## Tuesday, April 21, 2015

### Eli and the Merry Elves

Some time ago, Eli and his merry elves  put together a lengthy comment on an even more lengthy paper (aka piece of trash) by Gerhard Gerlich and Ralf Tscheuschner, that being a paper so bad that it really was not worth the work, except the work the merry elves did was a piece of play.

Now the Rabett is quite happy with the project. It was maybe the first published blog generated reply to such nonsense (thus the grandfather of the 97% paper), and even happier about those who took part, some of whom blog, some of whom tweet and blog to this day, Chris Ho-Stuart, Chris Colose, Joel Shore, Arthur Smith and Joerg Zimmerman.

A major part of the comment was showing that absorbing layer models of the atmosphere lead to a warmer surface, in perfect agreement with the second law of thermodynamics.  What happens, of course, is that each absorbing layer re-emits IR radiation, a part of which is absorbed by the layer below.  This slows the rate at which the lower level cools by radiation.  If the lowest level is heated by an outside source (such as the sun) and an equilibrium is established so that the energy into the system matches that of radiation from the system, then the temperature of the lowest level at equilibrium is higher than it would be in the absence of absorbing layers.

Of course, this did not meet with understanding amongst the lard heads, and Eli ran into it again recently on Bishop Hill.  Curiously Chris Colose has been thinking about the problem too and has a couple of recent  posts on the subject.

Eli's introduction to thermal radiation shielding was building very high temperature ovens (> 1200K) with multiple levels of radiation shielding during his graduate research, so, on an experimental level the answer was clear, but today while searching the net he came across a book on radiative transfer by Robert Siegel which considers the problem in detail starting with parallel piles of heat shielding layers which emit diffusely (e.g. the same in all directions)

in really complete detail.  The model includes different emissivities for the inside and outside walls of each shielding level.  Eli is not going to go full SoD on the bunnies, but those interested can find a detailed derivation of the heat flow per unit area between two parallel plates in just about any book on thermal transfer, or you can corner John Abraham at the next AGU.  When a steady state is established the amount of heat flowing per unit area through each level q must be the same

$\begin{matrix}&space;q\left&space;(&space;\dfrac{1}{\epsilon&space;_{1}}&space;+&space;\dfrac{1}{\epsilon&space;_{11}}-1\right&space;)&&space;=&space;&&space;\sigma&space;\left&space;(&space;T_{1}^{4}-&space;T_{s1}^{4}\right&space;)\\&space;q\left&space;(&space;\dfrac{1}{\epsilon&space;_{12}}&space;+&space;\dfrac{1}{\epsilon&space;_{21}}-1\right&space;)&&space;=&space;&&space;\sigma&space;\left&space;(&space;T_{s1}^{4}-&space;T_{s2}^{4}\right&space;)\\&space;&&space;\begin{matrix}&space;\cdot&space;\\&space;\cdot&space;\\&space;\end{matrix}&space;&&space;\\&space;q\left&space;(&space;\dfrac{1}{\epsilon&space;_{\left&space;(N-1&space;\right&space;)}}&space;+&space;\dfrac{1}{\epsilon&space;_{N1}}-1\right&space;)&&space;=&space;&&space;\sigma&space;\left&space;(&space;T_{s\left&space;(&space;N-1&space;\right&space;)}^{4}-&space;T_{sN}^{4}\right&space;)\\&space;q\left&space;(&space;\dfrac{1}{\epsilon&space;_{N2}}&space;+&space;\dfrac{1}{\epsilon&space;_{2}}-1\right&space;)&&space;=&space;&&space;\sigma&space;\left&space;(&space;T_{sN}^{4}-&space;T_{2}^{4}\right&space;)\\&space;\end{matrix}$                   (1)

Following Siegel, if we add these equations up, the right hand side is σ(T14-T24).  Dividing by the co-factor of q on the left hand side yields

$q=\dfrac{\sigma&space;\left&space;(&space;T_{1}^{4}-T_{2}^{4}&space;\right&space;)}{1/\epsilon&space;_{1}+1/\epsilon&space;_{2}-1+\sum&space;\left&space;(&space;1/\epsilon&space;_{n1}+1/\epsilon&space;_{n2}-1&space;\right&space;)}$                     (2)

Heat transfer books usually stop there, because the MEs are interested in how to design shielding for thermal or cryogenic applications.

