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

CO2 is not the only driver of climate

Posted on 25 October 2009 by John Cook

Climate scientists tend to go on a bit about CO2. However, as readers often point out, CO2 is not the only driver of climate. There are a myriad of other radiative forcings that affect the planet's energy imbalance. Volcanoes, solar variations, clouds, methane, aerosols - these all change the way energy enters and/or leaves our climate. So why the focus on CO2? Is it because scientists are all hysterical treehuggers determined to run peoples' lives with a one world government? Or is there a rational, scientific reason for this CO2 preoccupation? Let's find out which...

When I first started investigating global warming science, I attempted to discern the cause by a process of elimination. I studied all possible causes and ruled out any that couldn't be causing all the warming. As my understanding grew, I came to realise this was an inappropriate approach. Understanding what drives climate does not occur by a process of elimination. It's happens by a process of integration. There are many influences of climate and they all need to be considered together to gain the full picture.

For clarity, let me note a few definitions. Radiative forcing is loosely defined as the change in net energy flow at the top of the atmosphere. In this post, we're talking about the radiative forcing from 1750 to 2005. Values are taken from Chapter 2 of the IPCC AR4 which in turn took all their values from peer reviewed papers - apologies that I was too lazy to cite all the original sources. Positive radiative forcing has a warming effect (so obviously, negative radiative forcing has a cooling effect).

  • Surface Albedo has changed due to activity such as deforestation. This increases the Earth's albedo - the planet's surface is more reflective. Consequently, more sunlight is reflected directly back into space, giving a cooling effect of -0.2 Wm-2.
  • Ozone affects the climate in two ways. The depletion of stratospheric ozone is estimated to have had a cooling effect of -0.05 Wm-2. Increasing tropospheric ozone has had a warming effect of +0.35 Wm-2.
  • Solar variations affect climate in various ways. The change in incoming Total Solar Irradiance (TSI) has a direct radiative forcing. There is an indirect effect from UV light which modifies the stratosphere. The radiative forcing from solar variations since pre-industrial times is estimated at +0.12 Wm-2. Note that the radiative forcing from solar variations may be amplified by a possible link between galactic cosmic rays and clouds. However, considering the sun has shown a slight cooling trend over the last 30 years, an amplified forcing from solar variations would mean a greater cooling effect on global temperatures during the modern warming trend over the last 35 years.
  • Volcanoes send sulfate aerosols into the stratosphere. These reflect sunlight, cooling the earth. A strong volcanic eruption can have a radiative forcing effect of up to -3 Wm-2. However, the effect of volcanic activity is transitory - over several years, the aerosols wash out of the atmosphere and any long term forcing is removed.
  • Aerosols have two effects on climate. They have a direct cooling effect by reflecting sunlight - this is calculated from observations to be -0.5 Wm-2. They also have an indirect effect by affecting the formation of clouds which in turn affect the Earth's albedo. The trend in cloud cover is one of increasing albedo which means a cooling effect of -0.7 Wm-2.
  • Stratospheric Water Vapour has increased due to oxidation of methane and had a slight warming effect of +0.07 Wm-2.
  • Linear Contrails from aviation have a slight warming effect of +0.01 Wm-2.
  • Nitrous Oxide reached a concentration of 319ppb in 2005. As a greenhouse gas, this contributes warming of  +0.16 Wm-2.
  • Halocarbons (eg - CFC's) were used extensively in refrigeration and other industrial processes before they were found to cause stratospheric ozone depletion. As a greenhouse gas, they cause warming of +0.337 Wm-2.
  • Methane is actually a more potent greenhouse gas than CO2. Pre-industrial methane levels, determined from ice core measurements, were around 715 parts per billion (ppb). Currently methane rates are at 1774 ppb (eg - 1.774 parts per million). The radiative forcing from methane is +0.48 Wm-2.
  • CO2 levels have increased from around 280 parts per million (ppm) in pre-industrial times to 384 ppm in 2009. The radiative forcing from CO2 is +1.66 Wm-2. CO2 forcing is also increasing at a rate greater than any decade since 1750.

Here's a visual summary of the various radiative forcings:


Figure 1: Global mean radiative. Anthropogenic RFs and the natural direct solar RF are shown. (IPCC AR4 Figure 2.20a)

Putting it all together, Figure 2 compares the warming from human caused greenhouse gases to the total radiative forcing from all human sources.


