Friday, May 26, 2006



The effects of global warming

Want to know what global warming and rising sea-levels will do to your neighbourhood? Alex Tringle has a rough-and-ready overlay for Google Maps which shows you. Note that the IPCC predicts that sea level will rise only 0.09 to 0.88 metres in the next century; the real worry is those "large-scale, high-impact, non-linear and potentially abrupt changes", like the disintegration of the West Antarctic Ice Sheet - something which is looking scarily more likely the more we learn. If that happens, then downtown Wellington will be under water, and you'll be able to go swimming in Cathedral Square.

As I said, this is a rough-and-ready overlay, which ignores all sorts of details. Alex's caveats are here.

[Hat tip: Crooked Timber]

8 comments:

Looks like Auckland will be substantially unscathed even at a 10m sea rise.

Posted by Rich : 5/26/2006 01:37:00 PM

Excellent, time to buy beachfront property in Leeston. Or start planning a marina for Little River.

Posted by Weekend_Viking : 5/26/2006 01:40:00 PM

Just don't buy in Eastbourne; the road there is dodgy during spring tides, and any non-trivial sea-level rise will mean you own a house you can't get to.

Strangely, this fails to be reflected in property values in the area.

Posted by Idiot/Savant : 5/26/2006 01:57:00 PM

Viaduct basin in Auckland will finally look like Venice. I won't mind the sea lapping at the foot of my garden on Waiheke Island.

Posted by Uroskin : 5/26/2006 03:49:00 PM

Rich: Auckland looks OK because the radar height map has been bounced off the top of the buildings, same for all the coastal cities and forestry blocks.

For a real-world concept, compare every such place with Venice. It's sinking about 1m per century at the moment, and has historically sunk at about 0.5m per century. The whole world is sinking like that now, with every tidally affected flood being that much higher.

Posted by tussock : 5/26/2006 04:26:00 PM

Yes, but this misses the point slightly.

A sheltered spot that's fairly safe from erosion now will see an extra metre of water: inconvenient (as anyone who drives to or from Wellington could tell you) but not really a big deal.

But in some parts of NZs coasts they are eroding now (beaches losing way) in other parts the beaches are increasing. That's just normal coastal erosion with no global warming involved.

Global warming will mean increased storm activity (because it raises the temperature gradient between the atmosphere and the cold ocean depths) which will increase erosion.

Which means some parts of the coast which would normally have only one thing to deal with are now in for a triple-whammy: normal erosion plus extra erosion from heightened storms plus rising oceans.

Posted by Icehawk : 5/26/2006 04:55:00 PM

Of course, from the geological point of view, this is still nothing as compared to the sea level changes after the last couple of glaciations, and will not really appreciably change the coastal erosion rates that badly - NZ coastal plains have been steadily eroding since the end of the last ice age, and won't be heading out again until the next ice age starts another degradation phase.

Bear in mind that parts of NZ are trucking about at between 5 and 20 cm a year due to plain old plate tectonics, anyway - I can take you places on the north Canterbury plains that were submarine 25,000 years ago, and are now between 50 and 100m above sea level. Some bits of NZ are rising faster than global warming at current rates can physically raise sea level, and very few parts of NZ are actively subsiding.

Tussock: The tidally affected flood isn't appreciably higher yet - depending on whose fudge factor you use, there might be a few centimetres increase in average sea levels, but the baselines are variable depending upon who did the research and where.

In other words, I'm not fussed about sea level rise until I see the West Antarctic Ice sheet go, and it's a long way off that yet. I'm more concerned about the North Atlantic Drift slowing down, as that's got a longer history of serious climatic effects.

Posted by Weekend_Viking : 5/26/2006 05:58:00 PM

The place that will really get it is Mt. Maunganui - built on a sandspit. One big storm and the Mount becomes the Isle of Maunganui.

Posted by Rich : 5/27/2006 02:45:00 PM