Wednesday, August 31, 2011

Break Though in Hydrogen Storage - Ammonia Borane

Watts Up With That has a post on Hydrogen Getting the Dynamite Treatment. As with most break through reports, I take this with a grain of salt. Once cost estimate start rolling in, then I can get more serious.

The ammonia borane storage could have a fairly large safety impact as much psychological as real. Hydrogen explosions when properly contained are pretty destructive, but most motor vehicle crashes don't create great conditions for an optimum explosion. If you have ever seen the Hindenburg film, you have an idea of what happens. Under pressure a hydrogen leak will burn like a torch until the temperature of the tank rises enough for a rupture. Then you can get a pretty good bang similar to cooking off a propane tank. The biggest difference between propane and hydrogen is hydrogen has a larger range of combustion concentrations. Energy wise, hydrogen is pretty so so.

Psychologically, this may kick interest in hydrogen in the butt. Overcoming irrational fears seems to be the trick with any energy use now a days.

Since I am on the alternate energy subject, Nanosolar has an agreement with Belectric which used to be Beck Electric. Belectric is a big time installer of photovoltaic energy farms. This can be a big boost for Nanosolar and solar in general, but on a utility scale. Residential scale is my biggest interest because it is the way to go for personal energy independence. Utility scale PV is still a warm and fuzzy experiment and not a great investment without government subsidies. Cost effective PV on small scale makes much more sense economically and aesthetically.

I still haven't gotten around to building my prototype electrolyzer. I have had a few ideas on how to increase the operating pressure - safely. I don't want to build something that will blow up on me unless I want it to. It is still in the works though, stay tuned.

Monday, August 29, 2011

Atmospheric Center of Energy

Once upon a time, simple analogies seemed adequate to explain the atmospheric effect. The atmospheric effect may not be familiar to you. It is the effect formally know as the greenhouse effect or the Tyndal gas effect. In these politically correct times, the atmospheric effect seems perfectly Milquetoasty.

Because of the focus on potential warming, just about anyone with some schooling in science has an opinion on the atmospheric effect. That means they have to try and explain the inner workings of the atmosphere to some degree to impress upon their friends or family that they have some understanding of what happens. Since there is a lot that actually is happening, the explanations are far short in one area or another. Without a complete knowledge weighing them down, it is much easier to leap to conclusions. Since there are so many small effects, I doubt that anyone can be assured of a complete knowledge of the subject. I believe the best way to approach this issue is with a more complex explanation from a unique and centrist point of view. So I am defining or redefining the atmospheric center of energy.

The Atmospheric Center of Energy (ACE) is the layer of the atmosphere where the heat content of the atmosphere above equals the heat content below. This layer is approximately at the average cloud altitude. This is not an exact level, it would move around and vary with latitude and all that. It is what I imagine is a good transition layer for heat transfer in the atmosphere.

Thermal energy is kinetic energy because it is motion. So thinking of thermal energy as a potential energy is a little different, but not a bad way to look at the energy in the atmosphere if you consider the average temperature/thermal energy. While there are flows and fluxes in all direction, the average temperature can go up or down with any imbalance. In daylight, that layer moves up, at night it moves down. Kinetic energy moves by three basic means, conduction, convection and radiation. The only way the sun transfers significant energy to Earth is through radiation. What! The sun impacts tides so there is also gravity! Quite true. For now assume it is important but does not interfere significantly with the atmospheric effect.

The dominate method of heat flow varies with conditions. Heat moves inside solids almost exclusively by conduction. The almost is because radiation can flow through solids, but only in significant amounts when solid is transparent to electromagnetic radiation or is permeable to high energy particles. For example a solid block of rock salt crystal, transparent to infrared radiation, can radiate infrared energy from its surface and its interior. The distance the radiation can travel is limited by its path length that depends on the density and composition of the solid. For the radiant energy consider radioactive substances which release gamma rays, alpha and beta particles. Gamma rays can penetrate a good distance in less dense substances. Beta particles penetrate less than Gamma rays and more than alpha particles. Alpha particles are stopped by nearly any substance. What limits the particle's travel is their size, the bigger they are the less they penetrate. Gamma rays are in the electromagnetic category with high energy. It is their wavelength and energy that determine how far they penetrate a substance plus the properties of the substance. In liquids, convective heat transfer is added to the mix. Warmer liquid rises, colder liquid falls to replace the volume of the rising warmer liquid. I am sure you have heard of a lava lamp. Radiant heat can flow through liquids, just like solids, with the same restrictions. In gases, all the modes of heat travel are in operation, but conductive flow is more limited, convective flow can be more rapid and the path for radiant flow is easier, but still has the limits imposed in solids and liquids. Gravity, that other weird form of energy, can play a bigger role with the lighter gases, a decent role with the liquids and a smaller role with the solids.

As I mentioned, heat flows from warmer to colder, but then all things are relative. After Fukushima, nearly everyone is aware that gamma rays and beta radiation can flow into your warmer body. Some understand that a beta particle has a mass, even though it is extremely small, that is traveling at a high speed, so it can smack into you. Since the gamma rays are there too, people accept that gamma rays can smack into you and go deeper. Those same people tend to get lost when it comes to a photon of energy in the infrared band of the electromagnetic spectrum smacking into the Earth or you. It is the same thing though, because that photon is a discrete quantum of electromagnetic energy that exhibits properties of both waves and particles. While not perfect, atomic radiation in general is a example of electromagnetic radiation since that is how our sun creates the energy it provides. Different process, fusion versus fission and radioactive decay, but very similar properties for this illustration.

So what does the Atmospheric Center of Energy have to do with this crap? Well, since you asked. Even though the radiant energy transfer in solid and liquids is a little complicated, in a gas with varying density, temperature and composition, it can be more complicated. The center of energy is convenient for describing some of what is going on. While the conditions related to radiant energy change with density, temperature and composition, the density temperature and composition change with altitude due to gravity and heat content. The heat content decreases as gravitational impact decreases which reduces the density of the gas molecules. We can't do much with gravity, but we can find the average heat content or center of energy as I have called it. Energy is flowing in, out, up, down, sideways, through and not, i.e. potential energy, at this point, it is a pretty busy intersection.

It is at this intersection where I feel that those explaining and those attempting to learn atmospheric physics lose it. This is where that dreaded branch of mathematics despised by every self respecting empirical science buff comes into play - STATISTICS! Or as I prefer, probability. Because up from this ACE point is less dense and contains less energy, the probability of energy flowing out to space is greater than the probability of energy flowing into the surface. Remember the down part always contains the Earth which is warmer than space and the up part only has the sun to deal with half the time. Energy is being transferred around by the big three, conduction, convection and radiation. Up is less friendly for conduction and convection and down is less friendly for radiation. Convection is really the odd energy transfer mechanism out. Convection cannot happen without conduction or radiation heating something that can expand and move or rise against gravity. Conduction only requires a difference in potential energy and a path. Radiation only requires potential energy and a path. The parallels between conduction and radiation may help better explain things

Going down, the path for conduction gets wider because there are more molecules to bang into which are its path. Up radiation has a wider path because its best path is no molecules at all. Since there are still molecules at this intersection, the probability of banging into a molecule increases downward which increases conductive efficiency and decreases the efficiency of radiant heat transfer. If the Earth had no atmosphere, there would be no convection because there are no molecules to rise, no conduction because the are no molecules to create the path and plenty of radiant energy because the path would be perfect. So the analogy of resistance to heat flow is very good for describing the atmospheric effect if you think of a variable resistor for conduction and some kind of super duper statistical radiation variable resistance for radiation. There is only one big issue with the resistor analogy, that is the relatively clear path or radiation window from the surface to space.

