Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Settings


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Bluesky Facebook LinkedIn Mastodon MeWe

Twitter YouTube RSS Posts RSS Comments Email Subscribe


Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...



Username
Password
New? Register here
Forgot your password?

Latest Posts

Archives

Sun & climate: moving in opposite directions

What the science says...

Select a level... Basic Intermediate Advanced

The sun's energy has decreased since the 1980s but the Earth keeps warming faster than before.

Climate Myth...

It's the sun

"Over the past few hundred years, there has been a steady increase in the numbers of sunspots, at the time when the Earth has been getting warmer. The data suggests solar activity is influencing the global climate causing the world to get warmer." (BBC)

At a glance

Thankfully for us, our Sun is a very average kind of star. That means it behaves stably over billions of years, steadily consuming its hydrogen fuel in the nuclear reaction that produces sunshine.

Solar stability, along with the Greenhouse Effect, combine to give our planet a habitable range of surface temperatures. In contrast, less stable stars can vary a lot in their radiation output. That lack of stability can prevent life, as we know it, from evolving on any planets that might orbit such stars.

That the Sun is a stable type of star is clearly demonstrated by the amount of Solar energy reaching Earth's average orbital position: it varies very little at all. This quantity, called the Total Solar Irradiance, has been measured for around forty years with high accuracy by sensitive instruments aboard satellites. Its average value is 1,362 watts per square metre. Irradiance fluctuates by about a watt either way, depending on where we are within the 11-year long sunspot cycle. That's a variation of no more than 0.15%.

From the early 1970s until today, the Solar radiation reaching the top of Earth's atmosphere has in fact shown a very slight decline. Through that same period, global temperatures have continued to increase. The two data records, incoming Solar energy and global temperature, have diverged. That means they have gone in opposite directions. If incoming Solar energy has decreased while the Earth continues to warm up, the Sun cannot be the control-knob of that warming.

Attempts to blame the sun for the rise in global temperatures have had to involve taking the data but selecting only the time periods that support such an argument. The remaining parts of the information - showing that divergence - have had to be ditched. Proper science study requires that all the available data be considered, not just a part of it. This particular sin is known as “cherry-picking”.

Please use this form to provide feedback about this new "At a glance" section, which was updated on May 27, 2023 to improve its readability. Read a more technical version below or dig deeper via the tabs above!


Further details

Our Sun is an average-sized main sequence star that is steadily using its hydrogen fuel, situated some 150 million kilometres away from Earth. That distance was first determined (with a small error) by a time consuming and complex set of measurements in the late 1700s. It led to the first systemic considerations of Earth's climate by Joseph Fourier in the 1820s. Fourier's number-crunching led him to realise a planet of Earth's size situated that far from the Sun ought to be significantly colder than it was. He was thereby laying the foundation stone for the line of enquiry that led after a few decades to the discovery of what we now call the Greenhouse Effect – and the way that effect changes in intensity as a response to rising or falling levels of the various greenhouse gases.

TSI Solar cycles

Figure 1: Plot of the observational record (1979-2022) on the scale of the TSIS-1 instrument currently flying on the space station. In this plot, the different records are all cross calibrated to the TSIS-1 absolute scale (e.g., the TSIS1-absolute scale is 0.858 W/m^2 higher than the SORCE absolute scale) so the variability of TSI in this plot is considered to be its “true variability” (within cross calibration uncertainties). Image: Judith Lean.

The Sun has a strong magnetic field, but one that is constantly on the move, to the extent that around every 11 years or so, Solar polarity flips: north becomes south, until another 11 years has passed when it flips back again. These Solar Cycles affect what happens at the surface of the Sun, such as the sunspots caused by those magnetic fields. Each cycle starts at Solar Minimum with very few or no sunspots, then rises mid-cycle towards Solar Maximum, where sunspots are numerous, before falling back towards the end. The total radiation emitted by the Sun – total solar irradiance (TSI) is the technical term – essentially defined as the solar flux at the Earth's orbital radius, fluctuates through this 11-year cycle by up to 0.15% between maximum and minimum.

Such short term and small fluctuations in TSI do not have a strong long term influence on Earth's climate: they are not large enough and as it's a cycle, they essentially cancel one another out. Over the longer term, more sustained changes in TSI over centuries are more important. This is why such information is included, along with other natural and human-driven influences, when running climate models, to ask them, “what if?"

An examination of the past 1150 years found temperatures to have closely matched solar activity for much of that time (Usoskin et al. 2005). But also for much of that time, greenhouse gas concentrations hardly varied at all. This led the study to conclude, "...so that at least this most recent warming episode must have another source."

TSI vs. T
Figure 2: Annual global temperature change (thin light red) with 11 year moving average of temperature (thick dark red). Temperature from NASA GISS. Annual Total Solar Irradiance (thin light blue) with 11 year moving average of TSI (thick dark blue). TSI from 1880 to 1978 from Krivova et al. 2007. TSI from 1979 to 2015 from the World Radiation Center (see their PMOD index page for data updates). Plots of the most recent solar irradiance can be found at the Laboratory for Atmospheric and Space Physics LISIRD site.

The slight decline in Solar activity after 1975 was picked up through a number of independent measurements, so is definitely real. Over the last 45 years of global warming, Solar activity and global temperature have therefore been steadily diverging. In fact, an analysis of solar trends concluded that the sun has actually contributed a slight cooling influence into the mix that has driven global temperature through recent decades (Lockwood, 2008), but the massive increase in carbon-based greenhouse gases is the main forcing agent at present.

Other studies tend to agree. Foster & Rahmstorf (2011) used multiple linear regression to quantify and remove the effects of the El Niño Southern Oscillation (ENSO) and solar and volcanic activity from the surface and lower troposphere temperature data.  They found that from 1979 to 2010, solar activity had a very slight cooling effect of between -0.014 and -0.023°C per decade, depending on the data set. A more recent graphic, from the IPCC AR6, shows these trends to have continued.

AR6 WGI SPM Figure 1 Panel p

Figure 3: Figure SPM.1 (IPCC AR6 WGI SPM) - History of global temperature change and causes of recent warming panel (b). Changes in global surface temperature over the past 170 years (black line) relative to 1850–1900 and annually averaged, compared to Coupled Model Intercomparison Project Phase 6 (CMIP6) climate model simulations (see Box SPM.1) of the temperature response to both human and natural drivers (brown) and to only natural drivers (solar and volcanic activity, green). For the full image and caption please click here or on the image.

Like Foster & Rahmstorf, Lean & Rind (2008) performed a multiple linear regression on the temperature data, and found that while solar activity can account for about 11% of the global warming from 1889 to 2006, it can only account for 1.6% of the warming from 1955 to 2005, and had a slight cooling effect (-0.004°C per decade) from 1979 to 2005.

Finally, physics does not support the claim that changes in TSI drive current climate change. If that claim had any credence, we would not expect to see the current situation, in which Earth's lower atmosphere is warming strongly whereas the upper atmosphere is cooling. That is exactly the pattern predicted by physics, in our situation where we have overloaded Earth's atmosphere with greenhouse gases. If warming was solely down to the Sun, we would expect the opposite pattern. In fact, the only way to propagate this myth nowadays involves cherry-picking everything prior to 1975 and completely disregarding all the more recent data. That's simply not science.

Longer-term variations in TSI received by Earth

It's also important to mention variations in TSI driven not by Solar energy output but by variations in Earth's orbit, that are of course independent of Solar activity. Such variations, however, take place over very long periods, described by the Milankovitch orbital cycles operating over tens of thousands of years. Those cycles determine the distance between Earth and the Sun at perihelion and aphelion and in addition the tilt the planet's axis of rotation: both affect how much heat-radiation the planet receives at the top of its atmosphere through time. But such fluctuations are nothing like the rapid changes we see in the weather, such as the difference between a sunny day and a cloudy one. The long time-factor ensures that.

Another even more obscure approach used to claim, "it's the sun" was (and probably still is in some quarters) to talk about, "indirect effects". To wit, when studies can't find a sufficiently large direct effect, bring even lesser factors to the fore, such as cosmic rays. Fail.

In conclusion, the recent, post 1975 steep rise in global temperatures are not reflected in TSI changes that have in fact exerted a slight cooling influence. Milankovitch cycles that operate over vastly bigger time-scales simply don't work quickly enough to change climate drastically over a few decades. Instead, the enormous rise in greenhouse gas concentrations over the same period is the primary forcing-agent. The physics predicted what is now being observed.

Last updated on 27 May 2023 by John Mason. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.

Related Arguments

Further viewing

Related video from Peter Sinclair's "Climate Denial Crock of the Week" series:

Further viewing

This video created by Andy Redwood in May 2020 is an interesting and creative interpretation of this rebuttal:

Myth Deconstruction

Related resource: Myth Deconstruction as animated GIF

MD Sun

Please check the related blog post for background information about this graphics resource.

Denial101x videos

Related lecture-videos from Denial101x - Making Sense of Climate Science Denial

and

Additional video from the MOOC

Expert interview with Mike Lockwood

Comments

Prev  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  Next

Comments 251 to 275 out of 574:

