How much will sea level rise over this century? “Don’t know” is a good answer. “Not much” is looking like a bad answer that’s getting worse by the month. Last week a group of Northland Conservation Corps workers rode on a hikoi along Ninety Mile Beach to draw attention to the issue:
Tutor Mike Wikitera and his team erected five signs marking predicted sea level rises by 2030. The group, who rode horses to avoid adding to greenhouse gas emissions, erected the first sign at Shipwrecks Bay and placed the last one at Waipapakauri beach on October 30.
But what are the “likely levels” by 2030? The IPCC’s latest report projects between 18cm and 59cm by the end of the century, but only by excluding a very big unknown – how much ice will melt in Greenland and Antarctica. As more evidence of dramatic melt in Greenland arrives, it’s getting increasingly difficult to rule out multi metre rises. The latest number comes from Professor David Vaughan of the British Antarctic Survey, quoted in the Daily Telegraph [UK]:
Prof Vaughan says the main message is not to panic â€“ the effects of melting will be gradual, in the order of three metres per century if the evidence of the past 20,000 years is anything to go by.
Three metres per century? That’s towards the top end of current speculation. 30cm every ten years, ten times the current rate, compares with 17cm over the last century. Prof Vaughan’s right about panic. It’s not a good option, but extreme concern is certainly justified. For some dramatic pictures of what might happen, check out this Greenpeace report on climate change impacts on Spain, timed to coincide with the IPCC meeting in Valencia to ratify the AR4 synthesis report. To see what 3m might mean for NZ, go here and zoom in on your favourite bit of beachfront property. NIWA’s current advice to local government is to allow for 50cm by 2100. That’s in need of considerable upward revision.
Meanwhile, the impact of sea level rise is not just high tides and wet feet. Salt water intrusion into fresh water coastal aquifers can be bad news for agriculture and drinking water – and the problem may be worse than previously thought, according a new study reported by Science Daily. The BBC covers one of the areas at most risk – Bangladesh – in a new series, documenting a boat journey through the country.