Quote : i should say however, regardless of whether or not runaway warming will happen. I think it would be a good idea to ween ourselves off petrol/diesel fuels for any number of reasons. Check out MindCrimes "Iron, Fuel of the Futue" thread - amazing!

ive read through all of the iron for the future pages and im alittle worried about it! but thnak you saying what everyone else should be saying! Oil is running out and places hwere it is avialable are very unstable (and the same goes for gas aswell). People do forget about the other issues that global warming rises most of them just like to focus on the small picture and not actually look at the problems that are facing us! Yes i do agree that global warming is happening and everyone else i have my own opnion on what is causing it and what sort of evidence "experts" say!
One thing is certain about global warming and that is that it is scary all of the footage from flooding etc. And the only way you are going to get people to change their live styles on a massive scale is to scare them there is no other way. And in most cases its working!

Steve_M

quote:

The gist of it seems to be in Table 1 of the referenced Held and Soden paper.

Thanks Steve, I've read this paper and it really leaves me with thr following questions

1) Why is the Planck (I called it Boltzmann) forcing for radiation lower (by about 2.2 watts /m^2) Than the figure I calculated (5.42 watts/m^2)? My assumption was a T^4 relationship and given a radiation of 390 watts/M^2 before incrementing the temp by 1 deg C. The maths is Ok so either it's the T^4 or the 390 I guess.

2) Why isn't an increase in latent heat of evaporation effect shown in the analysis. If it's warmer there must be an increase in loss of latent heat of evaporation from the oceans and wet land? What is the increment due to 1 deg C rise since it makes a significant increase in the amount of water vapour in the atmosphere and I'd expect increase the amount of rain as well. If the article

http://oceanworld.tamu.edu/resources/oceanography-book/radiationbalance.htm

is to be believed there is about 78 watts/m^2 before any increment of temperature. I'd suggest it's reasonable to assume that all evaporation is driven above 0 deg C so at 16 deg C avg temp I'd expect 78/16= 4.9 watts /m^2 increase per deg C in this aspect of forcing, again a very significant amount given the numbers we're dealing with.

Son of Mulder

Re 1) I think (I'm not sure) that these are measured at different places - I've posed the question at realclimate - hopefully I'll get a less abrupt answer this time.

Certainly they do seem to assume a black body at the surface. I'm guessing that as radiative forcings are calculated at the top of the troposphere that it is the change in Planck radiation measured here (and the atmosphere is not a black body).

Re 2) For a given increase in temperature, increasing the amount of water vapour to a higher average value is a one-off change because any energy used to evaporate a water molecule is released within a few days when the water molecule condenses.

Steve, Thank for your continuing interest in the points I raise.

quote:

Re 2) For a given increase in temperature, increasing the amount of water vapour to a higher average value is a one-off change because any energy used to evaporate a water molecule is released within a few days when the water molecule condenses.

All my analysis to date is at the surface. So I'll wait for the response on 1.

Concerning the above (2) the latent heat is removed from the surface and released in the atmosphere where I believe 45% is radiated into space and the balance is radiated back to earth ie included in the radiation balance. But my point is that as at average 16 deg there is 78 watts/M^2 transported from the surface to the atmosphere as latent heat this will increase when the temperature rises so for the surface it acts as an extra negative forcing and I've estimated 1/16th of 78 because I know no better way of calculating the increment. So it's not one off amount as it's an extra part of the evaporation / precipitation cycle.

On a more general point - I'm afraid that the way these forcings and feedbacks get presented is asking for guys like me, with a lot of mathematical physics knowledge but little technical climate knowledge, to keep picking what seem to be holes like I'm doing here.

What would be helpful (to me at least) is the sort of Houghton diagram but showing all the forcing and feedback magnitudes at a series of equilibrium points

eg. baseline 1750 then say now vs 1750 with CO2 increased as it is and then say for 50 % and 100% extra CO2.

Then we'd see all the plusses and minuses on each chart including Boltzman and Latent heat etc and not have stuff hidden because it's a feedback not a forcing. It's precisely because the system is so full of feedbacks that anything other than this approach may be interpreted as trying to hide stuff from the mathematical punter like me.

Also a series of such charts for the surface, stratosphere and troposphere boundaries.

Then it would be clear what the predicted equilibrium energy balance would be at each boundary. Guys like me might then shut up or it may raise even more questions, but at least they're honest scientific questions devoid of all the politics and spin I've seen from both sides of the discussion.

quote:

On a more general point - I'm afraid that the way these forcings and feedbacks get presented is asking for guys like me, with a lot of mathematical physics knowledge but little technical climate knowledge, to keep picking what seem to be holes like I'm doing here.

