The Ministry for the Environment doesn’t leave local government bodies without advice about sea level rise as a consequence of climate change. I’ve been looking at their guide for local government Preparing for Coastal Change, published last month. It’s backed by a much longer website document Coastal Hazards and Climate Change rewritten last year by NIWA scientists Doug Ramsay and Rob Bell. The guide is thorough. It points out the impacts of climate change on other physical drivers which would exacerbate the problem of rising sea level. Storms, storm surge and storm tides, tidal range and high tide frequency, special estuary effects, waves, and the supply of sediment to the coast all add to the likely effects of sea level rise.
Category: Climate science
McKibben in Wanaka
American environmentalist, writer, educator and founder of 350.org Bill McKibben is in New Zealand this month, and will be speaking at Wanaka’s Festival of Colour on Wednesday 29th April. Bill will be on stage for two sessions at the Infinity Crystal Palace, the first of which — at 10-30am on the impacts of global warming — will also feature me: Bill’s covering the big picture, and I’m providing the local colour. It’s an honour to share the stage with Bill, and I’ll be in the audience for his afternoon gig (2-30pm), where he’s going to address how we can deal with the problem. I hope I’ve finished Deep Economy by then…
A coral room
Sea level rise is usually considered to be a relatively slow process, at least in human terms. Even a one metre rise over the next century (well within the bounds of possibility) is “only” one cm a year. It seems like a small number, even if when those small numbers start accumulating they bring big problems for coastal communities. Faster rates of rise are known from the past — up to a metre every 20 years during Meltwater Pulse 1A, a 5 metre sea level surge 14,000 years ago, as the great northern ice sheets broke up and the ice age ended. These sorts of rates are not generally considered likely for the near future, because we are in an interglacial and the most vulnerable ice melted a long time ago. However, a paper(*) in Nature this week suggests that a sea level surge of 2 – 3 metres 121,000 years ago, as the last interglacial was drawing to a close, could have taken place in as little as 50 years. Andy Revkin at the New York Times quotes from the study:
“The potential for sustained rapid ice loss and catastrophic sea-level rise in the near future is confirmed by our discovery of sea-level instability†in that period, the authors write.
The NYT is careful to point out that this new information is controversial, and will need confirmation before it’s accepted (see Revkin’s DotEarth blog post), but the most interesting feature of this sudden rise (if confirmed) is that it took place during an interglacial warmer than present, when sea level was higher, and when large parts of the Greenland and West Antarctic ice sheets are thought to have melted. In other words, melting ice sheets are prone to very rapid ice loss. The bounds of what’s possible in our future just took another step outwards.
(*) Rapid sea-level rise and reef back-stepping at the close of the last interglacial highstand, Paul Blanchon, Anton Eisenhauer, Jan Fietzke & Volker Liebetrau, Nature 458, 881-884 (16 April 2009) doi:10.1038/nature07933
Extreme Ice
“It’s a strange, evil, gorgeous, horrible, fantastic place,” calls out photojournalist James Balog as he abseils a short way down into a deep hole in the Greenland ice opened up by surface meltwater rushing down perhaps to bedrock hundreds of metres somewhere below. It’s understandable Balog should have mixed feelings. The view is stunning. But that rushing meltwater may be lubricating the great ice sheet at its base and hastening the movement of its glaciers to the sea.Â
The film which records this moment, Extreme Ice, is showing on the National Geographic channel on Sky on Wednesday 22 April at 9.30 pm and a couple of times more in succeeding hours. It will also be showing in Australia. I’ve had the opportunity to preview it. I recommend it highly.
Geoengineering on the table
John Holdren, recently confirmed as President Obama’s science adviser, has said in an interview that discussions at the White House include looking at geoengineering options to reduce the effects of global warming. He stressed that it would be a last resort, but can’t be ruled out of discussion if the failure to cut greenhouse gas emissions continues. He is concerned that several tipping points could be fast approaching, with chances of “really intolerable consequences”, instancing the possible loss of Arctic summer sea ice within six years, the release of frozen methane from thawing permafrost in Siberia, and more and bigger wildfires worldwide. He would much prefer to see the problem solved by reducing emissions of greenhouse gases, but global warming is happening so fast that geoengineering has to be looked at. “We don’t have the luxury … of ruling any approach off the table.”