350 Parts Per Million

[SnowBear]

In the UK people are starting to feel the effects of farming land going over to bio-fuel production.

Yesterday in the news they spoke on how food prices have jumped in the last year, partly due to rises in fuel costs to transport it, bur also changes in farming practices abroad.

The increases have been driven by a number of supply problems in key producing countries, mainly caused by bad weather and the increase in the use of land to grow crops for biofuel.

Those costs have been fed through to meat and dairy products as farmers pay more to feed their livestock.

Source: http://news.bbc.co.uk/1/hi/business/7362676.stm

biffvernon

You're right, it's not that easy. The "runaway" greenhouse effect is more to do with positive feedback, things like less ice means less reflection means more warming mean less ice means..., rather than CO2/temp function, logarithmic or otherwise.

But what has been driven down our throuts all along is about specifically CO2 and how its causing global warming. Isn't it what has been plastered all over the news and from conferences time and again? If CO2 isn't the main cause in such a big quantity as being made out, and even as millenia states its actully less effective at higher concentrations, two conclusions must be drawn, a/ Inaccuracies in the calculations and/or misinterpretation of findings in the media b/ something else is causing the main bulk of climate change. Which means it is unfair to use CO2 and how we are causing climate change as an excuse for that climate change.

This is why there are so many alternative views and so many are questioning the CO2 theory. Things do not seem to add up when it is looked at closely.

Edited April 24, 2008 by SnowBear

[Devonian]

I don't necessarily believe the scientific consensus blindly, but here's another aspect altogether:

Why not advocate giving people a choice, take a chance of the economy collapsing under strict environmental regulations, or take a chance on losing the arctic ice and making polar bears work harder for lunch.

In other words, give people a vote. It's called democracy.

I would vote for prosperity -- the consequences of widespread poverty will be far worse than global warming, if it turns out to be (a) true and (.b.) our fault.

And the green movement may already be responsible for the first wave of global economic downturn, as farmers turn away from growing food to growing bio-fuels.

It is as people say a matter of urgency and choice, but what do we choose?

Surely this is what happens now - we both live in democracies don't we? People know about AGW but the prefer not to vote to do much about it, accordingly the sceptics have for the time being won, and quite likely for some time to come. Result, we are taking the risk, we put prosperity first and caution second. I'm a democrat, I have to live with that.

[millennia]

Now, is it the professional Earth System scientists who have got it wrong or what?

Like scientists never get it wrong, we don't constantly get bombarded with the latest findings that say we have to live a certian way or shorten our lives, only to be told 10 months later that we should do the exact opposite?

In the US it's now almost impossible to get funding to research climate change unless you are in the CO2 AGW camp. That $5 billion juggernaut is going to take some stopping (especially when you see that people have discovered they can make a lot of money on the back of the carbon trade) so it's only common sense that the general perception will still be in favour of the "consensus". That does not mean the consensus is right, which seems to be the hardest fact for people to have to grapple with. Every scientist on the the planet could get a theory wrong, and be proved so by a single scientist in the future. It's very unlikely, but not impossible - which is why we should always keep an open mind and STOP shutting down arguements with this consensus nonsense.

With regard to the IPCC version of feedback, it is so strong that in order to fit the model to CO2 levels seen in prehistory you would be looking at surface temps in excess of 80C in the time of the dinosaurs (2000ppm) and by the time you reached the Precambrian (5000ppm) you could melt lead! Before anybody even dares to mention Venus please note these facts:

Venus is closer to the Sun, has an atmosphere 90 times the density of Earth with 96% CO2. The clouds are composed of sulphuric acid, which although appear to reflect a lot of visible light are transparent in the infrared (appear black on an infrared photo). Therefore vast amounts of heat pour in and a good deal is then trapped as 96% CO2 at 90 atmospheres is about 300,000 times the warming potential of CO2 on Earth at present. VENUS COULD NEVER HAPPEN HERE, but the IPCC seem to indicate so with their models and therefore have to be wrong because they can't reproduce the observed past.

[jethro]

Though you modestly admit that you "Don't personally understand", you claim to "think about it logically", and make the assertion "we'd have boiled away into oblivion long ago".

