Scroll To Top

## Thursday, October 2, 2014

### Don't ditch the 2°C target

Sou | 2:15 PM

Today at WUWT (archived here) Anthony Watts is delighted to read a comment at Nature from David G. Victor & Charles F. Kennel, who are arguing that the 2°C target be replaced with different and a more complicated set of indicators. I don't agree.

Ditching a target because it seems difficult is a no-no in planning unless the target is clearly wrong. This one isn't. The problem with ditching an agreed target is that it gives people an excuse to water it down. Rather than ditch the target, there should be a greater urgency applied to achieving it. If we fail, then we will need to know by how much we've failed and the consequences of that failure.

I don't mind adding another target, like the one that was described in the IPCC AR5 WG1 report - a cumulative carbon emission budget. However I think the Nature article is muddled and its suggestions are not all that useful.

Late in the article Victor and Kennel suggest a "volatility index". They describe it as:
...a volatility index that measures the evolving risk from extreme events - so that global vital signs can be coupled to local information on what people care most about. A good start would be to track the total area during the year in which conditions stray by three standard deviations from the local and seasonal mean.
That could have some value, but to my way of thinking, it's not going to be all that meaningful to most people. Single extreme events can get three standard deviations from the mean (which mean?), but it probably won't mean a lot to most people. And by the time most weather got that extreme, the horse would not just have left the stable, it would be so far away that there'd be no hope of chasing it down and getting it back.

### Cumulative emissions target

Victor and Kennel aren't the first by a long shot, who have criticised the 2°C target as being too simplistic and arbitrary. Scientists have long referred to a carbon budget. The IPCC AR5 WG1 Summary for Policy Makers has a section (E.8 Climate Stabilization, Climate Change Commitment and Irreversibility) that has information that sets out targets for cumulative emissions.
Limiting the warming caused by anthropogenic CO2 emissions alone with a probability of >33%, >50%, and >66% to less than 2°C since the period 1861–1880, will require cumulative CO2 emissions from all anthropogenic sources to stay between 0 and about 1560 GtC, 0 and about 1210 GtC, and 0 and about 1000 GtC since that period respectively. These upper amounts are reduced to about 880 GtC, 840 GtC, and 800 GtC respectively, when accounting for non-CO2 forcings as in RCP2.6. An amount of 531 [446 to 616] GtC, was already emitted by 2011. {12.5}

As was reported recently, at the current rate of emissions, we'll hit the limit in about 30 years. That's well within the time frame of most power plants, which are typically designed with a much longer time span than 30 years.

### No single indicator doesn't mean no simple target

Thing is, as stated in the AR5 IPCC report (12.5.4.3):
One difficulty of the concept with climate stabilization and targets is that stabilization of global temperature does not imply stabilization for all aspects of the climate system.

Simple targets are much easier to aim for than complex targets. David Victor and Charles Kennel write:
New goals are needed. It is time to track an array of planetary vital signs — such as changes in the ocean heat content — that are better rooted in the scientific understanding of climate drivers and risks. Targets must also be set in terms of the many individual gases emitted by human activities and policies to mitigate those emissions.

That's all well and good and I don't disagree with using more indicators - which scientists have been using for years, by the way. I do see problems with setting lots and lots of different targets as seems to be suggested. It would confuse most people and would muddy the waters rather than clarifying them. The following passage seems to indicate where David Victor and Charles Kennel are coming from. They wrote:
The 2009 and 2010 UNFCCC Conference of the Parties meetings, in Copenhagen and Cancun, Mexico, respectively, reframed the policy goal in more concrete terms: average global temperature. There was little scientific basis for the 2 °C figure that was adopted, but it offered a simple focal point and was familiar from earlier discussions, including those by the IPCC, EU and Group of 8 (G8) industrial countries3. At the time, the 2 °C goal sounded bold and perhaps feasible.
Since then, two nasty political problems have emerged. First, the goal is effectively unachievable. Owing to continued failures to mitigate emissions globally, rising emissions are on track to blow through this limit eventually. To be sure, models show that it is just possible to make deep planet-wide cuts in emissions to meet the goal. But those simulations make heroic assumptions — such as almost immediate global cooperation and widespread availability of technologies such as bioenergy carbon capture and storage methods that do not exist even in scale demonstration.

