Carbon taxes and agriculture: the benefit of a multilateral agreement

Reducing greenhouse gas emissions from agriculture is crucial to reach global and regional climate targets. However, the efficiency of unilateral climate policies aimed at taxing emissions might be hampered by carbon leakage. One way to eliminate leakage is to implement a global carbon tax. In this article, we study the effects of a carbon tax in agriculture on GHG emissions by simulating five policy scenarios using the CAPRI model; (i) an EU tax, (ii) an EU tax complemented with a border carbon adjustment mechanism (BCA), (iii) a global tax, (iv) a global tax scaled by GDP per capita, and (v) a low global tax at 1/10 of the tax level in the other scenarios. For the global scenarios, we also analyse the impact on food consumption and nutrient intake. We find that a global tax of EUR 120 per ton CO₂-eq could reduce global agricultural emissions by 19%, but also jeopardizes food security in some parts of the world. A global tax at 1/10 of that rate (EUR 12) achieves a 3.2% reduction. In contrast, a unilateral EU tax of EUR 120 per ton CO₂-eq, accompanied with a BCA, reduces global agricultural emissions by only 0.15%. A unilateral carbon tax in the EU causes significant emission leakage. This result depends strongly on differences in emission intensities between regions and on consumer preferences.A EUR 12 global carbon tax achieves a considerably larger global emission reduction than a EUR 120 unilateral EU carbon tax accompanied with a border carbon adjustment.A global carbon tax differentiated by GDP per capita is less effective than a uniform global carbon tax, as producers with higher emission intensities tend to get lower tax rates. Other ways of taking equity into account should be sought when designing climate policies in the agricultural sector. A unilateral carbon tax in the EU causes significant emission leakage. This result depends strongly on differences in emission intensities between regions and on consumer preferences. A EUR 12 global carbon tax achieves a considerably larger global emission reduction than a EUR 120 unilateral EU carbon tax accompanied with a border carbon adjustment. A global carbon tax differentiated by GDP per capita is less effective than a uniform global carbon tax, as producers with higher emission intensities tend to get lower tax rates. Other ways of taking equity into account should be sought when designing climate policies in the agricultural sector.

降低农业领域温室气体（Greenhouse Gas, GHG）排放，对于实现全球及区域气候目标至关重要。然而，旨在对排放征税的单边气候政策的效率，可能会因碳泄漏而受到削弱。消除碳泄漏的途径之一是推行全球碳税政策。本文依托CAPRI模型模拟五类政策情景，探究农业碳税对温室气体排放的影响：（1）欧盟单边碳税；（2）搭配边境碳调整机制（Border Carbon Adjustment, BCA）的欧盟碳税；（3）全球统一碳税；（4）按人均GDP调整税率的全球碳税；（5）税率为其他情景1/10的低税率全球碳税。针对全球碳税情景，本文同时分析其对食品消费与营养摄入的影响。研究结果显示，税率为每吨二氧化碳当量（CO₂-eq）120欧元的全球碳税，可使全球农业温室气体排放降低19%，但同时会危及全球部分地区的粮食安全。若将税率下调至该水平的1/10（即每吨12欧元），则可实现3.2%的减排幅度。相比之下，搭配边境碳调整机制的欧盟单边碳税（税率为每吨120欧元二氧化碳当量）仅能使全球农业温室气体排放降低0.15%。欧盟单边碳税会引发显著的排放泄漏，这一结论很大程度上取决于区域间排放强度的差异以及消费者偏好。税率为12欧元的全球碳税，其全球减排幅度远高于搭配边境碳调整机制的120欧元欧盟单边碳税。按人均GDP调整税率的全球碳税，其减排效果弱于统一税率的全球碳税，因为排放强度较高的生产者往往适用更低的税率。在设计农业领域气候政策时，应探索其他兼顾公平性的路径。欧盟单边碳税会引发显著的排放泄漏，这一结论很大程度上取决于区域间排放强度的差异以及消费者偏好。