OTOH, Rabett and friends were looking at the case of a planet where the amount of incoming energy from the Sun or the star of your choice is q.  The emissivity of the surface is going to be something like 0.95, that of the atmosphere at different levels, well that depends on the pressure, concentration and spectra of greenhouse gases, and, of course the specific humidity and where the clouds are.  For CO2 the contribution is going to be between 0.19 and 0.12.  For water vapor higher, as high as water vapor goes before condensing out

However, we can gain insight by setting ε1 equal to 1 and letting all of the other levels have the same emissivity, both inside and outside each shielding level.  In that case

$q=\dfrac{\sigma&space;\left&space;(&space;T_{1}^{4}-T_{2}^{4}&space;\right&space;)}{1/\epsilon&space;_{2}+N\left&space;(&space;2/\epsilon&space;_{s}-1&space;\right&space;)}$                                                           (3)

At a steady state, the same amount of energy has to be radiated to space.  If there are no shielding levels, the amount of heat radiated per unit time is σT1o4.  Consider the case where there is only the outermost heat shield (N=0) then

$\sigma&space;T_{1o}^{4}=\dfrac{\sigma&space;T_{1}^{4}-\sigma&space;T_{2}^{4}}{1/\epsilon&space;_{2}}$                                                                      (4)

Canceling σ, multiplying both sides by 1/ε2 and bringing T1o4 to left hand side we get

$\left&space;(1/\epsilon&space;_{2}&space;\right&space;)&space;T_{1o}^{4}+&space;T_{2}^{4}&space;=&space;T_{1}^{4}$                                                                   (5)

All terms on the left hand side are positive, ε2 is less than or equal to 1, therefore T1, the temperature where there is one heat shielding level is greater than T1o, the temperature of the surface if there is no blocking.

If there are N equivalent heat shielding layers between the innermost and outmost layers, then similarly

$\left&space;(1/\epsilon&space;_{2}+N\left&space;(&space;2/\epsilon&space;_{s}-1&space;\right&space;)&space;\right&space;)&space;T_{1o}^{4}+&space;T_{2}^{4}&space;=&space;T_{1}^{4}$                                   (6)

The added term on the left hand side is again positive (if εs =1 then it is simply equal to N.  If εs  < 1 then (2/εs -1) > 1.  In either case, especially the latter, T>  T1o . The same can be done for  spherical geometries, but one has to consider geometric factors, the ratios of the areas of the various shells to each other.

Siegel and other heat transfer books do the derivation.

How important are the geometric factors?  They scale as An/Ao where A=4πR2 so at the risk of offending the punctilious the ratio is (Rn/Ro)2 The radius of the earth is 6371 km.  Using a 10 km high atmosphere basically the troposphere, or at least the effective level which radiates to space in the CO2 bands,  (Rn/Ro)2 = (6381/6371)2 = 1.003, so there will be a .3% difference from treating the system as a nest of sphere's or a series of parallel plates.  Close enough.

## Friday, April 17, 2015

### Veep candidates bring a 0-5% increase in party vote in their home state

Got into a conversation about this yesterday:  how much help does a vice-presidential candidate provide in winning that candidate's home state? I vaguely recall that poli science says not much. I went and noodled around wiki and can now draw my own dramatic conclusion:  not much.

Wiki has all presidential results by state and year (e.g., here's Texas 1988) so it's simple to compare results before and after a state resident ran for vice president. In the last 30 years, not much happened, although 1992 and 1996 are hard to use because of a strong third party showing.  I'd say everyone brought in much less than a 5% bump, with only Bentsen and (sadly) Palin coming in at or slightly above that level.

This small of a bump suggests that veep candidates shouldn't be chosen based on the help they provide in their home state.