### Not good enough justification

In their article, David Victor and Charles Kennel gave various reasons for getting rid of the 2°C target. They were a bit muddled up but as far as I can tell they are as follows:
• 2°C no longer achievable
• It allows politicians to pretend they are acting when most of them have done little
• the goal is impractical, relating only to emissions and policies and doesn't tell governments and people what to do.

They argue that more indicators are needed. Then they say that the best indicator is the concentration of CO2. They don't suggest a number. Concentration is not dissimilar to the emissions budget that the IPCC itself proposed in the latest report. I think the emissions budget is a clearer and more direct concept than CO2 concentration. It is related to CO2 concentration but can be measured and monitored and is tied more directly to human actions. We have direct control over what we emit more than what happens after we emit it.

Then they suggest their volatility index, as I described above. That may be useful later this century but I'm not sure it will tell us a lot right now. There may be some value in an index based on multiple indicators but for most people, it will be less clear than single targets like 2°C or a limit of 1,000 gigatonnes of emissions since 1880. The latter two are clearer and more direct when it comes to messaging than multiple separate indicators or an index (which most people wouldn't understand).

David Victor and Charles Kennel say that new indicators "will not be ready for the Paris meeting". They probably mean that there isn't time to hold all the meetings required to agree on "new indicators". A set of indicators themselves could easily be identified - and have been over and over again in the literature. It's getting formal agreement that takes time.

Because the article doesn't provide very concrete suggestions and is muddled, it doesn't have a huge amount of value. I understand what David Victor and Charles Kennel are trying to argue, but it would have been better if they'd come up with something more concrete. It's the same as what many other people before them have been saying.

### On setting targets and indicators

I've been helping organisations set targets and performance indicators for many, many years. Some general rules are:
• Simpler is better than complex. If you can identify a simple, meaningful target to aim for, do it.
• Don't arbitrarily change a target because you think it can't be achieved. If it's important then stick to it. If you miss the target, the target itself will tell you by how much you missed it, and therefore how much corrective action is required.
• Make sure the indicator or target is measurable. That progress can be monitored readily.
• Use as few indicators as is absolutely needed, not as many as possible. Indicators are just that. They are a sign (much like doctors take your temperature to see if you are in good health or bad). Indicators should not attempt to cover all the "internal workings". That's making things too complicated. If the indicator shows something is wrong, that's when you examine the details to find out why you are going off track.

### It's not the science, it's politics

The biggest barrier isn't the science. That's quite clear on what is required. The difficulty governments face at the international level is getting people to agree not just on goals for emissions reduction, but clear, concrete action plans by which those reductions will be achieved.

The denialati would like to spin this comment to suit their own agenda, as if it's the first time that it's been suggested that keeping global warming to 2°C is now beyond us or that a 2°C target is arbitrary and not all that useful. What they don't acknowledge is that if we stay on our current trajectory we're likely to hit 4°C before the end of this century.

 Credit: CICERO via ScienceDaily.com

At WUWT, Anthony Watts copied and pasted part of the Nature article under a headline (archived here): "WOW. Nature article suggests ‘Ditch the 2 °C warming goal’". He doesn't make any other comment about it. He did add a comment from denier Roger Pielke Snr, which is worth as much as any of Roger's comments these days. Zero.

I see that Joe Romm at ClimateProgress and Stefan Rahmstorf at RealClimate.org have both weighed in on this article. Nice to know that they both agree with me in the main:) I've not yet read their articles but would expect that they would raise many more pertinent points than I do. Unlike HotWhopper, they carry a lot of weight in the worlds of science and politics. Go read what they have to say. I am.

