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When will the next ice age happen? - Lorraine Lisiecki


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Throughout Earth’s history, climate has varied greatly. For hundreds of millions of years, the planet had no polar ice caps. Without this ice, the sea level was 70 meters higher. At the other extreme, about 700 million years ago, Earth became almost entirely covered in ice, during an event known as “Snowball Earth.” What causes these swings in the planet’s climate? Lorraine Lisiecki investigates.

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Earth’s climate has often been much warmer or much cooler than it is today. About 700 million years ago, the earth was almost entirely covered in ice during events known as “Snowball Earth.” Later, Earth was entirely ice-free for hundreds of millions of years. Ice began to grow on Antarctica about 60 million years ago and ice sheets have intermittently covered portions of Greenland since 7 million years ago.

Atmospheric CO2 has been relatively low for the past few million years. During this time, changes in Earth’s orbit have been the dominant driver of climate change and have caused about ten glacial maxima, otherwise known as “ice ages.” The evidence of past climates can be found in sea sediments, tree rings, and cave rocks. Recently, the impact of orbital changes has been amplified by the reflectivity of growing ice sheets and the absorption of CO2 into the ocean.

During the Last Glacial Maximum (LGM), atmospheric CO2 was about 185 ppm (parts per million), which is about 90 ppm less than pre-industrial levels and more than 200 ppm lower than today. Several factors affect how much CO2 is absorbed by the ocean, including ocean temperature, biologic activity in the ocean, and ocean circulation (particularly the rate at which deep ocean water mixes back up to the surface). Paleoclimate scientists are currently working to better understand the relative importance of these different factors in explaining the lower CO2 during the LGM.

Current CO2 levels of approximately 400 ppm are higher than at any time in the past million years and are likely similar to the CO2 levels 3 million years ago, when there was considerably less ice on Greenland and West Antarctica.

To read more about CO2 measurements from ice cores, check out this site, which includes data collected from the British Antarctic Survey.

Without ice on Greenland and Antarctica, sea level would be 70 meters higher. Past sea levels were even higher because of the warming of the ocean. The ocean expands when it warms—and the size of ocean basins has changed as the result of plate tectonics.

During the LGM, the additional ice on land stored enough water to lower sea level by 130 meters. Sea level rose rapidly between 18,000 to 8,000 years ago as this ice melted.

Contributions to modern sea level rise include the melting of mountain glaciers and ice sheets in Greenland and West Antarctica, as well as the thermal expansion of seawater as it warms. The IPCC estimates that global mean sea level rise is likely to rise if fossil fuel emissions continue to follow historical trends. Therefore, reducing fossil-fuel emissions in the near future is important for reducing sea level rise.

Read more about observations of modern climate change and projections for future climate change here.

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TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Lorraine Lisiecki
  • Director Bálint Farkas Gelley
  • Script Editor Emma Bryce
  • Storyboard Artist Daniel Gray
  • Designer Petra Lilla Marjai
  • Animator Iván Tamás, Rebeka Király
  • Producer Bella Szederkényi
  • Composer James Wood
  • Associate Producer Bethany Cutmore-Scott, Elizabeth Cox
  • Content Producer Gerta Xhelo
  • Editorial Producer Alex Rosenthal
  • Narrator Pen-Pen Chen
  • Fact-Checker Francisco Diez

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