The effects of long-term changes in the Earth's magnetic field on the atmosphere: understanding the past; predicting the future

"The effects of long-term changes in the Earth's magnetic field on the atmosphere: understanding the past; predicting the future"

This project investigates the effects of changes in the Earth's internal magnetic field on the atmosphere and climate. The Earth's magnetic field has been changing relatively rapidly in recent times. During the last decade, the position of the north magnetic pole has been moving at its fastest rate recorded so far, at 40-60 km/year. In addition, the magnetic field strength has been steadily decreasing at a rate of 5-7% per century since 1840, which has led to speculations that we may be heading for a magnetic field reversal. Some studies have found correlations between changes in the Earth's magnetic field and climate parameters. However, the responsible mechanism for this link has remained elusive. This project will investigate one possible pathway by which the Earth's magnetic field could affect climate, namely the downward propagation of changes initiated in the upper atmosphere (~100-500 km). This is a novel idea that has not been investigated before.
Changes in the Earth's magnetic field directly influence the ionosphere, the charged portion of the upper atmosphere, and the magnetosphere, the bubble around the Earth that shields us from the solar wind. We will examine and quantify the effects of historical changes in the Earth's magnetic field that have occurred since 1600 on the coupled upper atmosphere and magnetosphere system, using simulations with the Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model. The responses found will be compared to observed long-term trends in the upper atmosphere and indices of geomagnetic activity, which measure perturbations to the Earth's main magnetic field as a result of ionospheric and magnetospheric current systems. We will also explore some potential future scenarios by extrapolating current magnetic field changes into the next 50-200 years.
We then investigate to what extent the effects found in the upper atmosphere influence the middle and lower atmosphere. We will do this using the Whole Atmosphere Community Climate Model (WACCM), a numerical model that extends from the surface to the upper atmosphere, partly overlapping with the CMIT model. At its top, WACCM will be forced with the upper atmospheric responses found in the first part of the project. We will determine whether downward propagation of these forcings causes a significant change in the atmosphere below. Any significant response in the troposphere will be compared to the correlations between magnetic field changes and climate parameters that have been observed.
By studying the effects of magnetic field changes on the climate over the past four centuries, this project contributes to a better quantification of natural sources of atmospheric variability. This is needed to attribute observed climate trends correctly and assess man-made effects on climate more precisely. Both are essential for developing mitigation strategies and for making accurate predictions of future climate. The project also offers a first insight into the effects of magnetic field changes that we can expect in the future. Especially a magnetic field reversal would almost certainly have dramatic consequences for the upper atmosphere and geospace environment, and the technological systems this environment hosts. However, the effects on climate are very hard to predict, as we currently do not know in what ways and to what extent the Earth's magnetic field can affect climate. The proposed project will be a first step in improving our understanding of the link between the Earth's magnetic field and climate.

1. Governments developing policies on climate change
The climate in the troposphere directly affects human daily life all over the world, and therefore a good understanding of long-term climate change, and the role of human activities in this, has become a high priority. In order to assess man-made effects on climate it is necessary to quantify all natural sources of long-term variability so that observed long-term changes are attributed correctly. The most important output from this proposal will be to put limits on the effects of changes in the Earth's magnetic field on the climate in the whole atmosphere for the very first time. Depending on the results, the project will demonstrate whether these additional processes must be incorporated into climate models, or show that the magnetic field changes are not important on timescales of decades to hundreds of years. Governments developing policies on climate change need this information to be able to decide on the best mitigation and adaptation strategies.

2. Users of applications dependent on space weather
Space weather conditions, of which geomagnetic activity can be considered a measure, affect a variety of applications, such as satellite communication and GPS navigation systems, spacecraft operations, aviation, and electric power grids. Problems can arise when geomagnetic activity is increased, usually associated with a disturbance in the solar wind. For instance, increased levels of energetic particles coming towards the Earth can be harmful to satellite systems and aircraft flying on high-latitude routes, while ionospheric irregularities can lead to service disruptions in any system making use of radio waves propagating through the ionosphere. As the Earth's magnetic field changes, the geographic regions mostly affected by geomagnetic storms (periods of increased geomagnetic activity), are likely to shift, the intensity and/or frequency of geomagnetic storms may change, etc. This project will quantify how changes in the internal magnetic field affect geomagnetic activity levels, and gives some insight into the magnitude and type of changes that can be expected in the future. In particular changes occurring over timescales of 2-3 decades will be relevant to, for instance, future satellite missions, as this roughly matches their typical lifetime (from inception to eventual re-entry into the atmosphere).
Long-term changes in the upper atmospheric density also affect satellites, as their orbits depend on atmospheric drag. Decadal changes in atmospheric drag hinder the ability of satellite operators to track and identify active payloads and debris, and also their ability to avoid collisions and make re-entry predictions. This project also quantifies how much change in neutral upper atmospheric density as a result of magnetic field changes can be expected, and thereby benefits satellite operators.

3. The wider public
The wider public and media have a keen interest in the climate, as it directly affects all of our lives. Clear communication of how this project addresses a potential contributing factor to the climate will therefore be beneficial to society in general. Members of the general public are also often interested in seeing the aurora, which are associated with geomagnetic storms. Long-term changes in the locations where the aurora may be seen (due to moving magnetic poles) and possible changes in their frequency and/or intensity are therefore likely to attract public attention and interest. This is also a good way to get school children excited about science and inspiring them to choose physics and other science subject. This is important for securing sufficient physicists and engineers at degree level for the future, which is essential for the future economy of the UK.

4. Scientific communities
Details are given under Academic Beneficiaries.