  1. Gord - It might help to go over the budget line by line (and elimate any wasteful programs that don't work, and provide more funding where good necessary programs are underfunded :) ): From: Kiehl and Trenberth http://www.atmo.arizona.edu/students/courselinks/spring04/atmo451b/pdf/RadiationBudget.pdf (All in W/m2): (PS most solar radiation is SW (shortwave) radiation, with wavelengths shorter than about 4 microns. Essentially all terrestrial radiation - radiation emitted by most of the Earth and atmosphere at their typical temperatures (the thermosphere is very optically thin - nearly transparent in general at relevant wavelengths for emission - and absorbs a very tiny fraction of total SW absorption - and so does not contribute much to this energy budget) is longer than about 4 microns; this is called LW (longwave) radiation.) --- 1. Total climate system: energy fluxes at top of the atmosphere: Absorption of solar radiation: 342 (incident) - 107 (reflected) = 235 (67 absorbed in atmosphere + 168 absorbed at surface) Emission of LW (longwave) radiation to space: 235 (195 from the atmosphere + 40 from the surface) solar energy in = 235 = 235 = LW energy out at the top of the atmosphere 2. Energy budget of the atmosphere: LW emissions from atmosphere: to space: 165 + 30 = 195 to the surface (back radiation): 324 total LW cooling of atmosphere: 324 + 195 = 519 Atmospheric heating: by LW radiation from surface: 350 by convection from surface: 102 (78 latent heat + 24 sensible heat) solar heating: 67 total atmospheric heating: 350 + 102 + 67 = 519 total heating of atmosphere by surface and sun = 519 = 519 = total LW cooling of atmosphere. No energy generated or destroyed in the atmosphere when in equilibrium. 3. Energy buget of the surface: Surface cooling: LW emission: 390 (350 absorbed by atmosphere + 40 directly to space) convective cooling: 102 (78 latent heat (evaporation) + 24 sensible heat) total surface cooling: 390 + 102 = 492 Surface heating: LW absorbed from atmosphere (back radiation): 324 solar heating: 168 total surface heating: 324 + 168 = 492 total heating of surface by sun and atmosphere = 492 = 492 = total cooling of surface to atmosphere and space by convection and LW emission. No energy generated or destroyed at/in the surface when in equilibrium. --- If there were an imbalance anywhere (in reality there are always imbalances, but over time, either in the global average of vertical layers, or for each location - accounting for horizontal heat transfer by winds and currents, they tend to average to zero except for changes associated with longer-term climate changes), heat would be accumulated or depleted, tending to cause (in the absence of sufficient latent heat of phase changes, etc.) temperature changes, which change the LW emissions, tending to bring energy fluxes toward balance. Bear in mind that Kiehl and Trenberth's budget is an approximation, and they point out in the paper that there is some significant uncertainty regarding how solar heating is distributed between the atmosphere and surface; I think any corrections in solar heating distribution would be mainly balanced by corrections in the convective transfer of heat from the surface to the atmosphere (technically, the heat must be conducted/diffused first into the air immediately next to the surface (which allows for some relatively small difference between the surface temperature and the air temperature effectively at the surface, considering the scale of the atmosphere as a whole), but convection takes it from there). Although they also use an approximation of the surface having perfect emissivity in the LW portion of the spectrum; this is a good first approximation, but I think it is actually somewhere between 0.9 and 1, so the radiation emitted by the surface is a little less than 390 (but still in that range) - however, depending on how emissivity varies by wavelength, this also means that some backradiation is reflected from the surface, so the total upward LW radiation at the surface will not be reduced as much as the emission from the surface will be for a downward correction of emissivity. Also, they did these calculations for globally-representative conditions, which will not always be globally averaged conditions because some effects vary nonlinearly (this is not a critism of their work - they discuss this in the paper). On that point, some correction in the opposite direction as that for imperfect emissivity might be made for surface LW emission because - as I recall from what I read - they used a global average surface temperature. When emissivity does not vary much over wavelength, total emission over the spectrum of relevant wavelengths is proportional to the fourth power of temperature, so horizontal spatial variability at any level tends to increase LW emission from that level for a given area-averaged temperature. Interestingly, the general tendency is for spacial variability to be reduced at the surface in response to global warming (because the positive feedback are particularly strong where snow cover and ice cover are reduced), which means a (slightly?) greater surface temperature increase will be required to produce the same change in global average surface LW emission (but there is also convection: see below). In the mid-to-upper troposphere, however, the general trend is for the warmer areas to warm more (in association with changes in the latent heating of the air due to greater humidity supply, etc, due to higher temperatures.), so less warming at that level in the global average would be required to produce the same global average change in LW emissions from those levels. These are examples of feedbacks. (Do not make the mistake of assuming climatologists have ignored them - although something can be ignored if it is very small in comparison to some other things - for example, the exact size of Lake Champlaign (sp?) in New York may have an effect on local climate but global climate - at least for sufficiently long term climate states (which, more than just being averages, actually encompass patterns in shorter-term variability - chaotic, cyclical, or otherwise) - is not generally sensitive to such a detail).
  2. Gord - I also saw somewhere above that you mentioned backradiation from the atmosphere being the basis of AGW theory. A couple clarifications: First: what is a theory. Some others have explained it perhaps better than I could and I will provide links to those explanations at a later time. For now, I must point out that for a body of understanding to have the title of theory, it is generally necessary to be about a 'big, general topic'. For example: The theory of biological evolution, the theory of quantum mechanics, the theory of general relativity. The understanding of human evolution is part of the theory of evolution; there is not a seperate theory of human evolution, because that is a specific instance of something more general (that's not to say that human evolution is identical to all evolution, but variations in how different organisms have or are evolving will be a part of evolutionary theory). With regards to AGW, this is an instance of climate phenomena, that is encompassed by climate theory. Within climate theory is the understanding of the greenhouse effect. Perhaps that might be called a theory in itself (theory of the atmospheric greenhouse effect on planets) - however, anthropogenic global warming is a specific instance of this, and the full effects of global warming require other aspects of climate theory (fluid dynamics, etc.) to be understood. However, any understanding of cause and effect must be considered theoretical - without theory, all we have is patterns with no explanation of how and why (see Hume). In that sense, the understanding of AGW is the theory of AGW, but in this case, 'theory' is not part of a title of a specific body of understanding, but the name of a kind of thing - that kind of thing being 'understanding'. --- Second: Backradiation necessarily does occur as part of a greenhouse effect, and it does have important effects. However, the greater control of surface temperature and temperature in general within the troposphere comes from radiative forcing at the tropopause level. A change in radiative forcing at any level is a forced change in radiant flux at that level. A change in radiant flux causes an imbalance, so that heat must be accumulating or will be depleted below that level. A change in radiative forcing can be caused by a change in LW optical properties (as in changes in the greenhouse effect caused by increasing CO2), a change in SW optical properties (changes in albedo), or changes in SW absorption below that level caused by changing incident solar radiation. Equilibrium is restored when resulting temperature changes cause changes in radiant fluxes so as to restore balance. Radiant feedbacks are caused by changes in optical properties caused by climate change (in the shorter term: clouds, humidity, snow, ice, vegetation, dust, vertical and horizontal temperature distribution); these feedbacks amplify or reduce the climate change necessary to restore balance. Radiative forcing at the tropopause level is important to the surface because, however the resulting accumulation in heat below that level is initially distributed, changes in convection that respond to it tend to spread the heating effect vertically, so that the surface and all levels of the troposphere tend to warm or cool together. Changes in the moist convective lapse rate in the tropics (the temperature decrease with height that is of neutral stability to moist convection) are a feedback, reducing the surface temperature increase relative to that in the mid-to-upper troposphere. In polar regions, the air is generally stable to localized convection (especially/(particularly?) near the surface and especially in winter), as heat is transported sideways from lower latitudes, while strong positive feedbacks enhance heating at the surface, so the surface warming tends to be greater than warming higher in the atmosphere at higher latitudes in general. The stratosphere in general tends to cool off with an increased greenhouse forcing because the upper atmosphere radiates more strongly to space and recieves less heat from below when LW opacity is increased (when LW opacity increases, the cooler troposphere blocks more radiant heat coming from the warmer surface, and, depending on initial optical properties, the upper colder troposphere may also block more radiant heat coming from the lower troposphere).
  3. Patrick - Re: Your Posts #267 A Solar Oven is neither a "heat engine" or a "refigerator in the sky". It does no work, nor does it require work to be done for it's operation. It simply reflects Electromagnetic fields from a focal point or to a focal point. It is just a mirror that has a parabolic shape. The Solar oven is, in fact, a parabolic antenna similar to all Satellite Dish antennas. All antennas are reciprocal devices that can be used for transmitting or receiving. The Solar Oven "receives" energy from the "warmer" Sun to heat "cooler" objects placed at it's focal point. The Solar Oven will "transmit" energy from the "warmer" object (water in the Brigham Young University experiment) placed at it's focal point to the "cooler" atmosphere. The temperature of the Solar Oven itself does not affect this outcome, as is evident from the Brigham Young University experiment: "At night the solar cooker needs to also be aimed straight up towards the cold sky. During the day the solar cooker needs to be turned so that it does not face the Sun and also points towards the sky." During the day, the Solar Oven's temperature is is warmer than it would be at night and it still cools the water at the focal point! ---------------------------- Any, radiation absorbed by a body will increase it's temperature. The Sun cannot absorb (and increase in temperature)energy radiated from the Earth because the only energy that caused the Earth's radiation came from the SUN! That is the same as saying that the SUN can heat itself....a violation of the Law of Conservation of Energy! ----------- You said.... "Why would the Earth cool if energy sources were eliminated? Might it be because it would continue to radiate to space as a function of it's temperatures, rather than simply shut down such radiation as a result of the loss of the sun?" The Earth, especially the Oceans, store heat and would continue radiate heat if the Sun were shut down....but only for a short period of time. If the Earth's molten core energy were also removed, the Earth would rapidly cool to near absolute zero. ------------ You said.... "At no point in Kiehl and Trenberth's diagram is energy being created or destroyed (except the sun - but that's a conversion of energy, not creation ex nihilo) or is the second law of thermodynamics being broken." Again, I totally disagree! The Law of Conservation of Energy is very clear..."ENERGY CAN NEVER BE CREATED OR DESTROYED" The In-comming Solar radiation (in Trenberth's paper) is only 342 w/m^2 and it is the ONLY ENERGY SOURCE. Even if ALL this energy (342 w/m^2) reached the Earth's surface and was ABSORBED it is IMPOSSIBLE for the Earth or the Atmosphere to radiate more than 342 w/m^2! Trenberth's Energy Budget shows that the Earth's surface radiates 390 w/m^2! 390 w/m^2 is GREATER than 342 w/m^2. A very, very CLEAR AND UNDISPUTABLE VIOLATION OF THE LAW OF CONSERVATION OF ENERGY! --- The 2nd Law of Thermodynamics states: "Second Law of Thermodynamics: It is not possible for heat to flow from a colder body to a warmer body without any work having been done to accomplish this flow. Energy will not flow spontaneously from a low temperature object to a higher temperature object." http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/seclaw.html#c3 1. The atmosphere is cooler than the Earth's surface and Trenberth's Energy budget CLEARLY shows Back Radiation from the cooler atmosphere being absorbed by warmer Earth! 2. The ACTUAL MEASUREMENTS conducted at the Physics Dept.of Brigham Young University, Utah clearly shows that the Back Radiation does not prevent water from freezing to ICE when the water is placed at the focal point of a parabolic mirror solar oven directed at the colder atmosphere. 3. The AUTHORS of the Physics Dept.of Brigham Young University, Utah paper attribute have concluded, correctly, that this result COMPLIES WITH THE 2ND LAW OF THERMODYNAMICS. 4. Both the 2nd Law of Thermodynamics AND actual measurements PROVE that the colder atmosphere cannot heat the warmer Earth. Trenberth's "Claim" that Back Radiation from the cooler atmosphere can be absorbed by warmer Earth IS A VIOLATION OF THE 2ND LAW OF THERMODYNAMICS.
