Simulations of past storminess

A new Postdoctoral researcher, Jane Earland, has joined the HoStIr team to work on work strand three. Her research will focus on using palaeoclimate models to investigate storminess in the warm mid Holocene (~6000 years ago), and warm and cool periods during the last 1000 years. But what are palaeoclimate models? And how can they tell us about past storms in the North Atlantic and Ireland?
Palaeoclimate models – what are they?

The earth system is made up of a series of components – mainly the land, the ocean, the atmosphere and sea ice. The purpose of a climate model is to produce a computer simulation that accurately represents this system. These models are extremely important for science because it’s impossible to take physical measurements of every part of the globe every day. We therefore need models which provide good representations of the earth to be able to perform global scale analyses.

To make global climate models, scientist first divide the components the atmosphere, land, oceans and sea ice into a 3D grid. They then use mathematical equations and powerful computers to run lots of lines of code which calculate the physical climate processes going on within each grid cell, and between grid cells that are next to each other. After these calculations are complete, the models produce outputs like daily sea surface temperature, wind speed, and sea level pressure, which can be used by analysts like Jane.

Once scientists have got their climate model up and running, they can change some of the input parameters which influence the climate, such as the greenhouse gas levels, the shape of the Earth’s orbit and the extent of ice sheets. By adjusting these parameters, they are able to see how the earth system responds in different climate states, such as when greenhouse gas levels are higher and temperatures are warmer. This approach has been used by the palaeoclimate modelling community to produce simulations of past cool and warm periods, such as the last ice age and warm mid Holocene. These simulations are called palaeoclimate models.
How can we use palaeoclimate models to track past storminess?
To look at storms in different past climate states, we use some of the same environmental parameters that scientists use to track and look at storms in the modern weather forecast – sea level pressure and northward and eastward wind. Data on these variables for the warm mid Holocene and past 1000 years, have been produced by groups of climate modellers across the world that are part of the Palaeoclimate Modelling Intercomparison Project, also known as PMIP.

With the sea level pressure and wind data, Jane can use computing techniques to extract the location of storms and their intensity from the palaeoclimate models. She will be focusing on storms that are generated in the North Atlantic and pass over Ireland. Once we have these data, we can compare them with storm proxy records from peat bogs produced by Lisa in the HoStIr team. Results coming soon!!