Introduction

In the face of increasingly severe environmental challenges today, particularly issues related to global warming and glacier melting, scholars have extensively explored methods to reduce carbon emissions (CE) to promote sustainable development. A substantial body of research suggests that improving energy structure (ES) and technological progress (TP) are crucial pathways to achieving carbon reduction (Li and Lin 2017). As a key factor influencing innovation and social development, intellectual property rights protection (IPRP) is also an indispensable part of the global economy (Zhu et al. 2022). However, over the past few decades, many countries have faced varying degrees of intellectual property infringement issues (Brander et al. 2017). With the international community’s collective efforts to reduce CE continuously strengthening, gaining a deeper understanding of the impact and mechanisms of IPRP on CE is of paramount importance for achieving global decarbonization goals.

Most existing studies focus on the innovation or growth impacts of IPRP. These studies illustrate that IPRP grants patent holders the right to control the knowledge they produce, thereby generating returns to fuel further research and development (R&D) investments. It also protects cutting-edge technology firms, enabling them to capture markets and earn substantial profits, ultimately fostering economic growth (Stiglitz 2017). Conversely, Auriol et al. (2023), Goldberg and Pavcnik (2007), and Madsen et al. (2010) argue that innovation and economic growth driven by “imitation” dominate in most developing countries. An excessive level of IPRP would restrict their ability to “imitate”, thereby impeding TP and economic growth.

However, the environmental impact of IPRP, particularly its effects on CE, has received little attention, despite being an important issue worldwide. Qian et al. (2023) regard China’s national intellectual property demonstration city policy as a quasi-natural experiment in intellectual property system construction and employ the differences-in-differences method to examine the impact of IPRP on CE. They find that the carbon reduction effect of IPRP is more pronounced in lower administrative level cities, small and medium-sized cities, and cities in western China. Yang et al. (2022), using a spatial econometric perspective and empirical evidence from a panel of Chinese cities, show that the spatial coordination of IPRP contributes to reducing CE. Similarly, Oyebanji et al. (2022), focusing on Spain, find that IPRP promotes the development of environmentally friendly technologies while reducing CE emissions.

Obviously, most studies are focused on specific countries or regions, lacking a global perspective, and there is no consensus that innovation, as a result of increased levels of intellectual property protection, can effectively reduce CE. In other words, the mechanism by which IPRP affects CE remains unclear. In addition, these studies often fail to fully consider the impact of other economic and political environmental factors, such as a stable political environment, as well as the nonlinear relationship between IPRP and CE.

Our study contributes to the existing literature in the following ways. First, we assess the impact of IPRP on CE by adopting a global perspective, which helps to evaluate the influence of IPRP on the worldwide environment more accurately. By using unbalanced panel data from 116 countries between 2008 and 2020, we find that an increase in the level of IPRP leads to an increase in CE, which challenges the traditional notion that IPRP unconditionally promotes environmental sustainability. Second, our results reveal the mechanism by which IPRP affects CE, providing a new perspective for policy formulation. Specifically, IPRP indirectly promotes CE growth by inhibiting ES improvement. On the contrary, IPRP may steer TP toward profitability rather than environmental sustainability, eventually increasing CE. Additionally, IPRP indirectly promotes the increase of CE by stimulating economic growth (EG). We also explore the moderating effect of political stability (PS) on the relationship between IPRP and CE. Finally, we find an inverted U-shaped relationship between IPRP and CE, indicating that the impact of IPRP on CE turns from positive to negative after reaching a certain threshold, highlighting the complexity and dual effects of IPRP. This finding significantly adds to the existing literature.

Literature review and hypothesis development

IPRP and CE

As the severity of global climate change increases, scholars have increasingly examined the impact of IPRP on the environment. Popp (2010) investigated how patent activities have facilitated the development of clean technologies, while Hall and Helmers (2013) examined the incentivizing effect of IPRP on eco-friendly technological innovation. Consequently, IPRP has provided crucial incentives for developing new low-carbon technologies (Guo and Jiang 2022). Patent protections ensure that innovators can reap rewards from their innovations, thereby stimulating investment in the development of environmentally friendly technologies. The advancement of renewable energy technologies, such as solar and wind, has been significantly aided by the economic incentives provided by IPRP. As patents expire, low-carbon technologies often become more widely disseminated, leading to reduced costs (Cho and Kim 2017). In the long term, this can promote the widespread adoption of low-carbon technologies in the market, thereby contributing to a reduction in overall CE.

Innovation theory posits that IPRP incentivizes technological innovation by granting inventors exclusive rights to their creations, providing financial returns that justify the costs of research and development (R&D) (Gangopadhyay and Mondal 2012). This framework suggests that IPRP should drive the development of new technologies, including those that can reduce CE. For instance, patents on renewable energy technologies such as solar panels and wind turbines can spur investment in these areas, leading to technological advancements and lower production costs over time (Popp 2010). However, the direction of technological innovation can be heavily influenced by market demands and profit motives. Firms may prioritize innovations that promise higher immediate returns rather than those that are environmentally beneficial but less profitable. This can lead to a situation where IPRP fosters advancements in high-carbon industries, perpetuating CE rather than reducing it (Kim et al. 2012). Hence, we hypothesize:

Hypothesis H1a: IPRP promotes an increase in CE.

