Who pays for whom? A bilateral carbon compensation mechanism for China’s provinces

In the modern world, the air we breathe and the climate we share are shaped by a complex web of trade. When a factory in one region builds a product for a customer in another, the smokestacks of that factory are often far from the city where the item is used. This creates a puzzle for climate policy: who is truly responsible for the carbon emissions generated? Is it the place where the smoke rises, or the place where the goods are bought? For decades, scientists have tracked these flows, realizing that wealthy, consumption-heavy regions often outsource their pollution to poorer, industrial regions. This spatial separation means that a province might look clean on paper simply because it sends its dirty work elsewhere, while another province bears the environmental burden for products it never consumes. To fix this imbalance, researchers have long debated how to assign responsibility fairly, moving beyond simple counts of local smokestacks to consider who benefits from the production and who has the resources to clean it up.

A new study by researchers at the Beijing Institute of Technology, Beijing Technology and Business University, and the Chinese Academy of Sciences tackles this puzzle by designing a system to determine exactly which Chinese provinces should pay compensation to others. The team built a detailed map of the country's economic and environmental flows, tracing how carbon moves from factories to final customers and how the income from that production is distributed. They combined three different ways of looking at the problem: counting emissions where they are made, where the final demand comes from, and where the financial benefits of production end up. By weaving these perspectives together, they created a mechanism that identifies not just the total amount of carbon a province is responsible for, but the specific direction of debt between neighbors. If a wealthy coastal city buys goods from an inland province, the study calculates whether that city owes money to the inland one, and how much.

The researchers found that as they moved from 2012 to 2020, the total amount of carbon responsibility being transferred between provinces grew significantly, rising from nearly 487 million tonnes to over 1,095 million tonnes. This increase reflects a deepening economic integration where the separation between production and consumption has widened. In 2020, the study identified clear winners and losers in this system. Provinces like Guangdong, Jiangsu, and Beijing emerged as the largest net payers, meaning they owe more in compensation than they receive. Conversely, provinces like Inner Mongolia and Hebei were the largest net recipients, holding the responsibility for emissions generated to satisfy the demands of others. The study shows that these roles are not random; they are driven by the specific mix of production and consumption in each region. For instance, while Beijing is a small producer of carbon itself, its massive consumption of goods from elsewhere makes it a major debtor in the system.

However, the researchers realized that a simple bill based on carbon flows would be unfair because not all provinces have the same ability to pay. A wealthy province can afford to invest in green technology more easily than a poorer one struggling with basic development. To address this, the team introduced a "capability index" that measures a province's economic strength, social development, technological innovation, and government response to environmental issues. This index acts as a modifier on the final bill. When a high-capability province pays a low-capability one, the payment is increased to reflect the payer's greater ability to contribute. When a lower-capability province owes money to a richer one, the payment is reduced. This adjustment shifts the financial burden significantly. In 2020, applying this capability index reduced the share of payments made by the half of the provinces with lower capabilities from nearly 40 percent to about 36 percent, while increasing their share of the money they receive. This ensures that the system supports those who need it most without letting them off the hook entirely.

The study also tested how different ways of valuing carbon would change the outcome. They compared a standard market price for carbon allowances against a method that looks at the specific cost each province would face to reduce its own emissions. This detail mattered more than expected. When the researchers used the specific cost of reduction for each recipient province, six provinces changed their status entirely. Some that were previously paying money switched to receiving it, and one that was receiving money switched to paying. This suggests that the price tag placed on carbon is just as important as the amount of carbon itself. If the price reflects the local difficulty of cutting emissions, the flow of money changes direction for several regions, highlighting that a one-size-fits-all price might not capture the true economic reality of climate action across a diverse country.

Perhaps the most striking finding is how stable or unstable these roles are when the rules change slightly. The researchers tested thousands of scenarios by adjusting the weight given to consumption versus income and the strength of the capability adjustments. They found that only a small group of provinces, about four, remained consistent net payers across all possible rule changes, and about nine remained consistent net recipients. The rest, nearly half of the provinces, were "switchable." Their status as a payer or receiver depended entirely on the specific policy choices made at the time. For example, a province might be a payer if the focus is heavily on consumption, but become a receiver if the focus shifts to income benefits or if the capability adjustment is strengthened. This instability means that there is no single, permanent answer to who pays whom; the outcome is a delicate balance of how responsibility is defined and how the ability to pay is measured.

The study concludes that a fair carbon compensation system for China must be dynamic and multi-layered. It cannot rely on a simple list of emissions or a fixed price tag. Instead, it requires a mechanism that constantly updates the flow of responsibility based on trade patterns, adjusts the financial burden based on local capabilities, and values carbon according to local costs. The researchers suggest that such a system should be viewed not just as a way to transfer money, but as a tool to coordinate regional development. The money paid by wealthy, consumption-heavy provinces could be directed toward helping industrial provinces upgrade their technology and transition to cleaner energy. By linking the responsibility for pollution with the capacity to solve it, the study offers a blueprint for a system where economic growth and environmental protection move forward together, ensuring that the provinces bearing the heaviest burdens for the nation's consumption are supported in their journey toward a greener future.