The study, authored by W. Cao, investigates how the two broad categories of environmental regulation shape corporate green innovation, and how that relationship is conditioned by two forms of climate-related risk that have grown increasingly prominent in both academic literature and policy debate: climate policy uncertainty and climate physical risk. Climate policy uncertainty refers to the ambiguity surrounding future climate regulation, the constant possibility that subsidies, carbon prices, disclosure requirements or emission standards may be tightened, loosened, delayed or abandoned. Climate physical risk, by contrast, describes the direct dangers posed by a changing climate itself, including extreme weather events, flooding, drought, heat stress and the damage these can inflict on assets, supply chains and workforces. The research finds that these two forces do not merely add noise to the regulatory signal; they actively reshape how regulation translates into innovation.

Formal environmental regulation has long occupied the center of environmental economics. The classic “Porter hypothesis” argues that well-designed regulation can spur innovation by forcing firms to confront inefficiencies they would otherwise ignore, a mechanism often described as “weak” Porter when regulation merely stimulates innovation and “strong” Porter when it enhances competitiveness as well. Command-and-control instruments, emission caps, technology mandates and market-based tools such as emissions trading systems each carry distinct incentives. A carbon price makes dirty production more expensive today, encouraging firms to invest in cleaner processes and products to reduce future costs. Technology standards push firms toward specific compliance paths, which can accelerate diffusion of known solutions but may crowd out exploration of alternatives. The study’s analysis of formal regulation builds on this foundation, testing whether the threat of penalty and the promise of competitive advantage are sufficient to mobilize firms’ research and development resources toward green patents and green technologies.

Informal environmental regulation operates through an entirely different channel. Communities living near polluting facilities, environmental organizations, journalists, consumers and employees all generate pressure that is not codified in statute but is nonetheless powerful. Firms that pollute visibly can face boycotts, reputational damage, difficulty attracting talent and heightened scrutiny from investors who increasingly integrate environmental, social and governance criteria into their decisions. Public attention can amplify or dampen the perceived cost of environmental misconduct, and media coverage of pollution events can trigger regulatory attention as well. The study treats this informal channel as a distinct regulatory force, and finds that it exerts its own measurable influence on green innovation, one that differs in both magnitude and character from the effect of formal rules.

A central contribution of the research lies in its treatment of climate policy uncertainty. The last decade has delivered vivid examples of why this variable matters: international agreements signed and then withdrawn from, carbon pricing schemes introduced and contested, green subsidy programs launched and later scaled back, disclosure rules proposed, delayed and revised. For a corporate decision-maker weighing a multi-year investment in clean technology, this uncertainty is not an abstraction. Green innovation typically involves high upfront costs, long payback periods and technology risk. If the policy environment that determines the future profitability of clean technologies is itself volatile, the expected return on those investments becomes harder to calculate. The study finds that elevated climate policy uncertainty weakens the positive effect of environmental regulation on green innovation, suggesting that firms hesitate to respond to regulatory signals when they doubt those signals will persist. In other words, regulation can only pull innovation forward when firms believe the pull will still be there tomorrow.

This finding carries an uncomfortable implication for policymakers. It is not enough to set ambitious environmental rules; the credibility and stability of those rules matter as much as their stringency. A regulatory regime that firms perceive as politically fragile may fail to unlock the private research and development spending that policymakers hope to mobilize, even if the rules themselves are strong on paper. The research thus adds an innovation-focused argument to the broader case for durable, predictable climate policy frameworks, including independent implementation bodies, multi-decade targets and transparent review processes that reduce the perceived risk of abrupt reversals.

The second moderating factor examined in the study, climate physical risk, operates differently. Physical risk is not about the credibility of policy but about the tangible exposure of firms, regions and economies to climate hazards. A manufacturing firm whose plants sit in flood zones, an agricultural processor exposed to drought, or a coastal logistics company threatened by sea-level rise all face direct financial stakes in a warming world. The study finds that physical climate risk changes the regulatory-innovation relationship, with evidence that greater physical risk can strengthen the responsiveness of firms to environmental regulation. When the dangers of a changing climate are felt directly in operations, insurance costs, asset values and business continuity, the strategic case for green innovation becomes more compelling. Regulation then acts not as an external burden to be minimized but as a signal aligned with the firm’s own survival interests, and the two pressures can reinforce each other.