  4. Gord - I know how a solar oven works. I don't disagree with your description of it. I looked over parts of http://solarcooking.org/research/McGuire-Jones.mht and do not see any errors there. It does not disagree with what I've been saying. That heat flows from hot to cold is just a useful simplication of the complete picture, which is that heat often flows in both directions but the net heat flow is from hot to cold. I had previously visited related portions of the hyperphysics site. There is nothing I saw that I disagree with here: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/seclaw.html#c3 ; but to clarify, the second law also applies to more than just heat flow and temperature variations, and can be expressed more generally in terms of entropy. Also, it is the net heat flow that is being discussed. To be clear, the second law does not allow heat flow from cold to hot along a second pathway even if the heat flow along a first pathway from hot to cold is greater; the net heat flow I've been refering to is along every possible channel of communication, every pathway of of heat flow (every direction, every wavelength and polarization of radiation, every time period - with one exception, which is if one tries counting individual quantized events as seperate pathways or defining groups of such events by the direction of heat transfer they can accomplish - alternatively, one would then need to take into account the actual energy distribution among individual particles in order to square this with the second law, although even that doesn't quite work - for example, in an elastic head on collision between two molecules of equal mass, if one is initially motionless (and thus not contributing thermal energy to the measure of thermal energy of the whole multimolecular assemblage) and a moving, energic molecule collides with it head on, and if none of the energy goes into rotational or vibrational or electronic energies of the individual molecules, than all the energy will be transferred from one molecule to the other in order to conserve momentum). You may want to explore some links from http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/seclaw.html#c1 ------ ENERGY CONSERVATION and SECOND LAW OF THERMODYNAMICS: "The Sun cannot absorb (and increase in temperature)energy radiated from the Earth because the only energy that caused the Earth's radiation came from the SUN!" You are suggesting that not one of any of the photons emitted by the Earth ever ever ever ever reaches the sun and is absorbed. That would be a miracle. The Earth emits radiation in all directions (not exactly evenly; the Earth appears colder from directly above either pole than from above the equator, and variations in temperature, humidity, ozone, cloud cover, etc, cause regional variations). The sun occupies a nonzero solid angle in the sky (PS an entire hemisphere - the sky seen from a flat plane at the surface - has a solid angle of 2*pi steradians; the entire sphere surrounding the Earth has a solid angle of 4*pi steradians). It is a very small fraction of all directions from Earth, but, except for the effects of spacial variations in emission over the Earth's surface, the sun will intercept that fraction of the total radiation emitted by Earth. The physical principles might be better illustrated by considering two infinite flat plates facing each other, and just considering the emission in the direction towards each other. Assume perfect blackbodies - emissivity = absorptivity = 1. One is in the range of temperatures found in most of the atmosphere or on most of the surface of the Earth (forget lightning bolts, the thermosphere, volcanic eruptions, welding arcs, meteors, etc.), the other has a temperature in the range of the photosphere of the sun. The second law implies that heat will not (in total effect - the net heat flux) spontaneous flow from the cooler plate to the hotter plate. Indeed, if we open up any channel of heat flow (have the space between them be at least somewhat transparent (radiation)- or somewhat thermally conductive, or a fluid that is allowed to move (convection), then the net heat flow will be nonzero and be from the hotter plate to the cooler plate. But does this mean that the cooler plate is not (in the case of radiation) radiating at all towards the hot plate? No. Think about that solar oven being used to cool; what was the temperature of the object being cooled? Was it hotter than the sun? No. Yet it was radiating heat. It will radiate heat as a function of it's temperature, no matter what it is radiating heat towards; it is only necessary to not aim it towards the sun to avoid heating it up because the sun is also radiating as a function of it's temperature and that temperature is hotter. "That is the same as saying that the SUN can heat itself....a violation of the Law of Conservation of Energy!" No it is not that at all. The energy came from the sun. A very very very very very small fraction of the sun's radiation is absorbed by the planets (aside from their albedos; most just escapes the solar system without intercepting any objects). A very very very very very very very very very very very very very very very very very very very very very very very small (but nonzero) amount of the energy radiated by the sun (a smaller fraction that intercepted by the planets) returns to the sun by emission from the planets and also by reflection from the planets. If the sun were completely surrounded by a perfect mirror, the sun would get back all the energy it radiates - it would be as if it saw another sun in all directions from itself. If the sun were completely surrounded by a perfect blackbody at absolute zero temperature, the sun would not get recieve any radiation. If the sun were surrounded by a blackbody with some nonzero temperature, the sun will get recieve some radiant energy. If that blackbody is at the same temperature as the sun, the sun (approximating it's visible surface as an isothermal blackbody) would recieve exactly the same amount of radiant energy that it radiates, and thus would not have a net gain or loss of radiant energy if it had no internal heat sink or source. If the blackbody were hotter than the sun, the sun would recieve more heat than it radiates and thus gain energy that way. Of course, the sun does have an internal heat source - nuclear fusion. This converts nuclear potential energy, measurable as an amount of mass that is lost - into heat energy. The Earth also has an internal heat source of a similar nature: radioactive decay. It also retains heat (from previous heat sources: radioactive decay, and energy from graviational potential energy that was present before the mass of the Earth came together and compacted and before the bulk of dense metallic iron sank to the center) at a higher temperature than the surface temperature within it's depths because the material it is made out of has only finite thermal conductivity and only convects at a finite rate. This geothermal heat is supplied to the surface of the Earth at a very small rate, a bit less than 0.1 W/m2, less than 1/2000 of the solar heating rate of the Earth and atmosphere. Most of this geothermal heat comes slowly and steadily through solid rock, not in singular episodic events. It can vary over geologic time, but even then, it's direct heating effects can generally be ignored in the study of climate change on the global and regional levels (except near the origin of the Earth, which was a bit over 4.5 billion years ago) (the indirect effects of geothermal heat - such as continental drift and mountain ranges, and the geological portion of the carbon cycle (very slow compared to recent anthropogenic CO2 emissions) - obviously have important climatic effects). --- In general, when other properties (optical properties of objects and the space between them, thermal conductivity, fluid viscosity, etc.) are held constant, a greater difference in temperature between a hot object and a cold object causes an increase in the net heat flow from the hot object to the cold object. In the case of radiation, this heat flow also increases if the average temperature of the two objects increases, because blackbody radiation intensity increases with increasing temperature in a nonlinear relationship with greater increases per unit temperature change at higher temperatures - especially at shorter wavelengths. The greater net radiant heat flux between objects with a greater temperature difference is due to the greater difference between the radiant flux in one direction and the radiant flux in the opposite direction. While some solar radiation is absorbed in the atmosphere, a majority is absorbed at the surface. However, a majority of radiation emitted to space is emitted from the atmosphere. Without some net heat flux from where solar radiation is absorbed to where radiation is emitted to space, heat will build up near the surface and be depleted at higher levels in the atmosphere. This causes an increasing temperature difference (if they are initially at similar temperatures) between the surface and near surface and the higher atmosphere. This increases the net upward heat flow from the surface and within the atmosphere to various levels within the atmosphere, by radiation and convection. This will tend to settle toward some equilibrium flux when the temperature difference is great enough to sustain a great enough flux of heat to connect the circuit between solar heating and radiant cooling to space. Thus the surface will be hotter than the Earth appears from space (from space, the part that radiates directly to space is visible - this is a distribution that includes a fraction of radiation from the surface, but overall is cooler than the surface). Thus the surface will emit more radiation upward than actually is emitted to space from the cooler atmosphere...etc.
  5. ... to be more specific. Let's start with an Earth with surface and atmosphere at absolute zero, so that they do not radiate any energy. But for the sake of illustrating the concept, let's leave the optical properties as they are (no cloud, humidity, snow and ice, or temperature-dependent optical property feedbacks). We now turn the sun on. 235 W/m2 are absorbed; 67 in the atmosphere and 168 at the surface. But the atmosphere and surface are not radiating any energy and there is no convection. So is energy being destroyed? No. Energy is accumulating in the atmosphere and at the surface. This raises the temperatures of both. As the temperature is now nonzero, they start to radiate LW radiation, but very small amounts, so there is still energy accumulation. As they heat up, they radiate more, and so the rate of energy accumulation decreases - but it doesn't stop until outward energy fluxes equal inward energy fluxes. But what happens as the surface and atmosphere heat up? --- At wavelengths where the atmosphere is almost transparent but not perfectly so, so that it emits and absorbs some radiation, it will emit about the same amount of radiation to the surface and to space and the absorption of radiation from the surface will be nearly evenly distributed through the atmosphere if position is measured by optical thickness. Most of the radiation emited by the surface will reach space. However, at wavelengths where the atmosphere is moderately opaque, it will emit more radiation downward to the surface than upward to space; this is because there is enough opacity such that individual layers of the atmosphere can partially hide each other - for radiation going in any direction, a layer will absorb some fraction of radiation from behind and emit with the same fractional emissivity it's own radiation as a function of it's temperature. Because the upper half of the atmosphere is generally cooler than the lower half (both in terms of mass and optical thickness at most wavelengths) (there is not much opacity at most wavelengths in the upper stratosphere and points higher - these layers are very thin by mass and by optical thickness), the atmosphere looks warmer from the surface than it does from space. At wavelengths where the lower atmosphere is very opaque, the atmosphere will appear to the surface to have about the same temperature as the air just above the surface, and the troposphere will appear from above (the lower stratosphere) to be at the temperature of air near the tropopause, and the surface will be essentially hidden from the stratosphere and space; all surface radiation at such wavelengths will be absorbed in the atmosphere. The greater the opacity of the atmosphere, the more concentrated near the surface the absorption of radiation from the surface is. At some wavelengths, the warmer upper stratosphere is opaque enough to partly block the coldness of the upper troposphere and lower stratosphere from being seen from space. --- All details aside, the atmosphere absorbs some radiation from the surface, so only a fraction of that radiation reaches space. The radiation from the surface that is absorbed in the atmosphere is an additional source of heat for the atmosphere, but note this heat is coming ultimately from the sun - the surface had to warm up to be able to emit this radiation. Meanwhile, the atmosphere, being not completely transparent, radiates upward and downward. It must do both, because it's optical properties are not limited to one direction. ---(one could imagine replacing air molecules and cloud particles with one-sided mirrors that are perfect blackbodies on the other side - in which case, they would reflect radiation coming from one direction and absorb and emit radition from and to the other direction. It would still equally opaque and equally transparent in both directions. In fact, it would break the second law of thermodynamics to have a material that allows, at the same wavelength, radiation through one way but not the other - because that would make it possible to build a perpetural motion machine - it would also be possible to build a perpetual motion machine if absorptivity did not equal emissivity, for similar reasons. )--- . If warm enough and opaque enough, even if cooler than the surface, it can emit radiation in total (to the surface and to space) a greater amount than the surface emits upward. There is nothing particularly mysterious about this. The surface material actually emits downward into the Earth about the same amount it emits upward; the downward radiation is only inconsequential because below the surface material is more material that is also very opaque - photons can only travel very very short distances in such a material, and over very short distances, there are not significant variations in temperature to cause a net radiant heat flux. ---(This also applies to the atmosphere for air-to-air heat exchange: at wavelengths with large opacity; the general behavior is that a net radiant heat flux at a location is caused by temperature variations that are visible from that location; if opacity is too low, temperature variations nearby will be almost invisible (they are nearly transparent); if opacity is too high, temperature variations over moderate distances are hidden from each other.)