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Aerosols, Clouds and Climate

Module description

Climate change is arguably one of the most urgent issues over the next two decades as humanity struggles to meet the 1.5C above pre-industrial target set by the Paris COP21. Concentrations of both greenhouse gases (GHG) and aerosols (particulate matter suspended in the atmosphere) have increased considerably since pre-industrial time. Whilst anthropogenic emissions of GHG warm the planet, aerosol emissions exert a significant, yet poorly quantified cooling that acts to offset a fraction of global warming from GHG. Reducing current uncertainties associated with estimates of climate change sensitivity to GHG emissions is hampered by our understanding of the strength of the cooling effect aerosol particles have on the climate via their interactions with clouds and sunlight. Despite decades of research the Intergovernmental Panel on Climate Change Assessment Report continue to highlight our low understanding of aerosol cloud interactions (ACI) and aerosol radiation interactions (ARI) as key uncertainties hampering our understanding of climate change.

This module is designed to explore the atmospheric physical processes determining the role of aerosols and their interaction with clouds and radiation on the climate to provide insight on the importance in reducing current uncertainties associated with ACI and ARI for adoption of more robust adaptation and mitigation strategies. The goal is to provide you with a familiarity of concepts essential to an understanding of the sources and transport of atmospheric particles and their sinks from removal processes associated with clouds, their effects on the radiative properties of clouds, and subsequently, the climate. The module provides an overview of current topics in atmospheric science research related to aerosol–cloud-climate and aerosol–radiation–climate interactions, including the thorny issue of ‘geoengineering’ i.e. could the cooling from aerosols could be enhanced to combat the effects of global warming. This applied science module is aimed at Natural Science and Mathematics students

Module aims - intentions of the module

The aim of the module is to provide a working knowledge of atmospheric aerosols and their role in climate change via their interaction with radiation and clouds. The module will introduce you to a hot topic in atmospheric science, aerosol?climate interactions, and why it is vital to reduce uncertainties in its scientific understanding if we wish to improve understanding of climate change. You will be provided with an understanding of: transport, sources, and sinks of aerosols, the physical basis for aerosol-cloud interactions, how clouds are affected by aerosols, how cloud processes act to remove aerosols from the atmosphere and an understanding of the concept of aerosol forcing by aerosol-cloud interactions (known as aerosol indirect forcing). You will also gain an understanding of basic radiative transfer and how aerosols interact with sunlight and terrestrial radiation. You will learn about the tools required to investigate these processes.

An understanding of these atmospheric processes will be placed in the context of observations and their representation in climate models used to assess their climate impacts. You will gain awareness of the important literature on the topic of aerosol-cloud-climate interactions, and increase proficiency in reading (and critiquing) this literature. Additional goals of the course are: to gain experience in handling and interpreting aerosol data from observations and climate models, and exposure to using statistical techniques and tools to interpret observations of aerosols and evaluate their representation in climate models. Furthermore, you will learn ways in which climate models are used to inform climate policy and decision making including emission reductions and ‘geoengineering’ i.e. the potential for offsetting the impacts of global warming utilising aerosol-induced cooling. 

Lecture materials and assignments strike a balance between principles of atmospheric science related to aerosols and clouds, and developing experience in using tools to link measurements of associated processes to improve understanding of how they are represented in models.

You will develop the following graduate attributes:

• People skills in communicating with peers and discussing scientific ideas
• Independent research skills related to further reading around the topic
• Applied thinking and problem solving – applying the knowledge you have gained to solve problems related to the interactions between aerosols, clouds and climate

Intended Learning Outcomes (ILOs)

ILO: Module-specific skills

On successfully completing the module you will be able to...

