Thursday, May 25, 2017

CO2 Atmospheric Absorption Is NOT Saturated

It is certainly an evergreen claim by the climate change disbelievings crew that the absorption of CO2 in the atmosphere is saturated.  What does saturated mean to them is a useful question to ask. A useful answer would be that the atmosphere is optically thick at the greenhouse effect relevant frequencies/wavelengths where CO2  absorbs, between about 620 and 840 cm-1.

It would also be useful to describe what is meant by optically thick and optically thin.  To do that we first need to define optical depth.  Optical depth is the fraction of light blocked in passing through a medium.  The transmission is the percentage of light that gets through.  Something is optically thick at a particular wavelength if no light can get through it, It is optically thin if most or all of the light can get through.  If an absorption is not optically thick, it can't be saturated

If the disbelievers are right at current concentrations CO2 is optically thick over the entire region.

We can check on that using Spectral Calc, a program that allows us to calculate the spectrum based on precision and verified measurements.  Let us imagine that the atmosphere is a tube with 400 ppm CO2 at 296K.  How much of the light is absorbed in a 1 m tube

At this point those interested in only the bottom line can skip down to the bottom of the post and pick up the figure the bunnies need for their tweet.


Most of the spectrum is due to transitions from the CO2 ground vibrational level to the first excited vibrational level  The sharp peak in the center is called the Q branch composed of lines that are very close together and corresponds to transitions where the rotation(al quantum number) of the molecule does not change.  The band to the left is the P-branch for transitions where the rotational quantum number decreases by 1.  The band to the right is the R-branch where the rotational quantum number increases by 1.

The two little sharp peaks to the right and left of the main bands are Q-branch transitions between excited vibrational levels.  Even at room temperature a small percentage of the molecules are vibrationally excited by collision.  Of course, they can also lose energy by collisions but there is an equilibrium between excitation and de-excitation by collisions with nitrogen and oxygen molecules (mostly) and a thermally driven equilibrium population in each vibrational level.  If a bunny squints really hard she can see the corresponding P and R-branches. These are called hot bands. Why the excited vibrational levels are split and even what excited levels they connect is complicated.  Google books provides an explanation.

If the distance is increased to 10 meters the lines of the 0-1 band are optically thick but there is still space between them, however, the lines do have wings and the wings overlap so even over a 10 m path, there is a noticeable underlying continuum mostly caused by collisional broadening.  The hot bands on either side of the Q branch are now easy to see.  The Q branch 0-1 band is optically thick
At 100 m or 0.1 km the 0-1 transition is almost optically thick and the 1-2 bands are very clear.  Using the squintosope, Q branches for higher lying hot bands can be seen at the edges
For a 1 km path length, most of the 0-1 transition is optically thick (saturated in the disbelieving sense) but light from the surface would still be seen in the wings, in the 1-2 and 2-3 bands.  
Finally at 10 km, while the center of the CO2 absorption is optically thick, there are still regions of the spectrum where light from the surface will get through the atmosphere.
Of course, increasing the amount of CO2 in the atmosphere will decrease the transmission in the wings of the bands.  At 560 ppm
and returning to 280 ppm
There are a few things that Eli has not considered in this post but they all would DECREASE the calculated optical thickness. Temperature and pressure decrease with altitude.  This post assumes both are constant. Their effects will be considered in detail in follow on posts,  Simply put the optical depth is directly proportional to density and path length, thus decreasing density with altitude, decreases the average optical depth and increases transmission across the spectrum.  Second at lower temperature there is less population in the excited vibrational levels and the hot bands at the edges of the spectrum are weaker, decreasing the optical depth in the wings, and increasing it in the center 0-1 band.  Since the 0-1 band IS optically thick at very small path lengths anyhow, this increases transmission.  Third, each of the lines is substantially broadened at atmospheric pressure.  A narrower comb of lines is optically thinner.  This would substantially decrease the continuum absorption between the lines.

Bottom line, the 667 cm-1 CO2 vibrational absorption is not optically thick across the entire region of absorption. It is not saturated.

Wednesday, May 24, 2017

What Rich Lowry said about Erdogan thugs attacking protestors in America

He got this one right, at least. Go read.

You don't often get a chance to read a National Review piece and agree with every word.