This image from Wikipedia shows the radiative spectrum of the window. At no point is this window 100% clear and you can see that there are several points where zero energy is transmitted due to water vapor and CO2 mainly. There are some chunks for ozone (O3) and a chunk for Oxygen (O2)near the zero wave length. This would be what it looks like if you are on the surface looking up or in a space ship looking down. At the Atmospheric Center of Energy, it looks the same if we look down and a little different as we look up. The zero percent areas due to H2O now have a little, say a few percent passing through. If we move up in the atmosphere a bit further, those H2O window grow more open. So I think it may be easy to see why water vapor that is warmed at the surface, rises with convection and condenses at or above this level can transfer its heat to space. The higher it condenses the faster it transfers heat to space. The reason that the window from the surface to space is not 100% clear, is mainly due to water and water vapor in the atmosphere. Liquid water has a little different radiation spectrum than water vapor in this range of wave lengths, so above the cloud level, the window become very close to 100%. Since CO2 is fairly well mixed, its parts of the window begin getting clearer higher as the density of the atmosphere decreases. If you figure out the area of the clear part of that image, you would have the amount of energy not transmitted by radiation from the surface to space or from the surface to the ACE.

"Now wait a minute! Radiation from the atmosphere is what slows down the rate of cooling which causes the surface to be warmer than it would if there was no atmosphere! Hurrumph! Hurrumph! Hurrumph!", you stubbornly interject. "Well, just hang on there a second bucko! From the ACE the window is clearer up so it is just as clear from up to the ACE, ain't it! So back radiation or down welling flux or whatever you what to call it, can happen more significantly the higher you go in the atmosphere. It is not my fault that from the center of energy down, it is easier for conduction to do the work." I respond with a chuckle.

"Well, heat cannot flow from cold to hot!" You exclaim with spit flying. "Great!", I say cleaning my glasses, "Then gamma rays can't cause cancer, so let's build more nukes. A photon of energy, whether from a gamma ray, cosmic ray or CO2 molecule goes where ever it goes. For enough of those photons to cause what you call heat flow, the source would have to be warmer, because the photons are also going up and to the sides. The down photons are just increasing the resistance to outgoing flow. If you think about the conductance from the center of energy to the surface, it is like you increased the voltage of the center of energy. That reduces energy flow to the center from the surface and increases the voltage at the surface. Kinda like charging a battery."

"Since you seem to have calmed down, think about that battery thing. A battery is potential energy waiting for something to do. The higher the voltage and the bigger the battery the more it can do. Since the atmosphere is storing more energy, the center of energy rises a little." Now grinning, I say.

The changes at the ACE are gradual, but imagine the radiation window above only has CO2, O2 and Ozone blocking part of the window. So let's look at the sunlight coming in. This is a link that shows a little better the goings on when the sun is shining. Unlike most descriptions, this shows what is happening with that 16 percent absorbed by the atmosphere. Two percent is absorbed by ozone, eight percent by oxygen and six percent by water vapor. A total of seven percent is scatter to the surface and 3 percent scattered to space. That seven percent scattered to the surface is 96 Watts/M^2 on a clear sky day, at high noon at the equator or 24 Watts/m^2 average for the day/night over the whole surface from scattering by oxygen. So on average, 24 Watts/m^2 of the controversial down welling radiation is diffused sunlight. The rest is not scattered back to space is solar energy, delayed on its way to the surface. Since most of the water vapor is absorbed below the ACE, most of it makes it to the surface as reduced conduction. That is also included in the controversial down welling radiation. Statistically, the vast majority of the down welling energy actually increases the potential energy below the ACE which reduces the rate of conduction from the surface. Statistically, most of the impact of CO2 on the down welling is radiation above the ACE downward, increasing the potential of the ACE which reduces the rate of conduction from the surface.

I will try and clean this up, but the perspective of the ACE, may help more people understand what is going on in the atmosphere, so they can move forward to what may change with more CO2, more or less clouds, more or less solar intensity, more of less aerosols and more or less water vapor.

How you understand the atmospheric effect doesn't really matter to most folks. To me though, without a more realistic understanding, you will probably miss some of the picture. How the radiation changes at the surface is more than just some big number getting a little bigger, it is a variety of several smaller changes interacting.

Sunday, August 28, 2011

The Coming Ice Age: Part IV CO2 Causing Cooling?

CO2 causes warming! CO2 causes cooling! What the hell is going on? The fact is that CO2 can do both. Thinking purely of the radiative impact, initially, CO2 causes a little cooling if a lot is added at once, then the warming impact catches up and over takes the cooling impact. It is kinda weird, but there is a pretty logical though a little complicated explanation.

The big thing is where is the energy coming from? Early when there is a rapid increase in CO2, the energy is coming from the sun until the surface temperature catches up. In the upper atmosphere, it is easier for CO2 to radiate to space than it is to the surface. Since a good portion of the incoming solar energy is absorbed by the atmosphere, a higher percentage of that atmospheric warming will be lost to space with a jump in CO2. The warming effect is happening just initially, the cooling wins out a little. Since there is a disruption of the outgoing energy flux, the surface temperature responds by warming until it reaches a new average temperature that is a little warmer and the atmospheric cooling and surface warming come into a new balance that is warmer if you only consider the radiative impact. Unfortunately, the world's climate system tends to be a little chaotic, so if you only consider radiation you miss the big picture.

In the first of the Coming Ice Age series, I emphasized the important role of water. Water vapor, only a part of the puzzle, is emphasized in the radiation impacts of CO2. In a warmer world the air can hold more water vapor, CO2 causes warming, more water vapor adds to the warming, so OH My God, we are in trouble!

If you only consider water vapor you are absolutely right. Clouds though are more than water vapor, they are condensed water droplets. Water reacts different than water vapor. So the cloud issue is one of the largest unknowns in the climate change debate.

The recent global not warming is likely due to cloud cover increase that causes more reflection of incoming energy than it does retention of out going energy. These changes in average cloud cover are likely associated with the longer term internal climate oscillations. The impact of these oscillations are considered trivial to long term climate because they should tend to average out. On very long time scales that is probably true. With more CO2 though, that can change in several ways.

The first is more radical internal climate variability. More water vapor in the atmosphere means more intense rain and snow events. So visions of snow in winter so rare that future children will be amazed, is totally bogus. Certain areas will have a lot more snow and a lot less snow with climate oscillations. Rain events will be a lot stronger and droughts a lot deeper. But stronger and deeper than what?

The rain and drought events so far are not exceptionally different than past recorded events and do not seem to be significant at all compared to thousand year events as best as we can tell. So while climate events will be more extreme, it is not easy at all to confidently predict how much more.

During the past 30 years of climate science, most of the period indicated warming that agreed very well with warming predicted by climate models geared to estimate the climate's sensitivity to increased CO2. For the past ten or so years, the climate appears to have shifted due to the change in one of the internal oscillations, the Pacific Decadal Oscillation (PDO) an now the sun is going into a quite mode, which the satellite era of science has never experienced. So there are a lot of questions that will get better answers.

