Nova’s Analogy

Nova’s Rerouting Analogy.

Jo Nova’s “pipes and dams” analogy fails in its purpose and highlights the flaws in this rerouting thinking.

http://joannenova.com.au/2015/10/new-science-11-an-alternative-modeling-strategy/

Nova’s Analogy.

Nova doesn’t understand her analogy.

An analogy is used without the realisation that an analogy cannot be expected to account for all the features that it is supposed to represent.

The obvious.

When greenhouse gases are added to the atmosphere it doesn’t stop radiation escaping to space when equilibrium is reached. If it did the Earth would not stop getting hotter and hotter. Conventional thinking with vast amounts of research and evidence are dismissed by this rerouting proposal.

The myth presented by the rerouting idea is based on the simplistic thinking that if the energy is just eventually all radiated to space by whatever means then the surface can’t get warmer. It also then assumes that if water vapour plays a part in this then it must be a negative feedback. This confuses the part that water vapour plays in the Planck response with the positive feedback due to water vapour.

The Explanation.

When equilibrium is reached in her very large “bath tub” the outgoing flow will still equal the ingoing flow. This is still true even as the pipes are partially blocked. David Archer I recall made some very good analogies using bath tubs for educational purposes. David Archer was well aware of how the analogy worked and its limitations.

It should have been obvious to Nova that if the level in the reservoir did not rise then the flow to the other pipes would not increase. As Nova herself should have realised... how would the other pipes know or even “think” that ....unless the reservoir level rose and added extra pressure to make these other flows increase?

This of course IS the Planck response. It is sometimes referred to as a negative feedback but what it really means is that the Earth’s surface and atmosphere heats up to a new level increasing the outgoing long wave radiation to what is was prior to the addition of the extra greenhouse gases.

When greenhouse gases are added to the atmosphere the initial outgoing LW radiation is reduced. The Earth responds by getting warmer until the outgoing radiation at the top of the atmosphere again is in balance with the incoming solar energy. The bath tub level raises until the total outgoing flows equal the incoming flows to the reservoir.

The analogy is limited.

The greenhouse effect works by greenhouse gases absorbing and emitting longwave radiation. When more GHG are added to the atmosphere more back radiation heats the surface which in turn increases the outgoing LW radiation and eventually (at equilibrium) the outgoing radiation will equal that of the incoming radiation.

Since CO2 raises the temperature of the atmosphere then the amount of water vapour will increase making the greenhouse effect larger. Thus water vapour will increase the amount of radiation to space but also the radiation back to the surface. This is a positive feedback and not a negative feedback.

Genuine research.

This rerouting  proposal  reminds me of a genuine scientific investigation by Lacis et al using GCM’s whereby different gases could be added to the atmosphere or removed from the atmosphere and the effects observed.

http://pubs.giss.nasa.gov/docs/2013/2013_Lacis_etal_1.pdf

By comparing the top of the atmosphere outgoing radiation with the surface radiation, a global average greenhouse effect, GHE, is experimentally observed on Earth to be about 152W/m². This can be verified using the GCM’s whereby all GHG are removed as seen in the short term. (Greater surface cooling is observed if these GHG are removed over longer terms because the ice albedo positive feedback kicks in). If CO2 is singly added to the GHG depleted atmosphere it creates about 40W/m2 immediately to the GHE. This value is larger than its contribution today because it overlaps with wavelengths that would be absorbed by water vapour, WV, mainly but also by other GHG. This overlap can be quantified by another experiment. If CO2 alone is removed from an otherwise complete GHG compliment then it reduces the GHE by 24W/m2. In this case the other GHG’s absorb wavelengths that would be absorbed by CO2. Lacis et al calculate a normalised GHE due to CO2 in our present atmosphere of 31W/m2 or about 20% of the GHE. Similarly it can be shown that WV contributes about 75% of the GHE. However, importantly, they also look at the response of a WV only depleted atmosphere and notice that within days the WV is returned due mainly to the influence on temperature from the presence of the other GHG’s and in particular CO2. (In fact they estimate that about 80% of the WV is returned due to GHG from similar experiments by finding out how much WV would exist without any of the other non-condensing GHG). This of course is a measure of the WV feedback.

Nova has crudely attempted to look at these overlaps, ignore the positive WV feedback and instead has confused the role of water vapour’s contribution to the Planck response as a negative feedback.

Rehashed Myths

David Evans and his rerouting negative feedback.