Monday, May 08, 2017

Probably Not The Place For This

Eli has been watching the reports on today's Senate hearing which features the Ted Cruz - Sally Yates death match.  The general feeling is that Yates did to Cruz what Macron did to Le Pen.  However, rather than getting too deeply into the legal parts of their interchange, the Rabett would like to point out that Yates READ most of her initial answer to Cruz (starting at 1:49 in the video below).

She was clearly prepared for the question.

You might ask what little birdy whispered in her ear, well, let's go to the video from three months ago

Somebunny was paying attention.

Friday, May 05, 2017

The New York Times approach to climate change

Behold the CrapWaffler, the writer that the New York Times thinks is a contribution to the climate change debate. It's what happens when you hire a climate denialist with the implied condition of employment that they can't completely lie about climate change, but merely smear uncertainty and misdirection about undertaking reasonable action (and Stephens still managed to get important things wrong).

The New York Times thinks it has added to the breadth of discussion on climate by getting as close to wrong as possible while not saying much of anything.

Stephens is shocked, shocked, that people would accuse him of "closet climate denialism". The term denier fit Stephens perfectly in 2015 when he wrote that temperatures would be about the same in 100 years, unless he was lying at the time about what he believed. It would be helpful if he now said his beliefs had changed, but all we get instead is crapwaffles.

I often read Razib Khan, an old-school Burkean conservative who also writes a lot about science. Several years back the NY Times hired him and then quickly dismissed him - he had unwisely associated with some simply vile racists, and guilt by association was enough to deem him unacceptable. I disagree, but to think Stephens, whose range is from wrong to crapwaffle, is better just tells you something about the Times. I recently subscribed to the Washington Post instead.

So skip Stephens, and read Razib to see what a thoughtful conservative would say.

P.S. And fellow bloggers, a reminder to add "no follow" whenever you link to Stephens. I'm pretty good about that when linking to denialists

Wednesday, May 03, 2017

Renewable Energy and Creative Construction

One of the weirdest flips in an exceedingly weird year has been the usual suspects going into complete meltdown about there now being extended periods where there is so much renewable energy from wind and solar and hydro that they are not just giving it away, they are paying you to take some of it.

Electricity has become like zucchini at the end of the summer, when gardeners leave a few hundred pounds on your doorstep, ring the bell and run.  Remember when the fusion and fission folk were talking about too cheap to meter, it's now a "problem" for renewables.

In any case, when there is money blowing in the wind somebunny will make money while the sun shines, and indeed this is a classic capitalist system opportunity, that somehow all the Randians and Trumplets let alone your average garden variety Bret Stephens don't appear happy with.  If there is a price differential arbitraging the electricity price is a great way to get rich and the technologies already exist.

There has always been a price differential between wee hours of the morning and the peak demand daylight hours, a differential that many industries have taken advantage of.  The guys with the green plastic eyeshades are no bunny's fools
Kentucky Electric Steel spends a lot of time and money trying to control our electric bill, over $2 million spread over the past eight years. This has reduced energy intensity from 743 kWh per billet ton in 2002 to 480 kWh per billet ton today. That represents an annual savings of over $600k with just our night-time operations; the savings would be even more if we ran during on peak hours, except that the higher power cost would eat them up! 
Aluminum smelters in Germany are already lapping up some of the freibier by using the molten metal as an energy storage medium from whose cooling they can draw power
By varying the rate at which the metal is produced, the plant will be able to adjust the power consumption of the 290-megawatt smelter up and down by about 25 percent. Trimet can soak power from the grid when energy is cheap. It can then resell the power when demand is at its peak. The company can temporarily reduce its power consumption by slowing the electrolysis, cutting the energy drain.
Using stored thermal energy is really old technology.  Ice houses that lasted through the desert summer have existed like forever in Iran and storage of heat from the summer to use in the winter is also a Canadian reality (tip o the ears to Andy Skuce )
The first of its kind in North America, DLSC is heated by a district system designed to store abundant solar energy underground during the summer months and distribute the energy to each home for space heating needs during winter months.
For decades large building have built tons of ice at night when electricity is inexpensive and used the ice to cool the building during the day.  Going by the name of ice storage air conditioning, the technique is now moving into residential units.  Eli first became aware of it in the context of labs using large ice systems for to supply coolants for lasers.  Storage heaters are also coming back driven by the low cost of renewable thermal.