Now, is it the professional Earth System scientists who have got it wrong or what?

Morning Biff, perhaps I didn't explain myself too well - tired after a long day, apologies.

What I do not understand is why some scientists and Hansen and the IPCC in particular, have made and steadfastly stuck to the decision that all feedback will be positive.

As Millenia (and others like Captain Bob) have pointed out, the accepted understanding of the CO2 mechanism, is that the first additions are the most important. If we add another 200ppm now (and I'm not suggesting we should) then it will have a negligible impact, compared to the first 50ppm. There's no dispute about this, it is an accepted fact, agreed upon by all scientists, from all sides.

To achieve the projected temperature increases along with the resulting consequences of sea level rises etc, then feedback needs to be positive. Take positive feedback out of the equation and no one, not even Hansen and the IPCC believe CO2 alone will increase temperatures a great deal further.

Thinking about it logically, it stands to reason that if feedback was always positive, then irrespective of our influence, the Earth would have got warmer and warmer and warmer over time. There have been periods in the past when temperatures have been higher than today, if feedback was all positive then we would be warmer still, there would have been no cold periods. Something must happen which cools or regulates the earth.

The fact that we don't know or understand all the details, shouldn't mean that we rush to impose the little bit we do know, as being the definitive answer. Data and new information is coming to light all the time, research is an on-going production line. When new information is discovered surely it makes sense to feed that info into our knowledge, adjust the models accordingly and see what comes out, not steadfastly stick to original ideas.

The IPCC report clearly says their understanding of some of the workings of the natural world is seriously inadequate, oceans, clouds to name but two. In order to make the models work, these areas have had to have assumptions made and the data fed into the system. It is this (based on assumptions) which leads to the projected high temperatures.

I can see why the assumption was made when it comes to warmer oceans, leading to greater evaporation, thus the creation of more heat trapping clouds, leading to more heat being retained, warming the oceans further. I'm not saying it was a fraudulent claim or a deliberate attempt to make a theory work, I'm just saying it was an assumed positive feedback which hasn't so far been replicated in the natural world. The opposite is happening.

Historically, empirical observation and evidence has always been used to test and validate/disprove a theory. I see no reason to change the way science works, has always worked. I could come up with the most outrageous ideas, but if they do not work in reality or bear no relationship to how things actually work in the real world, then my ideas should be thrown out or adjusted accordingly. Testing a theory applies to all areas of science, adjusting a theory to explain empirical evidence applies to all areas of science. Why should climatology be any different?

[Devonian]

OK, rewind for a minute regarding 350 because I need somebody to help me out here as my Physics degree appears to be failing me (along with the rest of my brain but that's another story).

From what I understand the function of CO2 concentration and temperature is logarithmic, which is widely stated and often cited as potential for "runaway" greenhouse effect - not that I am alledging any of you susbcribe to that theory . However going back over my atmospheric papers from when I was looking to be a meteorologist (before I realised there was more money in computers) the actual relationship is INVERSELY logarithmic - in other words the more CO2 you put into the atmosphere the less sensitivity the atmosphere has to it. On that basis the first 20ppm of CO2 in the atmosphere has more effect on temperature than the next 400ppm, and therefore an increase to 620ppm by 2150 - as espoused by some climate models - would have less forcing effect than the rise from 290ppm to today's current levels. If this is the case then the greenhouse effect is self regulating, which explains why levels of 2000ppm in the time of the dinosaurs didn't cook the planet. The fact that it was warmer would therefore be due to solar irradiance and different continent distribution. Certainly Pangaea must have been massively hot in its interior, several thousand km from any ocean - skewing the entire planetary average.

Humm, so it's just about CO₂? No, CO₂ is the main trigger, it matters, but it's not the whole story. So the warming due to CO₂ alone is only about a degree, but if that warming (as seems to be the case looking at the world) triggers other events that cause warming, and going by the past, it looks like the climate sensitivity to doubling CO₂ is about 3C - a figure not to be trifled with.