Second, increased climate extremes during a general cooling internal oscillation is likely to cause more cooling, IF water in its solid state, snow and ice, increases albedo to a point where it amplifies the impact of the cooling. That possibility increases with a cooling PDO and quieter sun. Should another internal oscillation synchronize with the PDO and quiet sun, the possibility increases greatly.

Third, with less outgoing radiation from the surface due to increased albedo, the cooling effect of CO2 on incoming solar energy will be enhanced. That will result in more cooling or less warming if you like, due to atmospheric CO2.

So there is the potential of a lot of stuff happening with more CO2. The scientific community in my opinion is screwing up royally by stressing their certainty in one scenario, when the uncertainty of the various scenarios in more important.

Friday, August 26, 2011

The Coming Ice Age? Part III Is it the Sun?

The sun provides nearly all of the energy for our climate system. The energy in the Earth's core is small by comparison so it can be neglected in most cases. The impact of volcanic aerosols generated by that internal energy is not negligible. Large volcanic eruptions, especially near the equator, can cause significant cooling for a year or two by reflecting solar energy and by absorbing solar energy higher in the atmosphere where it is more easily radiated to space. These aerosols, primarily sulfur based, change the chemistry of the atmosphere as well. There is a complex interaction of albedo, radiation height, radiation type, radiation intensity and chemical processes that all impact climate. Like we really need more complexity, right? The last three of those variables combine to create the most uncertainty in my mind.

The newly released Cern CLOUD report indicates that cosmic rays that increase in intensity during a solar minimum interact with the trace compounds in the atmosphere to create small particles that can "seed" clouds. These particle provide a surface making it easier form water molecules to condense. The particles created by cosmic ray interaction are smaller than required for efficient seeding of clouds. This process and the size of the particles present a statistical challenge for climate scientists.

Cosmic rays that penetrate the atmosphere increase as the solar energy decreases. If the cosmic rays increase cloud formation, the impact would amplify the change in solar energy which I have shown previously is on the order of 0.18 Watts/m^2. Albedo change provides a much greater change in solar energy absorbed, so more clouds would provide the umpf. By itself though, the change in cosmic rays doesn't appear to be that significant. Volcanic activity can amplify the cosmic ray impact by providing more feed stock for the chemical process. This increases the material and time for the cosmic rays to build bigger seed particles. With the volcanic aerosols more in the high atmosphere near the equator, more water vapor is available to form clouds around these particles.

This leads to a bit of a paradox, in order to trip the Earth system into an ice age, the Earth would have to be warmer than normal for there to be enough water vapor for a rapid change. Climate records show that climate is constantly changing with two set points, warm periods and ice ages. In either of those set point ranges there are minor warm periods and minor ice ages. The minor periods are primarily in the northern hemisphere where the percentage of land area to ocean area is higher. So these minor periods are "regional". With enough of the right conditions, these "regional" events have global impact.

This year's northern hemisphere weather shows how important the northern hemisphere is to global weather. Snowfall and spring precipitation pushed records thanks to the La Nina inspired change in weather patterns. The change is water vapor distribution has the potential to create snow pack deep enough and snow cover wide enough to increase albedo or reflectivity. The extent of the snow cover was not far enough south to have a major albedo impact this time. But imagine if you will, the snow that was in all lower 48 states, being a little heavier and lasting a little longer. The snow cover below latitude 45 has much greater impact on absorbed energy than the snow pack above latitude 50. The closer the snow gets to latitude 30 the much greater the impact becomes. So did we dodge a bullet? Maybe.

While the past year had a good amount of volcanic activity, most was above latitude 45 north or below the equator. This is not to imply that the volcano has to be located between the equator and latitude 45, but the aerosol cloud from the volcano impact the area between the equator and latitude 45 with the right mix of chemical compounds. The Laki volcano is located in Iceland near the arctic circle. When it erupted in 1783, it produced strong cooling dropping the average winter temperature in the US by nearly 5 degrees C. Thirty years later, Mount Tambora in Indonesia erupted causing a colder spring and summer. The location, timing and concentration of volcanic eruption greatly impact climate.

So how can these factors combine into the perfect storm? A large volcanic eruption with the impact of a Laki in the early spring, during a prolonged solar minimum during early transition to a cooling Pacific Decadal Oscillation with a strong La Nina could produce an increase in albedo of up to 5 percent in a very short period of time. If the volcanic climate cooling persists for two years approximately, we could tip into an ice age, minor or possibly major.

While I still have some work to do, somewhat surprisingly it looks like increased CO2 may provide enough water vapor increase to drive the cooling deeper than other wise. I will leave this with a link to a NASA animation of water vapor changes in 2005. If I can dig up the information for 2010 - 2011, the comparison may be interesting.

Thursday, August 25, 2011

The Coming Ice Age? Part II

In my first post on the Coming Ice Age I gave some rough estimates of the changes of surface reflectivity and a rough range of temperatures that may correspond to those changes. I am not all that concerned with how exact those estimates are, just that there appears to be more range for cooling and some range for warming that is likely buffered by the response of the climate to the increased warming.

The reason is that the sun may be entering an new minimum cycle similar to the Dalton Maunder minimum, thought to cause the last little ice age. With global warming all the rage, though not as raging as it once was, the new minimum is seen by some to be proof that increased CO2 is not that big a deal maybe even a good thing.

Current satellite data on the sun is providing much better quality data of the impact of the change, but seems to ask more questions than it answers. The total solar power or insulation TSI only changes about 1 W/m^2 during a minimum out of 1366 watts/m^2 average. That is not enough to make much change without some amplification of its change. There are theories a plenty of things than may amplify the sun's impact. I will let those lay while I stick with my train of thought. Do remember that 1 W/m^2 would only be felt as about 0.18 W/m^2 at the surface where a full one degree change in surface temperature would require and estimated decrease of 3.7 W/m^2

A.A. Tsonis has a few studies where he determines there have been climate shifts due to natural climate oscillation that can synchronize in warm of cool phases. His papers indicate one started around the year 2000, before the current solar minimum started to show itself. That shift appears to most likely caused by the cool phase of the Pacific Decadal Oscillation (PDO). The PDO seems to cause some changes in the El Nino / La Nina timing and intensities. Dr. Roy Spencer with the University of Alabama at Huntsville (UAH) has noted that there has been a change in the percentage of cloud cover in the tropics which may be due to the PDO shift. A 1% can in cloud cover results in nearly 3 W/m^2 or about 0.8 degrees possible temperature change which will likely be less than 0.4 due to atmospheric water vapor.

Clouds have a few impacts on climate that can cool or warm things. Cloud top reflectivity is one pretty important impact. In the the original post my rough numbers indicate the range and impact of albedo or reflectivity change. Since the climate appears to have two rough set points, it takes a little push to move from one to the other. Leif Svalgard, who is a scientist studying the sun, does not think the drop in TSI due to a minimum is enough. I completely agree, but I don't think the required push is as much as many may think. Combining Tsonis' method of determining climate shifts with past climate history and the newer solar TSI reconstructions, there may be part of the push available. The synchronizing of the solar minimum with a cooling PDO.

