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Listen "Martin Siegert - The planet's time machine"
Episode Synopsis
Martin Siegert, Deputy Vice-Chancellor at the University of Exeter and an antarctic glaciologist, explains how the poles are changing.
About Martin Siegert
"I am Deputy Vice-Chancellor at the University of Exeter and was Co-Director of the Grantham Institute, Imperial College London.
I am an Antarctic glaciologist who studies how the ice sheets have changed in the past, how they are changing now, and how they will change in the future."
The Antarctic time capsule
The reason that we’re keen on learning about the distant past is because our climate is changing, and it’s interesting for us to understand the times in the past when it’s been most similar to the climate we’re heading towards. For the last 170 years or so, the level of greenhouse gases in our atmosphere has been rising as a consequence of burning fossil fuels – what is known as anthropogenic warming: in 1850, the level of carbon dioxide in the atmosphere was about 280 parts per million, whereas now it’s over 415 parts per million. To know if this change makes much of a difference, we must put it into the context of our geological past. The Antarctic ice sheet is the planet’s own time machine as it holds air samples from previous times. By examining it, we can understand what the composition of the atmosphere was like back then and compare it to the present. How do the air samples come to be? The ice that’s buried deep beneath the surface of Antarctica was once snow that has been covered by subsequent snowfall. After about 70 years of burial from surface snow, the air within the snow gets cut off from the atmosphere above. It’s a little air bubble – a time capsule – that keeps going down with further snowfall. At the bottom of the ice sheet – it’s very thick: over 4,000 metres thick in some places – the age of that ice is somewhere around 800,000 to a million years old. What’s remarkable about it is that, essentially, we have a time machine that can take us back, allowing us to get a sample of the earth’s atmosphere between now and 800,000 years ago, as well as every year in between.
Key Points
• The Antarctic ice sheet is the planet’s time machine as it holds air samples from previous times. At the bottom of the ice sheet – it’s very thick: over 4,000 metres thick in some places – the age of that ice is somewhere around 800,000 to a million years.
• Currently, we are at 415 parts of CO2 per million, something we have never seen in the ice core record. We are concerned that we are heading to levels that we haven't seen since the Pliocene, between 5 and 2.5 million years ago.
• In the Pliocene, temperatures on this planet were somewhere around three or four degrees warmer than they are right now and the level of the sea was 20 metres higher than it is.
• Through satellite observations, we can be 100% sure that the polar ice sheets are starting to experience the most melting as a consequence of human-induced global warming. If it all melted, sea level globally would go up by about 60 metres.
• The level of CO2 is still rising, and if we don’t reduce our emissions to zero in about 30 years’ time, it’s completely possible for the level of CO2 in the atmosphere to get somewhere near 1,000 parts per million.
About Martin Siegert
"I am Deputy Vice-Chancellor at the University of Exeter and was Co-Director of the Grantham Institute, Imperial College London.
I am an Antarctic glaciologist who studies how the ice sheets have changed in the past, how they are changing now, and how they will change in the future."
The Antarctic time capsule
The reason that we’re keen on learning about the distant past is because our climate is changing, and it’s interesting for us to understand the times in the past when it’s been most similar to the climate we’re heading towards. For the last 170 years or so, the level of greenhouse gases in our atmosphere has been rising as a consequence of burning fossil fuels – what is known as anthropogenic warming: in 1850, the level of carbon dioxide in the atmosphere was about 280 parts per million, whereas now it’s over 415 parts per million. To know if this change makes much of a difference, we must put it into the context of our geological past. The Antarctic ice sheet is the planet’s own time machine as it holds air samples from previous times. By examining it, we can understand what the composition of the atmosphere was like back then and compare it to the present. How do the air samples come to be? The ice that’s buried deep beneath the surface of Antarctica was once snow that has been covered by subsequent snowfall. After about 70 years of burial from surface snow, the air within the snow gets cut off from the atmosphere above. It’s a little air bubble – a time capsule – that keeps going down with further snowfall. At the bottom of the ice sheet – it’s very thick: over 4,000 metres thick in some places – the age of that ice is somewhere around 800,000 to a million years old. What’s remarkable about it is that, essentially, we have a time machine that can take us back, allowing us to get a sample of the earth’s atmosphere between now and 800,000 years ago, as well as every year in between.
Key Points
• The Antarctic ice sheet is the planet’s time machine as it holds air samples from previous times. At the bottom of the ice sheet – it’s very thick: over 4,000 metres thick in some places – the age of that ice is somewhere around 800,000 to a million years.
• Currently, we are at 415 parts of CO2 per million, something we have never seen in the ice core record. We are concerned that we are heading to levels that we haven't seen since the Pliocene, between 5 and 2.5 million years ago.
• In the Pliocene, temperatures on this planet were somewhere around three or four degrees warmer than they are right now and the level of the sea was 20 metres higher than it is.
• Through satellite observations, we can be 100% sure that the polar ice sheets are starting to experience the most melting as a consequence of human-induced global warming. If it all melted, sea level globally would go up by about 60 metres.
• The level of CO2 is still rising, and if we don’t reduce our emissions to zero in about 30 years’ time, it’s completely possible for the level of CO2 in the atmosphere to get somewhere near 1,000 parts per million.
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