I've done a bit of a calculation on that basis - taking a rise from 380ppm to 420ppm by 2030 as a base the extra 40ppm would reduce emission from the Stratosphere to space by 0.4watts/m2. Converting this to temperature using Idso (1998) - 0.1C per watt/m2 - equates to a temperature rise of 0.04C. Even a rise to 620ppm would only add another 0.16C.

Why use Isdo? Has his work be backed up by others? Lets see those others then

Why is this wrong? This is based on the tested work of many scintists "Thus the RF for a doubling of CO2 is likely 3.7±0.4 W/m2 - the same order of magnitude as an increase of solar forcing by 2%.". Indeed, can Isdo be right given we've seen about .8C warming yet there is no credible evidence for a source for that warming other than anthropogenic effect?

Therefore on that basis, the basis of the INVERSELY logarithmic nature of CO2 concentration to temperature the entire AGW due to CO2 debate is hogwash. That just leaves AGW on land due to UHI, land use, etc - which seems to make sense.

An entire hypothesis tipped upside down because of a mathmatical error akin to the famous minus sign that caused an Apollo rocket to crash. Can't be that easy, can it?

I'll not clear a space on my mantlepiece for my Nobel just yet.....

I doubt you'll get a nobel if your work is based on one work (Isdo) that hasn't stood the test of critical examination - well as far as I know it hasn't.

[millennia]

Historically, empirical observation and evidence has always been used to test and validate/disprove a theory. I see no reason to change the way science works, has always worked. I could come up with the most outrageous ideas, but if they do not work in reality or bear no relationship to how things actually work in the real world, then my ideas should be thrown out or adjusted accordingly. Testing a theory applies to all areas of science, adjusting a theory to explain empirical evidence applies to all areas of science. Why should climatology be any different?

Because there's too much money at stake? Have we ever had a scientific debate of this magnitude with so many billion $ riding on it? This is why the debate has become unscientific, too many people on the gravy train (obviously not pointing any fingers on this forum, I mean research grants, carbon trading, etc.).

Sometimes the simplistic approach is closer to the mark than you might think. If you apply Beer's Law to observed values and extrapolate you could argue that by using real world observations you are already including background feedback, both positive and negative, as the resultant temperatures so far would have reacted to the CO2 concentration. Therefore even assuming CO2 is the driver of climate the logarithmic decay of Beer's law leads to a natural stability and it would be impossible to induce a temperature increase of more than 2C as we just couldn't produce that amount of CO2 and keep it in the atmosphere - I'm talking > 2000ppm here. Of course when you take the observation that CO2 reacts to temperature the dampening effect of Beer's Law becomes even more pronounced.

No, you cannot heat up the planet by anywhere near what the IPCC claim without extra heat input from the Sun, to suggest so is to suggest that the Earth's climate system is inherently unstable and likely to fly off to disaster with the slightest push - whereas the climate system is actually inherently stable and takes major influences like Sun output to make any meaningful change, and even then because of it's stability it just finds a new equilibrium.

Edited April 24, 2008 by millennia

[Devonian]

Morning Biff, perhaps I didn't explain myself too well - tired after a long day, apologies.

What I do not understand is why some scientists and Hansen and the IPCC in particular, have made and steadfastly stuck to the decision that all feedback will be positive.

As Millenia (and others like Captain Bob) have pointed out, the accepted understanding of the CO2 mechanism, is that the first additions are the most important. If we add another 200ppm now (and I'm not suggesting we should) then it will have a negligible impact, compared to the first 50ppm. There's no dispute about this, it is an accepted fact, agreed upon by all scientists, from all sides.

Is it, Jethro? Isn't the science clear that a doubling of CO₂ from ~270 to 580ppm will cause about 1C warming? I though most people (many of those being people well known for their scepticism about AGW as well) accept that doubling CO₂ alone has about a 1C warming effect? Just because the effect is logaritmic doesn't mean it's negligible does it?

To achieve the projected temperature increases along with the resulting consequences of sea level rises etc, then feedback needs to be positive. Take positive feedback out of the equation and no one, not even Hansen and the IPCC believe CO2 alone will increase temperatures a great deal further.

