Wednesday, January 18, 2012

Science of Sea Level Rise

In Queensland, this weekend there is an event called Witness King Tides. It encourages the community to go out and take a photo of the weekend's king tide - to illustrate what future sea level rise might look like.

So what's the story with sea level rise? Is it worth worrying about? In the recent past, maybe not. But on a warming globe, the rate of sea level rise increases. As water heats up it expands, and as more land-based ice (like from glaciers) melts, the runoff adds to the ocean. The more temperatures rise, the greater the effect. This is the range of projections illustrated by the CSIRO.

It's quite a wide range of possible outcomes but zooming in on the bottom left hand corner, and including recent measurements, this is what we get.

Clearly, we are tracking near the very top line of the projection range. This is the pathway that leads to almost a metre of sea level rise. (Previously i've written about how such a rise would lead submerge half of Bangladesh).

That the observations are already slightly above this top line is what has the scientists worried that even the most catastrophic projections could underestimate what might happen.

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