Climate Change Mystery Solved using Greenland Ice Cores?

Monday 08th Sep 2014 by theWeather Club

Image: Christine Zenino via Wikimedia Commons

It has long been agreed that carbon dioxide is the main cause of most of the post-industrial warming, yet there are historical periods when the connection between carbon dioxide and temperature rise is less obvious. New research - published in Science - exploring Greenland's ice sheets may now be able to explain this.

Approximately 20,000 years ago, the Earth was emerging from an ice age as orbital changed meant it began to receive slightly more solar energy. During this time ice sheets melted, sea levels rose and ocean circulations changed, and scientists think that these alterations caused carbon dioxide to be released into the atmosphere.

Whilst the rest of the northern hemisphere appeared to warm however, Greenland records show little variation in temperature for another 3,000 years, and until now, scientists had no idea why. It was even dubbed the ‘mystery interval’.

This new research suggests that temperatures actually did rise, but that the rise wasn’t captured by earlier ice core records. Oxygen in ice cores provide ‘proxy data’ and allow the reconstruction of past climates; instead, this new work explored nitrogen trapped in air bubbles. The chemical makeup of ice can be affected by changed to the water cycle, but air remains unaffected, thus this data can provide a more accurate reconstruction of paleo-temperatures.

The results showed not only that temperatures did indeed rise along with carbon dioxide during this ‘mystery interval’, but that the warming trend of around 5oC also matches with climate model predictions.

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