While IPRP significantly encourages technological innovation, its impact does not always align with the goal of reducing CE. Although IPRP can foster the development of new, more environmentally friendly technologies, these technologies may not always be the market’s preferred choice. Market dynamics may tend to favor established and more profitable high-carbon technologies (Wang et al. 2019). Due to their historical market dominance, fossil fuel technologies might see further development and consolidation due to IPRP. Through patent protections, IPRP has led to the privatization of crucial eco-friendly technologies, thus limiting their broader market application. This “patent thicket” can create barriers to innovative low-carbon technologies, particularly in markets requiring expensive licensing fees or with complex patent litigation (Cannuscio 2008). A strengthened IPRP can increase market concentration and reduce competition (Liu et al. 2018), with large corporations able to maintain market control in such environments through patents on key technologies. This control not only restricts the entry of emerging low-carbon technologies into the market but also perpetuates the reliance on existing high-carbon technologies.

Market failure theory suggests that the private market often fails to account for the social costs of environmental degradation. This theory highlights the role of government intervention in correcting market failures through regulations, subsidies, and other policy measures (Marjit and Yang 2015; Pigou 1920). In the context of IPRP, market failures can arise when the social benefits of low-carbon technologies exceed the private returns, leading to underinvestment in such innovations. IPRP can exacerbate these market failures by creating monopolies or oligopolies in the market for clean technologies, increasing the costs and reducing the accessibility of these technologies (Gallagher 2007). Patent thickets and high licensing fees can hinder the diffusion of green technologies, particularly in developing countries where the need for affordable clean technology is most acute (Hall and Helmers 2013).

The Environmental Kuznets Curve (EKC) hypothesis posits an inverted U-shaped relationship between environmental degradation and economic development. Initially, as an economy grows, environmental degradation increases, but after reaching a certain income level, further economic growth leads to environmental improvements (Grossman and Krueger 1995). This theory can be applied to understand the dynamic impact of IPRP on CE. At early stages of economic development, strong IPRP may lead to increased CE as firms focus on maximizing production efficiency and profitability, often relying on high-carbon technologies. However, as economies mature and the demand for environmental quality rises, stronger IPRP can shift the focus toward innovations that enhance energy efficiency and reduce CE, reflecting the EKC’s downward slope after a certain threshold (Dinda 2004; Sweet and Maggio 2015). Therefore, we propose:

Hypothesis H1b: With the expansion of IPRP, its impact on CE will shift from positive to negative.

In recent years, IPRP has become more powerful worldwide. Strict intellectual property rules and institutions have been established in many nations and regions, particularly in developed countries. This trend is reflected in stricter patent laws, copyright protections, and trademark regulations (Hori and Yamagami 2018). In environments with strengthened IPRP, technological innovation, and R&D activities are often concentrated in economically developed countries and large corporations (Qiu et al. 2021). This may lead to issues of accessibility and affordability of innovative technologies, particularly in developing countries. The major contributors to the world’s CE are currently from developing countries where the level of IPRP still significantly lags behind that of developed countries (Barros 2015). Global cutting-edge and green technologies are currently also concentrated in developed countries. We hypothesize from these factors that the current IPRP will increase the CE in the global context; however, as IPRP intensifies and expands, its impact on CE might shift from positive to negative.

Mediating effect of ES, TP, and EG

Most studies have contended that improvements in ES and TP are crucial pathways to reducing CE. Additionally, several studies have demonstrated that IPRP significantly influences these factors. For instance, Dechezleprêtre et al. (2013) found that stronger patent protections are associated with increased innovation in climate change mitigation technologies. Hasan and Kobeissi (2012) illustrated how patent protections incentivize investments in renewable energy technologies, which are essential for transitioning to a more sustainable energy structure. However, while IPRP fosters innovation and economic growth, the nature of this growth can influence CE. As shown by Aghion et al. (2016), technological innovations driven by market demands and profit motives can sometimes prioritize high-carbon industries, perpetuating CE. Therefore, in this section, we separately explore the mediating role of ES, TP, and economic growth (EG) in the impact of IPRP on CE.

Mediating effect of ES

Most studies have contended that improvements in ES are crucial pathways to reducing CE. The energy structure refers to the composition of different energy sources used within an economy, typically measured by the share of renewable versus non-renewable energy sources. Additionally, some studies have shown that IPRP is an important influencing factor in promoting ES (Moser 2005). Therefore, in this section, we separately explore the mediating role of ES in the impact of IPRP on CE.

Existing research has indicated that IPRP can improve ES by providing significant incentives for inventing low-carbon and renewable energy technologies (Liu et al. 2024). IPRP mechanisms, such as patents, ensure that innovators receive financial rewards for their inventions, reducing the risks associated with investing in new technologies. This assurance is crucial for driving R&D in alternative energy sources, including solar, wind, and bioenergy, which are essential for transitioning to a sustainable energy structure. The economic incentives provided by IPRP encourage firms to invest in the development of renewable energy technologies, thereby fostering a shift toward a cleaner energy structure (Song et al. 2023).

The theory of induced innovation posits that the direction of technological change can be influenced by economic incentives and policy measures (Hicks 1963). In the context of energy technologies, IPRP creates an economic environment that favors the development of renewable energy sources by making innovation in these areas more profitable. For instance, firms are more likely to invest in the development of solar panels, wind turbines, and bioenergy technologies if they can secure patents that protect their innovations and provide a competitive advantage in the market (Czarnitzki et al. 2015).

Moreover, the diffusion of innovations theory (Rogers 2003) suggests that the adoption of new technologies follows a pattern where early adopters are followed by the majority once the benefits and viability of the innovation are established. IPRP plays a crucial role in this process by ensuring that innovators can recover their investment costs and achieve profitability, thereby encouraging the initial development and subsequent market penetration of renewable energy technologies.