I'm afraid I'm working from a similar position to you, so appreciate your testing questions to force me to improve my understanding. I think I need to digest the bottom half of the simple model description in the realclimate site, but am guessing that the Planck feedback is the difference in the "Outgoing Longwave Radiation" of 235W in the diagram in the page you posted. I'll be back in a day or so with an answer I hope!

oceanworld.tamu.edu/resources/oceanography-book/radiationbalance.htm

quote:

Originally posted by Steve_M:
No, I mean total CO2 (including anthropogenic) - preindustrial levels were 280ppm. They are now 380ppm and rising at about 2ppm per year.

This is what bothers me: PPM--Parts Per Million. Yes, even small ppm counts can be significant in chemical reactions and many other situations(highly toxic poisons come to mind) but I do not believe that a few hundred ppm of CO2 is significant at all. It does not appear that CO2 alone, in the amounts measured, can have significant greenhouse effects. That a few molecules per million are causing a few degrees warming per 100 years is, to my pea-brained intellect, perposterous.
Anecdotal evidence on colder-than-average winters or hotter-than-average summers is, of course, meaningless. The combined ice coverage of both poles may be a better thermometer than all air and sea temperature reading methods combined. Even if the ice from both poles is diminishing, we needn't be so quick to point the finger at CO2 without ruling out other mechanisms, the Sun, cosmic rays, or whatever. We are, after all, coming out of an ice age.
This is my story and, for now, I'm sticking to it. I am persuaded by "the science" when all shadows of doubt are removed but, to my reckoning, the shadows are still quite dark.

phlipper, maybe this will help.

quote:

This is what bothers me: PPM--Parts Per Million.

Think of it like this. You are standing under a 1 meter square glass window (1 million square millimeters) and the sun is shining down on that window from directly above. Now imagine that the atmosphere contains 280 parts per million (each particle is 1 sq millimeter)of a black powder so in the layer of atmosphere touching the window above it is 280 sq millimeters that are black and cutting out light. Then immediately above that level there is another layer containing 280 particles of black powder covering another 280 sq millimeters. Now the atmosphere is more than 1 kilometer (1 million millimeters) thick so there is a pile of black powder of at least 280 million particles directly above the window.

I reckon that will cut out quite a lot of the sun's light.

A similar analogy can be applied to CO2 and how it such a small amount can keep heat in.

quote:

Originally posted by Son of Mulder:
phlipper, maybe this will help.

quote:

This is what bothers me: PPM--Parts Per Million.

Think of it like this. You are standing under a 1 meter square glass window (1 million square millimeters) and the sun is shining down on that window from directly above. Now imagine that the atmosphere contains 280 parts per million (each particle is 1 sq millimeter)of a black powder so in the layer of atmosphere touching the window above it is 280 sq millimeters that are black and cutting out light. Then immediately above that level there is another layer containing 280 particles of black powder covering another 280 sq millimeters. Now the atmosphere is more than 1 kilometer (1 million millimeters) thick so there is a pile of black powder of at least 280 million particles directly above the window.

I reckon that will cut out quite a lot of the sun's light.

A similar analogy can be applied to CO2 and how it such a small amount can keep heat in.

Sorry to but-in Son of Mulder, but that analogy is very helpful to me too. But can you just explain if the particles would actually be an opaque black or something more translucent to equate with a CO2 particle's properties of keeping in heat?

And, if the pre-industrial (and post-mini ice age) level of 280PPM is held to be an ideal by climate scientists, would your analogy not be more accurate if it added only 100 sq millimetre particles to a 1,000,000 sq millimetre area?

My point being that if the glass is already necessarily (and beneficially) imperfect in its overall transparency and if an added CO2 particle only impedes - rather than blocks - the exit of heat, then the effect of the 100 additional particles would be negligible.

If so, the analogy might be more accurate - and understandable - if it indicates that the increase of CO2 in the past 250 years is equivalent to sticking a sheet of tracing-paper slightly larger than A4 onto a 1 KILOMETRE sq window of frosted glass - and the area of that tracing-paper which is actually 'man-made' amounts to something like the size of a postage stamp?

Roger58

quote:

If so, the analogy might be more accurate - and understandable - if it indicates that the increase of CO2 in the past 250 years is equivalent to sticking a sheet of tracing-paper slightly larger than A4 onto a 1 KILOMETRE sq window of frosted glass - and the area of that tracing-paper which is actually 'man-made' amounts to something like the size of a postage stamp?

