This is Law Dome in East Antarctica.

For three months in early 2019, scientists set up a drill site to collect old air bubbles from deep ice.

Dr Peter Neff (Glaciologist, University of Washington)

It’s just about the most specific question we can ask about that little bit of atmosphere trapped in the ice, and it’s at the most specific site glaciologically. We can’t do it anywhere else.

The question they want to answer is: how has the chemistry of the atmosphere changed from pre-industrial times to today?

Dr Vas Petrenko (Ice Core Lab, University of Rochester)

We’re trying to understand specifically the change in the ability of the atmosphere to scrub a number of pollutants, gases like carbon monoxide, but also greenhouse gases like methane, as well as gases that are capable of destroying ozone in the stratosphere.

The natural ‘air purifier’ is a highly reactive molecule known as hydroxyl.

Dr Peter Neff (Glaciologist, University of Washington)

If we’re emitting a whole lot of methane these days by burning fossil fuels, we want to know how long those methane molecules are going to stay in the atmosphere and that is controlled by how they’re oxidised, how they’re rusted out of the atmosphere, and hydroxyl (OH) is the main oxidiser in the atmosphere, that’s what we’re chasing after here.

By melting the ice to extract the old air, the team want to reveal a mystery.

Dr Vas Petrenko (Ice Core Lab, University of Rochester)

We simply don’t know how the hydroxyl radical concentrations have changed further back in time, as well as ultimately how we have altered the concentration of hydroxyl radicals through our emissions.

Knowing the past will help to accurately predict the levels of all greenhouse gases into the future.

The security of our planet’s climate depends upon this knowledge.