The Aerosol Properties, PRocesses And InfluenceS on the Earth’s Climate (APPRAISE) programme was a UK NERC (Natural Environment Research Council) directed research programme designed to improve our ability to quantify the effects of atmospheric aerosol particles on the Earth’s climate system. The aims of APPRAISE were to investigate and understand the underlying properties of airborne particles that affect the lifecycle of aerosol particles which in the end are responsible for their effect on radiation and cloud formation (hence the aerosols direct and indirect radiative contributions to the earth’s radiation budget). The programme tackled the formation, transformation and interaction of particles in the atmosphere to establish and quantify key pathways in their lifecycle.

APPRAISE looked at the science of aerosols and their effects on climate, as understanding atmospheric aerosols is one of the most important ways we can improve models of likely climate change, particularly at regional scales. The five-year programme started in 2005 and ended in 2010, and contained three large consortia projects and 4 core projects.

The aim of APPRAISE was to understand and quantify how aerosols affect the Earth's radiation budget, by scattering and/or absorbing radiation, influence clouds, and hence indirectly affect climate and the hydrological cycle, and contribute to feedback processes between land, the biosphere and climate.

APPRAISE helps us understand and quantify how aerosols:

- Affect the Earth's radiation budget, by scattering and/or absorbing radiation
- Influence clouds, and hence indirectly affect climate and the hydrological cycle
- Contribute to feedback processes between land, the biosphere and climate

APPRAISE consisted of three consortium projects:

- The Clouds (Aerosol Cloud Interactions and Climate) project aimed to assess the relative importance of the key processes by which aerosol control cloud microphysics in mixed phase clouds, to determine the properties and role of ice nuclei and their interaction with mixed phase clouds, and to assess the role of absorbing material above, below and within clouds.

- The ACES project aimed to reduce uncertainties in our fundamental understanding of the formation of BSOA (Biogenic Secondary Organic Aerosol) and the subsequent impact on atmospheric composition, through coordinated chamber studies, field studies, process model development, and application of atmospheric models of chemistry and transport to assess coupling and feedbacks in the Earth system.

- The ADIENT (Appraising the Direct Impacts of aErosol oN climaTe) project aimed to provide information and understanding of the properties and processes that determine aerosol radiative properties and impact on a range of scales from close to source, through plume and to regional scales.

APPRAISE focused and coordinated NERC's investments in aerosol research. The programme strengthened expertise in the UK, built links between existing excellent science activities, and provided a framework for UK scientists to collaborate with international colleagues. The NERC/Met Office BAe research aircraft and instrumentation, and links to existing modelling programmes, helped the programme put NERC's strategically-important aerosol research at the forefront of international research in this field.

Keith Bower, University of Manchester, was the Scientific Coordinator for APPRAISE.