The climate contrarian longingly awaits for a new theory for climate change. The greenhouse effect has been rejected at every level from denying CO2 concentrations are growing because of human emissions, to denying there is a greenhouse effect, or accepting that there is a GHE but it is very small. The contrarian will happily believe all of these. Evans claims yes there is a greenhouse effect but it is very small and is preparing for his ultimate blog to falsely claim the climate sensitivity to doubling CO2 is less than 1C and when you include feedbacks it will be even smaller. This will be readily accepted by the gullible. His analogy he presents is flawed however and would in fact lead to the opposite...... ..runaway temperatures.

How is Evans going to do this?

He has prepared ground by inventing new terminology for the Planck feedback effect. He will be able to simplify this and then count it twice to introduce extra negative feedbacks.

A strategy that he uses is to say some fact, that he realizes the typical climate contrarian may be unaware of, and pretend it is something new. First, however, let us look at the Planck effect.

The Planck feedback effect.

When greenhouse gases are increased energy radiated to space via longwave radiation,LWR, is reduced for certain wavelengths. The temperature at the surface increases and radiation to space from other wavelengths are increased from the surface and gases in the atmosphere. (You can see the effect of a distorted frequency spectrum of LWR to space as viewed from satellites). Eventually equilibrium is achieved whereby the radiation coming into the atmosphere and leaving the atmosphere are once again balanced. On average this will mean that radiation to space occurs at a higher altitude. The only way equilibrium can be achieved is by higher temperatures being reached. The Planck effect stops further increases in temperature. It must exist otherwise temperatures would runaway and we would “cook”.

Now if this information is given to the typical contrarian it will be rejected. But if Evans pretends he has found something new, when he says radiation is rerouted, it will be readily accepted in the belief that a new negative feedback has been found.

http://joannenova.com.au/2015/10/new-science-7-rerouting-feedback-in-climate-models/

I expect we will see Evans making further use of this to achieve his unrealistic lower climate sensitivity in future blogs that is not only contrary to climate models but also paleoclimate evidence.

Evans will effectively use the Planck effect via the Stefan-Boltzmann equation and use it AGAIN when he introduces this as a negative feedback on top of this Planck feedback effect. He will count the same effect twice just under different names.

His electrical analogy using currents and resistors  however is fatally flawed.

According to this analogy if one of the “pipe” lines is blocked the current (outgoing heat) would be reduced and never reach equilibrium (meaning reach its previous value). The outgoing long wave radiation would be less than the previous outgoing LWR that was equal to the incoming solar radiation. We would cook. This is regardless of any other parallel resistors and should be obvious to those with a basic understanding of elementary “resistors in parallel” theory.

Again nothing new.

Not realizing his rerouting idea is just a flawed look at the Planck response he considers this in his next blog.

http://joannenova.com.au/2015/10/new-science-8-applying-the-stefan-boltzmann-law-to-earth/

“There is no single layer that radiates to space, instead emissions come from many different heights, depending on the wavelength. We could average the emissions into “one layer”, but doing that would lose detail that matters when computing sensitivity to increasing CO2.”

This is another example of pretending to say something new. However ironically, yet again, it is Evans who fails to take account of this and not the climate models.

After a rather trivial point including the emissivity of the Earth to LWR to be slightly less than 1 he decides to talk about an effective radiating temperature and a real Earth.

“While the numerical difference between T_R and T_e is insignificant, here we are concerned with OLR from the real Earth so it is more natural to use radiating temperature (and technically incorrect to use T_e, at least conceptually).”

Yet again it is Evans who fails to deal with a real Earth.

When Evans calculates the “Stefan-Boltzmann’s sensitivity” and claims it is different than Planck feedback it is different because it is he who has failed to take account of his two observations regarding single layers and the real world.

He has used a zero dimensional model for a back of the envelope calculation, (good enough for use in teaching elementary introductory aspects of climate science), assuming no changes in altitude for different wavelengths or changes across the surface of the Earth. He has also assumed a change in Te (or whatever he would like to call it) instead of a change in temperature at the surface for a given feedback response in W/m2 to achieve equilibrium. With a forcing due to greenhouse gases there is no change in Te when equilibrium is reached but there is a change in Ts.

Evans has calculated the simple rate of change of effective radiating temperature with respect to the outgoing radiation at the top of the atmosphere instead of the more complex but meaningful rate of change of surface temperature with respect to the outgoing radiation at the top of the atmosphere and hence arrives at the simplified Te/4R (or Tr/4R) approximation for the feedback free climate sensitivity parameter.