James: the C in CAGW is what ALL scientific scepticism is about..

Is that what all scientific sceptics believe or your personal position? I thought you were a 1-degree-er, believing in AGW but rejecting any idea of positive feedbacks. But if all you object to is the 'C', it sounds as if you would accept +ve feedback as well, but just not to the point that it does any serious harm: ocean pH might drop but no cause for panic; sea levels might rise but we've got the Thames Barrier so we're ok; etc. This seems contradictory, bearing in mind that, as Martin points out, +ve feedback systems are unstable.

I said I believed there are positive feedbacks, but I just believe they dampen out logarithmically, or that negative feedbacks compensate for them.

e.g. temperature goes up, water vapour goes up = more greenhouse gas, so you will get a bit more warming - this is a positive feedback - but a lot of it manifests as clouds, which have high albedo to incoming shortwave, so cool the climate by quite a way (more than the forcing caused by the vapour itself)

So if CO2 goes up
-> temperature rises
-> more water vapour in the air
-> temperature rises
BUT
-> vapour manifests as clouds
-> albedo goes up
-> solar insolation reduces
-> temperature reduces

I believe this will be proven (in time) to be the major dampening cycle of the atmosphere.

Even the Catastrophists believe the maximum positive feedbacks dampen out at 6-10 degrees, so all we're arguing is when the dampening happens. Since this is the most poorly understood part of climate physics, nobody really knows.

Until then I just "hope", based on the fact that if a rise from 200ppmv to 400ppmv of CO2 can trip a feedback runaway process, it would have done it by now. All it would take is a continent-wide forest fire, a couple of large volcanoes, meteor strike, etc. No such runaway has ever been seen.

I don't think anyone should be expected to conflate what everyone believes.

Personally - and I think TBYJ agreed - I think that an unstable system would have self-destructed millions of years ago. Since we are in a glacial era at the moment, we are even safer than usual re heating (not necessarily re cooling). In principle all CAGW sceptics must believe that NETT feedback is negative.

Many years ago I read that the Earth, having once had a largely CO2 atmosphere, would have succumbed to the "runaway greenhouse effect" like Venus if it had not been for H2O, which carries (latent) heat high into the atmosphere before condensing. That mechanism was reckoned to account for over 20% of the heat radiated awy by he Earth. Why do we never hear about changes to this huge contribution to cooling as increasing atmospheric temperature increases both the amount of H2O vapour and the heiht to which it can rise before condensation?

But the key point, whatever the mechanism, is that the climate is patently NOT unstable and is, in any case, in a safer glacial mode.

Comparisons with Venus are interesting (but dare I say a straw-man to attack). But does the climate need to behave as radically as that for change to be undesirable? I understand your points about the climate having been subject to intense natural abuse over the eons without flipping out completely. However, I think I am right in saying that the last 20,000 years have been unusually stable in earth history; there have been extreme variations going back in time. Such variations, if one believes them, might not have wiped out life, but they show that the system is not guaranteed to give us pleasant temperatures, whether we nudge it or not. It seems, from the historical record, that things can change rapidly. Since we don't know what causes these changes to any level of certainty, is it sensible to nudge it and just hope for a good outcome?

I understand the (serious) sceptical side a lot better now and cannot refute what you say. There might indeed be negative feedbacks that cancel the positive ones. It may well be that the positive feedbacks are not sufficient to whack us to Venus. Then again you might be wrong - there is no proof either way.

With this uncertainty, it seems sensible (to me) that we reduce emissions. The idea of a carbon tax is anathema to sceptics and yet the idea of throwing away 80% of the energy in fuel is uncontroversial. I fail to see a real difference.

Huh?
Petrol engine efficiency is are around 20% so we pay 5 times as much as we might for transportation fuel without complaint. Yet a tax that would encourage higher efficiency and/or alternative modes of transport is controversial. Go figure!

Talking about tax and efficiency at the end there was going off at rather a tangent from the discussion. Reading it, I look like a total whacko! It rather spoiled the post - sorry about that :-(

Let's just say that given the uncertainty, I think emissions reductions are the logical course of action. I also feel that such reductions can be positive to western economies.

Incidentally, I was just reading that Lindzen claims that CO2 levels have doubled since pre-industrial times and that we should have seen a rise of 3C in temperatures. How does that square with the 1C 'no-feedback' limit?

1) We can't "do a Venus" unless we get rid of all the water. Venus is a perfect comparison not a straw man.