RACookPE1978
October 1, 2014 at 11:02 am
So “NATURE” as a magazine and a publishing dictatorship with an enthralled base of eager parasites (er, writers and subscribers paid by the governments) IS a propaganda machine deliberately releasing press reports and press packages to deliberately spread its goal FOR GOVERNMENTS to be “led” into taking action by the people and editors writing for NATURE.
And here were, thinking “scientific journals” printing “peer-reviewed” propaganda (er, government press reports) ARE THE ONLY “allowed” unbiased source of scientific information! .

MattN  is very much mistaken. At current rates we'll double CO2 in around 35 years, by around the middle of this century. That's not a long way, that's very soon.
October 1, 2014 at 10:02 am
Considering the new Lewis and Curry paper pegs a doubling of CO2 at ~1.6C increase, we’ve got A LOOOONG way to go to get to 2C.
And as Steven Mosher says:
October 1, 2014 at 12:01 pm
“Considering the new Lewis and Curry paper pegs a doubling of CO2 at ~1.6C increase, we’ve got A LOOOONG way to go to get to 2C.”
It doesnt PEG. 1.6C is the central estimate

Although I don't agree with Stephen Rasey's interpretation, his comment does demonstrate in part why I'm not that keen on the suggestions in the Nature comment.
October 1, 2014 at 10:49 am
Agreed. They are changing the game.
But this recommendation amounts to
“Take 23 years of IPCC meetings and AR# reports and chuck them in the dust bin and start over.”.
Paris 2015 (which will still happen) is reduced from signing an impotent agreement to make a pledge to state a future goal on CO2 emissions to an agreement on “What shall we measure next?”

Katabasis asks, and got a few replies, including some from people who bothered to read the article:
October 1, 2014 at 10:16 am
So what hand-waving metric will take the place of global average temperature?

Mark Bofill sees some sense in the suggestion:
October 1, 2014 at 10:22 am
To be flip and a little silly, I was getting comfortable with the 2C thing. It was such an impossible carbon target to meet, it was fun to be able to say oh well, the last opportunity to act now to save the planet has passed, we missed the boat, let’s go home and adapt every time an alarmist set a last chance deadline. It’s sad to lose that low hanging fruit.
Ah well, I guess I mustn’t be lazy. It does make a little more sense to pay attention to things other than 2C. Guess it’s progress. Maybe someday folks will wake up and realize there are actual real solvable environmental problems other than AGW due to CO2 in this world!
lol. like that’d ever happen…

Sunspot makes a stupid comment, typical of WUWT, based on his personal incredulity:
October 1, 2014 at 1:52 pm
Just reading between the lines, I just cannot fathom the stupidity of supposably intelligent human beings that honestly believe that us mere mortals can control global temperature and or climate.

David G. Victor& Charles F. Kennel, "Climate policy: Ditch the 2 °C warming goal." Nature 514, no. 7520 (2014): 30-31. doi:10.1038/514030a

1. I think on balance I agree with you that an emissions budget is a better indicator for the reasons you state - it is more immediately relative to action than a CO2 concentration which is simple to grasp but open to a range of arguments. But I disagree about the volatility index. You main argument against that seems to be its relevance to 'most people', but what do you mean by most people? Surely the audience for that is the policy makers and advisors? Wouldn't an index of that nature provide a more nuanced (and directly rooted in real events) indicator of just what is happening?

After all, your view is that climate change will increasingly affect the globe and the denier argument is that the effects are as yet less apparent than has been projected. A volatility index or similar across a range of possible impacts offers a statistical measure of whether it is or is not happening.

Thats way more effective (and harder to ignore) than just a measure of CO2.

By extension, that array of indicators can better inform policies for remdiation in specific sectors of activity. More targeted indicators and targets lead to more effective policy because the problem is broken down into graspable chunks that can be acted upon.

Just saying "keep below 2C" when we are inexorably heading that way makes the problem seem unsolvable.

1. The main thing the world needs to do is quite simple. Reduce CO2 emissions by switching away from burning fossil fuel.

