ABSTRACT

Limiting global warming to well below 2°C requires a dramatic acceleration of decarbonization to reduce net anthropogenic greenhouse gas emissions to zero around mid-century. In complex systems – including human societies – tipping points can occur, in which a small perturbation transforms a system. Crucially, activating one tipping point can increase the likelihood of triggering another at a larger scale, and so on. Here, we show how such upward-scaling tipping cascades could accelerate progress in tackling climate change. We focus on two sectors – light road transport and power – where tipping points have already been triggered by policy interventions at individual nation scales. We show how positive-sum cooperation, between small coalitions of jurisdictions and their policymakers, could lead to global changes in the economy and emissions. The aim of activating tipping points and tipping cascades is a particular application of systems thinking. It represents a different starting point for policy to the theory of welfare economics, one that can be useful when the priority is to achieve dynamic rather than allocative efficiency.

Key policy insights

• Pricing policies and targeted investments that bring clean technologies below the threshold of cost-parity with fossil fuel technologies can trigger reinforcing feedbacks that cascade up scales to propel disproportionately rapid decarbonization.

• Traditional approaches to climate policy based on welfare economics principles of minimizing marginal abatement costs, and pricing externalities, are likely to miss these opportunities. Systems thinking can help identify ways for policy to drive effective change.

• Positive-sum cooperation between small groups of countries can accelerate the activation of tipping points in the global economy, facilitating decarbonization in all countries. Early opportunities for this are in the power and light road transport sectors, where clean technologies are increasingly competitive with fossil fuels.

• The value of decarbonization policies should be judged not just on their immediate effects on emissions within the implementing jurisdiction, but also for their potential to contribute to upward-scaling tipping cascades in the global economy.

摘要

要将全球变暖限制在远低于2°C的程度，需要大幅加速脱碳，以将人为造成的温室气体净排放量减少至本世纪中叶左右的零。在包括人类社会在内的复杂系统中，可能会出现引爆点，其中很小的扰动就会改变整个系统。至关重要的是，激活一个引爆点可以增加更大范围触发另一个引爆点的可能性，依此类推。在这里，我们展示了这种向上扩展的倾卸小瀑布如何加速应对气候变化的进程。我们专注于两个领域-轻便的公路运输和电力-各个国家尺度的政策干预已经触发了临界点。我们展示了辖区的小联盟与其决策者之间的正和合作将如何导致经济和排放的全球变化。激活引爆点和引爆小瀑布的目的是系统思考的特殊应用。它代表了与福利经济学理论不同的政策起点，当优先事项是实现动态效率而不是分配效率时，这可能是有用的。

重要政策见解

• 定价政策和有针对性的投资，使清洁技术低于化石燃料技术的成本同等水平的门槛，可能会触发强化的反馈，这些反馈会逐步扩大规模，从而推动不成比例的快速脱碳。

• 基于福利经济学原理（将边际减排成本最小化和定价外部性）为基础的传统气候政策方法可能会错失这些机会。系统思考可以帮助确定策略来推动有效变更的方式。

• 小国集团之间的正和合作可以加速激活全球经济中的临界点，促进所有国家的脱碳。早期的机会是在电力和轻型道路运输领域，在这些领域中，清洁技术与化石燃料的竞争日益激烈。

• 脱碳政策的价值不仅应根据其对实施管辖区内的排放的直接影响来判断，而且还应根据其对全球经济中不断扩大的小规模推波助澜的潜力进行判断。