OTOH, there's Florida - that's a very big swing state, and a 2% bump could be useful. I've thought a joint ticket of Jeb Bush and Marco Rubio could make winning Florida very difficult for Democrats. I believe Jeb isn't particularly popular in Florida and Rubio is only moderately popular, but people do tend to root for the home team.

## Thursday, April 16, 2015

### Under what circumstance does McConnell's message to foreigners to do less on climate change help America rhetorical question?

Slate has a good article on Republican politicians siding with America's foreign rivals when Democrats run the executive branch, multiple times throughout the years.

The latest version of this is Mitch McConnell's advice to foreign countries that "Considering that two-thirds of the U.S. federal government hasn’t even signed off on the Clean Power Plan and 13 states have already pledged to fight it, our international partners should proceed with caution before entering into a binding, unattainable deal." Ignore for the moment that these international commitments are voluntary, not binding. There is no circumstance under which this statement serves an American interest.

The Republican mantra has been the US shouldn't move forward without the cooperation of other countries:

Now McConnell is trying to stop that cooperation.

What's even screwier is that even if you think the American interest isn't in cooperating, but rather that the US should take a free rider position and let other countries do most of the work of combating climate emissions, then McConnell's statement to foreigners is still a bad idea. Trying to get them not to do the work just makes things worse for us.

Maybe one could take the position that climate change is a hoax, therefore there's no need to do anything at all, but McConnell has apparently used the "I'm not a scientist" incantation, and doesn't claim it's all a hoax:

If you don't know it's a hoax, then you should take feasible opportunities to help, or at least do nothing to interfere with other countries' efforts.

That second clip is partly revealing though when McConnell says a Kentucky senator's job is to fight for coal jobs in his state. What he really means is to fight for coal industry profits - if he were fighting for jobs, he'd have used his power to slow down the mechanization of the industry responsible for the vast majority of the lost coal jobs.

So what he's saying is his job is to fight for coal industry profits and not for the American interest in the world. That's what he's doing with his advice to foreign countries.

UPDATE:  credit where due, Jeb Bush surpasses the low bar set by his party and acknowledges reality of climate change (while not saying what he'd do as President).

## Monday, April 13, 2015

### A Train Wreck Avoided

As has been reported, the American Physical Society has requested comments on its Draft Statement on Earths Changing Climate. There was some amusement value in how the draft was presented.
“We have taken great care throughout this process, including focusing on consensus building that has resulted in a solid, science-based statement,” said William Barletta, POPA chair. “We now look forward to hearing from the Society’s membership.”
Those bunnies who have not been following what only a rabett of good will could describe as the rope-a-dope stylings of the APS Panel on Public Affairs, may need to do some reviewing, but the clatter of falling teeth filled the arena as Barletta described the workshop that Steven Koonin put together to educate the drafting panel he had carefully packed.
As part of the process, the Review Subcommittee convened a workshop on Jan. 8, 2014, with six climate experts. “We used this meeting to delve deeply into aspects of the IPCC consensus view of the physical basis of climate science,” said Barletta. “The Review Subcommittee’s goal was to illuminate for itself, for the APS membership, and for the broader public both the certainties and boundaries of the current climate science understanding.”
Anyhow, after wiser heads got in front of the moving train, the following statement emerged
On Climate Change: Earth’s changing climate is a critical issue that poses the risk of significant disruption around the globe. While natural sources of climate variability are significant, multiple lines of evidence indicate that human influences have had an increasingly dominant effect on the climate warming observed since the mid-twentieth century. Although the magnitudes of future effects are uncertain, human influences on the climate are growing. The potential consequences of climate change are great and the policies of the next few decades will determine human influences on the climate for centuries.