With the PDO shift, average temperatures have leveled off. The solar minimum has started in sequence with the PDO shift and atmospheric temperatures are still pretty level but some cooling of sea surface temperatures seems be be happening. Not enough to ring any alarm bells, but a slight drop. The La Nina cycled to neutral, but instead of a new El Nino, indications are that there may be a new La Nina on the way.

The record temperatures of 1998 have been attributed to the "Super" El Nino of the same year. With our moist atmosphere, it is easier to warm with an El Nino than it is to cool with a La Nina. Temperatures in general show more rapid warming than cooling due to atmospheric moisture. So it is possible that the new La Nina if it is fairly strong, will cause a slight decrease in temperature, maybe a little more with the solar minimum. Not enough for me to say, "Ha! Its the sun and natural variability!" Possibly enough for me to say, "Watch out if the Atlantic Multi-decadal Oscillation synchronizes with the PDO AND solar!" Which has a pretty fair possibility of happening in the next few years.

If those natural variations all synchronize, the result will be more than expected cooling. How much? I have no clue. I doubt as much cooling as the little ice age, that should take a little more pushing. That is where the other theories come into play.

One I consider a player is the reduction in UV intensity. UV has been recently found to vary more than expected. Most consider UV to be a minor player. That same "most" also underestimate, in my opinion, the impact on the deep ocean of the shorter wave lengths of light from the sun, UV being one. So we may have a variety of small impacts synchronizing to create a major impact. Not out of the realm of possibility for a system with dual set points, which has some level of instability. Interesting times may be heading our way.

Should the minor factors synchronize, albedo can amplify the cooling more than it can the warming. We have a tendency for ice ages historically, why should this Holocene be particularly special?

To hypothesize is easy, to theorize is not, scientifically speaking. So it will take more research on my part to flesh out this hypothesis. Anyone reading that cares to join in is welcome to help.

The Coming Ice Age?

Climate changes on different time scales for different reasons. Ice ages or glacial periods are followed or led by warmer periods or interglacial periods. Pondering what causes these changes has been a pursuit of man since the first tree was found in a block of ice that is a glacier. I have proposed that the Earth has two temperature set points, one cold (ice ages) and one not so cold (warm interglacial periods), with water controlling the thermostat.

This is nothing new. I am sure there are many papers with similar ideas using a variety of triggers that starts the ball rolling. One question is how big the triggers have to be?

Water, in its three stages controls the show. As a liquid it absorbs electromagnetic radiation only reflecting about 7% and as a solid it reflects about 95% and absorbs only about 5 percent. As a gas water vapor is great for moving heat around absorbing and giving off heat by conduction, latent heat or phase change and radiation. So to me, water runs the show.

At this point in time the earth and its atmosphere reflects about 30% of the solar energy the Earth system receives from the sun. During an ice age, more is reflected because there is more snow and ice. Even in an ice age, the water near the equator which receives the most solar energy does not freeze. If it did, the Earth would reflect too much of the solar energy and reach a snowball Earth tipping point. To recover from that, something catastrophic would be required to jump start the Earth which would mean that the fossils of critters that survived the ice age would be piled up in an easy to find layer and we would be taught about the remarkable recovery from the Shit Hit the Fan (SHF) era. There is evidence of some the Shit Nearly Hit the Fan eras, but some forms of life survived to start things anew.
Modern man is a product of the last SNHF era or recovery from the most recent ice age.

The reflectivity of the Earth, called albedo, which I can mix up absorptivity, is right now 30%, with most of that caused by clouds mainly in the tropics and sub tropics. Snow and ice at the poles and on top of mountain ranges contributes a small amount to the reflectivity because most of the snow is at the poles where solar radiation is much lower. The reflectivity cannot reduce much more. If all the snow and ice on the Earth melted, that may drop the reflectivity to 20% but all that water would produce more clouds so 25% is closer to the absolute minimum.

During an ice age the reflectivity increases, but it also has a maximum limit. This may be pretty hard to estimate. It is unlikely that the glaciers would expand to the tropics. The tropics are between 23.5 N and 23.5 S, the imaginary lines of the summer and winter equinoxes. Just for simplicity, I want to use 30 N and 30 S as my estimate tropical boundaries. Why? Because the sine of a 30 degree angle is one half. Since the Earth is pretty much a sphere, from equator to 30 N receives 50% of the solar energy of the northern hemisphere and the same thing from the equator to 30 degrees S. So 50% of all the energy the Earth receives is collected between 30 N and 30 S. If we assume that the cloud cover in this region remains about the same, we can assume that even during an ice age the Earth still absorbs 50% of the energy it absorbs in an interglacial period. Since the sun pumps out about the same amount of energy all the time, the worst case glacial albedo would 70/2 plus 30 equals 65 percent. So the range of albedo is in the ballpark of 25% minimum and 65% maximum, that means that the Earth can absorb between 75% and 35% of the solar energy available.

Since NASA has been kind enough to publish the solar energy available at the top of the atmosphere (toa) and we live on a pretty close to a sphere planet, the range of energy absorbed is 256 W/m^2 to 120 W/m^2. Power varies by the fourth root of the temperature, so while there is a big power difference, the temperature difference is not so big. So just using the fourth root, the apparent temperature at the toa would range from 2% more to about 16% less. This is based on the absolute temperature, which is about 255 K at the toa right now, so we have a rough range of 260 K to 214 K. While the average temperature of the surface depends on a bunch of stuff, a rough estimate for my purpose would be the same percentages of the 288K average surface temperature or 293K to 242 K as rough maximum average temperature ranges at the surface if albedo varies from 25% to 65 percent.

These are of course very rough numbers and not intended to be accurate enough to be useful for anything more than an illustration of the relative limits of climate change based on albedo change.

242 K is pretty cold. 274 K is zero degrees C and 242 is -32 degrees C or -26 degrees F. The temperature during the glacial periods is only estimated to be 6 degrees less or 282K. So why would my worst case be so much lower than 282K? Because of the location of the oceans.

The image above is an artist's conception of an Ice Age Earth from wikipedia. The northern hemisphere took the biggest hit because it has more land mass which doesn't benefit from the thermal mass of the ocean. So the 30N to 30S could be extend to 45N to 55S as to determine a more accurate maximum ice extent, or back calculating from the average temperature of the glacial period find that an albedo increase to 37% could produce that change. That would give us a more realistic maximum change albedo range of 25% to 40%.

While these are rough estimates, they show how lucky we are to live on a water world that has reasonable limits with our stable sun. Not that a new glacial period or 5 degrees of warming would be fun, but runaway conditions up or down are avoided thanks to the amount of water and where it is located.

Tuesday, August 23, 2011

Building a Better Discription of the Role of Our Atmosphere

I chose that title because I am going to work on this from time to time. This is related to the last post on the energy budget but I am going to try and stay more focused. The first part is incoming solar radiation and the atmosphere.

Going back to the NASA budget cartoon, the sun provides 100% of the energy to the Earth that is significant. There is energy from the Earth's core and people burn things, some there is other energy, but the most significant source is the sun. Of that energy, about 51% is absorbed by the oceans, 16% absorbed by molecules in the atmosphere and about 3% absorbed by clouds. The total absorbed is 70% of the solar energy available. The 30% not absorbed is reflected by cloud tops and the Earth surface.