The "volatility index" has not been well-defined in the Nature article. Nor can I envisage a composite index that will be any more useful than the 2°C target and arguably a lot less useful.

Talking about denier arguments are nothing but a red herring. Who cares what the 8% dismissives think? It's irrelevant. In this context countries are concerned about getting to an agreement about a plan by which the world will mitigate global warming.

There are many signs that climate change is happening, already. There are many fingerprints of climate change, as shown in one of John Cook's slides.

http://blog.hotwhopper.com/2014/09/more-on-john-cook-in-bristol-what-wuwt.html

More signs here:
http://blog.hotwhopper.com/2014/08/whats-happened-to-global-warming-in.html#charts

But that's not the point at issue here. The point is about a target or targets to aim for when developing action plans and intergovernmental agreements to reduce emissions. Simpler is better. Measurable is necessary. The two degree target is fine. I don't have a problem with also adopting a total emissions target, preferably with discrete steps. Eg by 2020, by 2030 and by 2050, for example. That's all that's required for your "graspable chunks that can be acted upon".

IMO an unclear, undefined, mixed up "volatility index" would only muddy the waters, not clarify them.

2. Sadly your 8% dismissives do count. Policy makers listen to constituents and worldwide the sceptical arguments seem well entrenched, aided by the pause. The 2C target is very likely not going to be met, but equally, the pause may mean that the 2C mark is reached later.

This means that governments can choose to enact policies that might potentially achieve the target while also contributing to setting in train other impacts that could have been ameliorated with earlier action.

Victor & Kennel are not necessarily arguing for complete abandonement of the 2C target, they are arguing for additional indicators which have greater relevance. A side benefit of a volatility index is a sense of impact that perhaps is missing in current debate.

What they are saying it seems to me is that a more relevant set of indicators, used to frame the policy debate, would provide a more illuminating and less easily ignored measure of effect.

Their proposed possibilities are not necessarily the right ones, they are simply proposing the idea. I think it's a good one. Developing those indicators may not be easy, but then they suggest it is entirely possible and soon.

I think your argument for a single 2C goal is too simplistic and we can already see its failure.

1. >>Victor & Kennel are not necessarily arguing for complete abandonement of the 2C target

How do you interpret: "Politically and scientifically, the 2 °C goal is wrong-headed"?

Since the authors don't, give us an example of a composition of their "volatility index", how you would interpret a change in the index and how it would be used to generate an intergovernmental agreement to reduce CO2 emissions more effectively than the current information used by governments.

Also, why do you believe extreme events are any more relevant/important than overall climate change? Than a marked change in where we can grow food and what can be grown, for example. Than rising seas, for example. Than the disappearance of Arctic sea ice, for example. Than the dropping of ocean pH, for example.

Is the collapse of WAIS an "extreme event" in your eyes? If we wait till it's completely melted before doing anything, then we're in for a very rocky road over the next few decades.

Extreme events are only one aspect of climate change that we need to deal with.

2. BTW, as you noted in your first comment, I am not arguing "for a single 2C goal". I am arguing that the 2°C goal should not be ditched. It's important. I also argued in favour of setting targets for total emissions.

What I am not in favour of is lowering the targets just because they are hard to achieve. And I'm not in favour of adding complexity if all it serves is to muddy the waters rather than clarifying what needs to be done.

3. The moment that poor nations start to defend themselves against the climate problems send to them by the rich nations, a 2°C target no longer makes sense. With geoengineering we could have no temperature rise, but still large and consequential changes in the climate. In that respect, agreeing on additional target that should not be crossed might make sense.

1. That's a good point, Victor. Although I don't know that it negates the wisdom now of having a 2°C target. Perhaps "a 2°C target on it's own is not sufficient", is a better way of putting it.

4. For mine, the target should be 350 ppm, and the route to reach it should be the quickest possible. The magnitude of our failure and of the resulting damage is - and will be - proportional to the extent to which we move away from that target, and to the time taken to reach it.

