price of CNY 95.96. The planned expansion to steel, cement, and aluminum sectors will add over 1,500 companies and 3 billion tCO₂e of additional coverage; the CCER offset mechanism, restarted in January 2024, has yielded 9.48 million tCO₂e from 9 projects (ICAP, 2024b). The Korean ETS, Asia's first mandatory national system, covers 816 entities representing 79 percent of national emissions and has generated KRW 1.4 trillion (approximately USD 1 billion) in total revenue; the Fourth Basic Plan (2026-2035) targets 75 percent benchmarking allocation, a market stability mechanism, and a futures market by 2025 (ICAP, 2024c). In Latin America, Colombia and Chile operate carbon taxes; Mexico is conducting a pilot ETS programme.

Turkey's Carbon Pricing Journey and the TR-ETS Context

Turkey is taking decisive steps toward the establishment of an explicit carbon pricing instrument. The IMF's comprehensive study on carbon pricing gaps finds that the vast majority of developing economies -- Turkey among them -- exhibit considerable differences between effective carbon prices and price levels consistent with 2030 Paris Agreement targets (Parry, Minnett, and Zhunussova, 2023). This is not a challenge unique to Turkey but rather a global structural reality, reflecting a natural stage in the process by which developing economies with historically low emission responsibilities build their carbon pricing infrastructure. Turkey established the concrete legal foundation for closing this gap through Climate Change Law No. 7552, enacted in 2024.

The Law established the legal foundation for TR-ETS. The system is expected initially to cover the power generation and energy-intensive industrial sectors (cement, iron and steel, refining, glass, ceramics). Design parameters -- scope, cap-setting methodology, allowance allocation mechanism, market stability instruments, and international linking possibilities -- have not yet been finalised, and their determination will directly shape the system's environmental integrity and economic efficiency.

The transition of CBAM to its definitive application phase has heightened the strategic importance of timely TR-ETS implementation. Under CBAM, a CBAM certificate payment is required for the embedded emissions of Turkish firms exporting to the EU; however, the carbon price paid in the exporting country may be deducted from this charge. The establishment of a functional TR-ETS would not only reduce the additional carbon costs that Turkish exporters would face at the border but would also ensure that carbon pricing revenues accrue to the Turkish treasury rather than the EU budget. For this reason, TR-ETS design is of critical importance not only from a climate policy perspective but also from the standpoints of trade policy and industrial competitiveness.

At this juncture -- when the global architecture of carbon pricing is rapidly expanding, regulatory frameworks are deepening, and border carbon mechanisms are beginning to reshape trade flows -- a systematic understanding of the theoretical foundations, design parameters, and empirical performance of carbon pricing instruments is a precondition for informed policy design and substantive public discourse.

References

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