Since I want to do comparisons of the in and out of the energy at the surface and hopefully the tropopause eventually, since the Earth system absorbs 70%, 72% of the absorbed energy is at the surface with 28% in the atmosphere. Since the sun only shines in the daytime, at least in my experience, This is the division of the total energy input into the system. Some can debate what the actual value of that energy is, but there is general agreement that this is the division of the energy.

Of the energy absorbed by the atmosphere, approximately half is can be considered transferred via various thermodynamic means to the surface and the rest lost to space. This point can be debated because the diameter of the Earth plus atmosphere is greater than the core diameter. For now we will assume a 50/50 split and possibly revisit the other possible value later. With this assumption, 60.5% of the solar energy at the top of the atmosphere is absorbed by the surface directly or via the atmospheric thermodynamics. So now I am going to give these percentages some numbers, using the 341 Watts/meter squared, the Earth system absorbs 239 W/m^2 with 172 W/m^2 directly absorbed by the surface, 67 W/m^2 directly to the atmosphere with 33.5 W/m^2 radiated to space and 33.5 W/m^2 transferred to the surface, bring the surface solar total impact to 205.5 W/m^2. These numbers vary from the values list on the Trenbert et al 2008 paper with cartoon. That cartoon has 161 W/m^2 to the surface and 78 W/m^2 to the atmosphere with no division of the atmosphere to Earth and space. Since the NASA budget cartoon is more widely accepted, I will continue to use their percentages and compare to Trenberth 2008.

At this point there is an easy comparison to the Postma online paper where Postma argues that the value should be 480 not 240 (~239), which just doesn't work. Since Trenberth uses 161 W/m^2 to the Surface and 78 to the atmosphere,the surface impact including the atmosphere is 200 W/m^2 instead of 205.5 to give you an idea of how close the two are together in this respect. During the day, approximately 480 W/M^2 is absorbed by the Earth/atmosphere with about 400 to 411 W/M^2 being absorbed by the surface assuming half of the energy absorbed by the atmosphere down wells to the surface and half is lost to space during the complex process of heat transfer being mainly radiative near the TOA and becoming a mix of radiative/convective/conductive below the TOA becoming more conductive/convective at the surface. Convection has a major impact because air near the surface rises (this is shown as thermals on the Trenberth drawing)and is replaced by sinking cooler air which is warmer than it would be because of the absorption of solar in the atmosphere. So a portion of the heat in the atmosphere is physically down welling, as in falling, to the surface.

At this point you may see why I am not disagreeable with the term "Down Welling" with respect to a cooler atmosphere contributing to the warming of the Earth or reduced cooling if you prefer. I am not fond of "back radiation" because while the radiate heat from the surface and lower atmosphere contribute to the warmth of the atmosphere, physical "back radiation" plays a very small percentage of the role.

For a second comparison, the NASA drawing shows 6% of the incoming solar directly radiated from the surface to space. This is the infrared energy that has a clear window to space. By NASA's cartoon that 6% is 20.5 W/m^2 with Trenberth showing 40 W/m^2. That is a substantial difference at first glance, but reasonable considering Treberth's goal. Trenberth's diagram better illustrates what is happening because the temperature that causes the up welling infrared is both from the surface and the warmer lower atmosphere and reason for the difference is more understandable with the next comparisons.

Per NASA, 23% or 78.4 W/m^2 is rising to the atmosphere as latent heat with water vapor. Trenberth's value is 80 W/m^2 by evapo-transpiration. Nasa has 15% or 51 W/m^2 to the atmosphere by surface radiation versus 23 W/m^2 per Trenberth (356 - 333 is the net to the atmosphere). This partially covers the surface up welling difference. Warm moist air rising with cold dry air falling is a common meteorological model. How moist and how dry is not described, so the convection is separated into latent and thermals or conduction.

NASA shows 7% or 24 W/m^2 rising from the surface due to conduction versus 17 by Trenberth labeled as thermals. Here, Trenberth seems to cover the rest showing that the atmosphere donates to the radiation lost in the free path out going radiation.

Going back to the balance in the atmosphere related to the surface, for the surface, Nasa has a total of 74.8 + 51 + 24 = 149.8 to the atmosphere + 20.5 to space I propose, equaling 170.3. Trenberth has 80 + 23 + 17 = 120 rising from the surface to the clouds plus 40 to the surface I point out, equaling 160 W/m^2 with an imbalance of 1 W/m^2. There is an imbalance of 1.7 W/m^2 in the NASA comparison due to rounding errors.

Comparing my calculation of the solar energy absorbed by the atmosphere on the surface, 205.5 - 170.3 = 35.5 W/M^2 NASA and 200 - 160 = 40 W/m^2 Trenberth, the solar energy absorbed by the atmosphere's impact on the surface. The difference is because I am using a frame of reference in the atmosphere, not at the top of the atmosphere. Where that point is located in the atmosphere is roughly where the up welling/ down welling energy is in balance, approximately at the bottom of the average cloud height.

Since NASA doesn't include the greenhouse effect in its budget and Trenberth uses total radiation up of 396 and down of 333 to illustrate the radiative impact, there are questions about the impact and sources of the downward radiation flux. This is where I may screw up so watch closely! The point I have picked, approximates the middle of the green house action. The difference in the net fluxes shown be Trenberth are 396 up - 333 down equals 63 W/m^2 net up. Since the solar impact is not separated 40 W/m^2 (or 35.5 from NASA's drawing) is the solar absorbed greenhouse impact and the rest, 23 W/m^2 (to 27.5)is Earth surface generated greenhouse impact. Remember that this is estimated and there are slight differences between the two budgets.

At the top of the atmosphere the main differences between the two diagrams is the 1 W/m^2 imbalance on the Trenberth drawing which is based on the model estimate of the imbalance due to CO2 (0.8 w/m^2 if you don't like the rounding). NASA assumes energy in equals energy out and Trenberth assume an imbalance due to CO2.

There are several reasons I break the drawings down this way, the main one though is to illustrate the Greenhouse effect or atmospheric gas vibrational mode effect. Some gas molecules are better absorbers/emitters of radiation than others due to the configuration of their molecules. Diatomic gases like nitrogen N2 and oxygen O2 have a simple two atom configuration. When excited by radiation they can only vibrate by stretching their bonds, pulling apart a little and springing back. Water, H20 has three atoms and a vee configuration, both atoms can stretch away at the same time, one can stretch away while the other springs back or the hydrogen atoms can swing toward each other the away from each other. So water has three fundamental vibrational modes. These are shown in this wikipedia article along with more interesting stuff. The "greenhouse gases" are called that because they have more vibrational modes which allow them to interact with electromagnetic radiation more efficiently than diatomic atoms. So there is a difference and because of the difference, so some molecules are much more effective interacting with different wavelengths of electromagnetic radiation (EMR), both incoming from the sun and out going from the surface, than others. Nitrogen and oxygen that make up 99% of the atmosphere are reasonable conductors of heat, but much less effective, even in much higher concentration, interacting with EMR. A simple illustration is right in your kitchen. Put a beef brisket in a pressure cooker with no water and another in a pressure cooker with water, which one do you think will cook better? Now most of the difference is the properties of steam, not just absorption of radiation, but it gives you an idea how differently water behaves when heated. So it is not unreasonable to believe water vapor behaves much differently to radiation than other gases. If you have ever seen dry ice, frozen CO2, you know that it behaves differently to heat than water. Dry ice sublimates, it goes straight from a solid to a gas. Because of their differences, CO2 just happens to interact more with EMR at certain wavelengths than water and much more than nitrogen or oxygen. Different people try to explain the greenhouse gases with different levels of success, I will just let you know there is a difference and you can study more if you like.

