The Royal Society of New Zealand has just published an interesting paper on sea level rise [pdf], the latest in a series on “emerging issues” of public concern. It’s a very good overview of the current state of our understanding of the risk of future sea level rises, reviewing the evidence that’s accumulated since the IPCC’s Fourth Report (AR4), and puts that information into the NZ context.
The paper suggests that as we’re learning more about the behaviour of the great ice sheets of Greenland and West Antarctica it’s becoming clear that there’s a risk of sea level rise this century much greater than the upper limits given in AR4 (which ignored increasing ice sheet melt). On the other hand, the extreme rates of sea level rise seen during the last deglaciation (4-5 metres per century at times) look less likely, with data from the last interglacial (LIG, aka the Eemian) suggesting 1.5 metres/century is more plausible.
The RS paper also includes a useful summary of various SLR planning guidelines issued around the world. New Zealand’s guidelines (Bryan’s take here), based on AR4, look to be on the low side, but speaking at the press conference to launch the paper, Prof Martin Manning, director of Climate Change Research Institute at Victoria University , suggested that in his recent experience Environment Court judges were taking care to stay abreast of current scientific knowledge. That’s important, because as NIWA’s Doug Ramsay pointed out at the conference, 12 of the 15 largest towns and cities in NZ are on low-lying coastal and estuarine margins, there’s been enormous pressure to develop on prime beachfront locations and large chunks of our road and rail infrastructure are within 5 metres of current sea level.