Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years

The study “Relationship between sea level and climate forcing by CO₂ on geological timescales” by Dr Gavin Foster and Professor Eelco Rohling,  published in the  Proceedings of the National Academy of Sciences  last month had quite an impact on the science websites and blogs.

In his Skeptical Science blogpost, Rob Painting discusses the key points of the study which has engaged scientists in a constructive debate in the comments section.

Key Points:

• Because the water contained in land-based ice sheets is ultimately derived from the ocean, over long (geological) timescales global sea level is largely determined by global temperature and, consequently, the temperature-dependent volume of ice stored on land.

• Since the concentration of carbon dioxide in the atmosphere (The Greenhouse Effect) exerts such a powerful influence on global and polar temperature, it therefore follows that it should also exhibit a strong relationship with global sea level over geologic intervals of time.

• Foster & Rohling (2013) examined time slices of paleo data covering the last 40 million years to uncover the details of this carbon dioxide-sea level relationship. Surprisingly, they found a consistent and robust relationship between carbon dioxide and sea level irrespective of other contributing factors.

• Based on the concentration of carbon dioxide in the atmosphere as of 2011, the authors estimated that future sea level is committed to rise 24 metres (+7/-15 m) above present-day once the land-based ice sheets have fully responded to the warming and the Earth is once more in equilibrium.

• The authors estimated that this sea level rise will likely take place over many centuries, if not several thousand years, but it nevertheless represents the long-term consequences of human industrial activity, and is further evidence that CO₂ is the Earth’s “main control knob” for global temperature.

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