Tag: Christchurch

TDB today: up a blind alley (without a paddle)

In this week’s post at The Daily Blog — Up a blind alley (without a paddle) — I ruminate further on the message to be gleaned from last week’s flooding in Christchurch, and how ignoring the shape of things to come makes for bad government and worse politics:

What happened in Christchurch was not a consequence of climate change (though the heavy rainfall is something expected to increase in a warming world), but an early warning of what will happen to coastal cities as sea level rise takes its toll over coming decades. With CO2 nudging 400 ppm, the planet can expect the sea to eventually stop rising when it is 15-20 metres higher than today. It might take a few hundred years to get there, but if we don’t act to reduce atmospheric carbon it’s not just a distant threat, it’s a long term certainty.

With another storm bearing down on the country from the tropics and severe weather on the cards for much of the country over the weekend, the government may well have to confront another flood emergency. We can only hope they learn something more than how to deploy the prime ministerial mop.

Lost in the flood

CantyfloodsNASAEO

This morning’s NASA Earth Observatory image of the day shows the impact of last week’s heavy rain in Christchurch and Banks Peninsula on the sea around. The light blue colours show sediment washed off the land. If you visit the EO page, they provide a helpful reference image: the region snapped from space in late February, when there’s no sign of any sediment at all.

Continue reading “Lost in the flood”

Sea level rise, earthquakes, and flying PIGs

ChristchurchT T2013

The first major study to look at the impact of sea level rise on Christchurch and Banks Peninsula following the 2010/11 earthquake sequence projects a watery future for many parts of the city and its surrounding shorelines. The image above ((Fig 3-4, p15 in the report.)) shows changes in ground elevation between 2003 and 2011 in the Christchurch region. Areas in green/blue have moved upwards by half a metre – particularly noticeable to the west of the estuary – and areas in red and yellow down, in many places along the Avon and subsidiary streams by a metre or more.

The report, Effects of Sea Level Rise on Christchurch City (pdf), by consultants Tonkin & Taylor was released last week and suggests that as a minimum planners should take into account a 1m rise in sea level over the next 100 years. Combined with the elevations changes caused by the earthquakes, this would mean significant shoreline retreats, increased flooding in many areas and the loss of hundreds of hectares of land to the sea. It’s well worth digging into the report to get the full picture, and it will make uncomfortable reading for many in the city.

Tonkin & Taylor prepared their study before the IPCC’s AR5 Working Group One report was released, and so based their SLR numbers on a literature search and the Royal Society of NZ’s 2010 paper. They suggest a “plausible upper range” of 2m over the next 100 years, with the behaviour of the West Antarctic and Greenland ice sheets in a warming world “probably the largest uncertainty in sea level rise projections”.

And now the bad news…

Continue reading “Sea level rise, earthquakes, and flying PIGs”

Down by the seaside

This year’s NZ Climate Change Centre conference, to be held at Te Papa in Wellington next month, focusses on sea level rise, and how communities can adapt to the inevitable encroachment of the ocean. The organisers have laid on some excellent speakers, include Aussie oceanographer and sea level expert John Church, as well as many directly involved with the issues raised by sea level rise in New Zealand. The conference programme aims to:

  • Present the latest science of sea-level rise associated with climate change, including the role of polar ice-sheet melt
  • Present a synthesis of recent projections for sea-level rise and discuss the uncertainties associated with these projections
  • Identify anticipated impacts on New Zealand coastal environment and infrastructure resulting from climate change
  • Discuss whether adaptive risk management for adapting to sea-level rise will be adequate given the ranges projected and their uncertainties
  • Stimulate discussion of how end-users can manage present and future coastal issues and how social and bio-physical scientists, central and local government, and infrastructure operators can work together with communities to build resilient systems
  • Describe approaches that have been taken to planning coastal futures, which take into account community and resource-user needs underpinned by plausible climate change projections, adaptive approaches to manage uncertainties, and sound approaches to developing coastal policies.

Sounds like a very worthwhile couple of days. It’ll be interesting to hear what the “synthesis of recent projections for sea-level rise” suggests we’re in for, so if any HT readers are planning to attend, I’d be very happy to carry some conference reports.

For what it’s worth, in my view two numbers and one uncomfortable fact are of prime importance. We’re committed to warming, and therefore to sea level rise. The peak level of atmospheric CO2 that we reach (unless we can cut it very quickly after the peak by active carbon removal) will set the final quantum of sea level rise the planet will experience. The latest paleoclimate evidence suggests that current CO2 levels are putting us on course for an eventual 20 metres of sea level rise. Pick your final CO2 concentration, and calibrate against times past. At 300 ppm in the last interglacial, sea level was 6 metres higher than present.

The consequence of where we end up on the atmospheric carbon scale is a long term inevitable and uncomfortable commitment to continuously increasing sea level. It might be enough for some purposes to consider only a metre or two over the the next century, but if you’re planning to rebuild a city, perhaps you should look a little further ahead. Fascinating discussions are in store in Wellington, I confidently predict…

I was lucky enough to attend (and speak) at last year’s conference ((The proceedings of last year’s forum are now available from the NZ CCRI.)), and I’m sure that this year’s effort will be just as worthwhile.

[Zep]

Sea level rise and the Christchurch rebuild

Jim Salinger delivered a timely warning in Christchurch this week when he pointed out that the city in its rebuild would be wise to work to at least a one metre estimate for sea level rise rather than the current estimate of 50 cm.

There’s a report on the Stuff website, and in the Waikato Times print edition there was a little more that evidently didn’t make it to the website.

The 50-centimetre estimate on which the council currently works is based on outdated science, Salinger said. Estimates of how much ice is melting in Greenland and Antarctica are more definite and the reviews are saying that we’re looking at a 50 to 160 cm sea rise. Some local bodies in Australia are now using a one metre estimate.

He illustrated with reference to areas like Brooklands “where you have the Waimakariri [River] coming out to the sea. You can have floods coming down the river at the same time as a storm surge, and they’re really at a lot of risk from inundation and flooding.”

In the Waikato Times piece he also referred to push-back from the insurance industry. “They may say, ‘If you build there we won’t insure you because the risk is too high’.”  The paper reported that Salinger had met with council staff the previous day to press the case for a one metre estimate, with a response from the council that it was “considering its options” and “would take Dr Salinger’s comments into account”.

Let’s hope they take them very seriously into account and incorporate them into their plans. It would be a supreme irony if the Christchurch rebuild paid attention to seismic safety but overlooked vulnerability to sea level rise. The infrastructure implications for New Zealand carried by a rising sea level are very great and very costly and will extend long into the future if global temperatures are permitted to rise to the height currently in prospect. If the Christchurch rebuild offers opportunity to pre-empt any of those future threats and costs, that’s an opportunity to be grasped.