--- And because at some wavelengths, the atmosphere has moderate to great opacity, the atmosphere radiates downward more than upward. Thus there is, in addition to radiation from the surface and atmosphere to space, downward radiation from the atmosphere to the surface and the upward radiation from the surface that is absorbed in the atmosphere. Energy is being both added to and removed from the atmosphere and the surface; because the surface is warmer than the atmosphere, it radiates more to the atmosphere than it absorbs from the atmosphere, so the net heat flow is from the surface to the atmosphere. As the surface and lowermost atmosphere heat up enough, the lower atmosphere becomes unstable to convection, and so convection will also transport heat from the surface to parts of the atmosphere. The entire system warms up until it can emit 235 W/m2 back to space, at which point, heat is no longer accumulating. Because solar absorption is shifted downwards relative to emission to space, there has to be an upward flow of heat between the solar absorption and emission to space. This requires some decrease in temperature over height. Thus: If the atmopshere were at the same temperature as a perfect blackbody that would emit 235 W/m2, then the surface would have to be warmer, and together they would emit more than 235 W/m2 to space because the atmosphere is not perfectly opaque (unless the surface has sufficiently low emissivity). So the atmosphere must be colder than that temperature. But if the surface were at the temperature at which it could emit 235 W/m2, the atmosphere, being colder overall, could not replace the amount it absorbs from the surface with the same amount to radiate to space - it radiates less to space than it absorbs from the surface, and thus the whole assemblage will radiate less than 235 W/m2. So if the surface's emissivity is not too far from 1, the surface temperature must be warmer than the temperature of a blackbody radiating 235 W/m2, and the atmosphere (or that part visible from space at the relevant wavelengths) will be colder than that same temperature. ---- The surface emits (using the blackbody approximation of perfect emissivity) 390 W/m2 and also cools by 102 W/m2 by convection because it is so warm. At equilibrium temperature, it has to be this warm in order to balance the 168 W/m2 of solar heating and the 324 W/m2 backradiation from the atmosphere - *** or else the conservation of energy could be violated ***(if more or less energy is flowing out than flowing in, then heat is being depleted or accumulated, and that tends to result in a decrease or increase in temperature, unless used up in latent heat, etc.)***. And why is the atmosphere so warm as to radiate 324 W/m2 downard? Convection still results in a general temperature decrease with height, and most of the mass (about 85 %) of the atmosphere is in the troposphere, so the atmosphere will emit more downward than upward, and it works out that it emits 324 W/m2 downard while emitting 195 W/m2 upward. If it is to have an equilibrium temperature, the atmosphere has to be warm enough to radiate these amounts in order to balance the 67 W/m2 of solar heating and the 350 W/m2 it absorbs from the surface and the 102 W/m2 it recieves from the surface by convection. And why do the surface and atmosphere together have to have the temperatures that they do? In order for the fraction of radiation emitted by the surface that is not absorbed by the atmosphere but instead goes to space (40 W/m2) and the radiation from the atmosphere to space (195 W/m2) to balance the 235 W/m2 of solar heating of the two. --- THIS does not violate any laws of physics. If you still do not see that, look at it using a recursive (or iterative) accounting method: Based on numbers from Kiehl and Trenberth (ignoring significant figures for the time being): Of total surface emission and convective cooling: 20.73 % is convection (entirely to atmosphere) 71.14 % is emission that is absorbed by the atmosphere 8.13 % is emitted to space. Of total atmospheric emission up and down: 62.43 % is downward to surface 37.57 % is upward to space. all in W/m2 (numbers will not add precisely due to rounding): STEP 1: 168 of solar radiation heats the surface and 67 heats the atmosphere - total is 235. 168 then leaves the surface to balance solar heating; of that: 13.7 goes directly to space. 119.5 is radiation absorbed by the atmosphere. 34.8 is convection to the atmosphere. 67 leaves the atmosphere to balance solar heating: 25.2 goes to space. 41.8 goes to the surface. Total to space: 25.2 from atmosphere + 13.7 from surface = 38.8. Notice that 38.8 is a lot less than 235 - there is 196.2 yet to radiate to space. Heat is accumulating. What is happening to it: STEP 2: From step 1: the surface transfered 154.3 to the atmosphere (119.5 by radiation, 34.8 by convection), and the atmosphere transfered 41.8 to the surface by radiation. Now, 41.8 leaves the surface to balance heating from the atmosphere: 3.4 directly to space 38.4 to the atmosphere (8.7 convection, 29.8 radiation absorbed by atmosphere). And 154.3 leaves the atmosphere to balance heating from the surface: 58.0 to space 96.4 to the surface Total to space from this step: 61.4. Still 134.8 yet to go to space. STEP 3. 96.4 leaves the surface to balance heating from step 2: 7.8 to space. 88.5 to the atmosphere (68.5 radiation, 20.0 convection) 38.4 leaves the atmosphere to balance heating from step 2: 14.4 to space 24.0 to surface Total to space from step 3: 22.3. 112.5 has yet to escape to space. STEP 4: 24.0 leaves the surface to balance heating from step 3: 2.0 to space 22.0 to the atmosphere (17.1 radiation, 5.0 convection) 88.5 leaves the atmosphere to balance heating from step 3: 33.3 to space 55.3 to surface Total to space from step 4: 35.2 Yet to escape to space: 77.3 STEP 5: 55.3 leaves the surface to balance heating from step 4: 4.5 to space 50.8 to atmosphere (39.3 radiation, 11.5 convection) 22.0 leaves the atmosphere to balance heating from step 4: 8.3 to space 13.8 to surface Total to space from step 5: 12.8 Yet to escape to space: 64.5 STEP 6 ... Do I need to continue? If you do steps until the amount yet to escape to space is very small, and then sum all the fluxes from all the steps, you'll find: -- surface emission + convection: 492 (102 convection + 390 radiation; of radiation, 350 to atmosphere + 40 to space; 350 radiation to atmosphere + 102 convection = 452 to atmosphere from surface) atmospheric emission to surface: 324 atmospheric emission to space: 195 total to space = 235 (195 from atmosphere + 40 from surface) -- With only steps 1 through 5, we had: surface emission + convection: 385.4 (79.9 convection + 305.5 radiation; of radiation, 274.2 to atmosphere + 31.3 to space; 274.2 radiation to atmosphere + 79.9 convection = 354.1 to atmosphere from surface) atmospheric emission to surface: 231.2 atmospheric emission to space: 139.1 total to space = 170.5 (139.1 from atmosphere + 31.3 from surface), with 64.5 yet to escape to space. ---- In reality, if we were not in a steady state or dealing with a climate change, the distribution of flux among cooling pathways as percentages of the heating from the previous step would not be constant among all steps.
  6. To sum up: from an iterative viewpoint (which is applicable to following a parcel of energy through the system - for example, the amount of solar radiation absorbed in 1 second = 235 J: 168 J at the surface and 67 J in the atmosphere): The reason why there are fluxes greater than solar heating is that some of this heat is emitted or convected several times between the surface and atmosphere before actually escaping to space. Each time it goes back and forth between the surface and atmosphere, it adds to the total fluxes between them.
  7. See also: http://www.realclimate.org/index.php/archives/2009/04/wilkins-ice-shelf-collapse/langswitch_lang/index.php?p=667#comment-119260
  8. Patrick - Re: Your Posts #273 etc. You said... "Gord - I know how a solar oven works. I don't disagree with your description of it. I looked over parts of http://solarcooking.org/research/McGuire-Jones.mht and do not see any errors there. It does not disagree with what I've been saying. That heat flows from hot to cold is just a useful simplication of the complete picture, which is that heat often flows in both directions but the net heat flow is from hot to cold." First, you have peviously stated that: Your Post #259 "THERE IS a refrigerator in the sky..." And, with reference to Solar Ovens: Your Post #267 "That's only true with some additional specifications. There are both heat engines and refrigerators in the sky." So, I take it that you now agree that there is no "refigerator in the sky" and Solar Ovens are not "heat engines" or "refrigerators in the sky"? --- With regard to: "That heat flows from hot to cold is just a useful simplication of the complete picture, which is that heat often flows in both directions but the net heat flow is from hot to cold." I TOTALLY DISAGREE as the 2nd Law of Thermodynamics is VERY CLEAR on this: "Second Law of Thermodynamics: It is not possible for heat to flow from a colder body to a warmer body without any work having been done to accomplish this flow. Energy will not flow spontaneously from a low temperature object to a higher temperature object." http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/seclaw.html#c3 There is no mention of "net" anywhere! In fact, the 2nd Law specifically states that it is "NOT POSSIBLE" for heat to flow from a colder body to a warmer body without any work having been done to accomplish this flow. This, OBVIOUSLY, does NOT allow ANY heat flow from cold to hot UNLESS work is done to accomplish this flow...and for a good reason!! The reason is that ANY HEAT flow from cold to hot objects without work being done to accomplish this flow will VIOLATE the Law of Conservation of Energy. Example: Your claim that the Earth's radiation can be absorbed by Sun. I repeat what I have already posted: "Any, radiation absorbed by a body will increase it's temperature. The Sun cannot absorb (and increase in temperature)energy radiated from the Earth because the only energy that caused the Earth's radiation came from the SUN! That is the same as saying that the SUN can heat itself....a violation of the Law of Conservation of Energy!" --- It should be obvious to you that both the 2nd Law of Thermodynamics and the Law of Conservation of Energy are BOTH correct and BOTH SUPPORT each other! Patrick, these are basic fundamental Laws of Science and saying that "it is the net heat flow that is being discussed" in 2nd Law is, obviously, not true. It is equivalent to saying that the Universal Law of Gravitation is really the "NET Law of Gravitation" and that some people could be blasted into space by gravity as long as most people remained Earth bound!....Producing a violation of the Law of Conservation of Energy! --- It seems that your posts are really about trying to dis-prove the 2nd Law of Thermodynamics and the Law of Conservation of Energy. In fact, your posts contain numerous examples of violations of these Laws of Science in an attempt to prove that these same violations comply with these Laws of Science. I don't understand your logic.
  9. It is obvious to me that the second law of thermodynamics and the conservation of energy do appear to be correct, no violation has yet been discovered and no one expects such a violation to be found (within this universe, etc.); provided that one considers mass to be a form of energy. It is also obvious to me that you have misinterpreted what these things mean. Since you take "hyperphysics" at it's word without qualification (PS that's no knock on the website; I think it's pretty good!), consider: ------------------------------ HEAT: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heat.html#c1 "Heat may be defined as energy in transit from a high temperature object to a lower temperature object. An object does not possess "heat"; the appropriate term for the microscopic energy in an object is internal energy. The internal energy may be increased by transferring energy to the object from a higher temperature (hotter) object - this is properly called heating. " If that is true, I've been a bit careless in terminology, but a few word substitutions would correct that in what I've written thus far - and in what I shall write, as I might slip up again... However, if it is the transfer of energy ... maybe the 390 W/m2 emission upward from the surface + 102 W/m2 convection and the 324 W/m2 downward from the atmosphere are not in themselves heat flows; it may just be the net flow of this energy that is the heat flow. Or maybe not... Anyway, consider this: ------------------------------ RADIATION: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c2 "The energy radiated by a blackbody radiator per second per unit area is proportional to the fourth power of the absolute temperature"... (see website for equation) "For hot objects other than ideal radiators, the law is expressed in the form:" ... (see website for equation) ... "where e is the emissivity of the object (e = 1 for ideal radiator). If the hot object is radiating energy to its cooler surroundings at temperature Tc, the net radiation loss rate takes the form" (see website for equation) I'll rewrite the equations here but replacing some variables and symbols with names: Ideal blackbody radiation: Power/area = sigma*T^4 where sigma = 5.6703*10^-8 W/(m^2 K^4) So that the radiant power is proportional to the fourth power of absolute temperature, and a 1000 K blackbody radiates with a power of 56,703 W/m2. And a 288 K blackbody (about the average surface temperature of the Earth) radiates with a power of about 390.1 W/m2. Sound familiar? For a nonideal radiator, the emission is a fraction of blackbody radiation is called emissivity, so that: Power/area = emissivity * sigma * T^4. And for a hot object at temperature T radiatively cooling to it's surroundings at temperature Tc, assuming the surroundings are effectively an ideal blackbody, the "net radiation loss" is Power/area = emissivity(of hot object) * sigma * (T^4 - Tc^4) A little math shows this is equal to: emissivity(of hot object) * (blackbody Power/area at T - blackbody Power/area at Tc) Nowhere does it say that the emissivity of the hot object must decrease to zero if it's surroundings are not at absolute zero. For clarification (you might find this if you follow links from http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c2 ), emissivity is a material property that can vary as a function of wavelength and this wavelength dependent emissivity can vary as a function of temperature OF the emitting surface (but not simply as a function of it's surroundings). Because the temperature of surroundings affects the wavelength distribution of their emitted radiation, this can affect the effective absorptivity of a recieving surface - for example, clouds have higher absorptivity for the radiation as a whole emitted from the surface and atmosphere (including other clouds) than they do for the radiation from the sun - but this