The entire premise of Victor and Kennel hints at movement toward a successful outcome where in fact we are moving ever more away from the best outcome. Until we reverse our perspective on what needs to be acheived all that we will accomplish is talk, talk, talk... we will fiddle until Rome had burned to the ground...

5. I'm with Bernard J.

We've already blown past 350 and we should be able to point out to people that it really isn't that hard to get back to there. It would have been easier if we'd started 30 years ago when we should have got our act together, but it's still doable. We've just ensured a harder time for ourselves in what we'll have to put up with while getting there.

We could have done it easy. We now have to do it hard. But we can do it.

1. While 350ppm is doable it would take quite a few generations wouldn't it? Unless there was some engineering solution (or geo-engineering or maybe a bio-engineering fix).

On the same principle as sticking to 2 degrees, I'm all for it as a target. Something to aim for. Particularly if there is a staged plan to get there - with milestones and timelines.

2. Yup. Even if we started with something as crude as blasting huge holes in the ground or blowing the tops off mountains to get CO2-absorbent rock pulverised rather than to get to fossil rocks. I'm pretty sure we'll eventually get around to this sort of thing once we move to the panicking all-hands-on-deck stage. (Last estimate I saw was $25 billion to absorb one year's emissions by doing this. Though I wasn't all that thrilled with their proposed dispersal mechanism.) There's really no need for a WW2 style effort, but the current stupidity and continuing feebleness of our efforts means that we'll probably push ourselves to that point. Or maybe I'm wrong and people will actually recognise there's a real problem when they see Tuvalu and the Maldives going under the sea and the inhabitants begging for a place to live? A target in those terms might also be an incentive to work on some sophisticated targeted stuff, like rehabilitating seagrass beds and coral reefs (and mangrove forests and whale populations and all the rest of it) along with the more obvious stuff like encouraging permanent trees in agricultural fields as well as in restored forests. Though those measures will be targeted as much at soil retention as at GHG absorption. Coming up with measures that people can *see* as benefiting their local or regional environment will be a bit tricky but worth doing if we can. Milestones and timelines for a CO2 concentration measure will be hard to deal with if we don't have other indicators. Once we, one way or another, do that we'll have to contend with changes in the ocean response and a whole lot of other stuff I'd rather not think of too much. The one and only thing we have in our favour is that we are supposed, in Milankovitch terms, to be on a cooling trajectory so we might hope that in a couple of centuries/ 5 or 6 generations? - if we've gone gangbusters on absorbing some of the surplus GHGs as well as stopping emissions - we'll get a reasonable temperature result. Sea level's a different matter though. No way are we going to save all those river deltas, ports, sewage processing plants and luxury seaside resorts at current sea level. It's just a matter of when - and how many/ how much - rather than if they'll be inundated or unusable or unsellable. 6. Not going to save all those ports and resorts? Are you completely nuts? At what, 2mm per year or thereabouts we'll see something like 160 mm by 2100. 6 inches. Of mean sea level. You'll be needing a few tipping points to improve your odds of inundation I'm thinking. Sea level rise hasn't changed at all in recent times, it's just not an issue. Even twice that, 12 inches of mean sea level won't have ANY effect in most places. Pop down to your local beach, I guarantee you it looks much the same as it did in 1900. At my local beach, there is NOTHING different now to when I was there as a kid half a century ago. 1. Uh, I believe that's around 3.2 mm annually, and increasing (but you knew that). And my understanding is that the greater impacts are expected to be from storms and flooding, not from a daily increase of .01 mm. But thanks for the "eyeball analysis" of your local beach! 