On Climate Science: As summarized in the 2013 report of the Intergovernmental Panel on Climate Change (IPCC), there continues to be significant progress in climate science. In particular, the connection between rising concentrations of atmospheric greenhouse gases and the increased warming of the global climate system is more certain than ever. Nevertheless, as recognized by Working Group 1 of the IPCC, scientific challenges remain to our abilities to observe, interpret, and project climate changes. To better inform societal choices, the APS urges sustained research in climate science.
On Climate Action: The APS reiterates its 2007 call to support actions that will reduce the emissions, and ultimately the concentration, of greenhouse gases, as well as increase the resilience of society to a changing climate. Because physics and its techniques are fundamental elements of climate science, the APS further urges physicists to collaborate with colleagues across disciplines in climate research and to contribute to the public dialogue.
Eli, not being at all shy, although frequently ignored (Cassandra was too, and that had a cost), submitted the following

My criticism of the draft statement is the lack of urgency.  Given that damage to the climate through emission of greenhouse gases accumulates and remains, this is a serious omission and I would strongly recommend inserting the second paragraph of the previous statement at the end of the current draft
The evidence is incontrovertible: Global warming is occurring. If no mitigating actions are taken, significant disruptions in the Earth’s physical and ecological systems, social systems, security and human health are likely to occur. We must reduce emissions of greenhouse gases beginning now.
The evidence that the damage will persist for centuries is inherent in every model of the carbon cycle from the simplest to the most complex, and dealt with by the IPCC WG1 reports.  The reason why urgency is needed at every point is explained by Stephen Gardiner in a Perfect Moral Storm
the presence of the problem of moral corruption reveals another sense in which climate change may be a perfect moral storm. This is that its complexity may turn out to be perfectly convenient for us, the current generation, and indeed for each successor generation as it comes to occupy our position. For one thing, it provides each generation with the cover under which it can seem to be taking the issue seriously – by negotiating weak and largely substanceless global accords, for example, and then heralding them as great achievements – when really it is simply exploiting its temporal position. For another, all of this can occur without the exploitative generation actually having to acknowledge that this is what it is doing. By avoiding overtly selfish behaviour, earlier generations can take advantage of the future without the unpleasantness of admitting it – either to others, or, perhaps more importantly, to itself.
In addition, I have comments on the process.  When APS schedules a policy statement it should ensure that the membership of POPA for that year includes several that have expertise and are respected in that area.  What happened in the case of the Earth's Changing Climate statement was seriously embarrassing to the Society and totally avoidable.

In the case of the Earth's Changing Climate statement, the chair of the drafting subcommittee was a serious mistake as, to be generous, his naivety about the physics of climate mislead both him and the drafting subcommittee.  Those doubting this would do well to read and exchange between Isaac Held and the committee from the experts's interview and a reply to the drafting subcommittee's chair from Andrew Lacis, a leading climate scientist

Second, it was disappointing to see that the panel selected to teach the drafting committee about Climate Change consisted of three mainstream experts and three outliers (Christy, Lindzen and Curry).  There are also those who are existentially frightened by what they see as the threat of climate change .  They were not represented, nor am I saying they should necessarily be in equal number, but I do say that the Panglossian outliers should also have not been involved.  There is a professional consensus in this area and if the drafting committee would need lessons  (which it should not) then extremists can only mislead non-experts

Eli has heard from others with slightly different takes.  It is certain that the draft statement is considerably stronger than the originally proposed one.  That is welcome.  Eli and friends had awaited a train wreck.  If one is recommending how to proceed when the need for dealing with the threats of climate change are acknowledged, the draft statement's emphasis on global warming as risk management can be rigorously defended.

However, as readers of Rabett Run know, the threat of climate change has NOT been acknowledged by a blocking minority and IEHO, a call to urgent action is still needed to get through their opposition.

It is important that the draft statement emphasizes the considerable human role in warming, the likelihood it will get worse in the future, and the serious risks involved. It also emphasizes the importance of reducing emissions.

On the other hand, the bunnies and the bunny clutchers know that there are elements of the APS membership who will fight to weaken the statement, and even a slight retreat from the strength of the statement as currently written would be an unacceptable loss.

Given that, at a minimum it is important for the membership to get behind the statement and back it. Shoving the Overton Window in the direction of strengthening the draft statement will help offset the voices that will no doubt cry out for eviscerating it and, if loud enough, might even succeed.