Figure 2: Probability distribution functions (PDFs) from combining anthropogenic radiative forcings. Three cases are shown: the total of all anthropogenic radiative forcings (block filled red curve); Long-lived greenhouse gases and ozone radiative forcings (dashed red curve); and aerosol direct and cloud albedo radiative forcings (dashed blue curve). Surface albedo, contrails and stratospheric water vapour RFs are included in the total curve but not in the others. Natural radiative forcings (solar and volcanic) are not included in these three PDFs. (IPCC AR4 Figure 2.20b)

Greenhouse gases and ozone contribute warming of +2.9 Wm-2. The majority of this is from CO2 (+1.66 Wm-2). This warming is offset by anthropogenic aerosols, reducing the total human caused warming to 1.6 Wm-2. So surprisingly, the warming from CO2 actually exceeds the final total radiative forcing. If ever asked how much CO2 contributes to global warming, you could say "all of it... and some!" But a more appropriate response would be to list the various contributors of forcing, both negative and positive, although this may cause the questioner's eyes to glaze over (and wish they'd never asked). Framing science is never easy.

The other important point to glean from Figure 2 is that we have a relatively high understanding of greenhouse gas radiative forcing. The probability density function (PDF) shows a much higher probability than the aerosols PDF, meaning the uncertainty associated with greenhouse gas forcing is much lower. This degree of confidence is also confirmed by experimental observations from both satellites and surface measurements which confirm the degree of enhanced greenhouse effect from rising greenhouse gases.

So bringing it all together, there are two reasons for the focus on CO2:

  1. CO2 is the most dominant radiative forcing
  2. CO2 radiative forcing is increasing faster than any other forcing

UPDATE: just read an interview with climate scientist Ken Caldeira which focuses on the issue of geoengineering. But one particular quote summed up the issues discussed above:

Question: They also write that you are convinced that human activity is responsible for “some” global warming. What does that mean?

Caldeira: I don’t think we can say with certainty whether we’re responsible for 90 percent of it or we might be responsible for 110 percent of it. But the vast majority of global warming, I believe, is due to human release of greenhouse gases to the atmosphere.

0 0

Printable Version  |  Link to this page

Comments

Prev  1  2  3  4  5  6  Next

Comments 201 to 250 out of 268:

