Sunday, November 10, 2024

No. The greenhouse effect does not work like that.

No. The greenhouse effect does not work like that.

Let's start over. Let's try to figure it out from first principles. First, what are we trying to figure out? A lot of people think that the global climate is changing. Well, of course the global climate is changing. The closest thing to stability of the global climate has been the recent 800,000 years, maybe longer but we don't have enough data to be sure. We are being generous to call that a period of stability, with five glacial - interglacial cycles included, But, yeah, relative to the enormous fluctuations in even the chemical composition of the atmosphere over the preceding 4 billion years, its been relatively stable. The climate has still been changing but almost repeating, staying within a range around an apparent quasi-equilibrium. It has been close enough to a balanced condition that the very weak and slow variations of the Milankovitch cycles has been enough to influence the timing of the changes. 

So, if the climate has always been changing, why the concern now? Starting a couple hundred years ago it was noticed that there had been a glacial period in the recent past. It was natural to wonder why the climate had changed and would it change again. The scientists were off to the races, but the sciences were very young and incomplete. They didn't have the tools or even the concepts needed to actually answer the question. They were brilliant and worked hard but didn't necessarily start off in the right direction. That's science. Let's use hindsight to avoid the pitfalls and look at the view as we stand on the shoulders of giants.

How did the Milankovitch cycles modify the climate? By changing the amount of time that the Earth was spending and at what distance from the Sun. The Milankovitch cycles are variations in the shape of the Earth's orbit around the Sun which changes the amount of energy it receives from the Sun.

How does the energy move from the Sun to Earth? Because both are in a vacuum, the only possible path is electromagnetic radiation. Other conceivable pathways are the solar wind and magnetic fields, but are negligible relative to the electromagnetic radiation pathway. What do we know about that radiation? The popular, but naïve notion is that it comes from the fusion of Hydrogen into Helium. The confusion is natural. The energy does comes from the fusion of Hydrogen into Helium, but not the electromagnetic radiation that carries that energy from the Sun to the Earth. Except for the Neutrinos, all of the energy released by Hydrogen fusion is absorbed in the core as heat, bring the temperature there up to 15,700,000K gradually tapering off over the distance to the photosphere to about 109 times the radius of the Earth to a mere 5,700K. From the photosphere the energy from the fusion of Hydrogen can finally leave the Sun as electromagnetic radiation by the mechanism of black body radiation. 

What have we been missing? Everything emits or absorbs black body radiation. No convenient electron energy level transition are required. There are both absorption and emission lines in the spectra of the Sun. But, most of the spectra is a continuous range of black body emissions. OK, the light has to be quantized too, so it is not really a continuous range. But the quantize increment must be somewhere close to the Planck length, give or take a few orders of magnitude. 

The energy from fusion in the core of the Sun is finally on its way to Earth in the form of black body radiation with an effective temperature of 5,772K. Then what? Some of the radiation may be absorbed and redirected by some atoms or molecules in the atmosphere, ozone is a good example. A lot more of the radiation is reflected back to space by the cloud tops. For the most part, the radiation reaches the surface, where it absorbed as heat. Some of the radiation is absorbed by the atmosphere, of course. CO2 in the atmosphere does absorb some of the radiation from the Sun and thereby adds some heat, but the amount is small simply because very little of the incoming radiation is at the wavelength CO2 can absorb. 

Robert A. Rohde, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

Where does that energy go from there? Remember, the photon that started from the photosphere of the Sun has been absorbed by the surface, whether land or water, and no longer exists. A few select wavelengths are captured by photosynthetic organisms and the energy is converted to chemical energy and some are captured by photovoltaic panels but it all ends up as heat, eventually. 

The explanations for how the greenhouse effect works all agree up to this point. The surface of the Earth gets energy from the Sun which warms the surface just like it always has. But how in the world  does that account for that heat getting trapped? A common assumption is that since the energy arrived as electromagnetic radiation, it must leave the same way. As if photons were persistent particles. The energy (that was the photons) brought by the photons persist, but the photons do not. 

Of course, some of that absorbed energy is indeed radiated back up as infrared radiation. And some is absorbed and re-directed by CO2 molecules. Some of the absorbed energy is transferred from the surface directly to the atmosphere by conduction and other processes that take place at the interface between the atmosphere and the surface. 

The common but unconscious assumption that the N2 and O2 molecules that comprise almost all of the atmosphere CANNOT absorb any of the infrared radiation from the surface is just wrong. It is true that they cannot accept the IR as internal vibrational energy of their molecular bonds, but they can absorb it as momentum of the entire molecule. That is because the temperature of the air is often close enough to the temperature of the surface to both accept and emit infrared where the black body spectrums overlap.

So, why does the concentration of CO2 matter? Because the higher the concentration of CO2 in the troposphere, the higher it will be in the upper atmosphere where the CO2 can capture outgoing IR and re-emit it in random directions - including down. That is where the greenhouse effect of CO2 happens. The thermal energy that would have otherwise left the planet is still here.