is because clouds have generally greater absorptivity in the wavelengths dominated by terrestrial emission (longer than about 4 microns) than those dominated by solar radiation (shorter than about 4 microns). BUT at any particular wavelength, the net radiative loss is from a hotter object to a colder object - for perfect blackbodies, power/area for any wavelength interval is greater at higher temperature; the emissivity is equal to absorptivity for each object (at local thermodynamic equilibrium) or layer or surface, etc, at each wavelength, and so when optical properties are varied, the absorption and emission change in proportion, so that a hot object cannot absorb more radiation emitted from a cold object than the same cold object can absorb from emission from the same hot object. Thus at every wavelength, the net radiation loss is from hot to cold. However, this can pass through a partially transparent layer of any temperature, as I explained previously. See: http://hyperphysics.phy-astr.gsu.edu/hbase/bbcon.html#c1 Blackbody radiation spectrum: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/radfrac.html#c1 Examples: http://hyperphysics.phy-astr.gsu.edu/hbase/bbrc.html#c1 AND for emissivity = absorptivity (why the surface does absorb radiation from the atmosphere, as they emit in some of the same wavelengths): "A Good Absorber is a Good Emitter" http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/absrad.html#c1 This section continues from the formula for net radiation loss, of a hot object at temperature T to surroundings at temperature Tc: QUOTE: "In this relationship the term with Tc represents the energy absorbed from the environment." Energy from the cooler environment is absorbed by the hot object! "This expression explicitly assumes that the same coefficient e [emissivity] applies to both the emission into the environment and the absorption from the environment. That is, a good emitter is a good absorber and vice versa; the same coefficient can be used to characterize both processes. Why is that true?" next paragraph - note the reference to the second law of thermodynamics: "Perhaps the most fundamental conceptual way to approach this question is to observe that a hot object placed in a room must ultimately come to thermal equilibrium with the room. The hot object will initially emit more energy into the room than it absorbs from the room, but that will cause the temperature of the room to rise and the temperature of the object to drop. But when they reach the same temperature, we can conclude that the amount of energy absorbed on average is exactly the same as the energy emitted. That is, the expression above for net energy radiated to the environment must give us zero when T=Tc." Their words, not mine. But I agree. "The above argument is based upon the Second Law of Thermodynamics in the form that states that heat will not spontaneously flow from a cold object to a hot object. If the absorption coefficient were higher than the emission coefficient for the object, then it could absorb net energy from the room even when its temperature were higher than the room." "But suppose you wanted to argue that a good absorber must be a good emitter based on the microscopic processes involving the atoms in the surface of an object. Then it becomes quantum question and involves the following ideas: " (see website for more). ---------------------------------------- I haven't found it in the "hyperphysics" website yet (but - please realize this - just because it is not explicitly mentioned in one website does not mean it is not true), but blackbody radiation is isotropic - the intensity (power per area per solid angle) does not vary over directions. Real materials can have direction-dependent optical properties. For an ideal blackbody at temperature T shaped as a thin plate with area A, the radiant energy flux per unit area from the plate's surface is the blackbody radiation at temperature T; the radiation has the same intensity in all directions but the projection of the area of the plate varies - just as one would recieve less radiant power per unit area from farther away, one would recieve less radiant power per unit area if viewing the plate slantwise instead of face-on. Either way, it is because the plate occupies a smaller solid angle from the viewing position. Conservation of radiant intensity in the absence of scattering, partial reflection, absorption, and emission is required by the second law of thermodynamics, because along every ray path in which object A can see object B, object B can also see object A, so both can exchange radiation along all such paths - at any wavelength and along any line of sight (even if bent at a perfect mirror or perfectly transparent lens), a hot object will have net radiation loss to a cold object if there is any thermally-emitted radiation exchanged. Hence, the highest temperature that can be achieved by focusing the sun's radiation on an object to heat it up is the temperature of the sun (if in space; othewise a bit less because of atmospheric scattering, even without clouds or much haze), in agreement with the second law of thermodynamics. Radiation at any wavelength and polarization (blackbody radiation is evenly distributed among polarizations) can be assigned a temperature based on the blackbody that would emit radiation at that wavelength and polarization with that intensity. This assigned temperature is reduced when radiation confined to nearly parallel rays are scattered (as sunlight is scattered to produce the blue sky and the light seen from clouds - sunlight is initially nearly parallel at great distances from the sun because the sun can only be seen within a small solid angle of directions) - this increase the radiation's entropy, and entropy = heat/temperature for heat flow. One other thing that can be mentioned, pertaining to lasers: entropy is reduced if some intensity of radiation is packed into a smaller interval of phase shifts relative to each other - coherent radiation has very low entropy, corresponding to the entropy of radiation from a blackbody at a sufficient temperature to produce such a concentrated radiant intensity per unit phase shift. Another reason to believe that some radiant energy can flow from colder to warmer: The blackbody radiation spectrums at different temperatures overlap - a white hot object emits more red light than a red-hot object of the same size and optical properties. Both red-hot objects and white-hot objects emit red photons. A red-hot object can even emit a few blue photons, though not many; a white hot object will emit many more blue photons. A violet-hot object emits even more blue photons, etc. The point is that, while temperature can be assigned to a population of photons (radiation intensity over a given wavelength interval, interval of polarizations, interval of phase shifts), a temperature cannot be assigned to an individual photon (just as it cannot be assinged to an individual molecule, atom, or electron, etc. - see: http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/ktcon.html#c1 ). So if a white hot object can absorb a yellow photon from a violet hot oject, why not absorb an identical photon from a red hot object. (PS for that matter, some optical manipulation could be used to make a white hot object appear to be a violet hot object with lower emissivity - by partially blocking lower-energy photons. This radiation could be absorbed by a blue hot object. However, this will not reverse the net radiation loss between the two objects; it will still be from blue-hot to white-hot. ------------------------------- "So, I take it that you now agree that there is no "refigerator in the sky" and Solar Ovens are not "heat engines" or "refrigerators in the sky"?" My pointing out that there is/are refrigerators in the sky was to correct your statement that their are none, but it has nothing to due with how the solar oven works. The solar oven itself is not a refrigerator or a heat engine; this has nothing to do with whether or not the atmosphere contains refrigerators and heat engines - it does; the heat engines are driven by the convective portion of heat flow from the surface to the various levels of the cooler troposphere, and the refrigerators-heat pumps are driven by a portion of the kinetic energy produced by those heat engines (but most, as I understand it, of the kinetic energy is lost to friction before it can drive any such refrigerator). The solar oven works by concentrating sunlight to work as an oven, and by allowing radiative energy transfer between the sky and an object while blocking such heat transfers between the object and heat from trees, buildings, and perhaps also the sky near the horizon - which will tend to appear warmer because the rays in near horizontal directions pass through longer distances through the warmer lower atmosphere, so that it is nearly opaque in that direction, whereas, under clear skies (or only high clouds) with sufficiently low humidity, the warmer lower atmosphere exceeds some level of partial transparency over a greater range of wavelengths when looking more straight upwards. I mention this last point because it helps explain how the solar oven used as a radiant cooler (not a refrigerator) can achieve temperatures (in the object being cooled) lower than the surrounding surface temperature, which cools at night by radiation upward to space and the cooler atmosphere, but over all directions (radiant intensity weighted by the cosine of the zenith angle for a horizontal surface, for geometrical reasons).
  10. 2 more things: "Any, radiation absorbed by a body will increase it's temperature."..."The Sun cannot absorb (and increase in temperature)energy radiated from the Earth because the only energy that caused the Earth's radiation came from the SUN!"..."That is the same as saying that the SUN can heat itself....a violation of the Law of Conservation of Energy!" When the sun radiates energy to the Earth it is losing that energy; if it got any back, it gains that energy. Nowhere in that statement is energy being created or destroyed; it is conserved all the way. The vast majority of what the sun loses will not come back, but the sun maintains its temperature because mass is being converted to energy in its core. It does not violate the conservation of energy to wrap a hot brick in aluminum foil. If the sun were surrounded by mirrors, would not the sun get back it's light? If not, why can you see yourself in the mirror? How could a mirror even exist without breaking physical laws? --------- "It is equivalent to saying that the Universal Law of Gravitation is really the "NET Law of Gravitation" and that some people could be blasted into space by gravity as long as most people remained Earth bound!....Producing a violation of the Law of Conservation of Energy!" That analogy doesn't work very well; if it were truly the net law of gravity, some of the rest of the people who are not blasted into space would have to sink down into the Earth. For example, if one person were at the long end of a very lopsided teeter-totter and a whole crowd of other people jumped off a tall cliff and landed on the short end, then the first person could be expected to fly upward. The potential energy of some large mass would be converted into kinetic energy that would be converted into the kinetic energy of a much smaller mass moving at faster speed, which will ultimately change into potential energy as the person slows down, being accelerated toward the Earth by gravity; if the person has enough energy to never completely stop than s/he has reached escape velocity, etc. Hey, that's what would happen (setting aside air drag, etc.)! Of course, it is not a net law of gravitation, but simply the conservation of energy, work, energy = force times distance, and a lever, etc.
  11. Patrick - Re: Your Posts #282...etc --- Heat Radiation Radiation is heat transfer by the emission of electromagnetic waves which carry energy away from the emitting object. For ordinary temperatures (less than red hot"), the radiation is in the infrared region of the electromagnetic spectrum. The relationship governing radiation from hot objects is called the Stefan-Boltzmann law: P = e*BC*A(T^4 - Tc^4) Where P = net radiated power (Watts), e = emissivity, BC = Stefan's constant, A = area, T = temperature of radiator and Tc = temperature of the surroundings or another body. ..when rearranged gives P/A = e*BC*T^4 - e*BC*Tc^4 (Watts/m^2) This is clearly a subtraction of propogating Electromagnetic Fields. http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html --- Propogating Electomagnetic fields are Vector fields and obey Vector mathematics. P/A = e*BC*T^4 - e*BC*Tc^4 (Watts/m^2) is the Resultant Vector Electromagnetic Field after subtraction. There can ONLY be ONE Resultant Vector Electromagnetic Field, having only ONE magnitude and only ONE direction. If T > Tc the direction is ONLY from T toward Tc and the magnitude is P/A. This complies with the 2nd Law of Thermodynamics. "Energy will not flow spontaneously from a low temperature object to a higher temperature object." If there were ANY flow from Tc to T (cold to hot) it would VIOLATE Electromagnetic Vector Field physics as well as the 2nd Law of Thermodynamics and Conservation of Energy. --------------- Regarding your discussion of emissivity and absorbtion being different, it does not apply to Trenberth's paper. He assumes that emissivity applies equally to absorbtion and emission. The only time I have heard of heat flowing from cold to hot is at the Quantum Level and was resticted to system masses of no more than a few "picograms"....obviously, not applicable to the Earth, Atmosphere and Sun system. --------------- You said.... "My pointing out that there is/are refrigerators in the sky was to correct your statement that their are none...." I have already posted a response to this before: --- My Post #264: The Trenberth Energy Budget shows that the Back Radiation flowing from the colder atmosphere and absorbed by the Earth's surface to be 324 Watts/m^2. (The Back Radiation ABSORBED by the Earth is, supposed, to Heat the Earth according to the AGW theory) Notice that the Back Radiation EXCEEDS the Solar Radiation (the only energy source)! Solar ovens (parabolic mirrors) have no problem concentrating the Solar radiation at it's focal point producing very high temperatures. Parabolic mirrors will concentrate IR energy (Back Radiation) the same way. Notice the authors of the paper state: "During both times, the solar cooker needs to be aimed away from buildings, and trees. These objects have thermal radiation and will reduce the cooling effects. At night the solar cooker needs to also be aimed straight up towards the cold sky. During the day the solar cooker needs to be turned so that it does not face the Sun and also points towards the sky." If there were a "refigerator in the sky" heat would flow from the colder atmosphere to the Solar Oven's focal point where this