Research reveals how Earth got its ice caps

For much of its history, the Earth has existed in a 'greenhouse' state without ice caps, and its current ice-covered state was only achieved through a lucky coincidence.

“We now know that the reason we live on an Earth with ice caps, rather than an ice-free planet, is due to a coincidental combination of very low rates of global volcanism, and highly dispersed continents with big mountains,” says Dr Andrew Merdith, from the University of Adelaide’s School of Earth Sciences, who completed the research while at the University of Leeds.

“These conditions allowed for lots of global rainfall and therefore amplify reactions that remove carbon from the atmosphere.

“The important implication here is that the Earth’s natural climate regulation mechanism appears to favour a warm and high-CO₂ world with no ice caps, not the partially glaciated and low-CO₂ world we have today. 

“We think this general tendency towards a warm climate has helped prevent devastating 'snowball Earth' global glaciations, which have only occurred very rarely and have therefore helped life to continue to prosper.”

Many ideas have previously been proposed to explain the known cold intervals in Earth’s history. These include decreased CO₂ emissions from volcanoes, or increased carbon storage by forests, or the reaction of CO₂ with certain types of rocks.

The researchers undertook the first ever combined test of all of these cooling processes in a new type of long-term 3D model of the Earth, which was first developed at the University of Leeds.

This type of ‘Earth Evolution Model’ has only recently been made possible through advances in computing.

In their study, published in the journal Science Advances, the research team concluded that no single process could drive these cold climates, and that the cooling in fact required the combined effects of several processes at once.

The findings will help to reconcile a debate in the Earth Science community about which processes were responsible for driving these cold periods.

Benjamin Mills, Professor of Earth System Evolution in Leeds’ School of Earth and Environment, supervised the project and says the results of the research had important implications for global warming and the immediate future.

“There is an important message, which is that we should not expect the Earth to always return to a cold state as it was in the pre-industrial age,” he said.

“Earth’s current ice-covered state is not typical for the planet’s history, but our current global society relies on it.

“We should do everything we can to preserve it, and we should be careful with assumptions that cold climates will return if we drive excessive warming before stopping emissions. Over its long history, the Earth likes it hot, but our human society does not.”