The mechanism by which physical risk amplifies regulatory effects is plausible on several levels. Firms facing material climate exposure are more likely to internalize climate considerations in strategic planning, more likely to disclose climate-related risks to investors, and more likely to see green technology as a hedge against operational disruption. Investors and lenders, increasingly attentive to physical risk in credit and equity decisions, may reward firms that reduce their exposure through innovation. Regulators, for their part, often target their most stringent requirements at the most exposed sectors, creating a coincidence of pressure and vulnerability that the study’s findings suggest can be productive for innovation output.

Methodologically, the study situates itself in the empirical tradition that measures green innovation through patent data, using counts of green patents or citations as indicators of firms’ inventive activity in environmental technologies. Patent-based measures allow researchers to observe innovation at the firm or regional level over time, though they capture only a portion of innovative activity, since much process innovation, tacit know-how and incremental improvement never reaches the patent office. The research distinguishes between formal and informal regulation using constructed indices and proxies that reflect the intensity of regulatory enforcement and the strength of public environmental pressure respectively, and it incorporates established measures of climate policy uncertainty and physical risk exposure into its econometric framework. By interacting these variables, the study can estimate not just whether regulation promotes green innovation on average, but how that promotion varies across different climate-risk environments.

The broader significance of the work extends into several live debates in sustainability science and policy. First, it speaks to the long-running question of whether environmental regulation harms or helps innovation, providing evidence that the answer is conditional rather than universal. Second, it elevates informal regulation from a background variable to a first-order explanatory factor, suggesting that civic engagement, transparency and public scrutiny are not soft complements to hard law but active drivers of technological change. Third, it demonstrates that the risk environment, both political and physical, is a genuine determinant of corporate environmental strategy, not merely context to be controlled for. Fourth, it implies that climate adaptation and mitigation policy should be evaluated jointly: a firm’s exposure to heat waves and floods changes how it responds to carbon rules.

For companies, the practical lessons are concrete. Firms can hedge climate policy uncertainty by diversifying their innovation portfolios, seeking technologies that remain valuable under multiple policy scenarios, and engaging in policy dialogue that supports stable frameworks rather than lobbying for regime volatility. Firms in high physical-risk regions can treat green innovation as risk management, aligning research and development with adaptation needs such as water-efficient processes, heat-tolerant materials and resilient supply chains. For investors, the findings suggest that climate policy uncertainty and physical exposure are material to the innovation trajectories of portfolio companies and therefore to long-term value.

For governments, the study’s message is equally direct. Regulatory ambition without credibility may squander its innovative potential, and regulatory design that ignores the physical realities firms face may miss opportunities to align public mandates with private incentives. The most effective policy mixes, the research implies, combine firm formal rules, a vigorous public sphere that sustains informal pressure, and credible commitments that reduce the political risk premium on green investment. As climate impacts intensify and policy debates grow more contested, understanding these interactions will only become more important for steering private ingenuity toward a low-carbon future.

The study, published in the open-access journal Scientific Reports, adds to a growing body of evidence that the transition to green technology depends not on any single lever but on the interplay of regulation, public engagement and the risk landscape in which firms operate. Its central insight, that formal and informal regulation work through distinct channels and are modulated in opposite directions by policy uncertainty and physical risk respectively, offers researchers a more refined template for analyzing environmental governance, and offers policymakers a reminder that in innovation policy, how a rule is perceived can matter as much as what it requires.

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.

Subject of Research: The spatial and temporal effects of environmental regulation on the synergistic reduction of air pollution and carbon emissions in China

Article Title: Spatiotemporal heterogeneity of synergetic enhancement in pollution and carbon reduction driven by environmental regulation: a marginal abatement cost perspective

Article References: Shi, W., Yang, J., Qiao, F. et al. “Spatiotemporal heterogeneity of synergetic enhancement in pollution and carbon reduction driven by environmental regulation: a marginal abatement cost perspective.” Clean Technologies and Environmental Policy 28, 238 (2026). Original research article

Image Credits: AI Generated

DOI: 10.1007/s10098-026-03596-4

Keywords: environmental regulation, carbon emissions, air pollution, synergistic reduction, marginal abatement cost, China, Geodetector, GTWR, market-based policy, voluntary regulation