energy would be concentrated. In Fact, according to Trenberth, the Back Radiation exceeds the Solar Radiation and is 163% GREATER THAN THE SOLAR RADIATION. If there really was a "refigerator in the sky"...The water at the focal point would NOT freeze, it would HEAT UP.....even MORE than it does with Solar Energy! Further, "a refigerator in the sky" still would need energy to operate and it would have to come from the SUN! All the energy radiated by the Earth and the atmosphere could still NEVER EXCEED the 342 w/m^2 Solar Energy!" --- My Post #265 "If there were "a refigerator in the sky" the atmosphere would have to be warmer than the Earth. A refigerator transfers heat from objects inside to the Radiating Tubes at the back. The Radiating Tubes are warmer than the surrounding air....so heat is transfered to the air. The atmosphere is, obviously, cooler than the Earth.....therefore...there IS NO REFIGERATOR IN THE SKY!" --- The POINT being: There is no evidence, at all, of there being a "refigerator in the sky". There is however, conclusive evidence that a "refigerator in the sky" does NOT EXIST! --------------------- You said... "The solar oven works by concentrating sunlight to work as an oven, and by allowing radiative energy transfer between the sky and an object while blocking such heat transfers between the object and heat from trees, buildings, and perhaps also the sky near the horizon - which will tend to appear warmer because the rays in near horizontal directions pass through longer distances through the warmer lower atmosphere, so that it is nearly opaque in that direction, whereas, under clear skies (or only high clouds) with sufficiently low humidity, the warmer lower atmosphere exceeds some level of partial transparency over a greater range of wavelengths when looking more straight upwards. I mention this last point because it helps explain how the solar oven used as a radiant cooler (not a refrigerator) can achieve temperatures (in the object being cooled) lower than the surrounding surface temperature, which cools at night by radiation upward to space and the cooler atmosphere, but over all directions (radiant intensity weighted by the cosine of the zenith angle for a horizontal surface, for geometrical reasons)." --- All radiation from the Spherical Earth and Spherical Atmosphere will occur normal to the surface. The Back Radiation from the Atmosphere will flow directly along lines to the center of the Earth. The max effect will occur if the Solar Oven is pointed at the Zenith....straight up!....day or night! In fact, this is exactly what the The ACTUAL MEASUREMENTS conducted at the Physics Dept.of Brigham Young University, Utah clearly states: "At night the solar cooker needs to also be aimed straight up towards the cold sky. During the day the solar cooker needs to be turned so that it does not face the Sun and also points towards the sky." ----------------------- You said.... "When the sun radiates energy to the Earth it is losing that energy; if it got any back, it gains that energy. Nowhere in that statement is energy being created or destroyed; it is conserved all the way. The vast majority of what the sun loses will not come back, but the sun maintains its temperature because mass is being converted to energy in its core." --- Again, I strongly disagree! The Sun is a constant energy source. It provides all the Energy to the Earth. The Earth IS NOT AN ENERGY SOURCE! Any energy that would be absorbed by the Sun from the Earth would CAUSE the SUN TO INCREASE IN TEMPERATURE! A very, very obvious violation of the Law of Conservation of Energy! Further, if the Sun actually increased in temperature, the Earth would receive this energy and increase in temperature. The Earth would radiate MORE energy to the Sun, causing the Sun to increase in temperature, causing the Earth to heat up even more....etc. What you describes is a Perpetual Motion machine in a positive feed-back loop that will increase it's temperature to INFINITY! An IMPOSSIBILITY. ----------------------- You said.... "That analogy doesn't work very well; if it were truly the net law of gravity, some of the rest of the people who are not blasted into space would have to sink down into the Earth." --- You did not understand my point. I said... "It is equivalent to saying that the Universal Law of Gravitation is really the "NET Law of Gravitation" and that some people could be blasted into space by gravity as long as most people remained Earth bound!....Producing a violation of the Law of Conservation of Energy!" What I am referring to is the DIRECTION of Gravity changing. As long as the NET direction of Gravity was "downward" most people would remain Earth bound. Those few people who had Gravity spontaneously change direction to "up" would be blasted into space. This also would violate the Law of Conservation of Energy. The 2nd Law of Thermodynamics has everything to do with DIRECTION of energy flow.....warm to colder bodies. "Second Law of Thermodynamics: It is not possible for heat to flow from a colder body to a warmer body without any work having been done to accomplish this flow. Energy will not flow spontaneously from a low temperature object to a higher temperature object." http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/seclaw.html#c3 In your case, you think that there can be a spontaneous change so that heat can flow cold to hot as long as the NET (most) of the energy flows from warm to cold. This also would violate the Law of Conservation of Energy. Both the 2nd Law of Thermodynamics and the Universal Law of Gravitation do NOT deal with NET effects....for a very good reason....the Law of Conservation of Energy! -------------------------- It seems that your posts are really about trying to dis-prove the 2nd Law of Thermodynamics and the Law of Conservation of Energy. I don't understand your logic.
  12. "It seems that your posts are really about trying to dis-prove the 2nd Law of Thermodynamics and the Law of Conservation of Energy." That's because you're confused. "I don't understand your logic." Then you probably won't understand any of this: ----- In the following and previously I have mentioned that radiant intensity is conserved along any path radiation propagates if there is no emission, absorption, scattering, or partial reflection along that path (perfect reflection without scattering - as with a perfect mirror surface - will conserve intensity, even if the mirror is curved on a macroscopic scale). There is an exception: when radiation propagates through materials, in the absence of reflection, scattering, absorption, or emission, the intensity is proportional to the square of the real component of the index of refraction. This can be proven with geometric optics. It is related to 'total internal reflection'. Assuming the second law of thermodynamics remains true, then it must be concluded that blackbody radiation intensity is also proportional to the square of the real component of the index of refraction of the medium in which the blackbody radiation is being considered. The index of refraction is of little importance to the macroscopic patterns of radiation transfer in the atmosphere when optical properties are stated as bulk properties of macroscopic parcels of air (obviously those properties arise in part from microscopic processes which may require taken into account the index of refraction - for example, in the evaluation of how cloud droplets scatter radiation). ----- "These objects [trees,buildings] have thermal radiation and will reduce the cooling effects." How could they? By your own logic, if the object being cooled just happened to be a slight bit warmer than those trees and buildings, the radiation from the trees and buildings must never ever ever reach the object that one is trying to cool. Isn't that a strange notion? ---- "If there really was a "refigerator in the sky"...The water at the focal point would NOT freeze, it would HEAT UP.....even MORE than it does with Solar Energy!" Are there refrigerators on airplanes? If an airplane with a refrigerator flew over, I don't think it's having a refrigerator would have much effect on radiation reaching the ground. There are heat engines in the atmosphere powered ultimately by the sun (via convection allowed by the distribution of solar heating and radiant cooling). If this were not true, there would not be much wind. Air accelerates when flowing from higher to lower pressure (horizontally - otherwise, gravity + pressure gradients affect acceleration), thus gaining kinetic energy - this process tends to be associated with warmer air rising and cooler air sinking - the warmer air's temperature drops more than the cooler air's temperature rises, so the average temperature drops, because heat energy has been converted to kinetic energy. Much kinetic energy is converted back to thermal energy by frictional dissipation, but at lower entropy so that it cannot be recycled very much into the atmospheric heat engine. But sometimes the reverse of the heat engine process does happen, and kinetic energy does work on the air, lifting cooler air up (and lowering its temperature) while warmer air sinks (and increases its temperature). This can be observed, most obviously in the global-scale overturning of the mesosphere, wherein the upper mesosphere over the summer polar region is refrigerated. All of which can adjust regional radiation patterns, but none of which is THE cause of backradiation from the atmosphere (the mesosphere in particular has very little effect on the radiant fluxes). The atmosphere radiates downward and upward because it is not perfectly transparent (emissivity is not 0) and it is not at absolute zero temperature - this would be qualitatively true even if there were no motions in the atmosphere. "Further, "a refigerator in the sky" still would need energy to operate and it would have to come from the SUN!" Yes, the vast majority of the energy does ultimately come from the sun. "All the energy radiated by the Earth and the atmosphere could still NEVER EXCEED the 342 w/m^2 Solar Energy!"" Then why is the Earth not frozen over? (think - how cold would the surface have to get to only radiate at the 168 W/m2 that it recieves directly from the sun?) Set aside the second law of thermodynamics for a moment; having radiant fluxes greater than 342 W/m2 does not violate the conservation of energy. If I started throwing balls to you, and you didn't start throwing them back until you had ten of them, mass is still conserved; you would just happen to have a reservoir of ten balls. Suppose three people, you, I and a third person (let's say Bob) have buckets of balls. Suppose every minute, I throw 10 balls into your bucket and 5 balls into Bob's bucket, and every minute, you throw 2 balls into the lake and Bob throws 13 balls into the lake. And every minute, you throw 20 balls into Bob's bucket and Bob throws 12 balls into your bucket. By how many does the number of balls in your bucket and Bob's bucket change in each minute? Answer: Zero. And that's true without needing either you or Bob to manufacture your own balls or destroy them. So you can throw 20 balls to Bob for every 10 balls I throw to you because Bob is throwing you 12 balls. How can Bob afford to throw you 12 balls when I only throw him 5? Because you are throwing him 20 balls. And in the back-and-forth of balls between you and Bob, you are not creating or destroying balls; nor are you constantly increasing your buckets' quantities of balls. -- "Any energy that would be absorbed by the Sun from the Earth would CAUSE the SUN TO INCREASE IN TEMPERATURE!"..."A very, very obvious violation of the Law of Conservation of Energy!"..."Further, if the Sun actually increased in temperature, the Earth would receive this energy and increase in temperature."..."The Earth would radiate MORE energy to the Sun, causing the Sun to increase in temperature, causing the Earth to heat up even more....etc."..."What you describes is a Perpetual Motion machine in a positive feed-back loop that will increase it's temperature to INFINITY!"..."An IMPOSSIBILITY." Have you forgotten what the law of conservation of energy is? It is actually separate from the second law of thermodynamics; the later could be violated without violated the first (though nothing I've suggested as being physically possible violates either one). The conservation of energy implies that if an object absorbs more energy than it emits, it will have a net energy gain. If it absorbs less than it emits, it will have a net energy loss. If it absorbs and emits the same amount, it neither gains nor loses energy (or gains and loses the same amount so that their is no net change in the total energy it has). In the buckets of balls illustration above, you and bob throwing balls to each other from those that you have does not create or destroy balls; you throw balls that you TAKE from your bucket. Likewise, if you picked up a ball from your bucket and bounced it off a wall and it landed in your bucket, your bucket will have only the same number of balls that it initially had. If you and I each had 100 dollars, and then I gave you ten dollars, and then you gave me ten dollars, and we repeated this all day long, by your logic, we'd be millionaires soon. But this is not what would happen; together we'd have the same total amount of money as when we started, because each time you get money from me, your gain is MY LOSS, and vice versa. If you have a heating element (the range on top of your oven - if you have an electric oven) that is glowing red (because it is hot), and you have a mirror, can you not see the heating element in the mirror if you angle the mirror just so? Do you not think that the heating element could 'see' itself in the mirror if you held the mirror up to it? ***And remember, it must be able to absorb the same photons that it could emit, or else you actually could construct a perpetual motion machine (as is the case if radiant intensity were not conserved in the absence of partial reflection, scattering, emission, and absorption). Therefore it could absorb photons from another object at the same temperature, or at any temperature sufficient to emit at least a few photons at the same wavelengths that the heating element is emitting.*** Mutual exchange of radiant energy could not be used to drive a perpetual motion machine by breaking the conservation of energy because it does not break that law. The radiant energy exchange between two objects at different temperatures cannot be used to construct a perpetual motion machine if the net heat flow is from hot to cold, and with radiant energy transfers behaving as I have described them, there is no way to get the net flow of heat to go from cold to hot spontaneously (without work input), so there is no way to run a perpetual motion machine that way. -- "A refigerator transfers heat from objects inside to the Radiating Tubes at the back. The Radiating Tubes are warmer than the surrounding air....so heat is transfered to the air. The atmosphere is, obviously, cooler than the Earth.....therefore...there IS NO REFIGERATOR IN THE SKY!"" That is like saying that your house is cooler than the outside air; therefore there is no refrigerator in your house. "There is no evidence, at all, of there being a "refigerator in the sky"."