No you're adding to the another column of atmosphere not just the surface and the relationship is such that double CO2 and you double it's direct effect ie logarithmic (so growth in direct effect diminishes for each fixed amount you add (but it still grows). This is an experiment that can be done in the lab and was first carried out in the 1890's.

My analogy was intended to show how 280 parts per million in a situation similar to the atmosphere could be extremely significant. Now I agree that physics of CO2 is different to the black powder analogy. Yes CO2 is far less efficient at stopping escaping Infrared but even so it has a quantifiable effect at 280 parts per million (the planet in 1760 was much warmer than it would have been without any CO2) and if we double the CO2 it will increase double the effect of CO2. By itself CO2 will cause some extra heating but the major issue concerns the feedbacks that potentially add to heating and allegedly overpower the negative feedbacks, the main one being water vapour, which has a far more powerful greenhouse effect (but also creates sunlight blocking clouds and takes latent heat of evaporation from the surface).

This scientific discussion is about at what temperatures an equilibrium occurs between extra quantities of CO2 and the other forcings and feedbacks and what might trigger a runaway heating.

quote:

Originally posted by Son of Mulder:
My analogy was intended to show how 280 parts per million in a situation similar to the atmosphere could be extremely significant. Now I agree that physics of CO2 is different to the black powder analogy. Yes CO2 is far less efficient at stopping escaping Infrared but even so it has a quantifiable effect at 280 parts per million (the planet in 1760 was much warmer than it would have been without any CO2) and if we double the CO2 it will increase double the effect of CO2. By itself CO2 will cause some extra heating but the major issue concerns the feedbacks that potentially add to heating and allegedly overpower the negative feedbacks, the main one being water vapour, which has a far more powerful greenhouse effect (but also creates sunlight blocking clouds and takes latent heat of evaporation from the surface).

Son of Mulder - thanks for your reply. I understand my mistake in trying to understand the analogy. I kept the area horizontal and must also include a vertical distance - making the glass a 1 km cube rather than a square.

But I still need to know what an 'ideal' CO2 level is. I understood that the atmosphere needs a quantity of PPM to sustain life (as we know it, Kirk), and it appears to me that the climate scientists are using the pre-industrail quantity of 280 PPM as the optimum and as the desired (but likely unachievable) goal of CO2 reduction. To my knowledge, this pre-industrial quantity is viewed by the scientists as purely un-man-made.

That is, if someone invented an enormous machine to suck in air and filter out CO2 - at what point would its job be done? I am basing my question on an understanding that CO2 influences all other atmospheric components as it seems the gist of the argument is 'get the CO2 level 'right' and all other levels will naturally adjust to be right as a consequence'.

Roger
Re: the ideal amount of CO2. This is a question that is not simple to answer, as there is a feedback where temperature increases decrease solubility of CO2 in the upper oceans. This is (probably) the reason for the trends in the ice core data that show temperature changes leading CO2 changes.
Assuming the ice core values are reasonably accurate (plus/minus a bit of data smoothing inherent in the sampling method; any discussion re the reliability of ice core CO2 measurement is for elsewhere), glacial periods generally have CO2 values around or a bit below 200ppm, recent interglacials around 280-300 and the mid Holocene a little higher, perhaps a bit lower than today's measured concentrations. As an absolute lower bound, photosynthesis shuts off at about 80-90ppm CO2.

Obviously, if we were to geo-engineer a solution (assuming that CO2 is a significant climate driver), we wouldn't want to push back to ice age or even LIA conditions (i.e the 280ppm pre-industrial values). More likely would be to aim to get back to and maintain the pre-WW2 values of around 310ppm, which is probably the 'natural' level for a comfortable climate.

Roger58

quote:

But I still need to know what an 'ideal' CO2 level is. I understood that the atmosphere needs a quantity of PPM to sustain life (as we know it, Kirk), and it appears to me that the climate scientists are using the pre-industrail quantity of 280 PPM as the optimum and as the desired (but likely unachievable) goal of CO2 reduction. To my knowledge, this pre-industrial quantity is viewed by the scientists as purely un-man-made.

That is, if someone invented an enormous machine to suck in air and filter out CO2 - at what point would its job be done? I am basing my question on an understanding that CO2 influences all other atmospheric components as it seems the gist of the argument is 'get the CO2 level 'right' and all other levels will naturally adjust to be right as a consequence'.

