Observing the changing atmosphere from the ground: requirements for global networks for short-lived atmospheric species

Atmospheric aerosol particles continue to contribute to the largest uncertainty in estimates and interpretations of the Earth’s climate. In substance, the magnitude of aerosol forcing is assessed to be –0.45 (–0.95 to +0.05) W m–2 for aerosol alone and –0.9 (–1.9 to –0.1) W m–2 when aerosol/cloud feedbacks are accounted for, both with a medium confidence level. The uncertainty is still very high although substantial progress has been made to understand climate-relevant aerosol processes, such as new particle and secondary organic aerosol formation mechanisms, or aerosol source attribution.


While the benefit of improved monitoring capabilities developed in the last decades, both from  satellites and ground-based has been clearly assessed for the production of more reliable data records, the need for maintaining and enhancing the capacity of the observing system to provide the additional constraints, in particular for the derivation of trends is still essential in climate change predictions.


It is the goal of the Global Atmosphere Watch (GAW) programme to ensure long-term measurements atmospheric parameters relevant to the climate in order to detect trends in global distributions in the air and the potential effectiveness of emission-control policies. With respect to aerosols, the objective of GAW is to determine the spatiotemporal distribution of aerosol properties related to climate forcing and air quality on multi-decadal time scales and on regional, hemispheric and global spatial scales. One major difficulty for the programme is the multi-variable aspect of aerosol forcing on climate: optical properties of an aerosol population are closely linked to chemical, physical and hygroscopic properties and also to the altitude-dependency of these parameters.


The implementation of observing networks from the ground is however not as straightforward as it seems. Ensuring long-term operation with skilled operators worldwide, controlling and improving data quality and enhancing use by the scientific community are complex and expensive actions when considered at a global scale. GAW is an essential pillar.


The course will discuss the strategy for implementing monitoring networks from the ground, evidencing the regional initiatives and presenting results from the last decade of operation with the Global Atmosphere Watch program. It addresses and discusses the most effective solutions for observation activities to be pursued and further developed in a sustainable manner.