Influence of Solar Variability and Volcanic Aerosol on the Climate System

Climate change is driven by a combination of anthropogenic influences, internal variability, and external forcing. To accurately quantify long-term climate change, it is essential to improve our understanding of these processes. Two significant external forcings are solar variability and volcanic eruptions. Solar variability, particularly the 11-year solar cycle, and volcanic aerosols from major eruptions play crucial roles in influencing the climate system. These climate forcings may be direct (e.g. solar heating or aerosol reflection) or indirect (e.g. via changes to the stratospheric ozone layer).

Climate models, such as the NERC/Met Office UK Earth System Model (UKESM), are ideal tools for analysing past climate changes. They incorporate detailed representations of important chemical and dynamical processes, allowing us to study the complex coupling pathways of these climate forcers. By enhancing the representation of solar variability and volcanic aerosols in UKESM, this project aims to provide valuable insights into their impacts on the climate system.

Objectives

1. Improve representation or key processes in UKESM: Enhance the model’s ability to simulate solar variability and volcanic aerosol processes.
2. Evaluate model performance: Use satellite-based datasets over the past few decades and reanalysis data to assess the accuracy of the improved UKESM.
3. Analyse solar flux variability: Focus on the 11-year solar cycle and its “top-down” mechanisms affecting the climate.
4. Study volcanic aerosol impact: Investigate the effects of major volcanic eruptions on stratospheric and tropospheric circulation.

Methodology

a) Model Improvement:

• Integrate processes from the Leeds TOMCAT Chemical Transport Model into UKESM.
• Focus on UV-induced changes in ozone concentration and their climatic impacts.

b) Data Collection and Analysis:

• Utilize satellite datasets and reanalysis data for model validation.
• Conduct simulations from 1960 to 2024, covering solar cycles 20 to 25 and major volcanic eruptions (Mt. Agung 1963, El Chichón 1982, Mt. Pinatubo 1991).

c) Simulation and Evaluation:

• Perform model simulations to study the influence of solar and volcanic factors.
• Analyze the results to understand the mechanisms driving climate variability.

Desirable Skills and Experience

• Aptitude for computer programming, particularly Python and FORTRAN.
• Experience with statistical analysis methodologies.
• Familiarity with climate modelling and data analysis.