  1. Gord, your examples of the need of a cooled detector are just guessing a reason when you don't know how it works. It has absolutely nothing to do with it. And about your "beloved" cancellation (sic) of light, this "cancellation" occurs at specific conditions and at particular points (or regions) in space, not everywhere. Also, you don't see that the effect is due to phase, which modulates the amplitude of the wave as function of time and space. You can not describe an energy flux this way becuase, in fact, it's not a wave. @WeatherRusty I know, there must be something pathological in me :D But i'm too curious to see how far a man who doesn't want to study and learn can go saying that the whole world is wrong. ;)
    0 0
  2. Cancellation and Black Body Radiation. Blackbody Radiation "Blackbody radiation" or "cavity radiation" refers to an object or system which absorbs all radiation incident upon it and re-radiates energy which is characteristic of this radiating system only, not dependent upon the type of radiation which is incident upon it." The radiated energy can be considered to be produced by standing wave or resonant modes of the cavity which is radiating." http://hyperphysics.phy-astr.gsu.edu/hbase/mod6.html#c1 Last time I checked, resonance and standing waves were a result of interference....so is cancelation of waves!!
    0 0
  3. PS: 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: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c2 --- Properties of electromagnetic waves "An electromagnetic wave, although it CARRIES no mass, does CARRY energy." "A more common way to handle the energy is to look at how much energy is CARRIED by the wave from one place to another." http://physics.bu.edu/~duffy/PY106/EMWaves.html --- Heat flux "Heat flux or thermal flux, sometimes also referred to as heat flux density or heat flow rate intensity is a flow of energy per unit of area per unit of time. In SI units, it is measured in [W·m-2]. It has both a direction and a magnitude so it is a vectorial quantity." http://en.wikipedia.org/wiki/Heat_flux ----------------------------------------------- All bodies that have a temperature will produce an Electromagnetic Field WAVES...continuously.
    0 0
  4. Gord, "cancellation" of waves, better know as destructive interference, is a local effect. Whenever the two waves happen to be in different places they are undisturbed by the preceding interference. This is what the principle of superimposition means. And rememeber, waves, not energy fluxes.
    0 0
  5. Thermodynamics applies to heat. Objects composed of vibrating atoms and molecules rearrange themselves when in direct contact according to the laws of thermodynamics depending upon how "hot" they are. Hot material objects or portions of them move about according to how hot they are in abidance with the Law. Electromagnetic radiation is not material and it is not heat. The Second Law does not apply. The atmosphere is warmed primarily by the Earth's solar warmed surface through radiation, conduction and convection. Only conduction and convection are restricted by the Second Law. The atmosphere does not warm the surface the same way as the surface warms the atmosphere. Generally speaking the cooler atmosphere can not conduct or convect warmth to the surface, but it can and does radiate to the surface because it has a temperature above absolute zero. There are four ways to end up with a warmer object, direct strong radiation toward it as for example the Sun does during daytime or place a warmer object in direct contact with it so that conduction and convection can take place. The fourth way is to allow or force the object to cool more slowly once it has been warmed by the first three. The greenhouse effect works by means of the fourth option. Take away the first three and the greenhouse effect will not work since it produces zero energy. Take away the Sun and none of the options work. ---- "All bodies that have a temperature will produce an Electromagnetic Field WAVES...continuously." All dense matter with a temperature will produce a continuous spectrum of ER. The emission by free electrons, atoms and molecules is not continuous as required by quantum mechanics. The discreet emissions of ER are smeared into a continuous spectrum by the density and temperature of the matter. For the same reasons, all dense matter regardless of temperature can absorb the full spectrum of ER or very nearly so if it is close to a perfect black body, which the Earth is.
    0 0
  6. Gord, the topmost animation on this page shows the passage of waves through their superposition and then unmodified onto their original destinations, as Riccardo explained.
    0 0
  7. Gord, see also the Wikipedia entry on Superposition, the section on Application to Waves.
    0 0
  8. This Zona Land site has great animations of wave interference! The ones of most relevance are Wave Interference 1, Wave Interference 2, and Wave Interference 3, which illustrate waves passing through each other unaffected after they have shared the local space where they superposed. The VRML Interference Worlds looks fun, though I haven't tried it.
    0 0
  9. Gord, re: #183 So, if greenhouse gases keep the Earth's surface from falling below -20C(or whatever number), doesn't the temperature of the surface have to rise above that when the sun is hitting it? Doesn't the fact that greenhouse gases absorb energy necessitate that the surface temp of the Earth must be greater than it would OTW be? Cheers, :)