2. Por ejemplo: http://blog.hotwhopper.com/2013/05/anthony-watts-trick-is-to-disappear.html 3. Hi Billy Bob, were you yelling at me or the world in general? I feel your pain. Yes, the IPCC (conservatively) expects seas to rise between 1/2 m and 1 metre by 2100 if we don't curb CO2 emissions enough. In fact scientists say they could rise by as much as two metres over the next seventy to eighty years and won't stop at that point. It depends on how fast the ice sheets fall into the sea from Greenland and Antarctica. The WAIS collapse has already started and is considered by scientists who know about this stuff to be unstoppable. So seas will rise by around four metres over the next few centuries, and it could be sooner (within the next 300 years) or later (taking a bit longer than 300 yearsl). You know port authorities know this and are planning accordingly. Local councils on the coast know this and are planning accordingly. How is it that you don't know this? Don't you read the papers? I thought you were a regular here at HotWhopper. Are you one of those people who thinks that ice doesn't melt in the heat? Tell me. If you were hurtling toward a cliff would you keep on driving? Would you think in your own mind that the cliff would disappear before you fell over it? That physics would break just for you, because in your world, no harm could befall you therefore it won't? Is that what magical thinking does to a person? (And you almost managed to persuade us you could think. Never mind.) 7. I do believe I have seen some recent papers that posit less than 3mm slr. However even at 3 its hardly alarming. How many ports, resorts and so on have we lost in the past century? Cmon be real. Again, remind me how awful these effects have been at your local beach. 1. The old "it hasn't happened yet so it can't possibly happen in the future" syndrome. It's treatable, Billy Bob. If you had the information we do today, in the 1950s you'd have been arguing that global temperatures had only risen by about 0.2C above the 1891 to 1920 average so they couldn't possibly rise by another 0.7 degrees Celsius. You'd have been wrong, wouldn't you. Read the references I gave you above and think about it. They have lots more references in them for you to read, too. That should keep you busy for a few days :) 2. "At my local beach, there is NOTHING different now to when I was there as a kid half a century ago." Really? "NOTHING" in "half a century"? Art thou blest with hyperthymesia so that thee canst remember nearly all details of thine life in near perfect detail or dost thou have savant syndrome which hast given thee a brilliant memory? If so, thee shouldst become a consultant for thy local beach historical society. "NOTHING"? Didst thou take extensive measurements, adjusted for time of observation relative to tides, which thee recorded in thy diary/log? What didst thou take as the reference point for thy measurements? There is a great opportunity for thou to consult thy diary/log for the pH measurements that thee took half-a-century ago and compare them with the present. "NOTHING"? No longshore drift at thy childhood beach, nor beach erosion, nor …? Is thy childhood beach geologically static? Enough of this being holier than thou. I shalt cease and desist. Or, in case the long "s" or "f" was still in use half a century ago, I fhalt ceafe and defift. 3. Hi, it's me again. " Even twice that, 12 inches of mean sea level won't have ANY effect in most places.." My local beach is part of a beach system that is protected by barrier islands. But, tell you what I see at my local beach every king tide and the highest spring tides: I see seawater backing up stormwater drains, spilling out of grates in gutters and spreading out across roads, footpaths and lawns in low lying areas. I see our local council and the neighbouring council, having to put in street signs that can be unlocked to reveal a warning about "saltwater across the road". I see the local councils blocking off roads during these 'high tide events' and advertising this fact in advance in the local free newspapers. Going on the collective memories of long term locals who lived here in the last century, these events are more disruptive, if not more frequent. Tell you what I see at my local beach, every time high tide events coincide with low pressure systems moving down the coast: I see massive coastal erosion. I see people driving from inland suburbs to watch the waves break across the seawalls onto the footpaths and roads before spilling into gutters. (Which event occurs when pressure systems result in strong winds on top of 'normal high tides'.) I see the local council spending$30M to repair and protect 200 metres of beach out of 5 km. I see the local council building groynes to try to prevent beaches from being washed away.

Tell you what I see at my local beach:
I see optimists putting crabpots down stormwater drains because, during 'normal' high tides, the water level is now just below the grates which are 50 metres from the open ocean.
I see the local council buttressing and extending existing seawalls. I see the pocket beach where I live being put on the list to be buttressed with a seawall.