If you accept that greenhouse gases are good absorbers and emitters of EMR, then you can think about how they have an effect on the surface. First think about the warming of the air by the sun. A good deal of that warming is lost to space but about half wants to move to the surface both in the day and at night. In the day, you can probably believe that it helps both warm the Earth and slow the rate of warming some. The evaporation of water from the surface happens mainly in the middle part of the day, which also helps slow the rate of warming. That rising water vapor with its latent heat increases the amount of solar energy absorbed in the day by increasing the amount of water molecules that can interact with the solar radiation. Most of the "warming" effect of the atmosphere containing greenhouse gases is directly do to solar energy directly, not energy radiated from the surface. Since the NASA diagram did not try and the Trenberth diagram lumps its down welling radiation together, that point is not obvious. So remember that the greenhouse effect is a two way street.

A perfect illustration of the atmospheric impact is here in the tropics. Where I live is surrounded by the ocean. Today's high temperature will be 90 degrees F with the low today of 83 degrees F. Brownsville, Texas, just a little north, near sea level and not surrounded by water will have a high of 97 and a low of 79. Water vapor does make a difference.

Getting back to the estimated solar contribution not included in the drawings I calculated earlier, the 23 to 27.5 W/m^2 is about a third of the atmospheric warming. If you take the solar energy absorbed by the air and clouds plus the rising latent heat, that works out to about two thirds so up welling would be about a third. While not a perfect check, it somewhat confirms my estimate at the surface using my frame of reference. CO2 in the atmosphere is well mixed, unlike water vapor which mainly stays in the lower atmosphere. This makes CO2's impact a little more complicated because it can help cool by blocking a portion of the down welling radiation high in the atmosphere and warm lower in the atmosphere by absorbing more outgoing radiation. Twice as much CO2 is estimated to increase the total down welling radiative impact by about 1 percent. Because of the interaction with wavelengths associated with water vapor and that an increase will increase the amount of water the atmosphere can hold, an estimate is about the best anyone can hope for. Clouds, made of water vapor, absorb about 3% of the incoming solar and reflect about 20 percent. So a one percent increase in clouds would erase the one percent increase in down welling due to doubled CO2. There would be an increase in the solar absorbed by clouds, but only about half that increase would impact the surface. The cooling effect of CO2 should offset much of the increase in incoming solar absorption. That may limit CO2's impact to mainly the one third out going radiation to the atmosphere and a fraction of the direct surface to space radiation, but the warming will also increase the amount directly radiated to space from the surface. So what heats where, by how much and at what wavelength all have to be considered.

While I don't have a problem with down welling radiation, the sky has a temperature after all, I do have an issue with causes warming by directly radiating the surface or if it is better thought of as slowing the rate of cooling. Since the Earth system tries to balance radiative flow, energy in equals energy out, the Earth will become warmer if something tries to reduce energy out and cooler if something reduces energy in. So it is more a matter of semantics, but common thinking in thermodynamics is heat flows from warm to cold. Radiation is a little more complicated because of its relationship with its atmospheric window. Radiation from a colder object can flow through a warmer object or layer, that happens in our atmosphere. Radiation can flow from a colder object to a warmer object. That happens also. In a vacuum, a colder object can cause a warm object to grow warmer by reducing the warmer object's net out going radiation flux. In our lower atmosphere though,the path of the flux in both directions is pretty well blocked, so conduction plays a large role in the heat transfer. Conduction is a one way street, so I am incline to stick to the old school rational. It doesn't much matter because the end result is Earth is warmer because of our atmosphere.

So without argument, I can accept that a doubling of CO2 will likely cause a one percent increase in down welling which results in a one percent reduction of the net out going radiation, which will cause some degree of warming for some time period. I am not convinced that change will cause feedbacks that increase the degree of warming or that the Earth system will not compensate for the change with more cloud cover, precipitation and/or changes in circulation patterns to reduce the increase in temperature. How the Earth responds to the change is the major issue of the global warming debate, not if the atmosphere contributes to the warmth of the surface.

Most of the debate recently on the Climate Etc. blog, centers around the issue of down welling energy, specifically radiation. I think that my taking a slightly lower frame of reference may reduce the differences there somewhat, at least among the more reasonable factions. The Postma skeptics are a whole different issue.

The Postma crew does not believe that the averaging of the incoming solar radiation is correctly calculate, that it should be twice as much. Postma considers the day side with its 480 W/m^2 and integrates the distribution of the atmosphere resulting in 610 W/m^2. This is were I have difficulty following his argument. I can see integrating the incoming solar at a point in the atmosphere where the atmosphere outside the radius of the Earth is warmed that can contribute to Earth atmosphere system. The sun's rays do pass through the atmosphere around the edge of the Earth's surface creating some beautiful sunrises and sunsets. This impact was brought up is 1996 in a paper by Albert Arkin in Science Magazine;

"An atmospheric general circulation model, which assimilates data from daily observations of temperature, humidity, wind, and sea-level air pressure, was compared with a set of observations that combines satellite and ground-based measurements of solar flux. The comparison reveals that the model underestimates by 25 to 30 watts per square meter the amount of solar energy absorbed by Earth's atmosphere. Contrary to some recent reports, clouds have little or no overall effect on atmospheric absorption, a consistent feature of both the observations and the model. Of several variables considered, water vapor appears to be the dominant influence on atmospheric absorption."

Since this issue was brought up by this and other papers well before the Trenberth budget, I don't think it unreasonable to assume it has been addressed. In any case, that small of a discrepancy does not resolve Postma's situation.

Postma accurately calculates the total solar input power at 1.22 x 10^17 Watts, since the area of the Earth is 5.1x10^14, the Watts per meter squared would be 239.2 or 478.4 for just the day side. He back calculate the total energy based on an average surface temperature of 1.99 x 10^17 W which implies an average surface radiating average temperature of 15 degrees C resulting in 390 W/m^2 or 780 W/m^2 for just the day side which be radiating at an effective temperature or 30 degrees C, twice the average of 15 degrees C. This also agrees well with the mainstream calculations considering the greenhouse effect. Here though, Postma concludes that that is impossible within the laws of physics. To reconcile his perceived energy deficit he concludes that the earth system or aggregate spherical ensemble (Earth plus atmosphere) has to be considered. This is not an outrageous way to consider the Earth energy budget, it is after all a combination of the Earth and atmosphere.

Unfortunately, Postma notes that the average surface temperature of the sunlit side does not achieve 30 degrees C. That is true, because the average surface temperature is 15 degrees C, the sunlit only hemisphere does not exist in reality. It is a concept of mathematics. The Earth rotates. Then Postma concludes that if the concept of mathematics radiated at 30 degrees C that it would emit 1.22 x 10^17 Watts which equals the total absorbed by the spherical ensemble from the sun, which is exactly what the mathematical concept should do. For the real world average temperature to not equal that of a mathematical concept of a hemisphere receiving "instantaneous" solar energy is not an unreasonable concept for most people to grasp. Postma is not most people so he determines that this concept would have a maximum temperature of 87.5 degrees C, a temperature not found on the real Earth's surface. Half of the 87.5 is 43.8 degrees C, pretty damn hot still. While 43.8 is hot, it is less than the warmest temperatures ever recorded.