    0 0
  10. shawnhet - Re:your post #209 You said... "So, if greenhouse gases keep the Earth's surface from falling below -20C(or whatever number), doesn't the temperature of the surface have to rise above that when the sun is hitting it?" First, you have to get Cause and Effect correct. The Earth is heated by the Sun (the only energy source). The Earth's radiation then heats the atmosphere to -20 deg C. The colder atmosphere does not heat the warmer Earth. The Sun, being the ONLY energy source, HAS to be the cause of the Earth's surface temperature. I have already posted numerous examples of how the Sun can produce the current Earth surface temperature. Don't you recall my posts directly to you on this subject? --------------- You said... "Doesn't the fact that greenhouse gases absorb energy necessitate that the surface temp of the Earth must be greater than it would OTW be?" No, of course not. The Greenhouse Gases only absorb enough IR energy from the Earth to heat up to -20 deg C. A body of -20 deg C cannot Heat a warmer Earth. I have also produced many posts on this before. Did you not see them? ----------------- Please review my previous posts before asking questions that have already been answered. That will save both of us time and needless repetition.
    0 0
  11. Gord, you might want to follow a sort of "lesson for laymen" (skip the first 10 minutes or so) given by Prof. Archer from the University of Chicago on the very basics of the greenhouse effect. Hopefully a full lesson from a climatoligist will clarify the missing concepts.
    0 0
  12. (This is my fourth attempt to get this posted without deletion - now subjected to new censorship) It appears that constant repetition of my posts are still required. Does anybody out there understand what "continuous" means? The Stefan-Boltzmann Law: Power/Area = Boltzmanns Contant X Temp^4 (watts/m^2) The only time there will not be an Electromagnetic Field produced is when T = 0. Clearly, if T is greater than absolute zero an Electromagnetic Field is produced....continuously. The Stefan-Boltzmann Law is A LAW OF SCIENCE. When some people say the EM field is not continuous it is an obvious contradiction of the Stefan-Boltzmann Law. -------------------- I have also repeatedly posted Physics Links that Heat Radiation is heat transfer by Electromagnetic Waves. Heat Radiation is heat transfer by electromagnetic waves. (see my post #203) Heat Flux is the representation of Heat Radiation as a Vector quantity that uses w/m^2 as the Magnitude of this Vector quantity. The w/m^2 is, of course, used in The Stefan-Boltzmann Law. Heat flux (see my post #203) Yet, there are people who continue to say that Heat Radiation and Heat Flux are not representative of Electromagnetic Waves. ----------------------- I have also repeatedly posted Physics Links that describe Interference including links that explain the phenomena very clearly using continuous waves. Interference (wave propagation) (see my Post #152) Cancellation of Light - Bubble example where light is totally cancelled (continuous waves) - Constructive and Destructive Interference as it relates to Diffraction (continuous waves). - more on Constructive and Destructive Interference (continuous waves) (the links are in my post #152) Despite all the evidence (known for hundreds of years) and all the evidence in their daily lives that the interference of continuous EM waves (eg. like Solar light) produces continuous interference patterns, some people still ignore these simple facts. ------------------------ Arguing with people that ignore these obvious facts and produce posts that contradict Laws of Science, is not only Tedious, it is Frustrating. We are in the 21 Century and this Science has been well known and used for over a hundred years. It would actually be funny, if it wasn't so sad. --------------------------- PS: John Cook will be deleting my comments if I copy and paste material from past comments. Presumeably, this will also include the Laws Of Science and Physics Links that I have previously posted. Since Laws of Science and Physics do not change, please do not attempt to re-write these Laws of Science or Physics based on "opnions". My hands are now effectively "tied behind my back" as far as disputing "opinion based re-writes" of these fundamental truths. Opinions are now in control, not the actual Science. Hopefully, John Cook will also delete those constantly repeated questions directed to me that required repetion of my previous posts. If this is not applicable to those people that constantly ask the same repeated questions of me, I will simply respond that the question has already been answered. Oh well, it was fun before the censorship became stiffleing. It would actually be funny, if it wasn't so sad.
    0 0
  13. Upon reviewing some of my previous posts (which I have stored on my computer), I find that they have also been deleted. I no longer have any desire to participate in this forum.
    0 0