Empirical studies support the notion that IPRP stimulates innovation in renewable energy technologies. Henry and Stiglitz (2010) found that stronger patent protections are associated with increased patenting activity in renewable energy technologies. This increase in patenting activity reflects greater investments in R&D and innovation in the renewable energy sector, which are essential for improving the energy structure. For instance, in the United States, the introduction of stronger patent protections in the renewable energy sector led to a significant increase in the number of patents filed for wind and solar technologies (Reichman 2009). Similarly, in Europe, countries with more stringent IPRP frameworks have witnessed higher levels of innovation in renewable energy technologies compared to those with weaker IPRP (Johnstone et al. 2010).

The case of Germany’s “Energiewende” (energy transition) illustrates how robust IPRP can drive the development and adoption of renewable energy technologies. Germany’s strong IPRP system has played a critical role in fostering innovation in solar and wind technologies. The country’s investment in R&D and the protection of intellectual property rights have enabled it to become a global leader in renewable energy, significantly improving its energy structure (Huenteler et al. 2012). Therefore, we hypothesize:

Hypothesis H2a: IPRP indirectly reduces CE by promoting the improvement of ES.

However, some studies argue that the patent protection mechanism of IPRP limits the accessibility and diffusion of renewable energy technologies (Gangopadhyay and Mondal 2012). High technological barriers and costs associated with patent protections hinder the widespread adoption of these technologies in broader markets, particularly in developing countries. This protection mechanism leads the market to continue relying on existing cheaper high-carbon energy sources. Studies hypothesize that IPRP leads to increased market concentration, thereby limiting new entrants, especially small and medium enterprises in the renewable energy sector (Hossain and Lasker 2010). Large firms are able to maintain their market position by controlling key renewable energy technologies, thus impeding the shift of ES toward cleaner and sustainable directions. In an environment with strong IPRP, firms continue to invest in traditional energy technologies that provide immediate economic returns rather than long-term riskier renewable energy technologies. This bias slows down the research, development, and promotion of renewable energy technologies, thereby inhibiting the improvement of ES (Raiser et al. 2017; Xu et al. 2023).

Under conditions of strengthened IPRP, governments face greater challenges in formulating and implementing policies that encourage renewable energy. Patent protection increases the costs of renewable energy technologies, affecting the government’s ability to promote these technologies (Lewis 2007; Maskus 2000). As a result, the high costs and restricted accessibility due to strong IPRP can hinder the transition to a low-carbon energy structure, especially in less affluent nations that lack the resources to invest heavily in new technologies. This leads us to hypothesize:

Hypothesis H2b: IPRP indirectly promotes an increase in CE by inhibiting the improvement of ES.

Mediating effect of TP

TP is another critical factor in reducing CE. The purpose of IPRP is to safeguard the advancements of innovators and stimulate further innovation. IPRP enhances the return on investment for enterprises and individuals in R&D by providing legal protections for new ideas and technologies. When companies know that their inventions can be patent-protected, thereby enjoying a period of market exclusivity, they are more likely to invest time and money in R&D activities (Gmeiner and Gmeiner 2021). For sectors requiring long-term R&D and substantial investment, such as pharmaceuticals and new energy technologies, IPRP offers a mechanism to ensure companies reap benefits from their long-term investments. This is crucial in advancing TP in high-risk areas and those with long payback periods (Wan et al. 2023).

By providing a fixed term of patent protection, IPRP ensures that companies can financially benefit from their inventions. This incentive mechanism is widely regarded as a key driver in developing new technologies. Technological innovation is encouraged by IPRP; however, innovation as a metric does not always translate into lower CE (Huang et al. 2020). For example, advancements in manufacturing technologies might increase production efficiency but also lead to higher overall emissions if the energy sources remain carbon-intensive. Thus, we hypothesize:

Hypothesis H3a: IPRP reduces an increase in CE by fostering TP.

While IPRP incentivizes technological innovation, it can also restrict the dissemination of these technologies (Ding and Xue 2023). Patent protections prevent other companies or research institutions from using these new technologies without permission, limiting their application and further innovation. In the field of environmental technology, this has resulted in critical low-carbon solutions being restricted to only a few companies. The theory of diffusion of innovations highlights that the spread of new technologies can be hindered by high costs and limited accessibility, particularly when protected by patents. This restriction can slow the adoption of green technologies, thereby reducing their potential impact on CE.

Moreover, the direction of technological innovation is strongly influenced by market demand. Under market-driven mechanisms, technological innovation leans toward areas with strong market demand and high economic returns, not necessarily those with the highest environmental sustainability (He et al. 2022). This market-driven approach can lead to a situation where, despite technological advancements, the applications do not contribute to reducing CE. For example, advancements in high-carbon industries such as fossil fuel extraction and processing technologies can improve efficiency but ultimately increase overall emissions due to higher production levels.

Furthermore, TP itself can bring additional environmental costs (Zhang et al. 2020). Some new technologies require the extraction of rare materials or involve production processes that generate significant emissions. The EKC hypothesis suggests that in the early stages of technological development, environmental degradation may increase before improvements are realized (Li et al. 2021). Therefore, while technological progress driven by IPRP can lead to innovations that reduce CE, it can also result in increased emissions in the short term due to the environmental costs associated with developing and implementing new technologies. Therefore, we propose:

Hypothesis H3b: IPRP promotes an increase in CE by fostering TP.

Mediating effect of EG

EG is another critical factor that can mediate the impact of IPRP on carbon emissions. The relationship between EG and environmental impact has been extensively studied, often in the context of the EKC. According to the EKC, environmental degradation tends to increase in the early stages of EG, but after reaching a certain level of income per capita, the trend reverses, and further EG leads to environmental improvements (Wang et al. 2024a; Wang et al. 2024b).