Thinking about it logically, it stands to reason that if feedback was always positive, then irrespective of our influence, the Earth would have got warmer and warmer and warmer over time. There have been periods in the past when temperatures have been higher than today, if feedback was all positive then we would be warmer still, there would have been no cold periods. Something must happen which cools or regulates the earth.

Yes, CO₂ concs fall. But that takes time, a lot of it. It takes a lot of time to sequestrate many GT of CO₂

The fact that we don't know or understand all the details, shouldn't mean that we rush to impose the little bit we do know, as being the definitive answer. Data and new information is coming to light all the time, research is an on-going production line. When new information is discovered surely it makes sense to feed that info into our knowledge, adjust the models accordingly and see what comes out, not steadfastly stick to original ideas.

Hang on Jethro, here you say 'we shouldn't rush to impose the little bit we do know as being the defintive answer', but the whole of your post is dismissing the work of Dr Hansen based on a few post here!

The IPCC report clearly says their understanding of some of the workings of the natural world is seriously inadequate, oceans, clouds to name but two. In order to make the models work, these areas have had to have assumptions made and the data fed into the system. It is this (based on assumptions) which leads to the projected high temperatures.

I can see why the assumption was made when it comes to warmer oceans, leading to greater evaporation, thus the creation of more heat trapping clouds, leading to more heat being retained, warming the oceans further. I'm not saying it was a fraudulent claim or a deliberate attempt to make a theory work, I'm just saying it was an assumed positive feedback which hasn't so far been replicated in the natural world. The opposite is happening.

Historically, empirical observation and evidence has always been used to test and validate/disprove a theory. I see no reason to change the way science works, has always worked. I could come up with the most outrageous ideas, but if they do not work in reality or bear no relationship to how things actually work in the real world, then my ideas should be thrown out or adjusted accordingly. Testing a theory applies to all areas of science, adjusting a theory to explain empirical evidence applies to all areas of science. Why should climatology be any different?

Well, you may know what the IPCC do, did, and fully understand it and know where they are going wrong. I don't.

How is it, with a few posts here you seem to think Millenia and CB know more and have proven Dr Hansen wrong. Isn't that a rather improbable idea?

Edited April 24, 2008 by Devonian

[Devonian]

Because there's too much money at stake? Have we ever had a scientific debate of this magnitude with so many billion $ riding on it? This is why the debate has become unscientific, too many people on the gravy train (obviously not pointing any fingers on this forum, I mean research grants, carbon trading, etc.).

Sometimes the simplistic approach is closer to the mark than you might think. If you apply Beer's Law to observed values and extrapolate you could argue that by using real world observations you are already including background feedback, both positive and negative, as the resultant temperatures so far would have reacted to the CO2 concentration. Therefore even assuming CO2 is the driver of climate the logarithmic decay of Beer's law leads to a natural stability and it would be impossible to induce a temperature increase of more than 2C as we just couldn't produce that amount of CO2 and keep it in the atmosphere - I'm talking > 2000ppm here. Of course when you take the observation that CO2 reacts to temperature the dampening effect of Beer's Law becomes even more pronounced.

No, you cannot heat up the planet by anywhere near what the IPCC claim without extra heat input from the Sun, to suggest so is to suggest that the Earth's climate system is inherently unstable and likely to fly off to disaster with the slightest push - whereas the climate system is actually inherently stable and takes major influences like Sun output to make any meaningful change, and even then because of it's stability it just finds a new equilibrium.

Why have so many climate scientists missed this but you spotted it in just a few minutes? I think it's highly unlikely you are right, but I'm a layman (who has only just looked up Mr Beer...) and I suggest you should have you views tested by someone more appropriate like a climate science proff at a uni or someone from the Met Office rather than those of us here none of which (as far as I know) are experts in this field? Come back when you have and let us know what they say will you?

Edited April 24, 2008 by Devonian

[jethro]

Is it, Jethro? Isn't the science clear that a doubling of CO₂ from ~270 to 580ppm will cause about 1C warming? I though most people (many of those being people well known for the scepticism about AGW as well) accept that doubling CO₂ alone has about a 1C warming effect? Just because the effect is logaritmic doesn't mean it's negligible does it?