Postscript:  As Hank says in the comments below:
I think in hindsight the APS will appear, well, to be physicists doing their usual thing, standing on the tracks and squinting into the light wondering why it's getting brighter faster and faster.

## Saturday, April 11, 2015

### EV costs at a tipping point for un-American countries

Un-American developed countries, that is. See here:

Bloomberg reprinted the above graph from a 2011 McKinsey report, and I added the green line for where we are today. Bloomberg adds the info that we weren't supposed to hit $300 until 2020 and that the market leaders are already there. Bloomberg goes on to note the obvious fall in gas prices so that currently, all EVs are less competitive than they were in 2011. A person buying a car today might think twice though about whether gas prices are going to remain low. What I thought missing from the discussion is the existence of developed countries not named United States of America, because of a little thing called the gas tax. In most of them, the price is over$4.50 (and also in many developed countries that don't produce oil). Forget the US - for the rest of the world, the tipping point is here.

Sadly though, I'm not aware of EV purchases in the rest of the world matching this prediction. Part of it could be that Nissan Leafs and Teslas simply aren't cheap for other reasons, and they need more development and more competition to knock down prices. The other and more depressing factor is that people aren't economically rational and may discount the future savings from not buying gas more than they should. Or just not be able to finance.

Overall though it's good news, and it should be interesting to watch overseas EV sales in the next few years.

UPDATE:  some good comments worth checking out. One point was that in countries with high gas taxes the electricity is also often expensive. I'd agree, but I doubt it come close to making up the difference.

Another point was about electric bikes - if you put them on the chart above, I think they'd win under any circumstances, and they'll do even better as batteries improve. Developing world countries are building and rebuilding their cities and towns on a much more massive rate than developed nations, and they have a real opportunity to center personal transportation around electric bikes, not cars.

### Support Continental Movement

Russell worries that no bunny cares about continental drift.  He needs to get out more

Bunnies can join the foundation at Paleoartisans (T shirts too)

## Friday, April 10, 2015

### Man bites dog

I've argued for a while that we should make use of analogizing sports statistics with climate/weather data, and Media Matters shows it happening (the analogy starts about a minute into the video).

Difference here being that it's a sports journalist using climate change to explain sports, saying a single piece of contradictory data doesn't refute an overall trend. Just as a single cold day doesn't refute climate change, a single exciting basketball game doesn't refute a bad system for administering basketball.

I think it's a good thing though - reinforcing climate change as a culturally-accepted fact.

## Thursday, April 09, 2015

### Identifying specific people in the Philippines who were killed by climate change

We know people have been killed by climate change. That's true both in the broader sense that every single weather event we experience is different from a parallel Earth that didn't go through decades of human GHG emissions, and more specifically that some killer weather has been made worse in general (e.g., heat waves). What's been difficult to say is whether a specific killer event is randomly-caused as opposed to being exacerbated by climate change (although maybe not always impossible). And even when you can definitively say a specific killer heat wave was made worse, it would be hard to say who was killed by the "natural" level of the heat and who was killed by the anthropogenic increase in severity.

Enter sea level rise.

SLR is the one thing that's different from weather - if an effect can be traced to sea level rise, it can be traced to climate change. In the case of mass casualties from tropical storms, this should be possible to figure out.

Haiyan/Yolanda's effects on the Philippines is the best example so far, although there doubtless will be more. Six thousand people were killed, with the storm surge considered the deadliest effect. Worst-hit areas had storm surges of 13 to 17 feet, with many people drowning in an evacuation center where the lower floors were submerged.

In most of the world, the present SLR is only a few inches, making it harder to attribute damage from sea level rise as opposed to the natural level of storm surge. Philippines is different, with three to four times the amount of sea level rise as the global average, making the surge about a foot higher than it would have been.

My assumption is that deaths attributable to Yolanda storm surge decreases with elevation, and that above a certain level, the amount of surge wasn't enough to collapse structures (people would have died above that elevation, but from other causes). The storm surge deaths in the foot of elevation below that certain level were caused by sea level rise and by climate change, and that foot of elevation change can be a pretty wide swath of flat land. Maybe someone can go and find who those people were.