IPRP can influence EG by fostering innovation and technological progress, which are key drivers of long-term economic development. By providing legal protections for new inventions, IPRP encourages investment in R&D, leading to technological advancements that can enhance productivity and drive EG. This EG, in turn, can provide the resources and incentives needed to address environmental challenges, including reducing carbon emissions (Su et al. 2022). Thus, we propose:

Hypothesis H4a: IPRP indirectly reduces CE by promoting EG.

However, the impact of EG on carbon emissions can vary depending on the stage of development and the nature of the economic activities driving the growth. In the early stages of economic development, growth is often associated with increased industrialization and energy consumption, leading to higher carbon emissions. As economies mature and shift toward more service-oriented and technologically advanced industries, the energy intensity of economic activities tends to decrease, potentially leading to lower carbon emissions (Stiglitz 2007).

EG, spurred by IPRP-induced technological innovation, can have dual effects on carbon emissions. On one hand, increased economic activity often leads to higher energy consumption and carbon emissions, particularly in industries reliant on fossil fuels. On the other hand, higher income levels can lead to greater public demand for environmental quality and more investment in green technologies and sustainable practices (Cheng et al. 2022).

The theory of endogenous growth, as proposed by Romer (1990), emphasizes the role of knowledge and technological change as key drivers of EG. Strong IPRP systems can enhance the accumulation of knowledge by protecting the returns on R&D investments, thus encouraging continuous innovation. This innovation can lead to the development of more efficient technologies and processes that reduce energy consumption and carbon emissions. For instance, advancements in energy-efficient machinery and industrial processes can lower the carbon footprint of manufacturing activities.

Moreover, the Porter Hypothesis suggests that stringent environmental regulations can stimulate innovation and improve competitiveness (Porter and Linde 1995). In the context of IPRP, stronger intellectual property protections can complement environmental regulations by ensuring that firms investing in green technologies can reap the benefits of their innovations. This dynamic can lead to a virtuous cycle where EG driven by innovation leads to improved environmental outcomes.

Empirical evidence supports the notion that EG driven by technological innovation can lead to reduced carbon emissions. For example, Popp (2002) found that investments in energy-efficient technologies have significantly reduced energy consumption and emissions in the United States. Similarly, research by Liddle and Lung (2010) indicates that technological advancements in energy efficiency are a key factor in decoupling EG from carbon emissions in developed countries.

In developed countries, EG driven by technological innovation can lead to significant reductions in carbon emissions through improved energy efficiency and the adoption of cleaner technologies. For instance, countries like Sweden and Denmark have managed to decouple EG from carbon emissions, largely due to their strong IPRP systems, which foster innovation in renewable energy and energy efficiency technologies. This decoupling is evident in the significant investments these countries have made in green technologies and infrastructure, leading to a more sustainable economic model.

However, the benefits of EG facilitated by IPRP are not always evenly distributed. In many developing countries, the gains from EG and technological innovation are often concentrated in certain sectors or regions, while large segments of the population continue to rely on traditional, high-carbon energy sources. This uneven distribution can limit the overall impact of EG on reducing carbon emissions (Teece 2018). For instance, in China, rapid EG has led to both increased carbon emissions and significant investments in renewable energy. The country’s IPRP system has encouraged technological innovation, leading to advancements in solar and wind technologies. However, the reliance on coal and other high-carbon energy sources for industrial growth has resulted in high carbon emissions, illustrating the dual-edged nature of EG as a mediating factor in the relationship between IPRP and carbon emissions (Zhang and Shan 2023). This suggests that:

Hypothesis H4b: IPRP indirectly promotes an increase in CE by fostering EG in high-carbon sectors.

Therefore, while IPRP-induced EG can drive the development of green technologies and reduce carbon emissions in developed countries, it can also exacerbate carbon emissions in developing countries if the growth is concentrated in high-carbon industries. This complex relationship underscores the importance of complementary policies that ensure the benefits of technological innovation and EG are harnessed to achieve sustainable environmental outcomes.

Moderating effect of PS

The role of PS in environmental policy implementation cannot be overstated. Politically stable countries are more likely to have the administrative capacity and institutional continuity necessary to enforce stringent environmental regulations effectively. This stability ensures that policies aimed at reducing CE are not only well-designed but also properly executed and maintained over time (Lawal et al. 2023). For instance, regulations on industrial emissions and energy efficiency standards can be strictly enforced, ensuring that technological advancements fostered by IPRP contribute to CE reduction rather than exacerbation.

PS also encourages governments to make long-term investments and plans, especially in R&D and promoting low-carbon technologies. Government backing can support areas that are overlooked by the private sector, particularly in clean technology R&D, where initial investments are high and the risks substantial (Abbas et al. 2023). In a stable political environment, governments can provide sustained funding for research initiatives, offer tax incentives, and create favorable market conditions for the development and adoption of green technologies. This support helps to offset the high costs and risks associated with pioneering new technologies, facilitating their commercialization and diffusion.

Furthermore, politically stable countries are more likely to engage in international cooperation, including technology transfer and environmental protection agreements. International cooperation is crucial for the global dissemination of low-carbon technologies and practices. Politically stable nations can enter into long-term commitments and partnerships, sharing knowledge, resources, and technologies to address global environmental challenges (Anser et al. 2021). These collaborations can lead to the standardization of green technologies, making them more accessible and affordable worldwide, thus amplifying the positive impact of IPRP on CE reduction.

Additionally, PS helps create an environment where private-sector innovation can thrive. Stable political conditions reduce the uncertainty associated with long-term investments in new technologies. When businesses have confidence in the continuity of supportive policies and regulations, they are more likely to invest in the development and deployment of environmentally friendly technologies. This private-sector involvement is critical for scaling up innovations and achieving significant reductions in CE.

