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Uncovering the history of Earth’s climate

To understand the history of climate change, researchers are digging underneath the ocean floor where organisms and plants have accumulated in sediment over millennia. Maureen Raymo studies this science of paleoclimatology using a vast collection of materials at Columbia University’s Lamont-Doherty Earth Observatory. NewsHour Weekend's Hari Sreenivasan reports.

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  • Hari Sreenivasan:

    This is the core repository at Columbia's Lamont-Doherty Earth Observatory. Each of these drawers holds samples taken from the beneath the ocean floor. It's a collection that has taken more than half a century to build, and a treasure trove of scientific data on everything from which plants and animals thrived millions of years ago to how the climate is changing today.

    Earlier I spoke with Maureen Raymo, a marine geologist studying climate change and the director of the core repository.

  • Maureen Raymo:

    They're records of time. You know they're going back in time. They're like tape recorders sediment sedimentary tape recorders of Earth's history. You can see they are from different places, they have different colors.

  • Hari Sreenivasan:

    Maureen Raymo is showing me a few of the more than 18,000 core samples that have been collected from the sediment beneath the ocean. Each core provides a physical record of the earth, typically representing hundreds of thousands of years

  • Maureen Raymo:

    What these cores have been most useful for is studying the history of Earth's climate. And if you think about the ocean that's like a giant you know it's like a giant bucket and everything that either blows in or is carried in by icebergs or grows on the surface of the ocean the plankton the animals the plants all of it ends up falling to the bottom of the ocean -and it just accumulates layer by layer by layer. So you have a record of time and you can see how the Earth's climate has changed through time how the plants have changed how the temperatures have changed.

  • Hari Sreenivasan:

    Raymo says the cores – like this one from the Mediterranean sea – provide a record of the natural cycles of the earth's climate.

    So right now I'm touching something that's 50 or 60 thousand years old?

  • Maureen Raymo:

    Yes.

  • Hari Sreenivasan:

    The cores also help scientists see how far off our climate is today from those cycles.

  • Maureen Raymo:

    One of the great scientific advances that came out of the Lamont core repository was the proof of the theory of the ice ages and this understanding that the ice ages come and go caused by variations in the Earth's orbit around the sun.

  • Hari Sreenivasan:

    So we should be heading towards another ice age?

  • Maureen Raymo:

    So right now the Earth's orbit should be making the earth cooler and the Northern Hemisphere and it's making and it's we're observing it's warmer and that's obviously because we're putting so much greenhouse gases into the atmosphere very quickly.

  • Hari Sreenivasan:

    The cores are collected on research vessels equipped with a system that lowers a specially-designed collection pipe to the sea floor.

  • Maureen Raymo:

    Imagine like you had a multi layer cake and a big straw and you just stuck your clear straw into your cake and pulled it out. And that's essentially what we do in the ocean except we have a giant steel tube with a the one ton weight of the top and it just be lowered on a winch when it gets near the bottom we release it and it just drives the core

  • Hari Sreenivasan:

    The tube is driven about 30 feet into the sediment and then raised back up to the ship.

    When you get down below the surface the geology is so different from ocean to ocean or even in the same ocean. I mean when you look at different samples different colors different textures…

  • Maureen Raymo:

    Right. Yeah. So you know there's areas of high productivity where there's lots of plavin animal remains. There is areas at high latitudes where we see lots of glacial deposits are places where there's lots of organic matter Yeah. You know the patterns of sedimentation in the ocean can tell you a lot about the processes that are going on today and in the past.

  • Hari Sreenivasan:

    Cores have been collected in oceans and seas all over the world. Each dot on this map represents a sample that the Lamont-Doherty Core Repository now stores.

    When you look where these cores are from all over the planet I mean 40 or 50 years ago the foresight to try to do this they weren't thinking about this library now. They were doing it for what they wanted to at the time right?

  • Maureen Raymo:

    Yeah well it's really true. I mean this is the largest core repository in the world. And part of that is due to the foresight of the first director Maurice Ewing of Lemont. And even though they didn't really know what they would do with the cores he said every day every ship has to stop and take a core. And so it is pure exploration and this huge collection accumulated and that's why it's so useful now because it's very very hard to raise the funding to go out and do a scientific expedition. So if you can do your work with material that already exists that's a big win for science.

  • Hari Sreenivasan:

    The core repository sends more than 3,000 samples a year to scientists all over the world. Raymo thinks of it as a "living museum."

  • Maureen Raymo:

    It's an it's an active source of material for researchers. The entire collection even though it looks like rusty old traces everything that's in here. The new material the old material. These cores were collected probably in the 50s right here. It's all digitized. It's all archived on computers. Any scientists in the world can search our collection they can look for material from a region they're studying that they want to know more about. And that's one of the reasons the National Science Foundation funds us, we're a community facility

  • Hari Sreenivasan:

    Raymo is leaving this week on an research expedition, which will be collecting new core samples near antarctica. she'll be on a ship for the next two months.

  • Maureen Raymo:

    It's going to a place that has never really been studied before in fact we don't even know what the age of the sediment at the bottom at the bottom will be. So you know the the ocean is vast. You know they say we know more about the surface of the moon than we know about the bottom of the ocean and there are still many many places to explore and many uncertainties about what happened in the past especially around Antarctica.

  • Hari Sreenivasan:

    Even as she brings back more samples, Raymo says there are still parts of the existing collection that haven't been fully explored.

  • Maureen Raymo:

    I would say about half of them have been studied in depth by scientists. But you know there's still a lot of undiscovered gold in this in this building.

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