Agriculture's Contribution to Climate Change and Role in Mitigation Is Distinct From Predominantly Fossil CO2-Emitting Sectors.

John Lynch,Raymond Pierrehumbert,David Frame,Michelle Cain

doi:10.3389/fsufs.2020.518039

Abstract

Agriculture is a significant contributor to anthropogenic global warming, and reducing agricultural emissions—largely methane and nitrous oxide—could play a significant role in climate change mitigation. However, there are important differences between carbon dioxide (CO2), which is a stock pollutant, and methane (CH4), which is predominantly a flow pollutant. These dynamics mean that conventional reporting of aggregated CO2-equivalent emission rates is highly ambiguous and does not straightforwardly reflect historical or anticipated contributions to global temperature change. As a result, the roles and responsibilities of different sectors emitting different gases are similarly obscured by the common means of communicating emission reduction scenarios using CO2-equivalence. We argue for a shift in how we report agricultural greenhouse gas emissions and think about their mitigation to better reflect the distinct roles of different greenhouse gases. Policy-makers, stakeholders, and society at large should also be reminded that the role of agriculture in climate mitigation is a much broader topic than climate science alone can inform, including considerations of economic and technical feasibility, preferences for food supply and land-use, and notions of fairness and justice. A more nuanced perspective on the impacts of different emissions could aid these conversations.

Highlights

The increased ambition of international climate policy, articulated in the Paris Agreement’s goal of “holding the increase in the global average temperature to well below 2◦C above preindustrial levels and pursuing efforts to limit the temperature increase to 1.5◦C above preindustrial levels” (UNFCCC, 2015), has increased scrutiny on the role all sectors can play in climate change mitigation
Agriculture’s Contribution to Climate Change & Mitigation of different gases can achieve in the context of the Paris temperature goal, but can inform policy decisions
Anthropogenic climate change is caused by multiple climate pollutants, with CO2, CH4, and N2O the three largest individual contributors to global warming (Myhre et al, 2013)

Summary

INTRODUCTION

The increased ambition of international climate policy, articulated in the Paris Agreement’s goal of “holding the increase in the global average temperature to well below 2◦C above preindustrial levels and pursuing efforts to limit the temperature increase to 1.5◦C above preindustrial levels” (UNFCCC, 2015), has increased scrutiny on the role all sectors can play in climate change mitigation. In many treatments of agriculture’s role in climate change, some key principles appear to be increasingly overlooked or misunderstood: how the impacts of methane (CH4) and nitrous oxide (N2O), the major greenhouse gases emitted from agricultural production, are distinct from each other and, in particular, from carbon dioxide (CO2). An appreciation of these differences is important to understand what the mitigation. In this paper we outline the roles of these different greenhouses gases, consider how their reporting might be improved, and explore some of the potential implications for overall climate change mitigation

AGRICULTURAL GREENHOUSE GAS EMISSIONS

COMMUNICATING EMISSIONS

Global Emission Reductions

Sectoral Roles

Findings

Integrated Assessment