PS also fosters an environment conducive to public-private partnerships. These partnerships can leverage the strengths of both sectors to accelerate the development and implementation of green technologies. Governments can provide the necessary regulatory frameworks and incentives, while private enterprises can bring in innovation, efficiency, and capital. In a stable political climate, these partnerships are more likely to flourish, leading to sustained advancements in low-carbon technologies.

Moreover, PS can enhance the effectiveness of environmental education and awareness campaigns. A stable government can implement long-term educational programs that promote sustainable practices among citizens and businesses. By raising awareness about the importance of reducing CE and adopting green technologies, these programs can foster a culture of sustainability that supports the goals of IPRP.

In summary, PS provides favorable conditions for formulating and implementing long-term, coherent environmental and intellectual property policies. In a politically stable environment, governments are better able to devise and implement policies to reduce CE, such as enhancing energy efficiency standards and promoting renewable energy (Pengfei et al. 2023). These policies help to mitigate the increase in CE caused by IPRP. Accordingly, we propose:

Hypothesis 5: PS reduces the promotive effect of IPRP on CE.

In the context of pursuing sustainable development and low-carbon economic transformation, balancing IPRP with environmental sustainability is a significant challenge for policymakers. Despite the fact that the relationship between IPRP and environmental sustainability has been studied in the literature, these studies do not have the analytical depth necessary to determine the precise and complete influence of IPRP on global CE. Existing research has been limited to specific countries and regions, and has not substantively explored the moderating role of PS. In addition, these studies often fail to fully consider the impact of other economic and political environmental factors, such as a stable political environment, as well as the nonlinear relationship between IPRP and CE. This article supplements the extant research by analyzing data from 116 countries between 2008 and 2020, providing new insights into how IPRP affects CE globally. The technology roadmap of this research is shown in Fig. 1.

Fig. 1
figure 1

Technology roadmap.

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Methodology specification and variable description

Model construction

The fixed effects model effectively controls for the unobserved heterogeneity that arises due to the unique characteristics inherent to each country. Based on our theoretical analysis and research hypotheses, we employed the following fixed effects model to examine the relationship between IPRP and CE. The robust standard errors were clustered at the national level, and the variables were log-transformed (except for ratio-type variables) to mitigate concerns about potential serial correlation and heteroscedasticity. This can be seen in Eq. 1:

$${{\rm{CE}}}_{{\rm{it}}}={{\rm{\beta }}}_{0}+{{{\rm{\beta }}}_{1}{\rm{IPRP}}}_{{\rm{it}}}+{{\rm{\beta }}}_{2}\,\sum\, {{\rm{Controls}}}_{{\rm{it}}}+{{\rm{\mu }}}_{{\rm{i}}}+{{\rm{\gamma }}}_{{\rm{t}}}+{{\rm{\varepsilon }}}_{{\rm{it}}}$$
(1)

in which \({{\rm{CE}}}_{{\rm{it}}}\) represents carbon emission; \({{\rm{IPRP}}}_{{\rm{it}}}\) is the intellectual property rights protection index; \({{\rm{Controls}}}_{{\rm{it}}}\) is the set of control variables; \({{\rm{\mu }}}_{{\rm{i}}}\) is the country effect; \({{\rm{\gamma }}}_{{\rm{t}}}\) is the period fixed effect; and \({{\rm{\varepsilon }}}_{{\rm{it}}}\) is the error term.

The mediation effect model is instrumental in providing a deeper understanding of the issue, demonstrating both the direct effects and the complex indirect pathways of influence. This is crucial for developing more effective policies and intervention measures. We employed the causal stepwise regression method of Baron and Kenny (1986) to test the mediating effects of ES, TP and EG. The model was as follows:

$${{\rm{CE}}}_{{\rm{it}}}={{\rm{\alpha }}}_{0}+{{{\rm{\alpha }}}_{1}{\rm{IPRP}}}_{{\rm{it}}}+{{\rm{\alpha }}}_{2}\,\sum\, {{\rm{Controls}}}_{{\rm{it}}}+{{\rm{\mu }}}_{{\rm{i}}}+{{\rm{\gamma }}}_{{\rm{t}}}+{{\rm{\varepsilon }}}_{1}$$
(2)
$${{\rm{M}}}_{{\rm{it}}}={{\rm{b}}}_{0}+{{{\rm{b}}}_{1}{\rm{IPRP}}}_{{\rm{it}}}+{{\rm{b}}}_{2}\,\sum\, {{\rm{Controls}}}_{{\rm{it}}}+{{\rm{\mu }}}_{{\rm{i}}}+{{\rm{\gamma }}}_{{\rm{t}}}+{{\rm{\varepsilon }}}_{2}$$
(3)
$${{\rm{CE}}}_{{\rm{it}}}={{\rm{c}}}_{0}+{{{\rm{c}}}_{1}{\rm{IPRP}}}_{{\rm{it}}}+{{{\rm{c}}}_{2}{\rm{M}}}_{{\rm{it}}}+{{\rm{c}}}_{3}\,\sum\, {{\rm{Controls}}}_{{\rm{it}}}+{{\rm{\mu }}}_{{\rm{i}}}+{{\rm{\gamma }}}_{{\rm{t}}}+{{\rm{\varepsilon }}}_{3}$$
(4)

in which \({{\rm{M}}}_{{\rm{it}}}\) includes ES, TP and EG.

