NCGG10

Background

Non-CO₂ greenhouse gases are important contributors to radiative forcing of the atmosphere and include methane (CH₄), fluorocarbons and SF6, and nitrous oxide (N₂O). Together these greenhouse gases have provided almost half of the present-day climate warming by all greenhouse gases, the other half being provided by the rapidly increasing CO₂ levels in the atmosphere (see Figure below). Without targeted climate mitigation policies on the non-CO₂ greenhouse gases their relative role would further increase during the 21st century relative to CO₂. Important worldwide initiatives such as the Global Methane Pledge (Glasgow 2021 /Dubai 2023) have been initiated to prevent such a growing role of methane. Provision of policy support for non-CO₂ greenhouse gases is a key objective for NCGG.

The NCGG community aims to provide consolidated policy support through scientific understanding, observations and modelling of all non-CO₂ gases and their variations and trends in the atmosphere from the landscape to the global scale with a focus on the non-CO₂ greenhouse gases as well as on other atmospheric components identified by IPCC in the emission-based climate forcing breakdown (see figure). The key components from an emission perspective include the gases NOX, NMVOCs, SO₂ and NH₃ as well as black carbon (BC) and organic carbon (OC) emissions. These emissions primarily contribute to the formation of aerosols and tropospheric ozone. Emissions of molecular hydrogen (H₂) and other gases in the atmosphere affect the chemical lifetime of methane also indirectly modifying the climate forcing of non-CO₂ gases. Provision of policy support for the indirect chemically-driven climate forcing components is an important secondary objective for NCGG. Copernicus (CAMS, C3S) and other environmental services within Europe as well as international and also global services may contribute to public awareness and policy support. 

The IPCC emission-based view on the effective radiative forcing per emitted component (until 2019) (IPCC AR6, figure 6.12). The warming since pre-industrial times through CO₂ and the combined non-CO₂ greenhouse gases are of a similar magnitude. Since the 2000s global aerosol decreases further contribute to climate warming (not shown).

The NCGG10 symposium will bring together scientists and engineers on the one hand, and decision makers in the public and private sectors on the other hand. As such, it will actively support the implementation of promising policies and technologies to reduce NCGG-emissions. Special attention will be paid to the Global Methane Pledge and to the relation between climate mitigation, climate justice and the SDG’s. Satellite observations of methane are expected to get an increasingly important role in (hot spot) methane emission detection and emission verification.

Against this background the objective of the NCGG series of symposiumis to bring together scientists, experts, decision makers and stakeholders in the field of Climate Change with a view of supporting the development of efficient and effective technologies and policies aimed at decreasing the radiative forcing due to non-CO₂ greenhouse gases and other non-CO₂ components with indirect climate impacts.

The symposium brings the experts together to inform and discuss. From the evaluation perspective with measurements and models, and from the inventory and scenario perspective, checking how to abate and mitigate and otherwise growing role of the non-CO₂ components in their contribution to climate warming in the next decades.