• 1. Describe basic atmospheric science and structure: pressure, temperature, density, the greenhouse effect.
• 2. Describe chemical and physical properties of aerosol particles, microphysical properties of clouds, their radiative effects, and how these are measured.
• 3. Given data describing the physical characteristics of aerosols, e.g. Mobility Particle Size Spectrometer (SMPS or DMPS) identify how the properties of the aerosol size distribution varies in different environments.
• 4. Manipulate and, given data identify susceptibility of cloud microphysical properties to aerosol perturbations under different environments.
• 5. Summarise key processes in which aerosol particles interact with clouds to affect the climate and discuss linkages between natural/anthropogenic aerosols and climate change.
• 6. Understand the relative role of aerosol scattering and aerosol absorption in climate change using theory and models.
• 7. Evaluate the representation of aerosols in global climate models and understand role of uncertainty in climate model parameterisation of aerosol-cloud and aerosol-radiation interactions for climate change predictions.
• 8. Examine and critique potential schemes to combat global warming using aerosols to deliberately brighten clouds or deliberately reflect sunlight away from the planet.

ILO: Discipline-specific skills

On successfully completing the module you will be able to...

• 9. Demonstrate and apply a knowledge and understanding of aerosols, and their interaction with radiation and clouds and the climate.
• 10. Describe and apply essential facts and theories in atmospheric science relevant to aerosols, and their interaction with radiation and clouds and the climate.
• 11. Describe and begin to evaluate aspects of current research in aerosols, and their interaction with radiation and clouds and the climate, with reference to textbooks and other literature sources.

ILO: Personal and key skills

On successfully completing the module you will be able to...

• 12. Communicate ideas effectively and professionally by written means.
• 13. Participate effectively and professionally in discussion of scientific ideas.
• 14. Interact effectively in a group.
• 15. Study independently
• 16. With limited guidance, select and properly manage information drawn from books and other literature sources.

Syllabus plan

Whilst the module’s precise content may vary from year to year, it is envisaged that the syllabus will cover some or all of the following topics:

• Atmospheric structure: pressure, density, temperature
• Atmospheric radiation: greenhouse effect, direct aerosol effect, indirect aerosol effect(s)
• The use of in-situ and/or satellite measurements to quantify aerosols and cloud properties
• Aerosol particles and their lifecycle: sources, sinks and transport. 
• Microphysical processes in warm clouds relevant to aerosol-cloud interactions.
• The importance of quantifying natural aerosol sources for understanding the impact of anthropogenic aerosols on clouds and the climate.
• Understanding of hypothesised natural feedback mechanisms between the biosphere, aerosols and clouds.
• Understanding of how the physical characteristics of aerosols are represented by climate models. 
• The role of aerosol – cloud interactions in climate model predictions of future climate change.
• The role of aerosol – radiation interactions in climate model predictions of future climate change.
• Climate geoengineering

Learning activities and teaching methods (given in hours of study time)

Details of learning activities and teaching methods

Formative assessment

Summative assessment (% of credit)

Details of summative assessment

Details of re-assessment (where required by referral or deferral)

Re-assessment notes

Deferral – if you have been deferred for any assessment you will be expected to submit the relevant assessment; in the case of the group essay and group presentation assessments, these will be replaced by an individual essay and individual presentation. The mark given for a re-assessment taken as a result of deferral will not be capped and will be treated as it would be if it were your first attempt at the assessment.

Referral – if you have failed the module overall (i.e. a final overall module mark of less than 40%) you will be required to sit a further examination. The mark given for a re-assessment taken as a result of referral will count for 100% of the final mark and will be capped at 40%.

Indicative learning resources - Basic reading

Indicative basic reading list:

• Atmospheric Chemistry and Physics: From Air Pollution to Climate Change, J.H. Seinfeld and S.N. Pandis, 3rd Edition, John Wiley and Sons, 2016.
• An Introduction to Clouds: From the Microscale to Climate, L. Ulrike, Luond, F., and Mahrt, F. Cambridge University Press, 2016.
• A Short Course in Cloud Physics, 3rd Edition, M.K. Yau R R Rogers, 1996.
• Atmospheric Aerosols. Properties and Climate Impacts, Boucher, O., Springer, 2015, ISBN 978-94-017-9649-1

Indicative learning resources - Web based and electronic resources

Exeter Learning Environment (ELE) page:

Indicative learning resources - Other resources

Other resources:

• Primary literature

Key words search

Atmosphere, Aerosols, Clouds, Climate