The moderation effect model enabled us to explore how specific conditions and variables influenced the relationship between IPRP and CE. We examined the moderating effects of PS by incorporating the interaction terms into the baseline model. The model was as follows:

$${{\rm{CE}}}_{{\rm{it}}}={{\rm{\beta }}}_{0}+{{{\rm{\beta }}}_{1}{\rm{IPRP}}}_{{\rm{it}}}+{{{\rm{\beta }}}_{2}{\rm{PS}}}_{{\rm{it}}}+{{{\rm{\beta }}}_{3}{{\rm{IPRP}}}_{{\rm{it}}}\times {\rm{PS}}}_{{\rm{it}}}+{{{\rm{\beta }}}_{4}\,\sum\, {\rm{Controls}}}_{{\rm{it}}}+{{\rm{\mu }}}_{{\rm{i}}}+{{\rm{\gamma }}}_{{\rm{t}}}+{{\rm{\varepsilon }}}_{{\rm{it}}}$$
(5)

in which \({{\rm{PS}}}_{{\rm{it}}}\) represents political stability.

Variable descriptions and data sources

Dependent variable

We used the total carbon emissions (TCE) and carbon emissions per capita (CEP) reported by the World Bank as proxy variables for CE. The data was sourced from the World Bank database (https://databank.worldbank.org).

Core explanatory variable

The GP index is one of the most commonly used indicators to measure IPRP, but unfortunately, the GP index does not have the annual data required for our study. Therefore, we used the intellectual property rights protection index reported by the International Property Rights Union (https://www.internationalpropertyrightsindex.org/) as a proxy for IPRP (Cho and Kim 2017).

Mediating variable

The mediating variables included ES, TP, and EG. We used the proportion of renewable energy consumption from the total energy consumption as reported by the World Bank as a proxy for ES. Existing studies typically use the number of publications and patent applications in frontier technology to measure TP. The R&D activity index in the Frontier Technology Readiness Index reported by the UNCTAD, which measured a country’s publications and patent applications in 11 frontier technologies, is a good measure of a country’s technology level. We used this as a proxy for TP. Data was sourced from UNCTAD (https://unctadstat.unctad.org/datacentre/). Based on existing research, we use per capita (constant 2015 US$) as a proxy indicator of EG.

Modulating variables

The modulating variable is PS. PS was measured using the political stability and absence of violence index from the World Bank database. A higher index indicated greater political stability in a country. Data was sourced from the World Bank.

Control variables

Based on existing research, we included trade openness, industrial structure, urbanization, and economic growth as control variables in our model (Hu and Yin, 2022). Data was sourced from the World Bank.

To provide a comprehensive overview, we performed a statistical analysis of the variables included in our model. Table 1 presents the basic statistical analysis of each variable. The standard error for CE was 1.83, indicating significant variation in CE among the sample countries. The highest, lowest, and standard errors for IPRP were 2.16, 0.79, and 0.26, respectively, indicating substantial fluctuations in IPRP during the sample period and providing a basis for our analysis. The characteristics of the other variables were also consistent with existing research and the actual conditions of the various countries.

Table 1 Description of the variables.
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Figure 2 presents the kernel density estimation of the variables. It can be seen from Fig. 2 that the curves for TCE and CEP gradually move to the left, with the vertical height of the wave peak increasing, while the curve for IPRP gradually moves to the right. This indicates that the CE of the sample countries has gradually decreased, while the IPRP has increased. This shift suggests an evolving relationship between IPRP and CE, which we explore further in our analysis.

Fig. 2
figure 2

Kernel density estimation plot.

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Findings and discussions

Baseline results

In Table 2, columns 1 and 2 include only IPRP as the independent variable, while columns 3 and 4 incorporate all control variables. The R-squared and Hausman test results suggest that it is necessary to use a fixed effects model for analysis. To ensure the robustness of our model, we performed a VIF test, which showed a maximum value of 5.72, indicating that our model does not suffer from severe multicollinearity. The coefficients of IPRP across columns 1–4 are all positive and significant, indicating that IPRP promotes CE, thereby supporting Hypothesis 1a. As shown in columns 3 and 4 of Table 2, the coefficients of IPRP are 0.273 and 0.261, respectively, and both are significant at the 5% level. This means that a 1% increase in IPRP decreases the TCE by 27.3% and the CEP by 26.1%, thus validating Hypothesis 1.

Table 2 Baseline results.
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This can be attributed to the fact that a strong IPRP can lead to a monopoly on certain key environmental or low-carbon technologies, driving up the cost of these products. This limits the widespread adoption of these technologies, especially in developing countries, which therefore need to use traditional technologies with higher CE due to cost factors (Wang and Wang 2018). Additionally, while IPRP encourages the development of renewable energy technologies, their high costs and patent barriers limit their global application (Ghisetti and Rennings 2014; Hoekman et al. 2005). Although technological solutions exist, the actual effect of reducing CE is suppressed due to these economic barriers.

Robustness test

We employed several methods to conduct robustness checks.

  1. (1)

    Replacement of the core explanatory variable. The intellectual property rights protection index reported by the World Economic Forum was used to replace the baseline IPRP.

  2. (2)

    Replacement of the dependent variable. We substituted the explained variable in the baseline model with the CO2 emissions (kg per 2015 US$ of GDP). The results are presented in column 3 of Table 3.

    Table 3 Robustness test results.
    Full size table
  3. (3)

    To eliminate the impact of the COVID-19 pandemic, we excluded samples from 2019 onward. The results of this are shown in columns 4 and 5 of Table 3.

  4. (4)

    Endogeneity analysis. To mitigate the effects of endogeneity, we conducted an endogeneity analysis using two-stage least squares (2SLS). The first-stage regression results are displayed in columns 1–3 of Table 4. Columns 4 and 5 of Table 4 use the Rule of Law (RL), and columns 6 and 7 reference Ding and Xue (2023) and employ the lagged IPRP by one period (L.IPRP) as an instrumental variable. Columns 8–9 use both the RL and the lagged IPRP as instrumental variables.

