The Green Wave Crash: Why Did Clean Technology Patenting Drop After 2010?

将经济增长与温室气体排放脱钩是避免灾难性的全球平均变暖水平高于工业化前水平2度的唯一途径，而不放弃经济增长。根据IPCC（2018），到2050年，温室气体排放必须减少到净零，以减轻气候变化的最严重影响。如果要实现这一目标，而不对经济和生计造成巨大损害，那么低碳技术的创新及其广泛传播至关重要（例如，Stavins，2007年; Anadon和Hollene，2009年; Popp等人，2010年）。随着有效减缓全球变暖措施的窗口逐渐关闭（IPCC，2018），低碳技术创新现在比以往任何时候都更加重要。那么，为什么在近20年的持续增长之后，低碳技术专利的份额有所下降呢？了解清洁创新减少的原因是制定适当的政策应对措施以解决问题的关键先决条件。目的是在观察到的下降与其原因之间建立可信的联系。使用一个新编制的数据集，我们探讨了最令人信服的解释，在文献中发现的清洁创新，即信贷约束，能源价格和环境政策的严格性下降。这些驱动因素中哪一个发挥了最重要的作用，将决定哪一项政策最适合扭转这一趋势。

Decoupling economic growth from greenhouse gas emissions is the only way to avoid catastrophic global average warming levels above 2 degrees compared to pre-industrial levels, without forgoing economic growth. According to the IPCC (2018), greenhouse gas emissions must be reduced to net zero by 2050 to mitigate the worst effects of climate change. Innovation in low-carbon technologies and their widespread diffusion are essential if this goal is to be met without inflicting vast damage on the economy and, consequently, livelihoods (e.g. Stavins 2007, Anadon and Holdren, 2009; Popp et al., 2010). As the window for effective global warming mitigation measures gradually closes (IPCC, 2018), low-carbon technology innovation is more important now than ever. Why then, has there been a drop in the share of low-carbon technology patents after almost two decades of sustained growth? Understanding the causes of the drop in clean innovations is a key prerequisite for developing an appropriate policy response that could remedy the problem. The aim is to establish a credible link between the observed decline and its causes. Using a newly compiled dataset, we explore the most compelling explanations for the observed decline in clean innovation found in the literature, namely credit constraints, energy prices and environmental policy stringency. Which of these drivers plays the most important role will determine which policy is best suited to reverse the trend.