Non-CO2 greenhouse gas sources

Overview

The non-CO₂ greenhouse gases methane (CH₄), nitrous oxide (N₂O) and fluorinated gases (HFCs, PFCs and SF₆) contribute to about a quarter of the human-made global warming in a 100 years perspective and to close to half of the warming in the shorter timeframe of 20 years, due to the strong but short-lived warming effect of some of these gases. Successful and rapid mitigation of the short-lived gases, in particular CH₄ and short-lived fluorinated gases, is one of few options the World still has at hand to keep below 2 degrees warming in the next few decades. Despite their relative importance in terms of warming, the non-CO₂ gases are considerably less researched and well understood in terms of mitigation opportunities than CO₂ emissions from the energy sector. Partly to blame is that they are technically more challenging to monitor and quantify, and that they stem from a multitude of different source sectors, which often are linked to activities that fill basic human needs with few readily available alternatives (e.g., food provision, cooling, waste and wastewater handling). These factors contribute to make non-CO₂ abatement particularly challenging. For 20 years, researchers in the PM group have built, and successfully put into use in various policy processes, a capacity in the Greenhouse gas and Air pollution Interaction and Synergies (GAINS) model to assess global and regional non-CO₂ greenhouse gas emissions and their future mitigation potentials and costs. Having established a detailed and well-documented global framework to assess the potentials for technical mitigation solutions, the scope is currently being broadened to non-technical solutions such as behavioral changes, as well as to how existing implementation barriers can be overcome. There are five dimensions along which the theme works toward achieving reduced non-CO₂ emissions globally:

• Exploring potentials and costs for implementation of technical and non-technical abatement measures at a country and sector level,
• Exploring potentials for changes in drivers of activities that generate emissions,
• Exploring barriers for uptake of mitigation measures and how governance and policies can overcome such barriers to effectively deliver emission reductions,
• Providing scientific model input to facilitate climate change mitigation policies in the European Union, as well as at the global scale, e.g., through contributions to UN assessments, and
• Through internal and external collaboration with atmospheric and inverse modeler groups, work toward reduced uncertainty in non-CO₂ emission estimates through validation of bottom-up against top-down estimates.  

While many technical measures can be implemented more or less with immediate effect with the right policy incentives, others will require a decade or two before the impact on non-CO₂ emissions takes effect (e.g., livestock breeding schemes or measures to divert organic waste out of landfills with already deposited waste generating emissions up to a few decades). Structural changes and changes in consumption patterns (e.g., human diet changes) often need more time to achieve impacts on emissions than technical solutions, while investments into infrastructure and institutions typically need long-term planning and the active involvement and support of the public sector.

Selected Relevant Projects & Collaborations

EUCLIMIT I-VII

Starting in 2007, IIASA’s GAINS model team has been part of the European-wide EUCLIMIT model consortium, which about every two years has provided scientific insights to the European Commission’s climate policy impact assessments. The role of the GAINS model has been to produce cross-country internally consistent emission and mitigation scenarios for the non-CO2 greenhouse gases methane, nitrous oxide and fluorinated gases. The results are presented as country-, sector-, and technology- specific bottom-up emission inventories, future emission scenarios, and marginal abatement cost curves. These are detailed enough to allow for country-specific assessments of the relative potentials and costs for non-CO2 GHG emission reductions across all the European Union Member states. Results are primarily used by the European Commission’s DG-CLIMA as input to the calculation of national emission reduction targets in the Effort Sharing Regulations, e.g., the 2030 targets which form part of the EU Green Deal.

Global Carbon Project

The GAINS model team has repeatedly contributed bottom-up assessments of anthropogenic CH4 and N2O emissions to the Global Methane Budget and Global Nitrous Oxide Budget of the Global Carbon Project (GCP). The GCP is a Global Research Project formed to work with the international science community to establish a common and mutually agreed knowledge base to support policy debate and action to slow down and ultimately stop the increase of greenhouse gases in the atmosphere.  

UNEP/CCAC assessments of short-lived climate forcers

The PM group regularly contributes to global and regional UNEP and CCAC Assessments of short-lived climate forcers as lead or contributing authors, e.g., Emission Gap Reports (2017, 2021), Global Methane Assessments (2021, 2022), Cooling Emissions and Policy Synthesis report (2020).

Arctic Monitoring & Assessment Programme (AMAP)

AMAP is the Arctic Council’s scientific program. It provides reliable and sufficient information on the status of, and threats to, the Arctic environment, and scientific advice on actions to be taken in order to support Arctic governments in their efforts to take remedial and preventive actions relating to contaminants and adverse effects of climate change. GAINS team members have repeatedly provided scientific input to AMAP assessment reports on short-lived climate forcers and acted as members of different Expert groups.

Advisory Roles

Lena Höglund-Isaksson: Scientific Oversight Committee of UNEP’s International Methane Emissions Observatory (IMEO).

Pallav Purohit: Member of the Technology and Economic Assessment Panel (TEAP) Task Force – XXXV/11 of the Montreal Protocol under UNEP.

Relevant Publications

2024

2023

2022

2021

2020

2019