..."There is however, conclusive evidence that a "refigerator in the sky" does NOT EXIST!" On the contrary, it is known that there is such a refrigerator, most obviously in the summer high-latitude mesosphere; but that has little to do with the basic principles of the greenhouse effect, back radiation from the atmosphere, or how a solar oven works either as a oven or as a cooler. ------ "All radiation from the Spherical Earth and Spherical Atmosphere will occur normal to the surface."..."The Back Radiation from the Atmosphere will flow directly along lines to the center of the Earth."... What ever gave you that impression? Radiation emitted thermally is not a laser beam. It is not coherent (the phases of individual photons are not aligned). It is not all parallel rays. If all radiation from the surface were precisely vertical, then how could it be that radiation from trees and buildings could affect the radiative cooling of any object on the surface? If you take a flat surface and heat it up so it glows red hot, you can generally see that red glow even if you are looking at the surface obliquely; if the optical properties do not vary over angle - for example, if the surface is a perfect blackbody - then the intensity of the radiation will be the same as viewed in all directions that enter the surface from the front, whether head on or slantwise; the radiant flux per unit area normal to the direction of view will be proportional to the cosine of the angle from perpendicular to the surface, as is the projected area of that surface onto the plane perpendicular to the direction being considered. --- More precisely, that is the case for the radiant flux per unit area normal to the direction that comes from a particular unit area of the radiating surface, at a given distance from that unit surface. If the radiating surface covers a large area in comparison to the distance from the surface where the measurement is made, if one moves the measuring location around in any direction, the radiant fluxe per unit area in each direction from the measurement point will stay the same (assuming intervening space is transparent), because if one gets farther away from the emitting surface, the radiant flux per unit area from each unit area of the emitting surface decreases but the amount of emitting surface contained within a given range of directions (a solid angle) increases so that the total radiant flux per unit area for any direction stays the same; if one slides around parallel to the emitting surface, any particular area of emitting surface in some direction will shift to a different direction but will be replaced as another equal area of emitting surface comes into view along the same direction. Furthermore, if one is close enough to the emitting surface relative to the emitting surface's expanse, one will find same radiant flux per unit area for any direction that approaches the surface from any angle, because the more slanted angles will have a view of a greater amount of emitting surface per unit solid angle, in inverse proportion to the decrease in radiant flux per unit area from each unit area of emitting surface with more slanted angles, due to both the unit surfaces being farther away and to the cosine of the angle for the projection of a unit area at a given distance. --- A much simpler way to explain this is that contributions to total radiant flux per unit area of a surface with some set orientation come from each direction with nonzero radiant intensity, in proportion to the intensity, the cosing of the angle of the direction from the normal of the surface, and the solid angle that the intensity covers. A solid angle is analogous to a field of view. As seen from the center of a sphere with a radius of 1, the entire sphere encompasses a solid angle of 4*pi; a hemisphere (such a the sky as seen from a flat plain with no hills, buildings, etc., interfering) has a solid angle of 2*pi; the solid angle covered by any object is proportional to the portion of the surface area of that sphere covered by the object's projection onto that sphere (by rays emanating or going toward the sphere's center). An object will appear bigger when it is closer because it makes a larger projection onto such a sphere; it fills a larger solid angle - hence, if it is emitting radiation, it will make a larger contribution to radiant flux per unit area when it is closer, while it's radiant intensity (flux per unit solid angle) remains constant if the space between is transparent. This is closely related to inverse square laws. ..."The max effect will occur if the Solar Oven is pointed at the Zenith....straight up!....day or night!" That's because that's the direction in which backradiation is generally the least. It is the shortest distance through any layer of the atmosphere, so one can see farther into the atmosphere, less of the warmer lower air and more of the colder layers of the upper troposphere and lower stratosphere, and also more of space itself. If you look closer to the horizon, the atmosphere appears more opaque, and individual layers appear more opaque, because the line of sight goes over a longer distance to get through each layer at such an angle. (If you cut a slice of apple thin enough, you can almost see through it. You can see more of an object through a fog if it is closer to you. Imagine a fog that is glowing incandescently - this is how the atmosphere (and surface) appears in the LW portion of the spectrum. But using visible light to illustrate the point, imagine a fog that is glowing white hot. A very thin layer of it won't appear as bright as a sufficiently thick layer that blocks almost all radiation from behind it. The totality of what you see will appear hotter if you are looking through the fog toward a blue-hot object, more so if the blue-hot object is closer or the fog is optically thinner. It would appear cooler if you are looking in the direction of a red-hot object, more so through an optically-thinner white-hot object. This assuming the red-hot and blue-hot objects have nonzero emissivities.) "In fact, this is exactly what the The ACTUAL MEASUREMENTS conducted at the Physics Dept.of Brigham Young University, Utah clearly states:" ...""At night the solar cooker needs to also be aimed straight up towards the cold sky."..."During the day the solar cooker needs to be turned so that it does not face the Sun and also points towards the sky."" That makes perfect sense given everything I've said. ------------- "The only time I have heard of heat flowing from cold to hot is at the Quantum Level and was resticted to system masses of no more than a few "picograms"....obviously, not applicable to the Earth, Atmosphere and Sun system." The entire mass of the known universe consists of many quadrillions of quadrillions of quadrillions of quadrillions ... of picograms. The second law of thermodynamics arises from the statistics of microscopic processes. Keep that in mind when discussing the Poynting vector ... ------------- "This is clearly a subtraction of propogating Electromagnetic Fields." ... "Propogating Electomagnetic fields are Vector fields and obey Vector mathematics."... "P/A = e*BC*T^4 - e*BC*Tc^4 (Watts/m^2) is the Resultant Vector Electromagnetic Field after subtraction."..."There can ONLY be ONE Resultant Vector Electromagnetic Field, having only ONE magnitude and only ONE direction." From: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html "P = net radiated power" NET! NET! NET! PS: See also: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/raddens.html#c1 -- http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/radpow.html#c1 (the later mentions radiation from multiple directions). The vector that describes the energy transport by electromagnetic waves is called the Poynting vector: http://hyperphysics.phy-astr.gsu.edu/hbase/waves/emwavecon.html#c1 Yes, at any given time and place, the total poynting vector has a single vector value - but that value may be a vector sum of contributing sets of electromagnetic waves. And on a microscopic level, it will fluctuate as individual photons pass by in various directions and at various energies. The average over a surface parallel to the Earth's surface will tend to point up or down, in the direction of the resultant (if you prefer that term to net) energy transport. But this has contributing components. The radiation from the surface is a large upward component. The radiation downward from the atmosphere is a smaller downward component. The average of the resultant is upward. So if that's what you go by, use the resultant. That combined with convection will just balance the solar heat absorption by the surface, in agreement with what you've been insisting. Why not just accept that Kiehl and Trenberth's energy budget diagram was showing contributing components, not the total. From a climatologist's point of view, those contributing components are useful to know. Actually, though, if you insist on only considering the total, the average resultant from all electromagnetic waves, then you must also include solar radiation. In that case, the global average at the top of the atmosphere and in the stratosphere is nearly zero. In the troposphere it must be downward in order to balance the upward heat transport of convection. And do not think that just because the average of the resultant tends to be vertical, that photons are not going in many directions. For example, the resultant of solar radiation may be downward, but you can see blue sky all over the sky - in fact, it generally appears brighter near the horizon (for the same geometrical reasons that make the LW glow of the atmosphere generally appears hotter near the horizon than straight upward when there are not clouds that are too close to the ground or the water vapor concentration is not too high, etc.
  13. "LW glow of the atmosphere generally appears hotter near the horizon than straight upward when there are not clouds that are too close to the ground or the water vapor concentration is not too high, etc." Of course, this varies by wavelength. I think it would make the greatest difference generally between about 8 and 12 microns. It might not make any appreciable difference near 15 microns, or longer than ~ 20 microns, or around 6 to 7 microns, etc. - or at such wavelengths where the atmosphere is sufficiently opaque, a thin nighttime inversion would actually make the atmosphere glow brighter closer to the zenith.
  14. It will help you a lot in understanding radiative energy transfer if you can visualize how things would look at different wavelengths.
  15. "This is closely related to inverse square laws." The relationship between the solid angle filled by an object from a point to the distance between that point and the object is such that the same inverse square laws for point masses and charges (gravitational force due to a point mass and electric force due to a point charge being inversely proportional to the square of the distance from that mass or charge) are analogous to the way radiant flux per unit area facing a point source of radiation varies with distance, and also, the analogy extends to distributions of masses, charges, and radiation sources - that outside of a spherically symmetrical distribution of such things, that force (equal to field line density - the gravitational or electric field flux per unit area) or radiant flux per unit area due to the distribution is inversely proportional to the square of the distance from the center; for a infinite straight line radiator, mass, charge, or current, or outside a cylindrically symmetrical distribution about the center of such a straigth line, the radiant flux per unit area, the gravitational field, the electric field, or the magnetic field will be in proportion to the inverse of the distance from the line; for an infinite flat surface or sheet with even distribution in directions parallel to the surface or sheet of radiation source, mass, charge, or current, the radiant flux per unit area, gravitational field, electric field, or magnetic field, due to that surface or sheet distribution, will be constant across all space on one side of the sheet. (An infinite sheet will fill a full hemisphere of solid angle as seen from any location).
  16. Patrick - Re: Your Posts #281, #282, #283, #284 etc. Again, I disagree with all these Posts. I really think that the Law of Conservation of Energy, the 2nd Law of Thermodynamics are beyond dispute. The Trenberth Energy Budget diagrams show the Earth radiating 390 w/m^2 and the in-comming Solar radiation (the only energy source) is only 342 w/m^2. This is a clear violation of the Law of Conservation Energy and is not disputable. The colder atmosphere Back Radiation of 324 w/m^2 is also shown to be absorbed by the much warmer Earth surface. This violates the 2nd Law of Thermodynamics and is proven to do so by actual measurements done by Physics Dept.of Brigham Young University, Utah. These same results have been verified by previous tests at Brigham Young University. The Back Radiation of 324 w/m^2 is also greater than the 198 w/m^2 Solar radiation reaching the Earth's surface (as shown in Trenberth's Energy Budget diagram). Another clear violation of the Law of Conservation Energy and is not disputable. Remember this Back Radiation is supposed to have caused the entire Earth to increase in temperature from -18 deg C to +15 deg C, according to the AGW'ers. But, obviously, it can't even prevent water from freezing when the Back Radiation is concentrated at the focal point of a Solar Oven, as proven in the Brigham Young University experiments. If the 324 w/m^2 Back Radiation actually reached the Earth's surface it should produce more heating than Solar radiation, even at night. There are probably over a million Solar Ovens on the planet and none will produce heating at night. If they did, the worlds energy problems would be solved. There is no "refigerator in the sky". No matter how much you want to believe that there is a way around the 2nd Law of Thermodynamics and the Law of Conservation, there is none. On that note, I will no longer respond to any of your posts where you have used repeated violations of these basic Laws of Science to make your points.