Yes, CO₂ concs fall. But that takes time, a lot of it. It takes a lot of time to sequestrate many GT of CO₂

Hany on Jethro, here you say 'we shouldn't rush to impose the little bit we do know as being the defintive answer', but the whole of your post is dismissing the work of Dr Hansen based on a few post here!

Well, you may know what the IPCC do, did, and fully understand it and know where they are going wrong. I don't.

How is it, with a few posts here you seem to think Millenia and CB know more and have proven Dr Hansen wrong. Isn't that a rather improbable idea?

I've got to be quick, work beckons....

Doubling of CO2 - 1c will not cause the projected devastation, positive feedback, leading to greater increases in temps are required for that.

Do we need CO2 concentration to fall in order to experience cooling? That assumption is based on CO2 being THE deciding factor in climate, nothing in the literature from either side which validates that.

Dismissing Hansen? Based on a few posts here? Er no, questioning his theory on positive feedback based on hours of searching, reading reams of information (peer reviewed), looking at the historical record and seeing nothing which supports his theory. Not all feedback is positive, never as been.

Yes, I do understand the IPCC report, I've spent goodness knows how long reading and learning, in order to understand it; how else could I comment upon it? Don't like analogies but will make an exception here; pan of water on heat, as it warms it evaporates, put a lid on and it will boil quicker as the trapped steam creates further warming. Simple kitchen physics, which has been applied to the warming oceans, more evaporation creating clouds, trapping heat, creating further warming.

[millennia]

Why have so many climate scientists missed this but you spotted it in just a few minutes? I think it's highly unlikely you are right, but I'm a layman (who has only just looked up Mr Beer...) and I suggest you should have you views tested by someone more appropriate like a climate science proff at a uni or someone from the Met Office rather than those of us here none of which (as far as I know) are experts in this field? Come back when you have and let us know what they say will you?

Just spent 10 mins answering this and then the post stuffed and I lost it all

Ok, I had a strong interest in meteorology/climatolgy at Uni when doing physics and although not part of the syllabus a lot of my work with gases, energy, etc concentrated on this because I was interested. This is where I first met Mr Beer and have only recently become reaquainted when a poster on another forum cited the logarithmic effect of CO2 heat absorbtion as a reason why we were going to turn into Venus in 50 years in other words he got the graph upside down. I set him straight but he was such a dribbling GW disaster fanatic all I got back was abuse. Luckily weirdos like that are absent on these fora.

To me Beer's Law is a prime example of basic and agreed Physics showing the inherent stability of the climate on Earth as it must actually be, otherwise we'd have had a catastrophe a long time ago. Simple findings like this may explain 90% of the system, and then the climate scientists need to a board full of equations and many years experience to find the other 10% - it becomes exponentially harder to detertime the truth the closer you get to it. Probably why Gore has such an easy time as he's often nowhere near it.

Anyway this reads nowhere near as well as the last post I lost so I'm going to leave it there, but I have one question in return; if I did back up my statement with climate scientists how many would it take before they were not labelled as just on the payroll of oil companies?

[Devonian]

Ok, I had a strong interest in meteorology/climatolgy at Uni when doing physics and although not part of the syllabus a lot of my work with gases, energy, etc concentrated on this because I was interested. This is where I first met Mr Beer and have only recently become reaquainted when a poster on another forum cited the logarithmic effect of CO2 heat absorbtion as a reason why we were going to turn into Venus in 50 years in other words he got the graph upside down. I set him straight but he was such a dribbling GW disaster fanatic all I got back was abuse. Luckily weirdos like that are absent on these fora.

I think we will see warming in line with IPCC projections - around ~3C if CO₂ doubles. Is that 'runaway'? No. Indeed is Venus runaway warming? No, I don't think it is getting warmer. But, might that 3C warming here trigger other changes further on in time? I think there is some evidence that a lot of warming might well release clatherite CO₂, peat bog CO₂, rainforest CO₂ - and that might (might) cause more warming. For thinking that kind of thing people like me are labelled scaremongers and worse (you hint at the kind of things in your reply). I dislike that - name calling just for thinking around something, yuck.