There is another, less direct effect. The energy not radiated away is then in the lower atmosphere, making it just a tad warmer. Being warmer, the lower atmosphere expands, pushing the upper atmosphere a little higher, resulting in adiabatic cooling of the upper atmosphere. The black body radiation from the N2 and O2 up there is therefore just a little lower and cannot radiate as much as it otherwise would. 

Is the CO2 effect saturated?

Even IF the CO2 effect in the lower atmosphere is saturated, it is not saturated at the top of atmosphere where it really matters. 

H2O is confined to the troposphere and CO2 is not. That is a crucial difference. The amount of H2O in the atmosphere is not changing except for the wild fluctuations of the weather. The long term average is maintained by the very large exposure to liquid water over most of the planet. The greenhouse effect of H2O is much like the calculated predictions, keeping in mind that the N2 and O2 in the troposphere also have black body radiation spectra overlapping with that of the surface.
CO2 has little effect in the troposphere where H2O dominates. However, ABOVE the troposphere the situation is reversed. CO2 thins out with increasing altitude, so at some altitude and above, the CO2 cannot be saturated. Up there it can and does capture IR in its spectral range and redirects some of it back down, blocking the transport of some energy away from Earth and to space.




Monday, January 5, 2015

Emergency preparations

For electric power outages longer than half an hour, or so, It is possible and even practical to have a generator to provide power for the necessary appliances. Freezer, refrigerator, electric control for a gas furnace, some lights, and even tv and radio are fairly low power. Look at the name plate of all of these you want to be able to maintain functional through a power outage of perhaps a few days. Add up the number of Watts they use. That gives you a rough starting point to shop for generators. I have a 3000 Watt generator that is more than enough for me. This one is just a small and cheap one to show how inexpensive it can be. http://www.lowes.com/pd_473285-48270-APG3014_0__... The simplest way to hook one up to the house wiring is not legal so have an electrician install a switch and instruct you on how to turn some circuit breakers off to reduce the load. The labor will be the biggest expense. Here is an example of the low end switches. http://www.lowes.com/pd_394441-48019-TF151W_0__... Gasoline is still the least expensive and easiest to store for emergency backup. Once you have your generator and can hook it up, the only limit to how long you can run it is the amount of gas you have on hand. A few 5 gallon cans of gas can be handy to have around for many things. You are already thinking along these lines so i hope you proceed with it. Emergency preparedness is a good thing. The exact nature of an emergency is impossible to predict, by definition. But the basic needs are almost always the same. Shelter, water, food and fuel.

Wednesday, November 12, 2014

Prof Wade Allison

Why radiation is safe & all nations should embrace nuclear technology - Professor Wade Allison

Thursday, March 13, 2014

Radiation is Freightening

The possible proliferation of nuclear weapons is not really related to the fission nuclear power plants, except as a red herring employed by the fear mongering crowd. The same is true of the potential nuclear fallout from the detonation of nuclear weapons or "accidents" at fission nuclear power plants. The lack of danger from nuclear fallout has been demonstrated by the many above ground weapons tests half a century ago and the worst case scenario at a nuclear power plant already happened at Chernobyl - lots of very nasty fallout from inside the core of a running reactor spread of Europe, yet no related increase of cancers in 3 decades. It turns out that exposure to low level ionizing radiation is not a significant cause of cancer. We have learned that almost everything can contribute to causing cancer, but it requires several events.
The prolific estimates of thousands or more of cancer deaths have been proven false.

Radiation is scary because we know enough about it to know that some radiation is dangerous. For most of us, we first learn about radiation with the story of Madam Curie's discoveries and subsequent early demise. Her work was so dangerous because she was making discoveries. No one knew the danger. But, thanks to her and the many researchers that followed her, those same experiments and observations can be done safely. We now know how to prevent the damage. Some radiation is dangerous but with knowledge and respect we can (and do) work with radiation sources safely.

Monday, December 30, 2013

Recursion

Recursion


Recursion is a fundamental property of reality. The laws of physics operate on the present instant to produce the next. Although the progress of time from one instant to the next for us seem seems to be continuous but is not. There is some minimum time interval, probably near the Planck time. 

The resolution of the Ultraviolet catastrophe was to assume that there is a finite minimum frequency. Without that assumption, the energy would become infinite as the wavelength decreases to zero. Length, time, and energy all had to have some minimum quantity, called quanta. The size of the minimums just had to be finite - not zero. The size turns out to be some 35 orders of magnitude smaller than our familiar world. 

Some very simple recursive systems display complicated, even unpredictable behavior. Conway's Game of Life is an example well worth the time to investigate. If you want a deep dive into the concepts, I recommend a book, A New Kind of Science by Stephen Wolfram.