Not all the storm deaths within that band would've been caused by the surge, but deaths from collapsing structures seem to be pretty likely candidates. Many people lower down would've also been killed by sea level rise, or others higher up killed by other climate change effects on the storm, but they're hard to identify. What I'm trying to show here is the faces of people we could say with a fair degree of certainty were killed by climate change.

And if no one gets to figure this out with respect to what happened in the Philippines, then there's always next time.

### Andy Lacis Writes to Steve Koonin

At Climate Etc, Andy Lacis has had it (in a polite sort of way) and writes in the comments to Steve Koonin an admonition to stop being silly.  Eli thought this important enough to post by itself, as many will not wade through the muck to get to it.
----------------------------

Steven,
Physicists should take the time to understand their physics better.
Only 1% to 2% . . . that may sound small and insignificant . . . but it isn’t.
It is well known that the normal human body temperature is about 310 K. Furthermore, it is also well known that a seemingly small change (up or down) in absolute body temperature by only 1% (3.1 K, or 5.6 F) would make one sicker than a dog, and, that a 2% change in body temperature (up or down by 6.2 K, or 11.2 F) will virtually guarantee a dead body. From this, it should be sufficiently clear that, when viewed in absolute energy terms, the viable margin between life and death in the Earth’s biosphere is remarkably narrow – so much so that a seemingly insignificant 1% to 2% change in the total energy of the global environment will invariably result in serious disruption of the established infrastructure of life in the biosphere.
There is no substitute for appealing directly to basic physics for physical insight and better understanding of the ongoing global warming problem. And I do recall one particular case in the 1970s (in which you might have participated) when the JASON group of physicists was tasked to weigh in on the then open question of radiative forcing due to doubled CO2. At that point in time, the JASONs had available the computational resources to calculate one of the earliest line-by-line radiative forcing determinations for doubled CO2. They found the downward flux change at the ground surface to be less than 1 W/m2, from which they erroneously concluded that the radiative forcing caused by the doubling of atmospheric CO2 was “not all that significant”.
While the JASON group’s radiative calculations were numerically on target, the JASONs were clearly mistaken in their interpretation of the calculated results. Radiative forcing takes place over the entire atmosphere, and not just at the ground surface. If they had to select a single point on the vertical profile that best describes the radiative forcing by CO2, they should have selected the tropopause point, where the instantaneous flux change due to doubled CO2 is nearly 5 W/m2 for a clear-sky atmosphere. Moreover, the JASONs did not take into account the additional radiative magnification that is invariably contributed by the longwave opacity from water vapor and cloud feedbacks, which are several times larger than the radiative forcing due to CO2 alone, and therefore should have been included in their analysis.
In simple terms, the basic essence of the global warming problem is best understood as a straightforward problem in global energy conservation, as was first noted by Joseph Fourier in 1824. Specifically, the global-mean surface temperature of the Earth is about 288 K, which implies that the Planck emission from the ground surface must be about 390 W/m2. Furthermore, the global-mean solar energy absorbed by the Earth is observed to be about 240 W/m2 (with about 100 W/m2 reflected directly back to space).
Given that the Earth should be in near-global energy balance, this implies that the Earth must radiate about 240 W/m2 of longwave energy out to space (as has also been verified by satellite measurements). Absent the greenhouse effect, the 240 W/m2 of absorbed solar energy can only support a surface temperature of 255 K. This “missing energy” circumstance led Joseph Fourier to conclude that there must be thermal heat energy radiated downward from the atmosphere to supply the additional heating of the ground surface.
The flux difference of 150 W/m2 between the 390 W/m2 emitted by the ground surface and the 240 W/m2 of LW flux going out to space at the top of the atmosphere is a direct measure of the strength of the terrestrial greenhouse effect. Greenhouse action builds up the surface-emitted flux to 390 W/m2 and creates the ensuing reduction by 150 W/m2 of the outgoing longwave flux to space – all accomplished by radiative energy transfer means (via sequential emission, absorption, and re-emission interactions).
Physicists should also appreciate the nature of the Clausius-Clapeyron relation, and the fact that it is exponential in temperature. Undisturbed, with a source of liquid water, the atmosphere is always striving to reach an equilibrium 100% relative humidity. In simple terms this means that the holding capacity of the atmosphere for water vapor doubles for every 10 K increase in atmospheric temperature. And, there is no doubt that water vapor is a very potent greenhouse gas.
Detailed radiative attribution calculations show explicitly that water vapor accounts for about 50% of the 150 W/m2 of greenhouse effect, and that longwave cloud opacity accounts for 25%. Both of these radiative effects are due to the climate system’s fast feedback processes. The remaining 25% of the greenhouse effect comes from the radiative forcings by the non-condensing greenhouse gases (which incidentally also act to sustain the terrestrial greenhouse effect at its present strength). Of the non-condensing greenhouse gas contributions, CO2 is by far the strongest contributor accounting for about 20% of the 150 W/m2 greenhouse effect, with the remaining 5% due to minor GHGs like CH4, N2O, O3, and CFCs.