Except for the scientific brain fart, Postma's math is very good, his visualizing of concepts not so good. His confusing mathematical conceptual models with reality should limit his scientific career options. I, being a fishing guide, can have all the scientific brain farts I like without suffering loss of career options I am not pursuing.

Back to my ideas based on the lower frame of reference. With two thirds of the atmospheric warming due to the solar input absorbed by the atmosphere and latent heat rising, one third would be due to conduction and outgoing radiation which are related. The temperature of the Earth causes both. Separating latent makes a great deal of sense because latent heat is much greater than sensible heat which is the majority of the conduction.

This is a work in progress that will probably die, but I may continue with the Sky Dragons if the hurricane season insists.

Sunday, August 21, 2011

Earth's Energy Budget Controversy: Circular Argument at its Finest

The argument over the impact of changing CO2 on the Radiation Energy Budget of the Earth frustrates the hell out of me. For CO2, the impact is on the 15% of the outgoing radiation absorbed by the atmosphere. Absorbed is the first problem. CO2 has an emission and absorption spectrum where it interacts with electromagnetic radiation. Absorbed does not mean "trapped", delayed is better but still subject to confusion, interacts is what happens and there are consequences following that interaction. The net effect is that it slows the flow of radiant heat from the Earth slightly. The 15% on the NASA chart is based on the total energy provided by the sun to keep things simple. The NASA cartoon or diagram is a very useful basic tool.

Before when I posted on the radiation budget as a puzzle, my answer was that the numbers on the NASA cartoon would not change or have very little change with twice as much CO2. I still believe my answer is 100% correct.

With the Radiation Budget provide by Kieth Trenbert, there are similarities and differences to the NASA cartoon. The biggest difference is that Trenberth uses radiant energy flows or fluxes to include what he perceives to be the balance with a minor adjustment for CO2 warming that is determined by a model because it cannot be accurately measured. There is nothing wrong with than as long as it is understood what the purpose of the work is. This work is responsible for the "travesty" quote by Trenberth where he thought it was a travesty that there was missing heat. Nothing particularly unusual about that, it is not an easy task to determine because there are inaccuracies and uncertainties. Because of the intent of his work, the values are recorded differently with more focus on the difference between the outward radiation and the inward radiation.

The simplified Trenberth radiation budget cartoon is useful for his intended purpose, but since it is not a direct comparison to the NASA budget cartoon, it creates a lot of valid questions for those that look at radiation and heat transfer in the old school way. The old school understands that the direction of heat flow is from warm to cool and while there is radiation from the sky to the surface, the net is from the surface to the sky, i.e. flow is always out at night and only in during the day. The modeled value that Trenberth uses is the energy imbalance caused by increased CO2 so his cartoon indicates that the sky is "physically" warming the surface. Whether that is possible according to the laws of physics is debatable. Technically, that is possible, as a general rule it is highly unlikely for any significant amount or time period. His cartoon indicates something that may be happening in the magnitude indicated by the model, that is not physically measurable. Could it happen? Yes. Would it last a significant time period? Not likely. There are constant brief radiation imbalances and adjustments, that is why the old school prefers to use the net flow, to simplify the situation.

Since Trenberth drew his cartoon the way he did, it is difficult see what change CO2 could have and why. Major problem for those trying to understand a rather complex issue. One person that is skeptical, Tall Bloke is his internet pen name, wanted to know what part of the down radiation is "new". That is a valid question that is not obvious in most diagrams of the "greenhouse" effect.

Neither Trenberth nor NASA makes it all that easy to answer the "new" energy question. "New" Energy may be defined as energy directly supplied to the Earth system. The sun warms the air above us and the clouds directly with approximately 19% of its total energy available at the Top of the Atmosphere (TOA). Moisture rising from the surface to the sky may be considered new, because it has latent, meaning hidden, heat. The latent heat is given up to the sky primarily by condensation when the water vapor becomes precipitation. As most everyone knows, the temperature of water remains constant while it is changing its state from solid to liquid or liquid to gas. So the evaporation of water does not have a major impact on surface temperature other than to stabilize the temperature somewhat during the evaporation and the main impact is felt with condensation when the heat is released. Since evaporation is at or near the surface and condensation starts high in the atmosphere on average, latent cooling is a major player accounting for 36% by NASA and 40% per Trenberth of the atmospheric warming while cooling the surface. If you combine the solar and latent factors, 61% (NASA) to 79% (Trenberth)of the warmth of the atmosphere is due to "new" energy.

This is very important for people trying to teach atmosphere radiation physics, the source of the heat and its location in the atmosphere. The reason being that radiative heat transfer of gases changes with the optical depth of the paths of radiative flow. This is known as the radiation window, the optical depth for different radiative frequencies. The higher the molecule is in the atmosphere, the cleaner the window is to space and the dirtier the window is to the surface.

While all that is fairly simple, here is were things start getting interesting. Greenhouse gases make the window dirty, it is much dirtier at the surface than it is at the top of the troposphere, that layer of the atmosphere we live in. Anyone that has climbed a mountain or flown in an airplane knows it get cooler the higher you go. That is because with the cleaner window up and the dirty window down, it is easier for the heat to leave going up so it leaves faster. In the middle layer of the troposphere it is a little easier up than down and at the surface it is barely easier to leave up and damn near impossible to go down. So knowing how much "new" energy there is and where it is important.

As a note, some try to explain the decrease in temperature with altitude with only the gas laws and gravity. That is not a complete explanation because of the three types of heat transfer, conductive, convective and radiant, conductive and convective decrease with altitude while radiant increases with altitude, all have to be considered for a valid explanation.

The new energy from latent heat rising and solar warming of the clouds is easiest to locate, it is about midway to the top of the troposphere where it is easier out than in. So more CO2 will make the up dirtier and the down dirtier which will result in very little change to the impact of these "new" energies. The CO2 may slightly increase the cooling relative to these "new" energies, but not much, at least now right away. The solar absorbed by the atmosphere is a little different. If it is spread uniformly from the top down, then CO2 will increase the top absorption and decrease the bottom absorption which will result in more cooling. If most of the solar absorbed by the atmosphere is near the surface, likely, then the impact is much more dependent on the radiation spectrum of the absorbing molecules and the spectrum of the molecules being energized by collision with the absorbing molecules. That is pretty complicated.

For old energy you have conduction or thermal updrafts and radiation from the Earth's surface. These will be most impacted by the increase in CO2 because they start at the dirtiest window. CO2 will only make it dirtier. So while more CO2 will not "trap" the heat, it will make its road to the TOA longer or slower. Longer is a good term because the path length of the radiation decreases with a dirtier window. The distant to the top is the same, but the heat has to take more, shorter paths and detours.

So most of the confusion is that the pros don't explain that CO2 only has a major impact on about a third of the heat energy traveling from the surface to space. Looking at Trenberth's cartoon it is easy to imagine that two thirds of the energy at the surface is due to down welling radiation, but two thirds of that two thirds is due to "new" energy that will have little change due to changing CO2. So in my opinion, Trenberth's cartoon would be much improved if it separated the distribution of the down welling radiation by source, if his intent is to explain the greenhouse effect.