  14. I think Gord is confused. He (or she) is confusing a physical phenomenon with the representation of it. He can apply formulas but lacks a real understanding of the physical phenomena they describe. I don't care whether he is an engineer, student engineer, whatever. He may be more skilled that I at playing with formulas but he does not understand the stuff he keeps on posting in the belief it answers pertinent questions. I am unimpressed. Everyone I could ask abouth this who studies or teaches physics confirmed my understanding of it. NASA confirms it, every single physics link out there confirms it as well if one looks close enough. He is considering one side of a heat transfer in isolation although that side does not exist in isolation of the larger transfer that makes it possible in the first place. The overall exchange of energy between the surface and atmosphere complies with the 2nd law. I believe that I made a number of petinent points in post #149 that were not answered appropriately. Gord keeps on repeating stuff that does not, in fact, support his interpretation. OK so the Sun heats the Earth, which then heats the atmosphere, what happens at night? If there is no such thing as a GH effect, why are the daily temps, nightly temps and average temps not similar to those found on the Moon? What do we have on Earth that prevents our temps to drop near absolute zero at night? Oceans? Why does Antarctica NOT drop near absolute zero during the Austral winter? Why is the surface of Venus warmer than Mercury's and how does Venus maintain nearly identical temperatures on its sunny and shady sides? Makes NO SENSE without a GH effect. Looking back at post # 168, Gord's calculations bring 2 objects in equilibrium both radiating 90W when we started with 90 and 60. Looks strange. We started with a total of 150, the object transferring energy has not cooled and still radiates at 90W, but the other one has warmed and now also radiates at 90W. A total of 180, compared to the 150 we started with. Looks funny. I don't believe Gord knows what he's doing. I have already spent way too much time on this but it appears to me that his calculations on Earth temps are equally mistaken, and what I found in the response to the G&T paper makes a lot more sense. Response to the Gerlich and Tscheuchner paper disputing the existence of GH effect: http://rabett-run-labs.googlegroups.com/web/G%26T2.11.doc?hl=en&gda=GiEkiT8AAAAXmxShcFP2xrtZ1iQa9EYObLHe1BSUDn5EEukXYSRaprw7opP7C43-G-AfaR61VoGccyFKn-rNKC-d1pM_IdV0 If nothing colder can radiate EM radiation, how can I see a glowstick whose surface is much colder than the surface of my eyes? Why is NASA insulating spacecrafts with radiant barriers since, according to Gord, they can not radiate any IR back to the body they insulate? How can the action of cooling a spectrometer CREAT a IR flux going against an immensely larger and warmer body (Earth's surface?). And even if that was the case, why would the IR flux observed increase as altitude decreases and the proximity to the larger warmer body increases? And what emits this IR radiation in the first place? It makes no sense whatsoever.
    0 0
  15. Gord, re #210 (and I apologize if this has already been covered). If the atmosphere can absorb and emit IR radiation won't this imply that the surface will not cool as quickly as it would OTW? If not, why not? Put another way, wouldn't the complete absence of GH gases mean that all the incoming solar radiation would be radiated away from a lower height in the atmosphere(since there would be nothing to impede the radiation). Since Earth has a lapse rate(ie temperature decreases as we rise above the surface), doesn't any absorption of IR radiation in the atmosphere necessitate that the surface must get warmer? If not, why not? Cheers, :)
    0 0
  16. Shawnhet - re:your post 215 Yes, it has been covered before....many times. Why would you even think that the colder atmosphere would somehow cause the Earth's surface to not cool as quickly? How can a cooler atmosphere impede the Earth's radiation when the Earth provides the energy to heat the colder atmosphere? The Sun HEATED the Earth, and the Earth's radiation HEATED the the atmosphere and all the Radiation is then transferred to cold space. Look, let's examine a common device known as a Heat Sink. It is used to cool electronic devices like the Microprocessor in your computer. The electrical power (Sun) heats the Microprocessor (Earth) just like the Sun heats the Earth. Lets say the Microprocessor operates with (and has to dissipate) 10 watts of power (Sun) and it's surface area is 0.01 m^2. The Electromagnetic Field radiated by the Microprocessor (Earth) is 10 Watts/0.01 m^2 = 1000 w/m^2. The surface temp of the Microprocessor can be calculated by the Stefan - Boltzmann Law. Power/Area = Boltzmann's Constant X Temp^4 Temp^4 = 1000 w/m^2 / 5.67 X 10^-8 = 1.76 X 10^10 Temp = 364 K or 91 deg C We want the Microprocessor to drop in temp by placing a Heat Sink on it that will only be heated to 25 deg C or 298 K A Heat Sink (atmosphere) is initially at room temperature (20 deg C) and is placed on the Microprocessor (Earth) with a slight air gap so heat transfer by radiation is dominant. The Heat Sink has to have a larger surface area. Power/Area = 5.67 X 10^-8 X 298^4 = 447 w/m^2 Area = 10 Watts/447 = 0.022 m^2 The Microprocessor and the Heat Sink will now operate at a temperature of 25 deg C. So what happened here? The Electrical power provided is 10 Watts (the Sun). The Microprocessor (Earth) that was operating at 91 deg C transferred heat energy to the cooler Heat Sink (atmosphere)(initially at 20 deg C) raising it's temp to 25 deg C. The Microprocessor (Earth) and Heat Sink (atmosphere) stabilize at a temperature of 25 deg C and 10 watts of power is still dissipated to the suroundings (analagous to cold space). Did the Heat Sink (atmosphere)impede the Microprocessor (Earth) radiation?....Of course NOT! Did the Heat Sink (atmosphere) cause the Microprocessor (Earth) to "not cool as quickly" and increase in temperature?....Of course NOT!...EXACTLY THE OPPOSITE OCCURED! ----------------------- The only difference between this example and the SUN - EARTH - ATMOSPHERE - COLD SPACE system is that the Heat Sink was assumed to have an emissivity of 1. If the Heat Sink (atmosphere) had an emissivity less than 1 it would not have absorbed all the heat energy of the Microprocessor (Earth) and would have had a temp lower than 25 deg C....just like the real atmosphere is colder than the Earth. ------------------------- This may be one of my last posts on this forum. Too much repetion is required explaining the same Physics over and over again and answering the same questions over and over. And, there is FAR too much censorship!
