The advantage with Greenlivingpedia is that it is not constrained by Wikipedia policies and protocols, and currently there are no industry or government hacks doctoring the content, as is the case with many Wikipedia articles.

With world C02 levels now at 380ppm how long will it take for sea levels to rise 15m? I think I may move to a mountain . . .

Another one relates to aerosols. Generally if we clean up air pollution more solar radiation will get through. This is quite a significant factor as shown on this NASA GISS graph.

I believe soot from industrial pollution in Greenland and the Arctic is also a factor, reducing the reflectivity of ice.

The main way of slowing the process is to put less carbon into the atmosphere. Other than that we can implement schemes to take carbon out of the atmosphere, by planting trees, certain agricultural practices etc. Flannery reckons that just as we sometimes have to cut off a badly damaged leg or arm off we might have to take drastic action by putting a protective film of sulphates into the atmosphere to shade the earth at the expense of turning the sky white.

West Antarctic and Greenland ice sheets are vulnerable to even small additional warming. These two-mile-thick behemoths respond slowly at first, but if disintegration gets well under way, it will become unstoppable. Debate among scientists is only about how much sea level would rise by a given date. In my opinion, if emissions follow a business-as-usual scenario, sea level rise of at least two meters is likely within a century. Hundreds of millions of people would become refugees, and no stable shoreline would be reestablished in any time frame that humanity can conceive. (Emphasis added)

Hansen sees his duty as a scientist to give us his best estimate of what’s going to happen, given scientists’ current state of knowledge. He knows, as should we, that it is never going to be possible to predict exactly how the disintegration of ice sheets will unfold.

I’m quite familiar with this territory, albeit with less at stake. In a quarter of a century in the public service we were often called upon to make decisions without the luxury of precise information. You do the best you can with the information you have.

In view of what we found in the post and comments above two metres would cause a lot of grief. Furthermore, if we get two metres this century there is likely to be worse to come in the following century. As he says, finding a stable shoreline, and most of our industrial infrastructure is near the shoreline as well as much fertile agricultural land, will not be possible for centuries.

I’m planning to have a closer look at Greenland and Antarctica in my next post, which I’m thinking should be up by Monday morning.

Typically a 1 in 100 year extreme sea level under late 20th century conditions becomes a 1 in 10 to 20 year event by 2030 and a 1 in 3 to 4 year event by 2070

That’s using the dud IPCC projections.

With Steve D’s wondrous map I had a look at Byron Bay. At 14 metres I’m seeing 3 islands where the headlands are.

Where we are in Ashgrove we’re 80m above sea level according to the boy’s bike. But on the map the water inundates the oval the Broncos train on next to their clubhouse with 14m.

That’s only Greenland, plus W Antarctica, plus thermal expansion and maybe a bit of E Antarctica, where a rim around the edge would surely go as well.

I’ve heard the theory that looking after Melbourne would be simple because you could just roll a couple of loads of cement across the heads at the end of Port Phillip Bay and all would be hunky-dory…

Can the same thing be done around the straights of Gibraltar?

It’s not going to be pretty sight if New York gets the treatment, but it might be the salvation of the world.

Yes, both sea level rise, and larger storm surges, will increase the regularity and severity with which saline water encroaches upon low-lying coastal water tables and damages infrastructure. These risks were a particular focus of a recent meeting of climate change scientists in Sydney (Greenhouse 2007, October 2007: abstracts at http://www.greenhouse2007.com). One report, by J Hunter [pg 37 of abstract book], used extensive coastal tidal gauge data to show that for every 10 cm of sea level rise, the risk of a given extreme event tripled.

To put this in context, a rise in average sea level of just 30 cm (at the low end of projections and likely to occur within decades) would cause a ‘once-in-a-century storm’ to reoccur every 3 years. Thus major hazards for coastal infrastructure arise long before complete inundation, as you note.

I understand that New York has 2400 km of coastline to protect. Then there is the problem of salt penetration into city aquifers.

I don’t think adaptation is realistic. Mitigation is the only way to go.

the safe level of atmospheric carbon dioxide is no more than 350 ppm (parts per million), and it may be less. Carbon dioxide amount is already 385 ppm and rising about 2 ppm per year. Shocking corollary: the oft-stated goal to keep global warming less than two degrees Celsius (3.6 degrees Fahrenheit) is a recipe for global disaster, not salvation.

That’s James Hansen at Huffington Post.

on costly flood defences for protection

How floodproof are these things? I’ve heard the theory that looking after Melbourne would be simple because you could just roll a couple of loads of cement across the heads at the end of Port Phillip Bay and all would be hunky-dory…

And what about the cost? Are these systems really feasible for all those 22 cities in the firing line – particularly if they’re going to be starting from scratch?

Jovial Monk, I’ve been checking out some of the cities around Australia and Adelaide doesn’t seem to be worse that anywhere else, which surprised me. The problem is going to be in the first instance storm surges on top of king tides. Places subject to extreme weather events can mostly expect such events more often.

A storm a few years back dropped the rockwall about 35cm, harbinger of what is to come?

Most of them are likely to be the rich and they probably have a boat in their backyard anyway.

Thanks for that, Always good to fill in some of the blanks.