Wednesday, May 02, 2012

Dispatch from Kiribati: Can you "see" sea level rise?

Tarawa, Kiribati - This is my fifth time visiting Kiribati for research. I'm here working on a coral monitoring project together with my colleagues at the local government. For more, check out my Scifund site, which is dedicated to raising funds for the in-country side of the coral research. People at home often ask whether I have seen changes in the islands. I don't think the questioner is interested stories about new maneabas, the emergence of kava as a social beverage, or the increased availability of vegetables. Back home, we do seem to have a morbid fascination with seeing the islands that are "sinking" due to sea level rise, never mind the fact that the islands aren't "floating" in the first place. I'll spare everyone a lecture on colonialism, race and definitions of vulnerability - there are, after all, towns in the Greater Vancouver Area with similar population to Tarawa and even less topographical relief - and get to the physical question.

The short answer, I suppose, is yes. I can point to many shorelines that don't look the same as they did seven years ago. The long answer, however, is that the change is quite often not what you might expect on a planet with a rising ocean. In many cases, there's more land.  The reason is that shorelines are constantly changing in response to natural variability and human disturbance, in addition to the global trend. That's the subject of my recent article in EOS and our video "Lessons of Bikeman".

Case in point: The above photo is of a house in Bikenibeu, a south Tarawa islet, during the 2005 storm I mention in the paper. My first trip to Kiribati happened to coincide with that El Nino-driven storm, the strongest Tarawa had experienced in ~30 years. Winds peaked right at high tide. The beach "should" be about the edge of the photograph. The combination of a high astronomical tide and 40 mph+ westerly winds blowing across the unprotected lagoon slammed waves into homes and buildings and over the causeways between islets.

I went by that house a couple days ago and snapped another picture, around but not exactly at high tide. It's not from the same angle, and some new foliage is obsuring the house, but you can still see the kitchen, and you can get a sense of the beach slope. That storm, and some subequent storms, scoured a lot of the sand off the beach, leaving the back part of the house perched more on coral rock (a bit hard to make out; the equatorial sun makes lighting photos difficult!). But, overall, seven years later, the house is not really much closer to the sea.

Is sea level rise a hoax? Of course not. There's overwhelming evidence that the global sea level is rising, and that humans are the cause. But that doesn't mean you can fly to Kiribati and find "proof". As I write in the conclusion of the EOS paper.

The coastal environment, like the weather, is evolving because of natural climate variability and direct human disturbance, as well as a global trend. A particular flood event, whether it occurs in a low- lying atoll like Tarawa or in New York City, cannot be blamed on global sea level rise any more than a particular heat wave can be blamed on climate warming.
Instead of incorrectly attributing individual flood events or shoreline changes to global sea level rise, scientists and climate communicators can use such occurrences to educate the public about the various natural and human processes that affect sea level, the shoreline, and the shape of islands. This would better prepare the public and policy makers for the changes that societies are likely to experience as global sea level rises in the coming decades.

I'll try to write more about our work here before hopping on a boat for the outer atolls.

1 comment:

Henk L. said...

Simon, there was some discussion at
Mark Lynas site re your EOS paper.
Perhaps you can weight in?