To me Beer's Law is a prime example of basic and agreed Physics showing the inherent stability of the climate on Earth as it must actually be, otherwise we'd have had a catastrophe a long time ago. Simple findings like this may explain 90% of the system, and then the climate scientists need to a board full of equations and many years experience to find the other 10% - it becomes exponentially harder to detertime the truth the closer you get to it. Probably why Gore has such an easy time as he's often nowhere near it.

'Gore' - dead giveaway

But, it's also clear there have been ice ages, and events like the PETM - several degree events, either cold or warm. It's also the case some people, people who like you disagree AGW is significant, argue that the climate is unstable and changes all the time as a way of arguing away the warming (stick around you'll see examples) - from my perspective a inconsistent 'heads you lose, tails I win' kind of science.

Anyway this reads nowhere near as well as the last post I lost so I'm going to leave it there, but I have one question in return; if I did back up my statement with climate scientists how many would it take before they were not labelled as just on the payroll of oil companies?

I don't use that argument. I don't think it's valid. I do think many, most even, who don't think AGW is significant are genuine and aren't funded by big oil. otoh, people like me are ....

[Admiral_Bobski]

I think we will see warming in line with IPCC projections - around ~3C if CO₂ doubles. Is that 'runaway'? No. Indeed is Venus runaway warming? No, I don't think it is getting warmer. But, might that 3C warming here trigger other changes further on in time? I think there is some evidence that a lot of warming might well release clatherite CO₂, peat bog CO₂, rainforest CO₂ - and that might (might) cause more warming. For thinking that kind of thing people like me are labelled scaremongers and worse (you hint at the kind of things in your reply). I dislike that - name calling just for thinking around something, yuck.

I thought it was all agreed (by some) earlier on in this thread that a doubling of CO2 would lead to 1C of warming, not 3C. Or are you saying that the actual doubling of CO2 will cause 1C of warming and the rest will be effected by positive feedbacks? Is it runaway? Not if it ends there. But of course there is the problem of continuing CO2 increases, and therefore more warming, and therefore more positive feedbacks, and that is where the "runaway" issue comes into it - a lot of AGW proponents (not necessarily anyone on the boards, I hasten to add) seem to think that CO2 will continue to be emitted and that warming will continue ad infinitum. As for Venus, it has been speculated that it got the way it is by some sort of "runaway" greenhouse effect, but as far as I am aware that is entirely speculative.

But, it's also clear there have been ice ages, and events like the PETM - several degree events, either cold or warm. It's also the case some people, people who like you disagree AGW is significant, argue that the climate is unstable and changes all the time as a way of arguing away the warming (stick around you'll see examples) - from my perspective a inconsistent 'heads you lose, tails I win' kind of science.

Do the people you mention call climate "unstable", or would it be fairer to say that they call it "variable"? The AGW proponents' suggestion seems to be that there is an "ideal" temperature for the Earth with little margin for natural variation - effectively a static equilibrium. What skeptics such as myself say is that the Earth exists in a surprisingly variable state of dynamic equilibrium, which is not the same thing as saying that the climate is unstable.

CB

[Devonian]

I thought it was all agreed (by some) earlier on in this thread that a doubling of CO2 would lead to 1C of warming, not 3C. Or are you saying that the actual doubling of CO2 will cause 1C of warming and the rest will be effected by positive feedbacks?

Yup, ~3C as a result of CO₂ doubling (and we're still a long way from that).

....

Do the people you mention call climate "unstable", or would it be fairer to say that they call it "variable"? The AGW proponents' suggestion seems to be that there is an "ideal" temperature for the Earth with little margin for natural variation - effectively a static equilibrium. What skeptics such as myself say is that the Earth exists in a surprisingly variable state of dynamic equilibrium, which is not the same thing as saying that the climate is unstable.

CB

How could I think it's in a static equlibrium when I posted metioning the Ice Ages and the PETM - and which 'AGW proponents' deny either? I do think the climate is 'forcable' and acted upon by 'forcings'. I suspect we disagree as to which ones matter atm and whether is is sensible or not to keep CO₂ below 350 ppm.