A key point to keep in mind is that it is these non-condensing greenhouse gases that act as the principal radiative forcing agents of the climate system. Because of their thermodynamic, chemical, and radiative properties, CO2 and the minor GHGs are chemically slow-reacting with atmospheric lifetimes ranging from decades to many centuries. Once they are injected into the atmosphere these gases effectively remain there indefinitely by not condensing or precipitating at prevailing atmospheric temperatures as they continue to exert their radiative forcing.
Since CO2 is the strongest and most effective of these non-condensing radiative forcing gases, it then follows that CO2 can be identified as the principal LW control knob that governs the global climate of Earth. The fact is that the other forms of radiative climate forcing (e.g., changes in solar irradiance, surface albedo, and aerosol forcing) are small by comparison. This makes the case for recognizing CO2 as the principal climate control knob that much more compelling.
Atmospheric water vapor, on the other hand, has the role of principal fast feedback process in the climate system by condensing and precipitating from the atmosphere in response to changes in local meteorological conditions (constrained by the exponential temperature dependence of the Clausius-Clapeyron relation), meaning that the atmospheric distribution of water vapor (and clouds) can change rapidly on a time scale of hours and days in response to changing weather conditions.
Applied radiative forcings that heat (or cool) the atmosphere cause more (or less) water vapor to evaporate, which generates more (or less) longwave opacity, which then contributes more (or less) radiative greenhouse effect. Such changes in water vapor cause big changes in radiative heating or cooling, but the changes are limited in magnitude by how much change the water vapor undergoes in reaching its new equilibrium distribution.
Because of this, water vapor and clouds act to magnify the initial radiative perturbation, but cannot on their own initiative manufacture or impose a warming or cooling trend on global climate, even though they contribute more strongly to the atmospheric radiative structure than the radiative forcing gases that actually drive and control the global temperature trend.
The physics cause-and-effect nature of the global warming problem is not all that complicated. The basic “cause” component of global warming has been clearly identified and understood for many decades, and has been accurately quantified by precise measurements of atmospheric CO2 (e.g., the Keeling curve).
This is fully corroborated by the latest annual data report of fossil fuel extraction that now approaches 10 gigatons of carbon/yr (roughly equivalent to 10 cubic km of coal/yr, which when burned, adds about 5 ppm CO2 to the atmosphere, half of which remains there for many centuries). The radiative effects of CO2 are fully known from well-established understanding of greenhouse gas radiative properties and radiative transfer modeling of the atmospheric structure.
How can a physicist not comprehend that it is atmospheric CO2 that is the principal radiative forcing agent for the ongoing global warming? . . . and not be concerned that water vapor, as the climate system’s principal feedback agent, has an exponential dependence on temperature?
To be sure, there are other factors that contribute to climate change. But decades of measurements and analysis have shown that variations in solar irradiance, land use, aerosols, ozone, and other minor greenhouse gases, while making a contribution, are small by comparison to CO2.
Of greater interest is the “unforced” variability of the climate system on decadal time scales that arises from changes in ocean circulation patterns that are effectively un-influenced by changes in atmospheric radiative forcing. The deep ocean is a very large cold storage reservoir. An upwelling blob of cold ocean water can put a “pause” in the ongoing global warming, temporarily diverting the greenhouse “heat” to warming the ocean. But once that cold blob of ocean water has been warmed up to its equilibrium temperature, it is back to the business of continued global warming. And also note that the ocean cannot cause a decadal warming spurt – the deep ocean is colder than the surface biosphere, so it cannot be a source of heat.
Significantly, the key climate system components (water vapor, clouds, ocean) are not configured to respond to radiative and/or temperature perturbations on a sufficiently small enough incremental scale that would permit a monotonic approach to global energy balance equilibrium. Instead, there is always over-reaction such as when water vapor condenses en mass to produce storms, coupled with the similarly over-reactive responses by atmospheric and ocean dynamics to pressure-temperature and salinity differences, to produce the quasi-chaotic weather and the longer-term climate noise that characterizes the climate system.
Physicists should not be confused by these random-looking quasi-chaotic fluctuations about the local climate equilibrium point, and should instead focus more on the changing energy balance equilibrium point of the climate system. They should also pay attention to the geological record that points to an atmospheric CO2 level of 450 ppm as being incompatible with polar ice caps, a level that is expected to be reached by the end of this century. While it may take a thousand years for the polar ice to melt, the future course is being prepared for a 70 meter rise in sea level.

