The limits of carbon reduction roadmaps.

In their Policy Forum “A roadmap for rapid decarbonization” (24 March, p. [1269][1]), J. Rockstrom et al. propose a simple “carbon law”—halving anthropogenic carbon dioxide emissions every decade—to support global efforts toward net zero emissions by about 2050. This carbon law conflicts with recent advances in the social sciences on pragmatic, politically feasible climate policy. The carbon law is based on three unrealistic assumptions about how governments formulate and implement climate policy. The first assumption is that nonbinding global targets send a credible signal about climate policy to policy-makers and investors. In fact, climate policies are only credible when they are supported by domestic public opinion and powerful interest groups ([ 1 ][2]–[ 3 ][3]), and the carbon law does little to build domestic political coalitions for ambitious climate policy. A second assumption is that a geometric progression in emission reductions over time serves well the goal of robust and resilient climate policy. Under the decentralized Paris Agreement, countries can choose their own targets. Therefore, global emissions pathways offer little guidance as to what any given government should do nationally, and may even undermine the credibility of the climate regime when governments choose policies that contradict the carbon law, as they are entitled to do under the Paris rules. Finally, the carbon law assumes that pivotal emerging economies—the primary source of future emission growth—have the political and institutional capacity to base their policies on global targets and timetables. Realistic emissions goals must take into account the political and implementation challenges that countries face in energy and environmental policy. For example, replacing fuel subsidies—which encourage households to consume large amounts of inexpensive energy—with cash transfers targeted to the poor would reduce wasteful energy consumption and empower the recipients of the funds ([ 4 ][4], [ 5 ][5]). However, it is much easier for the government to regulate fuel prices than to identify poor households and ensure that they, instead of middlemen and corrupt officials, receive the money allocated to reducing poverty. Global roadmaps do little to relax political constraints on policy reform and may even raise barriers to progress by setting unrealistic expectations. Robust plans to decarbonize nations must, instead, be tailored to local conditions and acknowledge the momentous difficulty of policy implementation. These plans should address the root cause of the problem: domestic opposition to ambitious climate and sustainable energy policies. Policymakers interested in rapid and robust progress toward decarbonization should thus focus on developing realistic short-term strategies that both reduce emissions and strengthen over time the advocacy coalition in favor of low-carbon growth. 1. [↵][6]1. J. Hovi et al ., Glob. Environ. Polit. 9, 20 (2009). [OpenUrl][7] 2. 1. L. Hughes, 2. J. Urpelainen , Environ. Sci. Pol. 54, 52 (2015). [OpenUrl][8] 3. [↵][9]1. J. Meckling et al ., Science 349, 1170 (2015). [OpenUrl][10][Abstract/FREE Full Text][11] 4. [↵][12]1. D. G. Victor , “The politics of fossil-fuel subsidies” (Report for the Global Subsidies Initiative of the International Institute for Sustainable Development, Geneva, 2009). 5. [↵][13]1. A. Cheon et al ., Comp. Polit. Stud. 48, 370 (2015). 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