    0 0
  17. Gord, your example is missing a piece from its initial condition. At the very beginning, before you add the atmosphere as a heat sink, you must have outer space as a heat sink.
    0 0
  18. Gord, for a Stefan-Boltzman calculation of an atmosphere-free Earth's temperature (i.e., naked exposure of the Earth's surface to the infinite heat sink of outer space), see the web pages by Nolan Atkins that are part of his Lyndon State College course, but only the two sequential web pages here and the next one. Let's first come to understanding only with that case before adding the atmosphere. (So please don't reply with calculations about what happens with an atmosphere.) Do you agree with the calculations, results, and interpretations on that short sequence of two web pages?
    0 0
  19. Gord, re 216 it is not the temperature of the atmosphere that inhibits the cooling of the surface, but its chemical composition. As to why this should be impeded for the simple reason that some IR is absorbed before it can be emitted to space. I think that amount of energy emitted to space must eventually balance with the amount of energy received from space. Your heat sink example misses the relevant issues of the GH effect namely the lapse rate and the fact that some IR energy is absorbed prior to emission. No one is arguing that energy in shouldn't equal energy out. THe point is that one can potentially have many different operating temperatures for *the surface of the microprocessor* depending on how efficiently it can radiate its heat energy. If the microprocessor is less efficient at radiating its heat energy(perhaps because it is wrapped in insulation), then its temperature goes up, but not because the temperature of the heat sink warmed it, but because it could not radiate *its own heat* as effectively. Just so you have a relatively complete picture of what happens in the atmosphere per my POV- a GH gas free atmosphere would dissipate heat directly from its surface, giving it an average surface temperature of ~-18C. Now, when we add more GH gases to the atmosphere, *the surface cannot radiate that heat as effectively* so in order to balance the incoming and outgoing energy higher levels of the atmosphere must radiate more energy than they would OTW. The only way the higher levels of the atmosphere can do this is by raising their temperature. However, given that the Earth has a lapse rate, *the only way for the temperature of the atmosphere to go up is for the temperature of the surface to go up higher than that of the atmosphere*. This explanation has nothing to do with the temperature of the atmosphere increasing the temperature of the surface anti-thermodynamically(by heat flowing from cold to warm), as you seem to think. All heat energy comes from the sun, however, the physical properties of the atmosphere and the need to balance the incoming and outgoing energy combine to raise the surface temperature by changing *how heat moves from hot to cold*. Cheers, :)
    0 0
  20. Tom Dayton -re:your post #217 If you read my Post#216 AGAIN, you will see that I explain that all the radiation is ultimately transfered to cold space. HINT: Repetion is TEDIUS.
    0 0
  21. Tom Dayton -re:your post #218 Your link ignores the Fact that the Sun is the only energy source. (my very first Post#15 on this forum began with this and continued throughout all my other posts...did you somehow miss all those posts?) The Sun can and does produce all the energy required for the current Earth surface temperature. I have produced many, many examples including Physics links that prove this including many calculations that show that the addition of an atmosphere will cool the Earth, not warm it. The Earth and atmosphere are not energy sources and cannot create energy. Yet, your link has the Atmosphere causing Te to rise from 255K (the temp produced by the only energy source, the Sun) to 288K. Your link has the Atmosphere CREATING energy, an impossibility. Typical. Why don't you read what I have already posted instead of producing endless links that violate the The Law of Conservation of Energy? What purpose do you hope to achieve by posting links like the above? HINTS: - The Law of Conservation of Energy won't change and my answers won't change, no matter how links you produce that violate this and other fundamental Laws of Science. - Repetion is TEDIUS.
    0 0