2) The last 20,000 years have seen temperatures higher than the present - one reason the Hockey Stick team confined their temperature statement to 1,000 years (while citing CO2 levels on million-year-plus timescales) - a dead giveaway in my view. They have also seen temperatures much lower; but the glacial temperatures see-saw within a range - no tipping points.

3) Lindzen and CO2: like Gore, you imply that this is necessarily (unique) cause and (inevitable) effect. But we know from (2) that changes in temperature like this are absolutely typical of the last million plus years...

4) I nearly said "...and have not been catastrophic" but, of course, that would be absolutely false. Most of the last million years has seen (e.g.) most of Europe and North America under a kilometre (?) thick ice sheet. The really big temperature disasters are natural ones, and research on long-term climate change should be looking at mitigation and adaptation for the next deep glacial.

3)

Sorry -

3) If you cite Lindzen you need to include his actual point/argument - not, I think, the point you made.

On Venus: sorry, agreed it is a valid comparison (if debunking a runaway heating scenario). But I think my point stands - it doesn't have to get that bad to be a worry.

On glacial see-saws and no tipping points, what do you call a tipping point and how do you know there were none? I'm not being intentionally dense. If you define a tipping point such that beyond it, temperatures rise exponentially to infinity, then clearly there were none. If you define it, for example, such that the system switches from one mode of stability to another, then the accuracy of the proxies for the last 20k years becomes very important (and sceptics don't tend to believe proxies). And you could imagine other instabilities involving 'tipping points' beyond these two examples. Proving they don't happen seems a stretch too far.

On Lindzen and 3C: whoops, I misunderstood an out of context quote from him! How could I? It was late and it struck me as interesting. I should have turned on the brain before posting. Oh well....

On thermodynamics, I am aware of the limitations, but cars vary from SUVs that get 10-15mpg to super efficient designs that get 50-60mpg (number out of thin air, but I don't think they are significantly wrong). Guess which ones people like to buy in the US and other low-tax or subsidised-fuel country. In other words they don't care that they are throwing away the energy.

Is 30% really a limit for power stations? Surely not!

I had seen the Wiki articles but refrained from posting references (I got the impression Wiki is mistrusted by BHers in general, not just on climate related things). Those figures are typical, not best case. I know there are limits to efficiency but my guess is that most older power station designs did not care too much about lifetime energy costs, but rather about the build cost (in the same way that builders install heating systems without insulating them etc) . One might hope that this would no longer be true, but I am very doubtful - it all depends who pays for the fuel; the builder certainly doesn't.

Getting rid of all the hot water need not be impossible. I imagine there are many industrial processes that could use it if only the facilities were built with efficiency in mind. It needs planning and forethought, but it is clearly possible. CHP for domestic use is also possible (although hard to retrofit). I can see no reason, whatever ones position on AGW, why efficiency should not be a top priority.

What do you have against emission controls? Have you lived in a city without them? Are you asthmatic? Probably not or you might think differently. The Tesla is likely to give your Volvo and the T-bird a good run for their money and is far more efficient as well. Look at MacKay's analysis of electric cars - he finds they can be 5 times as efficient as fossil fuel cars.

Emissions controls are the wrong end of the horse. I have nothing against more efficiency in power use, who would? Who wants gases belching into the sky if we can avoid it? But the idea that you can simply turn off the power stations and somehow global civilization peacefully will settle into a new energy use equilibrium is nonsense. It is the stuff of civil wars and starvation.

No skeptic wants to burn fossil fuels (well, the tiny percentage who actually ARE big oil may disagree, but for the most part we all agree it's a road to nowhere). We all realise that fossil fuels have a definite end-point. But if we want to switch to different energy sources, we're going to need 50-100 years of development in true decentralised power generation over a range of technologies, coupled with real changes in society to cut down on the amount of travelling and cargoing.

Trying to replace massive centralised fossil power stations with massive centralised windmill farms is stupid and wrong. Energy generation needs to be localised.

Making people travel to their workplaces, and shipping good across the world is stupid and wrong.
Making people have to live their lives to a 9-5 Mon-Fri schedule is what causes energy peaks that less reliable cleaner energy sources inadequate.

These things need to change, these will stop us having to use fossil fuels. In the west, we could manage most of this now. But until we get the world to a similar technological state as we are, it's useless us doing it. We need to use the last x years of fossil fuels to do that.

A few flooded seafront properties and bands of farmland having to move 50km north, even if it happens - we can deal with it.