I take a different approach. I think it's fair to argue that pre 1750 CO2 levels were not manmade. I don't think it's the right concept to set the pre 1750 levels as an optimum or desired goal. It should be what is the range of CO2 levels within which the human race can continue to generate the greatest good for humanity. See http://en.wikipedia.org/wiki/Utilitarianism

for what I mean.

Climate is part of the equation because if every where became a desert (that wasn't flooded) it would be pretty tough and if everywhere became an Ice sheet similarly (obviously extremes but I think there is quite a large, comfortable space between).

Energy is part of the equation see the attached chart which puts much of the energy usage talk into perspective.

http://www3.sympatico.ca/drrennie/spike.html

If there's not enough energy no amount of low energy light bulbs will help the earth's massive population and it'll get tough that way.

We're stuck with our production of CO2 for many years and scientists have suggested that 560 ppm of CO2 should be our target to enable a migration from fossil to other energy sources.

So I'd suggest 280-560 ppm as the window.

quote:

Originally posted by Son of Mulder:
We're stuck with our production of CO2 for many years and scientists have suggested that 560 ppm of CO2 should be our target to enable a migration from fossil to other energy sources.

Son of Mulder - I don't understand this comment. Can you expend on it?

quote:

So I'd suggest 280-560 ppm as the window.

If this is "the range of CO2 levels within which the human race can continue to generate the greatest good for humanity" would it be acceptable to choose 420ppm as being the average optimum, if a single figure is insisted upon - with allowance for some safe movement in either direction from this figure?

I'd like to leave out - for the time being - any contributing factors to a level, such as human energy generation.

Sorry if I'm being thick, but Dr Ian B suggested 310ppm as the 'natural' level for a comfortable climate.

quote:

Originally posted by Roger58:
Can you expend on it?

Whoops, it would probably be better (and less messy) if you expand upon it.

Roger58 - expend or expand I know what you mean.

quote:

Son of Mulder - I don't understand this comment. Can you expend on it?

This presentation explains where I'm coming from on this.

http://www.princeton.edu/~cmi/research/Integration/Presentations/Socolow.pdf

quote:

If this is "the range of CO2 levels within which the human race can continue to generate the greatest good for humanity" would it be acceptable to choose 420ppm as being the average optimum, if a single figure is insisted upon - with allowance for some safe movement in either direction from this figure?

I disagree - if the objective is to turn around the use of fossil fuels then we need a realistic achievable and safe target, not one we'll change when the going gets tough. Because of the enormity of the task we should give ourselves as much space as possible.

quote:

Originally posted by Roger58:
Sorry to but-in Son of Mulder, but that analogy is very helpful to me too. But can you just explain if the particles would actually be an opaque black or something more translucent to equate with a CO2 particle's properties of keeping in heat?

And, if the pre-industrial (and post-mini ice age) level of 280PPM is held to be an ideal by climate scientists, would your analogy not be more accurate if it added only 100 sq millimetre particles to a 1,000,000 sq millimetre area?

My point being that if the glass is already necessarily (and beneficially) imperfect in its overall transparency and if an added CO2 particle only impedes - rather than blocks - the exit of heat, then the effect of the 100 additional particles would be negligible.

If so, the analogy might be more accurate - and understandable - if it indicates that the increase of CO2 in the past 250 years is equivalent to sticking a sheet of tracing-paper slightly larger than A4 onto a 1 KILOMETRE sq window of frosted glass - and the area of that tracing-paper which is actually 'man-made' amounts to something like the size of a postage stamp?

There are 1,000,000 sq m in a sq km, so 280 ppm is equivalent to 280 sq m, and the increase in the past 250 years equates to another 100 sq m. This is a little more than your A4 and postage stamp! Or did I miss your point about the tracing paper?

Son of Mulder,

This kept me awake last night! I think I have a basic understanding now.

The energy balance analysis in the Held and Soden paper is related to energy balance at the top of the troposphere. If we look at the diagram in the link you posted:

oceanworld.tamu.edu/resources/oceanography-book/radiationbalance.htm

Longwave emissions from the atmosphere into space are 195W/m^2 (I'm not sure why it is split into 165 and 30. I don't think the 40 figure counts as radiation from the atmosphere as it passes directly through the atmosphere from the ground).

An emission of 195 from the atmosphere translates to a nominal temperature of the atmosphere of 258K using the formula in the realclimate simple model (lambda times sigma times T^4). Using this formula, the difference between 258 and 259 (assuming the whole atmosphere also warms 1K) is 3W/m^2 - so it is lower than your number partly because the upper atmosphere is colder, and partly because of this lambda factor (emissivity) which appears to be .769 for the atmosphere but .95-1.0 for the earth's surface.