So the next time your electric provider tries to leave some zucchini on your doorstep, smile and use it to charge your batteries, heat or cool your house or some other creative construction.

Friday, April 28, 2017

The Data Lies. The Crisis in Observational Science and the Virtue of Strong Theory

The problem with data fetishists is their choking down a daily flagon of numerical drivel without analyzing the brew.  One of the things that a good scientist knows is how to interrogate the numbers, not waterboard them.  Truth is that useful models improve flaky data and the statistical treatment thereof.

An introduction  for Eli was a talk that Drew Shindell gave, twenty maybe more years ago with a title that ran, "Which should your trust, the data or the models?" about global temperature data in the late 19th century.  The useful conclusion was trust neither, but use them together to produce understanding and improve both.  Yes theory can improve measurements and data.

A nice example is how NIST's acoustic thermometer can be used to define the thermodynamic temperature scale.  Starting with the theoretical result for the speed of sound in an ideal gas as a function of temperature (theory), a carefully built device to measure the same can be used to build a model of the response of platinum resistance thermometers as a function of temperature and then by applying the model PRTs can be used to more accurately calibrate other thermometers.

How about statistics, well most of what passes for statistical analysis these day is unconstrained, so it can wander off into never never land where never is stuff like thermodynamics and conservation laws.  Bart had a nice example of this when discussing the usual nonsense about how observed temperature anomaly data could be explained as a random walk

As you can see, the theory is valid: My weight has indeed remained between the blue lines. And for the next few years, my weight will be between 55 and 105 kg, irrespective of what I eat and how much I sport! After all, that would be deterministic, wouldn’t it? (i.e. my eating and other habits determining my weight)

Wow, if that’s the case, then I’ll stop my carrot juice diet right now and run to the corner store for a box of mars bars!! And I’ll cancel further consultations with my dietician. Energy balance… such nonsense. Never thought I’d be so happy with a root!
The other side of this is the replication crisis hitting the social sciences, most prominently psychology, well, also other stuff.  To disagree with the first link, unlike physical sciences psychology has no well established theoretical consensus against which nutso outcomes can be evaluated. Science is about coherence (a no on that as Alice’s Queen would say) consilience (baskets full of papers having nothing to do with each other but taken together mutually supporting) and consensus (everybunny with a clue agrees on climate change or at least 97%).

So the question really is what should a lagomorphs's prior be for statistical validity.  Clearly, if all you have is the data, the standard of proof for any assertion about the data has to be very high.  Wrong answers at low levels of proof are a reason that out on the edge physicists demand 5 sigma data before accepting that a new particle has been found, that's saying that there is 1 chance in 3.5 million that the discovery was in error if that standard is met. 

On the other hand, in the well established interior of a field, where there is a lot of supporting, consilient work, a whole bunch of basic theory and multiple data sets, 5 chances in 100 can do the job or even 10 in a hundred.  Of course 30 in 100 is pushing it.

Andrew Gelman has a useful set of criteria for priors (same holds for frequentist approaches).  Among his recommendations are for weakly informative priors that
should contain enough information to regularize: the idea is that the prior rules out unreasonable parameter values but is not so strong as to rule out values that might make sense
and those priors should be
Weakly informative rather than fully informative: the idea is that the loss in precision by making the prior a bit too weak (compared to the true population distribution of parameters or the current expert state of knowledge) is less serious than the gain in robustness by including parts of parameter space that might be relevant. It's been hard for us to formalize this idea.

Sunday, April 23, 2017

March for Science - San Francisco

Together with in-laws and friends, including (unlike me) an actual scientist, we went on the march in San Francisco yesterday.

The most hand-written/individualized signs I've seen on any march. Quite a young crowd too, and I'd guess two-thirds female. We'll see if there's a long-term effect - I'm sure it depends on what people continue to do after the march.

UPDATE:  here's something to do about it - get organized, and train to run for office:
Overview: Join us for a day of building political power for the climate movement by training bold, progressive climate activists to elected office at all levels. Potential candidates need to be identified, recruited, trained, and supported in order to achieve elected office—and once there, held accountable by the climate movement.

This training is for you if:
  • You consider running for office yourself in the next 1-3 years
  • You want to help a friend run for office
  • You want to learn how a local electoral strategy could help your campaign