Global ChangeIntersection of Nature and Culture

New sea level rise estimates—getting worse

Monday, December 7th, 2009

Sea level is a notoriously difficult thing to predict.  Currently, it is not something that climate models (process models based on the transfer of heat and matter) are very good at because we are still learning how ice sheets and glaciers behave.

Therefore, scientists have taken a different approach, using simpler models that relate sea level height to temperature, which climate models are good at predicting.

In the early edition of this week’s Proceedings of the National Academy of Sciences (open access), Martin Vermeer and Stefan Ramstorf apply¹ an updated version of one of these new models.

Several important points:

• Thermal expansion of the ocean is a big driver of sea level rise—between 55-70%.
• Even the low-emission scenario indicates sea level rising 1 m by 2100.
• Higher emission scenarios suggest it may be as much as 2 m.
• Both of these are about 3 times higher than the 2007 IPCC report suggests.
• Like the IPCC report, this model does not include the possibility of more catastrophic thaw of major ice sheets like Greenland and Antarctica (which is really hard to predict).  So the potential for even greater—perhaps significantly greater—sea level rise exists.
• A sea level rise of 2 m will be devastating to Louisiana, south Florida, and coastal North Carolina as this EPA website demonstrates.
• To the extent that we are already committed to some warming, we are likely already committed to sea level rise.  This study suggests at least 75 cm.

¹Vermeer, M and S. Ramstorf (2009) Global sea level linked to global temperature. Proceedings of the National Academy of Sciences

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