Mattias Green and his team investigate the climate of Early Earth to determine the drivers for long-term climate variability, before life evolved, using a hierarchy of climate models
There are probably more planets than stars in the Milky Way, ranging from very hot gas giants to smaller and denser rocky planets, like our own. With this ever-increasing number of exoplanets being detected, the probability of finding planets that can host life in a form we recognise is also on the rise. The potential presence of liquid water on a planet, thus making it ‘habitable’, depends on a complex relationship between the type of star and the distance of the planet from it, as well as the length of day on the planet, what gasses make up its atmosphere and the distribution of land and ocean. The traditional habitable zone around a star stretches, for our solar system, from Earth to Mars. This zone has been nicknamed the Goldilocks zone because it is neither too hot nor too cold for a planet to reside in it. However, the Goldilocks zone was recently expanded when it was shown that Venus could have been habitable in its youth, because of a fortuitous combination between atmospheric composition, day length and distance to the sun.
There is consequently a direct link between a planet’s climate and its habitability and the climate is controlled by a range of parameters. Consequently, understanding the interactions between these parameters is imperative for our understanding of Earth-like planets, and thereby limiting the planets we will have to investigate to find habitable worlds.
In this project I will use early Earth as a proxy for Earth-like planets and investigate Earth’s climate during the period 3.5–2.7 billion years ago. The aim is to determine the drivers for Earth’s long-term climate variability and how they interact to control climate when life started evolving. This will be done using a hierarchy of climate models, capable of simulating planetary climates and the information we have about Earth at the time. One missing parameter is what Earth’s surface looked like, so I will use a suite of maps (see above) to tackle this. I will also look at the response of Earth’s early climate to parameter settings outside of what Earth experienced, for example looking at very short or long day lengths. By combining the results from our simulations I hope to characterise the climate on Early Earth and provide guidance on which parameters are needed for an Earth-like planet to be habitable.