    Table 4 2SLS results.
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The results in columns 1–5 of Table 3 indicate that in various robustness checks, the IPRP was significantly positively correlated with CE, consistent with the baseline model results. The results in columns 1–3 of Table 4 show that RL and L.IPRP significantly correlated with IPRP. As shown in columns 5–9 of Table 4, the Under-identification test, Sargan test, and Weak identification test indicated that our 2SLS regression results were valid. The sustained significant positive IPRP coefficient indicates that there were no serious endogeneity problems in our baseline model and that the results were reasonably stable.

Heterogeneity analysis

According to the classification standards of the World Bank, we examined the heterogeneity of the impact of IPRP on carbon emissions in high-income countries (HIC), upper-middle-income countries (UMIC), and lower-middle-income countries (LMIC). As shown in Table 5, the coefficient of the interaction term for HIC is significantly negative, while the coefficient for UMIC is also negative and significant for TCE. In contrast, the coefficient of the interaction term for LMIC is positive and significant for TCE. This indicates that an increase in IPRP is conducive to reducing CE in HIC and UMIC, while it promotes CE growth in LMIC.

Table 5 Heterogeneity analysis results.
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The observed heterogeneity can be explained by several factors. In HIC and UMIC, there is usually a more robust IPRP system, which incentivizes businesses and individuals to allocate more resources and funds toward developing environmentally friendly technologies, thereby reducing CE. Moreover, these countries typically possess stronger regulatory and enforcement mechanisms, ensuring the execution of environmental policies and stimulating enterprises to adopt environmental technologies and practices (Denoncourt 2020; Habib et al. 2019).

In contrast, in LMIC, the IPRP system may be less developed, or regulatory enforcement may be inadequate, limiting innovation and technological development. Furthermore, these countries may rely more on traditional industries with high CE, such as energy production and heavy industry, which are often less protected by intellectual property rights or exhibit lower levels of innovation. Therefore, increasing IPRP levels may lead to technological limitations, restricting the application of environmental technologies and instead promoting the growth of CE (Correa 2000; Moschini and Yerokhin 2008).

These findings support our hypothesis that the impact of IPRP on CE is moderated by the level of economic development and regulatory strength of the country.

Mechanism analysis

Table 6 presents the results of the mediation effect tests. As indicated in columns 1–3 of Table 6, the coefficient of IPRP on ES was significantly negative, while those on TP and EG were significantly positive. The results in columns 4–9 of Table 6 show that the coefficients of ES on TCE and CEP were significantly negative, while those of TP and EG on TCE and CEP were significantly positive. This demonstrates that IPRP indirectly promoted an increase in CE by suppressing ES and enhancing TP and EG, thus validating hypotheses H2b, H3b, and H4b.

Table 6 Mechanism analysis result.
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Several factors justify these findings. (1) First, against the backdrop of the global strengthening of IPRP, the transition to ES was delayed. Despite the presence of renewable energy technologies, continued reliance on and investment in traditional fossil fuel technologies remain dominant, leading to an increase in CE (Hall and Helmers 2013). Additionally, IPRP exacerbated the dependency on traditional high-carbon energy technologies (Yang and Maskus 2009). Many large energy companies possess numerous patents related to fossil fuels, and the patent protection of these technologies hinders the development and market penetration of emerging low-carbon energy technologies (Khor 2012). Efficient but patented fossil fuel technologies remain more market-competitive in the short term compared to emerging renewable energy technologies. (2) Although IPRP incentivizes technological innovation, such innovations do not always reduce CE. These technological innovations often focus more on increasing production efficiency and profit rather than working to reduce CE. Some efficient production technologies and energy-intensive industrial technologies, in fact, lead to an increase in CE (Popp 2006; Zhang et al. 2023). Furthermore, IPRP leads to a research and development focus skewed toward high-profit rather than environmentally sustainable directions. Where the market demand for certain high-emission products is high, companies prioritize the development of these products over low-carbon or eco-friendly technologies (Stiglitz 2014). (3) By protecting the rights and interests of innovators, IPRP enables enterprises to invest more resources in technology research and development, thereby promoting technological progress and industrial upgrading (van Stel et al. 2019). These technological advances not only improve production efficiency but also give rise to new industries and markets, thereby promoting EG. However, EG is often accompanied by increased production and consumption activities, ultimately leading to an increase in CE. In other words, IPRP indirectly promotes the increase of CE by promoting EG (Cheng et al. 2024; Hao et al. 2021).

These findings have significant implications for policy. While IPRP incentivizes technological innovation and economic growth, it simultaneously contributes to increased carbon emissions. This paradox arises because IPRP tends to favor traditional high-carbon technologies and delays the transition to environmentally sustainable solutions. Technological innovations under IPRP often prioritize efficiency and profitability over carbon reduction, exacerbating carbon emissions in the process. Policymakers should consider revising intellectual property rights frameworks to better support the development and adoption of low-carbon technologies. This may include providing incentives for renewable energy innovations and ensuring that patent protections do not stifle the growth of sustainable technologies. Additionally, there should be an emphasis on aligning economic growth strategies with environmental sustainability goals to mitigate the adverse effects of IPRP on carbon emissions (Mao and Failler 2022; Zhang and Zhang 2024).