So, in answer to the "Again, remind me how awful these effects have been at your local beach.", it's just my opinion, but there's been an awful lot of local government work done to reduce or prevent those awful effects that you can't see at your local beach. That's if you do live near a beach because anyone who doesn't factor in the combined effects of winds, weather events and tides on top of rising sea levels is not a 'beach person'.

4. No change at beaches? I can assure you that there have been substantial changes at many of our local beaches, even though Adelaide does not face the open Southern Ocean - we're "safely" on the margins of the much calmer St Vincent's Gulf. Many beaches now display a narrow strip of sand, rather than a wide and welcoming expanse. Our beachside councils have been trucking sand from some areas to other denuded ones for decades now.

And it isn't the year by year creep that affects anyone. It's the once in 10, 20, 50, 100 year storms that wipe out jetties, scour away sand and/or sandhills and flood nearby homes and businesses. Seeing as many of our beachside suburbs are built on what used to be sandhills, and even more on what were once extensive reedbeds, there'll be some weeping and wailing and asset depreciation in too many people's futures.

8. Get a grip guys. Yes sea levels do appear to be rising and have been for quite some time. But there's precious little acceleration in recent times, in fact I think the strongest period of anything approaching 'acceleration' was about 50 years ago. Assuming around the 2-3mm/yr rate over the past century, we have around 200-300mm since 1900. Yes these are rubbery figures - I can't be bothered going off to get the exact numbers but I think it's close enough for the argument. Now, that's scarcely less than we can expect this century at current rates - rates I might add that have been largely stable for the past century.

Now, where's all these ports and luxury resorts and so on that have sunk into the sea? I'll tell you where they are - right where they've always been. Yes, the slow rise of sea level may have meant some issues in some places, but generally this has been dealt with. And yes, there will be places that will be affected more due to this slow rise in future, but that's hardly a surprise to anyone, and certainly not catastrophic. I think we can handle that.

George M, we are talking the sorts of effects that result in the catastrophes Sou outlined above. I am highly doubtful anything like that has happened where you live. Yes there is erosion which varies with the years, the weather and other local effects. But where I live, I am pretty sure that peak tides have the same impact they always did. I am not aware of a single house, business or building that has had to be removed or closed down due to these seasonal events. I am also pretty sure that the coastline is largely where it always was, give or take a metre of two due to erosion.

Adelady, Adelaide is subsiding as far as I know. That's not sea level rise you're facing there I'll wager. Find me an adjusted sea level record for Adelaide beaches - with land subsidence factored out. Have you been for a wander along say Henley Beach lately. What do you see there? Same buildings that have been there for the last 100 years or so? Yes you do. Well, except for all the new multi-million dollar mansions that have been built in the past 20 years...

George, what you describe is the normal ebb and flow of erosion and so on. The longer term trend might be for those to worsen if sea level continues to rise. And yes, that's something councils might have to factor in. But so far it's not that obvious - I suspect other factors at play in your case. I can't speak for your region - I haven't seen records of past events or beach impacts. How much is due to local conditions not related to sea level rise? Land reclamation, changes in water tables, drainage, river patterns, sea currents and so on? The exact things you describe used to happen at my local beach when I was a kid, and still do today. But no structure has been changed as a result as far as I can see.

As for surges and storms, Adelady, regardless of any sea level rise, the impact can only be worse when a storm surge arrives when local water level is higher than a previous historical norm. That is, if the range of tides are from 2-3.5 metres over the past 50 years and a surge arives with the tide at 2.5 metres, then the effect is not outside of a predictable range. Even if highest high water is now 3.6 metres. My guess is that more often than not a surge/storm will not occur when the tide height is outside the historical range. At least for the near to medium term, and probably even this century, I'll wager.

9. "Adelady, Adelaide is subsiding as far as I know. That's not sea level rise you're facing there I'll wager. Find me an adjusted sea level record for Adelaide beaches - with land subsidence factored out. Have you been for a wander along say Henley Beach lately. What do you see there?"

Not quite right. According to the Adelaide coast management plan *parts* of the beaches are subsiding. The average rate of net sea level rise for the whole area is 1-2 mm - which is pretty much what I'd expect seeing as we're protected from the open ocean.

