Source attributions of radiative forcing by regions, sectors, and climate forcers

TL;DR

This study quantifies the contributions of different regions, sectors, and climate forcers to global warming pathways toward 1.5°C and 2°C targets, highlighting the importance of negative CO2 emissions and land-use effects.

Contribution

It introduces a comprehensive attribution method using the normalized marginal approach with updated emissions and land-use data to assess forcing contributions toward climate targets.

Findings

Most regions and sectors must keep forcing at or below current levels for 1.5°C.

Negative CO2 emissions significantly contribute to achieving climate targets.

Land-use albedo effects differ from previous studies, affecting future forcing scenarios.

Abstract

It is important to understand how the emissions of different regions, sectors, or climate forcers play a role on pathways toward the Paris Agreement temperature targets. There are however methodological challenges for attributing individual contributions due to complexities associated with a variety of climate forcers affecting the climate system on different spatial and temporal scales. Here, we use the latest historical and future emissions data for a comprehensive set of climate forcers as well as land-use datasets and apply the normalized marginal approach to quantify the forcing contributions of regions, sectors and forcing agents toward the 2C and 1.5C targets. We show that most of the worldwide regions and sectors need to maintain forcing levels not higher than present levels to attain the 1.5C target of the Paris Agreement, while slightly higher future forcing levels than present levels are allowed for the 2C target. Our results illustrate the importance of negative CO2 emissions, which contribute -0.75+/-0.44 Wm-2 and -0.42+/-0.27 Wm-2 to the 2C and 1.5C targets. Less negative forcings, or more positive forcings are also identified for the land-use albedo for the 2C and 1.5C scenarios compared to existing studies.