Your questions are about radiation balance at the surface, and what happens to the increase in 5.5W/m^2 that occurs when the surface temperature rises 1C. In the following discussion, it doesn't matter very much what causes the 1C rise (greenhouse gases, solar, or whatever) it just assumes that for some reason, the surface has warmed 1C.

If we look again at the diagram in the link you posted, most of the figures on the right-hand third of the diagram will increase by 5.5/390, or 1.4% following the 1C rise. Only 10% of surface emissions go straight into space, so this amounts to 0.5W of the additional 5.5W radiation.

The remaining LW warms the atmosphere as does the increase in thermals and evapotranspiration. The warming of the atmosphere increases the amount of radiation emitted by the atmosphere, of which more than half goes back to earth (the back radiation) and the remaining radiation goes into space. The 3.2W/m^2 Planck figures appearing in the Held and Soden paper relate to the increase in that latter figure plus the extra .5W that gets through the atmosphere from the ground (the outgoing longwave radiation).

Specifically regarding the evapotranspiration, now I think I understand what you are saying. Is this reflected in the lapse rate negative feedback mentioned in the Held and Soden paper. From realclimate:

quote:

All models suggest that the troposphere warms more than the surface... This amplified warming of the troposphere represents a key negative feedback in models because it further increases the thermal emission of energy to space.

Steve,

Thanks for the analysis, sorry it kept you awake. Now if we look at the surface and the balance there

Before 1 deg increase

168W absorbed by surface +
24W thermals-
78W evaporation -
390W surface radiation -
324W back radiation +

Net = 0W

After 1deg rise

168-x?W absorbed by surface + reduced by extra clouds???
24+ y? W thermals- warmer surface would increase thermals?
78+(78/16)?W evaporation - warmer so more evaporation
390+5.4W surface radiation - Boltzmann
324 +z?W back radiation + since warmer atmosphere

Net =???

Can you find x, y, z and the additional evaporation figure.

Son of Mulder

quote:

After 1deg rise

168-x?W absorbed by surface + reduced by extra clouds???
24+ y? W thermals- warmer surface would increase thermals?
78+(78/16)?W evaporation - warmer so more evaporation
390+5.4W surface radiation - Boltzmann
324 +z?W back radiation + since warmer atmosphere

Net =???

Read a couple more papers referenced by the Held and Soden one. But I think I'm going to ask one of my climate scientist mates about the y value.

x is a funny one. I had understood that cloud feedbacks are believed to produce more warming and this turns out to be correct. However, there are two components to this effect. Cloud amount influences how much sunlight is reflected away from earth. In some models this goes up with warming and in others it goes down with warming (so x can be positive or negative). However, the models in which extra clouds reflect more sunlight also show a stronger greenhouse effect from the extra clouds. And the net effect is that in all models, cloud effects are expected to increase warming.

z then depends on the amount of warming of the atmosphere, so less clouds suggests less atmospheric warming and thus less back radiation. More clouds suggest the opposite. Ditto for thermals and evapotranspiration.

quote:

Originally posted by Son of Mulder:
phlipper, maybe this will help.

quote:

This is what bothers me: PPM--Parts Per Million.

Think of it like this. You are standing under a 1 meter square glass window (1 million square millimeters) and the sun is shining down on that window from directly above. Now imagine that the atmosphere contains 280 parts per million (each particle is 1 sq millimeter)of a black powder so in the layer of atmosphere touching the window above it is 280 sq millimeters that are black and cutting out light. Then immediately above that level there is another layer containing 280 particles of black powder covering another 280 sq millimeters. Now the atmosphere is more than 1 kilometer (1 million millimeters) thick so there is a pile of black powder of at least 280 million particles directly above the window.

I reckon that will cut out quite a lot of the sun's light.

A similar analogy can be applied to CO2 and how it such a small amount can keep heat in.

Not a good example at all. By this reasoning, sunlight would be totally blocked. In reality, the tiny bit of CO2 in the atmosphere absorbs IR and emits IR radiation. This results in a virtual reflection back into space and some absorbtion(warming) in the air, sea, and ground. We can say that CO2 and other greenhouse gasses cause the IR to stick around a little longer than they would if they were not present in the atmosphere. Still, CO2 is only a tiny part of the atmosphere. Water vapor, a GHG that is by a few orders of magnitude more prevalant, should be the larger concern of any discussion or model.