The huge amounts of energy fluxes Trenberth show up and down are just as misleading as trying to explain the decrease in temperature with altitude with just the gas laws and gravity. The impact of radiation decreases with altitude while conduction and convection increases. Molecules with heat energy are constantly moving and collide with other molecules more often when there is a higher concentration of molecules per volume. The collisions transfer energy via conduction basically. When they are in contact they can transfer energy without having to radiate that energy. There is more to it than that, but the process is more conductive that radiative. When molecules transfer heat radiatively, they emit or absorb photons of energy within their radiative spectrum. With collision, CO2, water vapor or any molecule can swap energy with any other molecule most likely nitrogen which makes up most of our atmosphere or oxygen which comes second. Nitrogen and oxygen swap energy with other molecules nearly exclusively by collision. They do emit radiant energy, only the amount emitted via radiation is miniscule compared to collision and much lower than CO2 or water vapor. What nitrogen and oxygen do though is transfer energy from one type of greenhouse molecule to another. Radiative transfer is restricted to the spectrum of the molecule emitting, collisional transfer is not. So when a CO2 molecule bumps into a nitrogen molecule, then the nitrogen bumps into a water vapor molecule, that photon of energy from the CO2 can be emitted by the water vapor at a different wavelength. Neat huh? So now the CO2 energy can increase conduction also called thermals or rising air and latent heat. So the radiative heat transfer picture gets muddy near the surface. The "greenhouse" gases can absorb photons of radiation but it is almost impossible for them to radiatively emit because of collisions. So the down welling radiation which does exists causes an increase in the overall rate of energy transfer between molecules but reduces the rate of flow of heat to the TOA. This is a bit of a paradox, increased down welling radiation higher in the atmosphere does cause the surface to be at a higher temperature, but conduction and convection are the means of heat transfer that increase at the surface, since emission of radiation by "greenhouse" gases is pretty well maxed out at the surface.

There are plenty points to debate on the climate change front, but the fact that there is warming of the sky that warms the Earth is not one. That warming can be expressed as net radiation flux increasing, causing slower cooling or individual fluxes up and down or sideways doing that same thing, but either way the sky has a temperature and anything with a temperature radiates energy which impacts the radiate energy flow rate of any other object, dependent on the temperature difference between the objects, the radiation window between the objects, the absorption/emission spectrum of the objects, the effective thermal conductivity and their separation. Simple right?

Update: Since I am talking about the sky, I should have had the effective thermal conductivity which I added in bold. In a vacuum things are purely radiative, in the atmosphere, even pretty high, there are molecules that can collide. So the temperature difference and the effective thermal conductivity play a role that decreases with increased altitude, minor I know, but I was being a smart ass.

As usual this was just a quick post while waiting on something to dry, so there may be a few typos or minor errors, but it should be pretty accurate.

Thursday, August 18, 2011

Pondering Climate and the Greenhouse Effect

While most of the world has moved on to other more pressing issue, the climate change debate still rages among the devoted. Joseph Postma is a smart guy with degrees and everything that believes that CO2 has no significant impact on climate at all. Postma has a published paper, The Model Atmospheric Greenhouse Effect,where he attempts to set the scientific world straight. I can't really comment on the paper because the error in calculating the average solar power at the Earth's surface is so obvious, I won't waste my time. A year or so ago when I first heard of this my bullshit detector went off and I did the rough calculations myself and they happen to agree with NASA and the rest of the mathematically literate world, not Mr. Postma.

Most view Postma arguments comical or worse, but he some sway in the radical skeptic community. One defense he uses for his calculations is that there would be no liquid water on the planet if NASA's numbers are right. He is wrong, but the liquid water thing is something I have never written about.

Water is a remarkable substance. While all life needs to consume water to survive, water is much more important to our survival. On our world which has a surface covered with 70% water, things are a lot different than if there was less or if it were not located where it is. For example if the water was only at the poles and all the land mass was at the equatorial region, there would be no life as we know it. If there was 50% water and 50% land the same thing. Climate is somewhat stable because of the amount, location and properties of water. Our climate is extremely sensitive to water in all its phases.

First, think about the reflectivity of the Earth or its albedo. Snow is highly reflective, the tops of clouds highly reflective and liquid water high absorptive of solar radiation. Snow and ice reflect between 90 and 95 percent of the sun's rays. Water absorbs about 93% of the sun's rays. Same molecule, radically different properties. Water also has one of the highest thermal capacities of any element as a liquid, solid or vapor. It is remarkable.

The average albedo of the Earth right now is about .7 meaning we absorb about 70% of the solar radiation. The vast majority of that albedo is due to water which covers most of the Earth's surface and a good portion of the atmosphere. While the climate change debate is mainly about CO2 which may cause a percent or so change in the outgoing radiation that cools the Earth, water can make a 10% change in the outgoing and the absorbed incoming with just a little push.

With climate, water's importance is best viewed by the conditions during the glacial periods. Some trigger, an asteroid impact, slight change in orbit, passing through a comet's tail can reduce the absorbed solar radiation enough that more ice and longer lasting snow cover persists for a while. This decreases the Earth's albedo which decreases the heat absorbed, decreasing the heat stored in the oceans. The Earth moves toward what has been called a snowball Earth. Unlike too much global warming, too much global cooling has happened pretty regularly. Luckily, Snowball Earth is not really a complete snowball. Glaciers move further towards the equator and move closer to the surface, but never completely cover the entire planet. If they did, Earth would not recover without another catastrophic event. All indications I have seen indicate that the Earth recovers naturally until the albedo increases to a magic number that cues a new interglacial period like the one we enjoy now.

It is not really magic, but the combination of the right albedo, the right solar cycle series and the right amount of volcanic activity cue the change. There is not a lot of solar change, nor a lot of volcanic change, but a little of each change albedo which feeds back on itself to cause the big change. Just like the right decrease in albedo triggered and amplified the cooling, the right increase in albedo triggers the warming. The Earth has two temperature set points controlled primarily by albedo which is controlled by water.

Mr. Postma seems to think that the calculated average solar energy input is not enough to sustain liquid water. In my opinion this is the most glaring error of his paper. Even in the glacial periods which have much lower solar energy absorbed there is still liquid water near the equator. Since there is much more water along the equator than there is land, even a snowball Earth can sustain life.

Water is also the largest unknown in the global warming debate. A warmer world means the atmosphere can hold more water vapor which can either add to the warming or tend to reduce the warming. The room for warming to increase albedo is not as large as the room to reduce albedo. There will always be ice and snow at the poles in winter which will persists into the summer. The normal weather patterns with more water vapor in the air means the chance of larger snow storms and rain storms increase, both reduce albedo. The warming can cause longer and more severe droughts, but droughts are over land and most of the droughts will be in the temperate latitudes. Droughts in the temperate zones have less impact on albedo, tend to increase atmospheric dust which can promote cooling and increase radiative cooling locally because of less water vapor.

Increased water vapor also tends to block a portion of the CO2 radiative impact at the surface. The reason most impact of increased CO2 should be at the poles and upper troposphere is because there is less competition with water vapor.

So while there is no guarantee that warming will not be enough to worried about, thanks to water the likelihood of catastrophic warming is reduced.

Note: The average albedo is more like 30% meaning the absorbed is 70%. So the references to albedo are reversed, but the idea remains the same.