China’s environmental policies are not producing the same climate and air-quality results everywhere—and a new analysis suggests that treating the country as one uniform system could undermine efforts to cut both carbon emissions and pollution. A study of 30 Chinese provinces between 2006 and 2022 finds that environmental regulation generally strengthened the combined reduction of greenhouse gases and conventional pollutants, but that the effectiveness of each policy type depended strongly on geography, time and local economic conditions. The researchers describe this combined benefit as the synergistic enhancement of pollution reduction and carbon mitigation: one intervention can deliver progress on both fronts when it changes the way energy is produced, consumed or regulated.
The findings, published in Clean Technologies and Environmental Policy by Wei Shi of Northwest Normal University and colleagues, arrive as governments worldwide search for policies that can tackle climate change without separating it from immediate public-health concerns. Carbon dioxide is the principal long-lived greenhouse gas driving global warming, while pollutants such as fine particulate matter, sulfur dioxide and nitrogen oxides damage lungs, ecosystems and infrastructure. The two problems often share sources, especially coal-fired power plants, heavy industry, transport and inefficient combustion. Yet the relationship is not perfectly automatic. A technology that removes one pollutant may consume additional energy, while a policy aimed only at carbon could leave other harmful emissions unchanged. The study therefore asks not simply whether environmental regulation works, but where and through which mechanisms it produces the greatest combined benefit.
To measure that benefit, the researchers used a marginal abatement cost perspective. Marginal abatement cost is the additional expense of achieving one more unit of emissions reduction after cheaper opportunities have already been used. In practical terms, replacing an outdated coal boiler may deliver relatively inexpensive early reductions, whereas squeezing further emissions from an already cleaner system may require costly equipment or process redesign. Comparing the costs associated with reducing pollution and carbon helps reveal whether reductions are coordinated efficiently. The study used these cost relationships to evaluate the pollution-and-carbon-reduction synergy, rather than relying only on separate emissions totals or a simple index of environmental quality. The approach is intended to capture both the scale of environmental improvement and the resources required to achieve it.
The analysis divided environmental regulation into three broad categories. Command-and-control regulation, designated ER1, includes legally binding standards, inspections, mandated technologies and administrative penalties. Market-based regulation, or ER2, uses economic signals such as environmental taxes, emissions trading and charges that make pollution more expensive or cleaner production more attractive. Voluntary regulation, ER3, encompasses actions encouraged by public disclosure, corporate responsibility, environmental information, social pressure and other forms of participation that are not imposed solely through direct government orders. These categories overlap in the real world, but separating them allowed the team to compare their relative explanatory power and investigate whether combining them produced more than the sum of their individual effects.
Across the provinces and the study period, the intensity of regulation followed a clear hierarchy: command-and-control measures were strongest, followed by market-based tools and then voluntary approaches. At the same time, both estimated marginal abatement costs and the overall pollution-and-carbon-reduction synergy showed an upward trend. The researchers report that the two measures also displayed a degree of synchrony in their movement through time and space. That pattern does not mean that higher costs automatically caused better environmental outcomes, or that every expensive policy was efficient. Instead, it suggests that China’s evolving environmental effort involved increasingly demanding reductions alongside a growing ability to coordinate climate and pollution goals. As low-cost improvements are exhausted, achieving additional reductions can require greater investment, stronger institutions and more sophisticated policy design.
One of the study’s most striking results is that the regulation type used most intensively was not the one with the greatest explanatory power. The researchers found that voluntary regulation had the strongest relationship with the synergistic outcome, followed by market-based regulation and then command-and-control regulation. In the study’s statistical framework, this ranking indicates how much of the spatial variation in synergy could be associated with each regulatory category; it is not a direct measure of how many tonnes of emissions each policy removed. Voluntary measures may matter because they influence behavior beyond formal compliance, encouraging firms to disclose environmental information, adopt cleaner technologies and respond to community expectations. They can also reinforce formal rules by increasing visibility and accountability. Market incentives, meanwhile, can redirect investment and reward firms that reduce both fuel use and pollution. Command-based rules remain essential, but their impact may depend on enforcement quality and on whether regulated industries have the capacity to innovate.
The researchers also found that regulation types interacted in powerful ways. Pairing any two of the three categories produced either dual-factor enhancement or nonlinear enhancement. Dual-factor enhancement means the combined influence of two policy types was greater than the contribution of either acting alone. Nonlinear enhancement indicates that the relationship was more complex still: adding one instrument could change the effectiveness of another by amplifying it disproportionately. A market mechanism may work better when emissions are monitored and standards are enforced, while voluntary disclosure may have greater consequences when taxes, permits or penalties create financial reasons to respond. This is the logic of a policy portfolio. Rather than choosing between regulation, markets and public participation, governments may obtain stronger results by making the instruments complementary. The analysis does not establish a simple universal recipe, but it does challenge the idea that a single policy lever can deliver the fastest route to cleaner air and a safer climate.
Geography emerged as a major part of the story. Command-and-control regulation was particularly prominent in eastern coastal provinces, with its influence gradually extending into central and western regions. These coastal areas have long hosted dense populations, export-oriented manufacturing and energy-intensive industries, creating both severe environmental pressures and relatively strong administrative and financial capacity. Market-based regulation showed a different spatial pattern, described by the authors as higher in the north, lower in the south, and stronger inland than along the coast. That configuration may reflect differences in industrial structure, resource use, energy systems and regional exposure to environmental risks, although the study identifies patterns rather than assigning a single cause to each one. Voluntary regulation was more influential in the west and lower in the east, with notable clustering in regions possessing ecological advantages. In those areas, environmental quality, conservation and local participation may carry particular economic and social value.
The geographic differences matter because a policy that performs well in one province may deliver weaker returns elsewhere. Coastal manufacturing centers may need stringent industrial standards and technology upgrades, while northern and inland regions may gain more from market signals tailored to coal, heavy industry or energy consumption. Western provinces may benefit from strengthening public participation, environmental transparency and incentives that protect ecological assets, rather than simply importing regulatory models designed for densely industrialized cities. The study’s use of Geodetector helped identify the magnitude of spatial associations and the interaction between factors, while geographically and temporally weighted regression, or GTWR, allowed the estimated relationships to vary across locations and years. Unlike a conventional regression that assumes one average effect for the entire sample, GTWR calculates locally and temporally changing coefficients, making it better suited to a country where economic development and regulatory capacity differ sharply from province to province.
The authors present the results as evidence for more differentiated environmental policy, but the analysis also comes with important boundaries. It covers 30 provinces, autonomous regions and municipalities from 2006 through 2022, excluding Tibet, Hong Kong, Macao and Taiwan because of data limitations. The underlying information came from statistical yearbooks, environmental databases, policy and legal records, economic datasets, the China Emissions Accounts and Datasets and surface PM2.5 observations. Where data gaps existed, the researchers used interpolation to fill missing values, and the study’s datasets are available from the corresponding author on reasonable request. Statistical associations cannot by themselves prove that a particular regulation caused a specific change, especially when policies, technology, investment and economic restructuring evolve together. Even so, the study offers a detailed map of how environmental governance appears to interact with the dual challenge of air pollution and climate change. Its central message is increasingly difficult to ignore: the race to cut carbon and the fight for clean air are often connected, but the connection is shaped by place. Policies designed with that complexity in mind may turn overlapping crises into overlapping solutions.