Edited April 24, 2008 by Devonian

[VillagePlank]

Do the people you mention call climate "unstable", or would it be fairer to say that they call it "variable"? The AGW proponents' suggestion seems to be that there is an "ideal" temperature for the Earth with little margin for natural variation - effectively a static equilibrium. What skeptics such as myself say is that the Earth exists in a surprisingly variable state of dynamic equilibrium, which is not the same thing as saying that the climate is unstable.

It is unstable. The same way turbulence flowing down a river is.

[millennia]

But, it's also clear there have been ice ages, and events like the PETM - several degree events, either cold or warm. It's also the case some people, people who like you disagree AGW is significant, argue that the climate is unstable and changes all the time as a way of arguing away the warming (stick around you'll see examples) - from my perspective a inconsistent 'heads you lose, tails I win' kind of science.

Hmmm, so I actually have contrarian views to some non AGW types by thinking the climate is stable - just goes to show it's not a polarised arguement. To me an Ice Age is just a readjustment to a new equilibrium, which suggests stability not instability. Think of a plane, inherently unstable planes like Spitfires and Typhoons have to be constantly tweaked and adjusted to stay in the air - let go and you crash almost instantly. A stable aircraft correctly trimmed will stay pretty much at altitude and on couse when you're not even at the controls. From that I see the earth's climate as stable - it doesn't need tweaking.

I don't use that argument. I don't think it's valid. I do think many, most even, who don't think AGW is significant are genuine and aren't funded by big oil. otoh, people like me are ....

Good because there does seem to be a lot of contrary evidence to AGW published by climate scientists that is just dismissed this way, which makes you wonder how you can get the point across. Glad you are more open

[Admiral_Bobski]

Yup, ~3C as a result of CO₂ doubling (and we're still a long way from that).

Is that from CO2 doubling alone, or CO2 doubling plus feedbacks?

How could I think it's in a static equlibrium when I posted metioning the Ice Ages and the PETM - and which 'AGW proponents' deny either? I do think the climate is 'forcable' and acted upon by 'forcings'. I suspect we disagree as to which ones matter atm and whether is is sensible or not to keep CO₂ below 350 ppm.

Okay, perhaps I could have worded that better - I didn't mean an actual, rigid static equilibrium, but rather that the equilibrium we have is very delicately balanced, though still dynamic. If increasing CO2 by a bit is enough to cause catastrophic warming then the climatological equilibrium must be very finely balanced indeed, and as has been mentioned earlier (by my lover (apparently!) Jethro among others) if it was this finely balanced we would surely have seen a similar catastrophe in the past.

I'm not sure what your comment "and which 'AGW proponents' deny either?" is getting at. I don't think I mentioned any denial in my post. Perhaps you would care to clarify your point so that I might be able to defend mine.

As for forcings, they exist with or without mankind's influence and are therefore a part of the natural dynamic equilibrium. I'm going to have to go with millennia on this one (just to complete the menage a trois!) with regards to CO2 concentrations.

It is unstable. The same way turbulence flowing down a river is.

I suppose it depends upon how you define "unstable". Turbulence in a river doesn't, generally speaking, make the river explode. Perhaps it would be fairer to use the term "catastrophically unstable"?

CB

[Devonian]

Is that from CO2 doubling alone, or CO2 doubling plus feedbacks?

CB

Climate sensitivity - CO₂ plus feedbacks.

[jethro]

This seems rather pertinent to this discussion....

http://climatesci.org/2008/04/22/internal-...by-roy-spencer/

[Admiral_Bobski]

Climate sensitivity - CO₂ plus feedbacks.

Thanks for that Dev - I just wanted to clarify that so I can see where you stand. I don't agree with you, as you are probably aware (!), but a 3C warming from CO2+feedbacks is a lot more reasonable than a 3C warming from CO2 alone. Knowing where the goalposts are might help in determining whether or not those goalposts can be moved in the future (for either of us, that is)!

CB

[laserguy]

As for Venus, it has been speculated that it got the way it is by some sort of "runaway" greenhouse effect, but as far as I am aware that is entirely speculative.

Being about 30,000,000 miles closer to the sun helps,too .