  17. Falsification Of The Atmospheric CO2 Greenhouse Effects Within The Frame Of Physics. International Journal of Modern Physics B, Vol. 23, No. 3 (30 January 2009), 275-364 Notice what is said in the Abstract: "The atmospheric greenhouse effect, an idea that authors trace back to the traditional works of Fourier 1824, Tyndall 1861, and Arrhenius 1896, and which is still supported in global climatology, essentially describes a fictitious mechanism, in which a planetary atmosphere acts as a heat pump driven by an environment that is radiatively interacting with but radiatively equilibrated to the atmospheric system." AND... "According to the second law of thermodynamics such a planetary machine can never exist. Nevertheless, in almost all texts of global climatology and in a widespread secondary literature it is taken for granted that such mechanism is real and stands on a firm scientific foundation." http://arxiv.org/abs/0707.1161
  18. I am really amused when I read "science" like this: ---- The Greenhouse Effect "Absorption of longwave radiation by the atmosphere causes additional heat energy to be added to the Earth's atmospheric system. The now warmer atmospheric greenhouse gas molecules begin radiating longwave energy in all directions. Over 90% of this emission of longwave energy is directed back to the Earth's surface where it once again is absorbed by the surface. The heating of the ground by the longwave radiation causes the ground surface to once again radiate, repeating the cycle described above, again and again, until no more longwave is available for absorption." http://www.physicalgeography.net/fundamentals/7h.html ---- Tutorial on the Greenhouse Effect- University of Arizona "In this case, the Earth still gains 240 Watts/meter2 from the sun. It still loses 240 Watts/meter2 to space. However, because the atmosphere is opaque to infrared light, the surface cannot radiate directly to space as it can on a planet without greenhouse gases. Instead, this radiation to space comes from the atmosphere. However, atmospheres radiate both up and down (just like a fire radiates heat in all directions). So although the atmosphere radiates 240 Watts/meter2 to space, it also radiates 240 Watts/meter2 toward the ground! Therefore, the surface receives more energy than it would without an atmosphere: it gets 240 Watts/meter2 from sunlight and it gets another 240 Watts/meter2 from the atmosphere -- for a total of 480 Watts/meter2 in this simple model." http://www.lpl.arizona.edu/~showman/greenhouse.html ----- Somehow, they must have missed the fact that the Sun is the only energy source and what they describe is really a perpetual motion machine in a positive feed-back loop.
  19. corrections/clarification: Another reason objects in the solar oven may reach lower temperatures at night than the surrounding land surface is that they are not connected to the heat capacity of the land surface (bearing in mind that the later is effectively limited for any heating cycle by the time it takes for heat to diffuse over distance; I think for the diurnal cycle, the surface can store and draw heat to and from depths of maybe 20 cm ?). Depending on local weather conditions, Brigham Young University may be a better site to use the solar oven for cooling purposes than other places - places with higher humidity and lower elevation. An object being heated by 168 W/m2 solar radiation and 324 W/m2 from the atmosphere will warm up or cool off until it loses, by convection and radiation emission, 168 + 324 = 492 W/m2. Even with a majority of the 324 W/m2 of atmospheric radiation remaining, removal of the 168 W/m2 of solar heating will cause that object to cool to a lower temperature until it only loses by convection and emission 324 or less W/m2. ----- Locally, the average Poynting vector of diffuse solar radiation, from blue sky or clouds, may tend to be nearly straight downward, but obviously the Poynting vector of the direct (beam) solar radiation will vary, being nearly horizontal (and per unit area horizontal surface, nearly zero) close to sunrise and sunset. ________________________________ Gord: "Falsification Of The Atmospheric CO2 Greenhouse Effects Within The Frame Of Physics." I, and many others, have been over that piece of trash before - see this selection of comments (all of mine and a few of some others, but feel free to see all responses by others, of course): http://www.realclimate.org/index.php/archives/2009/03/olympian-efforts-to-control-pollution/langswitch_lang/in (*** indicates comment by another person) Radiation in the atmosphere: 131 - 17 March 2009 at 11:40 PM 132 - 17 March 2009 at 11:50 PM 133 - 17 March 2009 at 11:55 PM 144 - 18 March 2009 at 1:32 PM *** 145 - 18 March 2009 at 1:44 PM 149 - 18 March 2009 at 11:29 PM 150 - 18 March 2009 at 11:42 PM 186 - 19 March 2009 at 11:00 PM 188 - 19 March 2009 at 11:28 PM Responses to G&T: *** 163 - 19 March 2009 at 11:21 AM (note link!) 189 - 19 March 2009 at 11:37 PM - http://www.realclimate.org/index.php/archives/2009/03/olympian-efforts-to-control-pollution/langswitch_lang/in#comment-115353 *** 194 - 20 March 2009 at 7:59 AM 210 - 20 March 2009 at 5:58 PM 211 - 20 March 2009 at 6:08 PM 231 - 21 March 2009 at 2:12 PM 232 - 21 March 2009 at 4:05 PM 254 - 23 March 2009 at 1:35 PM 267 - 23 March 2009 at 8:16 PM 268 - 23 March 2009 at 8:24 PM 269 - 23 March 2009 at 8:29 PM *** 271 - 23 March 2009 at 11:17 PM 274 - 23 March 2009 at 11:48 PM *** see link in response to 297, 24 March 2009 at 12:40 PM 308 - 24 March 2009 at 11:13 PM (note links!) 309 - 24 March 2009 at 11:43 PM 310 - 24 March 2009 at 11:52 PM *** 314 - 25 March 2009 at 7:18 AM 323 - 25 March 2009 at 6:07 PM *** 337 - 28 March 2009 at 9:03 AM - http://www.realclimate.org/index.php/archives/2009/03/olympian-efforts-to-control-pollution/langswitch_lang/in#comment-116369 not dealing specifically with radiation: 148 - 18 March 2009 at 11:11 PM 230 - 21 March 2009 at 2:05 PM ________________ "I am really amused when I read "science" like this:"... "The Greenhouse Effect" http://www.physicalgeography.net/fundamentals/7h.html "Tutorial on the Greenhouse Effect- University of Arizona" http://www.lpl.arizona.edu/~showman/greenhouse.html The first one states that 90 % of atmospheric radiation is to the surface; I think the actual value is different (and it could be described more clearly, though I am only going by the excerpt you provide). The second implies that none of the radiation directly from the surface reaches space, and that the atmosphere emits equally upward and downward; these are not true, but the excerpt refers to a 'simple' model; often when a concept is introduced it is introduced with a very simple model that illustrates a process qualitatively but cannot readily be applied to actual situations. "Somehow, they must have missed the fact that the Sun is the only energy source and what they describe is really a perpetual motion machine in a positive feed-back loop." Somehow, amazingly (to the point that I have wondered if you are being honest in your demonstration of apparent inability to understand physics and also perhaps lack of basic arithmetic skills - or perhaps you are not even trying to understand anything), you have missed the fact that they, Kiehl and Trenberth, climatologists in general, and myself, all realize that the sun is the only significant energy source (tides, geothermal heat fluxes being tiny) in the energy budget of the climate system. You also seem to have little understanding of what a perpetual motion machine actually would do. ---- "No matter how much you want to believe that there is a way around the 2nd Law of Thermodynamics and the Law of Conservation, there is none." Same to you. With variation over wavelengths, overall the atmosphere looks cooler from above than from below because of the general temperature decrease with height in the troposphere; it radiates more downward than upward. (The atmosphere recieves more heat (from convection and radiation) from below from the solar-heated surface than it does directly from radiation; convection can reduce the temperature decrease with height only to a moist-adiabatic limit (where it occurs - within the troposphere).) Whereever there is radiative energy exchanged by thermal emission and absorption between bodies which are themselves in local thermodynamic equilbrium, the net flow of energy is from warmer to cooler, because for two objects, at any given wavelength, each of any emissivity (with absorptivity = emissivity) as any function of wavelength, for each line of sight (whatever turns it may take by scattering, refraction, or reflection) that connects the two, of the radiation emitted and absorbed by the objects being considered, there will be greater radiant intensity in the direction toward the cooler object than in the reverse. You can add the two sets of electromagnetic waves and find an average Poynting vector that goes from warmer to cooler, if you prefer that. But at any given wavelength (and direction, polarization, etc., for local thermodynamic equilibrium), an object has to have the same absorptivity as emissivity - for reasons stated in the "hyperphysics" website that you trust for your information about the second law of thermodynamics. If this were not true, then I could build a perpetual motion machine. If an orange hot object can emit red photons to a red hot object that absorbs them, and yet not absorb any red photons from that red hot object, then its optical properties are such that I could substitute a blue hot object for the red hot object, use an optical filter so that only red photons can go between the objects (other photons being reflected back to the objects), and have the white hot object spontaneously lose heat to the blue hot object. Using spontaneously heat flow from the blue hot object to the white hot object along a different path, I could run a heat engine. This set-up would convert heat energy to work energy in a manner that decreases the entropy of a closed isolated system; it would draw in heat energy at high entropy (low temperature) to run a perpetual motion machine. That would violate the second law of thermodynamics. And I AM TELLING YOU that this will not happen in physical reality. (In case you need another analogy, in thermodynamic equilibrium in a chemical reaction, the forward and reverse reactions are happening at the same rate; it does not mean activity on the molecular level has ceased.) The optical properties will not spontaneously change just by moving external objects around. Have you ever had your stovetop heating elements on? Did you notice them glowing red? Did you turn on an incandescent light bulb (filament hotter than red-hot) while the heating element was on? If so, did the heating element suddenly stop glowing in order to avoid radiating millions of photons toward the bulb, to avoid one of those photons being scattered into the bulb (as the light from a frosted light bulb is scattered on the way out) at the right direction to hit the filament and be absorbed? That's not how physical reality works. "On that note, I will no longer respond to any of your posts where you have used repeated violations of these basic Laws of Science to make your points." Those violations are a figment of your lack of understanding. Anyway, I ought to be saying that to you.
  20. "If this were not true, then I could build a perpetual motion machine. If an orange hot object can emit red photons " Later in that paragraph I accidentally switched "orange hot" for "white hot" - out of habit. Either would work in this example. Sorry for the confusion (Don't think you've gotten me to waste my time writing stuff you don't care about, Gord - I wrote this for the benifit of third-party readers).
  21. Patrick - You are entitled to your "opinions". It appears that is all you have posted. Laws of Science are generally accepted as being fundamental truths in any scientific endeavor or discussion. I do accept attempted re-writes, attempted dis-proofs or use of analogies that violate these fundamental laws to be a valid basis for any scientific debate. My posts are based on established Laws of Science and actual physical measurements that have been duplicated and verified. Third-party readers, who accept these Laws of Science as being valid, are my target audience.
  22. Gord - You might want to actually talk to a physics professor sometime.
  23. Clarification end of my comment 254: ..."much much greater forces (Winds, climate-driven buoyancy variations, tides) shape the ocean's conditions and dynamics and variability in these dwarf any short-term volcanic effects (Panama wasn't built in a single millenium). " I was refering in that context to just the direct geothermal heating effects, and not the radiative forcing of volcanic aerosols. ---- Other notes (with no significant climatological implications) Relativistic effects - if two blackbodies are moving toward each other, their radiation will be blueshifted upon absorption relative to the energy it had upon emission. The blackbodies would appear to be hotter to each other than they actually are. Where does the energy come from? For simplicity, consider two blackbody surfaces sliding toward each other like pistons in mirrored tube, so they only see each other and nothing else. 1. As the pistons move toward each other, the volume in between decreases. At thermodynamic equilibrium, the volume between bodies with nonzero emissivity will be filled with radiation with some energy density that depends on the temperature of those bodies. Even outside of equilibrium, the volume between the two blackbody pistons will contain photons being exchanged. As that volume shrinks, the energy density of that space will tend to increase due to the blue-shift that causes (if the blackbody pistons are insulated on their opposited sides) the temperature of the pistons to rise, but not enough to maintain the same total energy of the photons in the space between the pistons. Thus, the decreasing total energy of the radiation contained between the pistons is due to a net transfer of energy to the pistons. 2. Energy is also added to the system by the work that must be done against radiation pressure to push the pistons together.
  24. Re Quietman - My earlier use of a ratio of 30,000,000,000,000,000 for the heat capacity of the climate system to the heat capacity of the solar wind may have been a bit off. If the solar wind plasma has a specific heat comparable to air, the heat capacity per square meter of the faster-reacting portion of the climate system (including the top 100 m of the ocean) is about 100,000,000,000 times that of the solar wind passing through a square meter in about 20 years. 150,000 K / 100 billion = 0.0000015 K. That doesn't include the factor of 4 for spherical geometry, although it also doesn't include the ratio of the effective capturing area to the area of the Earth.
  25. Patrick My point is simply that it is yet another variable that was not accounted for in the models. There are just too many factors ignored for the models to work.

Prev  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  Next

Post a Comment

Political, off-topic or ad hominem comments will be deleted. Comments Policy...

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

Link to this page



The Consensus Project Website

THE ESCALATOR

(free to republish)


© Copyright 2024 John Cook
Home | Translations | About Us | Privacy | Contact Us