### Beneath Contempt

Steve Koonin has emerged from the woodpile to defend his clowning in the APS POPA process and the Wall Street Journal on Judith Curry's blog.

Alerted by Willard and ATTP, the bunnies crossed their ears and read Koonin's lament, only to see

An even simpler indication of the percentish influence is to note that a 3 C mean global surface temperature increase on a base of 288 K is also about a 1% effect.
This is beneath contempt.  Without greenhouse gases the surface of the earth would be near 255 K on a simple calculation known to all, and indeed, ~255 K is the measured temperature of the Moon's surface.  Arthur Smith had a complete discussion of this on arXiv a while ago. Eli would not be surprised to see such a lights out statement from Willard Tony or the good Biship, indeed it would be a step up in the usual.  However, by rumor, while it is true that the temperature of the surface would go to 3K or so if the sun did blow out, that is not scheduled

But it is all of a piece.  Let the Bunnies look at Dr. Koonin's take on forcing from CO2, which, of course is logarithmic.
An alternative way of seeing the physical smallness of anthropogenic influences is to look at how the long-wave absorptivity of the clear sky increases with CO2 concentration – this is the physical input to GCMs that varies directly. Figure 4 from Harde shows that a doubling from the pre-industrial 280 ppm to 560 ppm increases the absorptivity by about 1% on a base of 82%, or, again a percentish shift. An even simpler indication of the percentish influence is to note that a 3 C mean global surface temperature increase on a base of 288 K is also about a 1% effect.

Eli had some comments about Harde, suffice it to say it doesn't rain much on Harde world, but the radiative transfer stuff is fine.  However, let the bunnies take a look at that figure again.  The low point for CO2 mixing ratio is about 180-200 ppm, last seen at the bottom of ice ages.  It might have been a bit lower in snowball earth, but again Steve "Lights Out" Koonin wants to compare CO2 forcing for 560 ppm to CO2 forcing for 0 ppm, a condition which has never been seen in the 4 billion years or so the Earth has existed.

ADDED FOR CLARITY: So Eli thought he would help Steve Koonin on the road back to reality by drawing a line between the CO2 absorptivity under ice age conditions and today.  The net effect of the rise from 200 to 280 ppm is smaller than what would be expected in doubling CO2 from 380 to 760 ppm as shown in the Harde graph (Koonin didn't read Harde/the graph correctly It shows a doubling from 380, not 280, but the answer is the same)

Indeed, beneath contempt.