  22. Gord, ""Now, when we add more GH gases to the atmosphere, *the surface cannot radiate that heat as effectively* so in order to balance the incoming and outgoing energy higher levels of the atmosphere must radiate more energy than they would OTW. The only way the higher levels of the atmosphere can do this is by raising their temperature. However, given that the Earth has a lapse rate, *the only way for the temperature of the atmosphere to go up is for the temperature of the surface to go up higher than that of the atmosphere*." You have cause and effect reversed and you have CREATED energy. Just like the Microprocessor (Earth) and Heat Sink (atmosphere) cannot "ever" radiate more energy than it receives from the Power Supply (Sun), the Earth and Atmosphere cannot "ever" radiate more energy than it receives from Sun, the only energy source." No, I haven't created energy. The Earth's surface is not radiating all the energy it receives to space. Whenever this occurs, the surface must warm in response. The mechanics of the process involve the eventual heating of the atmosphere to a level where sufficient heat can be radiated to space. The sequence of causation is as follows A-B-C A. because the atmosphere absorbs IR energy and prevents all the heat from the surface from radiating to space B. the temperature of the upper atmosphere must increase but, in order, for the temperature of the upper atmosphere to increase. C.the temperature of the Earth's surface must also increase because the Earth has a lapse rate Nowhere does this involve the creation of energy, as any process that impedes radiation flow will cause warming. IAC, if you don't want to deal with the specifics of my POV, I don't have much to add. You can, of course, disagree with the idea that GH impede the flow of radiation to space, but it is contrary to the laws of science(as you put it ;) to pretend that a hypothetical system where radiation is impeded will not be warmer than one where it isn't or that this increase in warmth is a violation of conservation of energy. "They ALL have heat flowing from the Cold Atmosphere to a Warmer Earth!" No, they all have *radiation* flowing from the atmosphere to the warmer Earth as many others have pointed out. If you keep bringing up examples that don't have the same properties as the greenhouse system, you will not get very far in your argument. Cheers, :)
    0 0
  23. shawnhet - re:your post#222 Gee, I see that my post that you are responding to has been deleted. (Perhaps, John Cook could post why....are there more new censorship rules?) ---- Your A-B-C left out the only energy source, the SUN. If A, B or C has more energy being radiated than the Sun provides then energy was CREATED....PERIOD. ---- The "Greenhouse Effect" links state that Heat Energy is RADIATED by the colder atmosphere to a warmer Earth. In case you still don't understand, heat transfer by RADIATION is one of the three methods of Heat Transfer. Heat transfer "Heat transfer is the transition of thermal energy from a hotter object to a cooler object.." Radiation "Radiation is the transfer of heat energy through empty space." "No medium is necessary for radiation to occur, for it is transfered through electromagnetic waves.." (PS: I have not posted this link before) http://en.wikipedia.org/wiki/Heat_transfer Further, The Greenhouse Effect as described by the physical geography in my post#17 explains how longwave radiation from the colder atmosphere heats the ground. Did you not read it?
    0 0
  24. I believe this discussion will continue forever untill Gord does not convince himself that the net flux from an object at Te in an environment at Ta is proportional to (Te^4 -Ta^4). Once he posted this relation but didn't grasp the meaning: the net flux depends on ambient temperature too. By the way, a similar concept also apply to heat conduction and heat convection, the heat flux depends on the temperature gradient for the former and on temperature difference for the latter. In no cases this imply that a cooler object warms a warmer, whch in fact do not happen; less cooling is not warming. Claiming that a dependence on a gradient of some sort violates physical laws would require do dismantel a good part of known physics.
    0 0
  25. Riccardo -re:your post #224 Don't you remember my post to YOU on this subject? (see my post#150) Funny how I have produced so many, many posts on this and Riccardo can't seem to remember any of them? Funny how Riccardo can't seem to find ANY Physics links to back-up his "opinions"? Funny how Riccardo has not been able to answer the questions I asked him?
    0 0
  26. Gord, i might say the same but it would bring us nowhere; I have a diffrent attitude. Here is where you wrote the correct net flux. There's the evironment temperature in it. This is what i was referring to and where your claims of violation of the second law of thermodynamics are wrong. You produced many posts but each and every time we pointed out the errors. You did not discuss any of them but repeated the acritical copy&paste ad infinitum. Really useless indeed. There's nothing to link on high school level physics, there is no doubt nor controversy on it. What is required is critical thinking, analisys, looking at the consequences. You're are surprised, i see, but that's just because you do not have much confidence with this basic physics.
    0 0
  27. Gord, you comment #221 did not answer my question in #218. I asked you whether you agree with just those two particular web pages, that the temperature of the Earth would be 255 K without an atmosphere--if nakedly exposed to the heat sink of outer space. Instead of answering, you ignored my request and commented on the remainder of the web pages on that site. It is difficult to discuss a chain of reasoning with you, if you won't discuss each link in the chain, one at a time. Let's see if we agree on that early link in the chain: Just those two web pages, please.