Moderating effect analysis

Table 7 reports the results of the moderating effect analysis. To reduce the multicollinearity problem that may be caused by interaction terms, we decentralized the data before regression (Robinson and Schumacker 2009). The findings in Table 7 demonstrate that the interaction term of PS was all negatively significant. This suggested that a stable political environment diminished the facilitative effect of IPRP on CE, thereby validating hypothesis H5. This may be due to, political stability contributed to the implementation of effective environmental regulatory measures. Restrictions on high-CE technologies and support for clean technologies offset the potential impact of IPRP on the increase in CE (Lin et al. 2023; Zhang 2021).

Table 7 Moderating effect analysis results.
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Further analysis

To examine whether a nonlinear relationship existed between IPRP and CE, we incorporated a quadratic term of IPRP (IPRP2) into the baseline model. Table 8 reports the results of the nonlinear analysis. The results from Table 8 indicate that the coefficient of IPRP is significantly positive, whereas the coefficient of IPRP2 is significantly negative, suggesting a nonlinear relationship between IPRP and CE.

Table 8 Further analysis results.
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For a more intuitive observation of this nonlinear relationship, we calculated the inflection point using TCE as an example and plotted the nonlinear fitting curve, as shown in Fig. 3. The inflection point, approximately equal to 1.8, is represented by the green dashed line in the figure. For ease of viewing, the minimum and maximum values of the explanatory variable IPRP are also marked with red solid lines in the graph. The calculated inflection point lies to the left of IPRP’s maximum value, indicating an inverted U-shaped relationship between IPRP and CE. This shows that initially, IPRP promoted an increase in CE, but as IPRP continued to rise (beyond the inflection point), its impact on CE turned negative.

Fig. 3
figure 3

Nonlinear fitting diagram.

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To further illustrate this relationship, we calculated the marginal effect of IPRP on CE and plotted the results with 95% confidence intervals. From Fig. 4, it can be observed that on the left side of the inflection point, as the value of IPRP continuously increased, its marginal impact on CE progressively decreased. On the right side of the inflection point, as the value of IPRP continued to increase, its marginal impact on CE became increasingly negative, demonstrating a shift from positive to negative beyond the inflection point. This shift validates Hypothesis 1b.

Fig. 4
figure 4

Marginal effect diagram.

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Several factors justify these findings. Initially, IPRP promoted investments in existing technologies and production processes, which were often high in carbon emissions. Enterprises enjoying intellectual property protection tended to optimize and expand their existing fossil-fuel-based technologies, thereby increasing carbon emissions in the short term. The market preferred to continue utilizing and developing mature and economically viable high-emission technologies, limiting the development of renewable energy and other low-carbon technologies, and thus promoting increased carbon emissions for a certain period (Acri née Lybecker 2014; Chu 2013).

As IPRP continued to strengthen, there were greater investments and innovations in low-carbon and clean technologies. At that stage, technical advancements started to focus more on greener alternatives, such as energy-efficient and renewable energy technology. With the rise in environmental consciousness and the demand for sustainable development, the market and consumers began supporting low-carbon products and technologies more extensively. This trend promoted the further development of low-carbon technologies and progressively decreased reliance on high-carbon technologies (Cao et al. 2023; Weyant 2011). Therefore, the relationship between IPRP and CE is characterized by an inverted U-shape.

Conclusions

Through an empirical analysis of data from 116 countries spanning 2008 to 2020, our study delved into the impact of IPRP on CE. Our results showed that IPRP generally raised CE. Rather than encouraging environmentally sustainable growth, IPRP may tend to boost high-CE technologies and sectors in the current global economic system. The mediation effect results indicated that IPRP indirectly fostered CE growth by inhibiting ES’s improvement, demonstrating that IPRP exacerbated the dependence on traditional high-carbon energy sources, hindering the transition to cleaner, more efficient energy systems. The analysis also revealed that although IPRP promoted TP, this advancement similarly promoted the growth of CE. In addition, IPRP indirectly promoted the increase of CE by promoting EG. The results of the moderation effects suggested that PS effectively mitigated the adverse impacts of IPRP on CE. This showed that ensuring political stability can alleviate the negative environmental impacts of IPRP. Lastly, we revealed an inverted U-shaped relationship between IPRP and CE. This indicated that in the initial stages, IPRP promoted an increase in CE but as IPRP surpassed a turning point its intensification suppressed the growth of CE. This provided an important perspective for understanding the dynamic changes in IPRP’s environmental impacts at different stages of development.

Based on our main findings, we propose the following policy recommendations. (1) Governments should incorporate special incentives for environmental technologies into intellectual property laws and provide expedited patent examination procedures and fee reductions for low-carbon and clean energy innovations, thereby encouraging more R&D investment in environmentally friendly technologies. (2) Given that IPRP suppressed the improvement of ES, policymakers should increase funding support for renewable energy R&D and promote the commercialization and market penetration of these technologies through subsidies and tax incentives. (3) Governments should ensure that environmental protection regulations are in alignment with intellectual property policies. Stricter patent examination standards need to be applied to technologies that will cause significant environmental damage. (4) The international community should strengthen cooperation in green technology, particularly in promoting the transfer and application of technology to developing countries. This includes simplifying intellectual property and technology transfer procedures and providing technical and financial support to developing countries.

While this study has shown significant insights and added to the extant literature and understanding of this issue, there are distinct limitations. The definitions and measurements of the core variables (like IPRP and CE) posed particular challenges. Although we strove to ensure the accuracy and representativeness of these variables, their measurements were limited by data availability and quality. The moderating variables considered in the study, such as PS, contained inherent complexities that could not be fully addressed in the analysis. Multiple factors influence each of these variables and result in them exhibiting different characteristics in different countries and at each time point. By focusing on countries undergoing rapid changes, such as emerging or developing economies, further studies will be able to yield additional findings to supplement the ones outlined in this article.