James, I wonder whether you are right: "who wants gasses belching into the sky if we can avoid it", sounds obvious, unless one considers those gasses to be harmless. Sceptics do not consider CO2 a pollutant - it is comparable to water vapour. So what reason would sceptics in general see for reducing it? Introducing emissions control legislation or even removing lead from petrol do not seem to be zero resistance paths. There are too many vested interests.

Local generation of energy sounds great but I don't know how practical it is in the UK. As you say, windmills are not the answer - the energy density is too low. But the other options don't look great either - I recommend SEWTHA by MacKay for some sense about sustainable energy. I'm inclined to favour small modular nuclear stations and fast reactors to burn up plutonium stocks. And Desertec.

Where does this idea of turning off the power stations and doing without come from? I've seen angry comments on these lines in BH, but they seem nonsensical. No politician is going to do that (Japan excepted of course where 50 nuclear stations have been taken offline. They seem to be coping without civil war).

Yes you are right Martin, if fossil fuels are used to generate the electricity. Quoting from SEWTHA/MacKay :

"You’ve shown that electric cars are more energy-efficient than fossil cars. But are they better if our objective is to reduce CO2 emissions, and the electricity is still generated by fossil power-stations?
This is quite an easy calculation to do. Assume the electric vehicle’s energy cost is 20 kWh(e) per 100 km. (I think 15 kWh(e) per 100 km is perfectly possible, but let’s play sceptical in this calculation.) If grid electricity has a carbon footprint of 500 g per kWh(e) then the effective emissions of this vehicle are 100 g CO2 per km, which is as good as the best fossil cars (figure 20.9). So I conclude that switching to electric cars is already a good idea, even before we green our electricity supply."

The Tesla is quoted as 15kWh(e) per 100km.

So why "emission control rubbish" Martin, or was that a little ill-considered phrase slipping in? (I suffer from that problem too ;-)

We're way off thread now, so let's wander a little further and maybe close the circle.

The country with the highest life expectancy is Japan, and that is a country highly dependent on urban living, motorised transport, etc. Compare them with the poorer African states where life expectancy is well less than half the Japanese (or Western European) figure. It's nothing to do with electric cars. More generally, compare life expectancy to wealth:

http://en.wikipedia.org/wiki/File:LifeExpectancy_GDPperCapita.png

The CAGW people think it's worth sacrificing economic growth to "mitigate" rather than "adapt" to a risk that is in any case highly overstated. IPCC is Health-and-Safety Bureaucracy writ large, and our pounds, euros and dollars are being frittered away to address - ineffectually (because CO2 cutbacks are having, and will have, negligible effect) - the imagined Storms of James Hansen's Grandchildren. Ultimately it is the life expectancy and standard of living of ALL our grandchildren, especially in the third world, which will be cut back.

It has often been pointed out that the greatest lifesaving drug of all time - aspirin - would never has passed the first health and safety check. The greatest driver of prosperity - the internal combustion engine - would have been another casualty.

Logico, we have been OT for three days now so why not continue :-) You're assuming that cutting CO2 and other emissions must necessarily reduce economic growth worldwide. Is this really so?

My guess is that solar PV will be at grid parity within 5 years, so for anywhere with sunshine and deserts, the game will be over for fossil generation anyway. Cheap, distributed, energy will be available to most of the world's people. Europe must concentrate on making North Africa prosperous enough to accept the use of its deserts as a power source for us and for them too. These are not things that will impoverish anyone. Neither will electrifying our transport and economy or improving efficiency all round.

Suggesting that western populations in general care very much whether the third world is in poverty is a stretch.

Bitbucket, within 10-20 years, our existing coal and gas power stations will come to the end of their life, and will be turned off. We are not building new ones to replace them. We are not building nuclear to replace them. We are building windmills to replace them.

When the brownouts come, expect riots.

"It's almost beside the point. We KNOW from spectral analysis of downward longwave radiation measured at night (so not solar) that the atmosphere is radiating back at measurable quantities - namely from H2O and CO2 because we can see that in the spectral bands. These are measurements, not models."

How are those measurements changing as CO2 increases? How is the satellite-measured total radiation from the earth changing as time goes on? It seems to me that there are ways of showing the changes in progress and that we aren't hearing much about the results. Maybe I am ill-informed, but I read a lot of climate blogs and don't see anything about real direct measurements, just models and proxies. Am I naive to expect to see such data?

Do power stations have a defined 'end of life' beyond which they cannot be operated? Seems unlikely to me. Nuclear ones, maybe, but even they are extended where it is deemed necessary/safe. Your doomsday scenario will be postponed.

Without massive investment to convert them, yes they do. We would need to be planning and starting to do it right now.