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We're in a hotel conference room, Quernavaka, Mexico, in the year 2000.

And against the gentle patter of an academic presentation, one delegate is shifting irritably in his seat.

This is a meeting of Earth scientists, people who study the swirling interactions of ocean and air, rock and wind and tide and rain, and Paul

Crutson is getting cross. He's already a Nobel Prize winner, known for his breakthrough work on the ozone layer.

He's doing his best to listen, but the speakers are referring over and over again to something

called the Holocene, the geological time period stretching back about 12,000 years.

But Paul believes, Paul knows that the world is now radically different.

Talking as if it isn't is missing something fundamental, something really urgent.

He shoots up.

Stop saying the Holocene, he barks.

We're not in the Holocene anymore.

When a Nobel Prize winner intervenes, everybody listens.

But one attendee ventures cautiously,

if we're no longer in the Holocene, what period are we in?

What the people in this room could not have known then

was that this brief exchange would launch a global

quest, a quest which would reveal striking insights into our changing earth, a quest that would

end in maddening failure. I'm Hannah Fry, a mathematician who studies patterns in human behaviour.

And from BBC Radio 4, this is Uncharted, tales of data and discovery.

I first visited Crawford Lake in either 1984 or 85.

This is Francine McCarthy, a professor at Brock University in Canada.

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