I'd blinkin well hope that Henley was doing OK. I've been there quite a few times recently for lunches with family. It's north of the worst affected southern beaches Seacliff to Glenelg. Remember the natural drift of sand is from south to north and it's been exaggerated and intensified by the loss of substantial portions of the seagrass beds which used to stabilise sand to an appreciable extent. All seagrass meadows have now retreated further than 500 metres offshore. This at least means that any artificial reefs installed to manage sand movement won't cause them any damage - there's nothing left _to_ damage.

I've only looked, so far, at the first item on this pretty comprehensive list from the Dept of Environment http://www.environment.sa.gov.au/our-places/coasts/Adelaides_Living_Beaches/Resources .
There's a similar, but nowhere near as good, document from Onkaparinga Council about the further south beaches - Aldinga, Willunga, Christies and the rest. The one thing I wasn't aware of is that Brighton/Seacliff is now replenished from Mount Compass of all places. I hadn't realised that the sand pipeline from Stanvac was no longer operating at all.

10. Adelady, I apologise for not doing the research necessary to properly assess what you are saying. I wish I had the time to do it because SLR deeply interests me, simply because I wonder at exactly why I don't actually see it happening.

Sou's post made extravagant claims about loss of sea ports, resorts and so on. I observed that at most beaches I have been to, there is little evidence of major change related to SLR over the past century.

I make the same claims about Adelaide. You offer a net rise of 1-2mm (per year I assume) but don't tell me what the error margin is. But even at 2mm, we would see something like 200mm of sea level rise for the past century. How much has that 8 inches of SLR affected Adelaides coastline?

Bear in mind that even without ANY SLR, coastlines are dynamic and cannot be expected to remain static over long periods. Changes in weather patterns, currents, river drainage, etc etc will all have impacts. You talk of sand movements and changes in seagrasses, but don't explain the relationship to sea levels.

My point is that very little of deep significance has happened at Adelaide due primarily to SLR. What exactly has the last century of 8 inches of SLR done, beyond some impacts of erosion and sand deposition? And can you disentangle those impacts from the many related causes, even such as land reclamation etc?

Unless there are major changes in the next century, as Sou suggests, we are not going to see anything more dangerous by 2100 than we've already seen. You have not a shred of evidence for the claims of loss of seaside resorts, ports and so on.

And given that there is no sign of any significant acceleration in SLR over the past 50 years or so and that as yet, the models projections for surface temp increases have not been borne out, I'm not losing any sleep over catastrophic sea level rise. Perhaps, neither should you.

Go for a wander down Henley Beach, it's one of the nicest beaches in Asutralia. And remember, with or without AGW, it will not stay that way forever.

11. All we need now is for Spangled Drongo to appear.

Should he do so, redirect him to the last arse-whipping he received at Deltoid.

12. Attitudes vary around the world, the worst cases may well not be in Australia or the UK but planning ahead would be good! Here in the UK a few years ago there were some interesting approaches suggested - retreat? defend? or attack? http://www.buildingfutures.org.uk/projects/building-futures/facing-up, the full report can be downloaded & makes for thoughtful reading.

13. I wouldn't have called that an arse whipping Bernard. I think he did pretty well, and raised some quite substantial points that remain unresolved... What it did demonstrate is the utter unwillingness of people like you to deviate from company policy.

KatyD, there cannot be any 'worst' cases over the long term when it comes to sea level rise due to CO2. If sea level is rising due to AGW, it sort of has to rise everywhere. Localised SLR divergent from overall trend must be largely due to local phenomena. Planning would do well to consider those.

Instead of commenting as "Anonymous", please comment using "Name/URL" and your name, initials or pseudonym or whatever. You can leave the "URL" box blank. This isn't mandatory. You can also sign in using your Google ID, Wordpress ID etc as indicated. NOTE: Some Wordpress users are having trouble signing in. If that's you, try signing in using Name/URL or OpenID. Details here.