    0 0
  28. Gord, "Your A-B-C left out the only energy source, the SUN. If A, B or C has more energy being radiated than the Sun provides then energy was CREATED....PERIOD." Gord, obviously, the sun is what warms the surface before IR radiation is emitted in A. I have not created energy by adding GH gases, I have changed how and where that energy is emitted to space, that combined with the fact that Earth has a lapse rate is what causes the surface to be warmer, not the creation of energy. IAC, there is no point continuing to argue this point, so I will pose some simple questions here: do you think it is possible to vary the emissivity of the atmosphere by varying GH gases? Assuming arguendo that this can happen, what would be the consequences IYO? Would any part of the atmosphere be heated? If so, which parts? Cheers, :)
    0 0
  29. commenting on IPCC radiative forcing diagram: gee...so many anthropogenic causes and just one natural variable? does that seem a little biased? has the IPCC really investigated all the variables, or did they decide that humans were the cause before the investigation?
    0 0
  30. Gord, I must say I admire the patience with which you, Gord, have explained some physical basics that for some reasons are called laws. The reasons should by now be clear to even the most stubborn ones. I thank you for the lessons.
    0 0
  31. "The electrical power (Sun) heats the Microprocessor (Earth) just like the Sun heats the Earth." Gord, have you ever been wondering of the purpose of cooling paste put between a heat sink and the object which is to be cooled?
    0 0
  32. Your site is excellent! But it took me eons to find you. I just want to add that deforestation creates an enormous carbon source, which I suspect, would more than cancel out any advantage in cooling the planet due to albedo effect. Do you have any idea exactly by how much?
    0 0
  33. To understand the warming you must also understand the cooling. Radiation emissions are a result of the planet cooling. Convection is also a result of the planet cooling. Lastly evaporation is a result of the surface cooling. Since convection is is more efficient at cooling than radiation, any increase in surface temp will create a greater increase in convection than radiation. Since convection is not impeded by anything other than less dense air above the convection column, convection will remain the most efficient means to cool the surface up to the tropopause. Even without evaporation, any trapped radiation will simply be transfered to the tropopause via convection. The greater the trapped radiation, the greater the convection rate. How are these givens accounted for in the AGW model?
    0 0
  34. theendisfar - explain to me how evaporation/convection are relevant to the energy imbalance at TOA please? Some info to help you perhaps at: http://www.realclimate.org/index.php/archives/2009/01/faq-on-climate-models-part-ii/ Remember too that "AGW" is really a byproduct of our current theory of climate. You test the theory in conventional ways - use the theory to make predictions; test them against observations from real world. Works pretty well.
    0 0
  35. RE#233 theendisfar You need to cite evidence for your claims or at the very least some physical arguments based on direct observations of gas systems. Your statements do not explain or contribute anything. If we can understand where you are coming from then we can answer your questions.
    0 0
  36. theendisfar, the first paper I can remember where moist convection has been included in a climate model dates back to 1964: Manabe, S., and R.F. Strickler, 1964: Thermal equilibrium of the atmosphere with a convective adjustment. Journal of the Atmospheric Sciences, 21, 361–365. And be sure that the problem was known well before 1964. You're a little late with this breaking news on convection.
    0 0
  37. Re 234, 235, and 236 Thank you for your replies, I am pleased to have a detailed discussion on this subject. So that I may better understand at what level I need to be responding will you please let me know if you are trained in physics? I am happy to provide and accept links as evidence, but I need to know whether the person 'providing' material understands the evidence or is simply referring to it as Peer-Reviewed and therefor fact. Can we agree to review the 'facts' ourselves? I claim that I have enough understanding of thermodynamics and related physical sciences to discuss these topics with anyone. I am not claiming this for any other reason than to let you all know that what I write is completely within my understanding and I will not be parroting someone else's understanding. I expect the same of you. I wish to convey that I do not have a problem with AGW believers, I only wish to get some answers and to provide some myself. While I will not resort to ad hominem, feel free to be as condescending as the moderators will allow, I understand emotions sometimes run high. With that, I look forward to gaining a better understanding of the believer's position and hopefully I can help you all understand the position of a scientific skeptic. My name is Steve A. Morris, but will keep theendisfar to remain consistent. Thanks
    0 0
  38. @234 scaddenp, Not sure I understand you question exactly, but here's a start. Assumption: By TOA, I assume you mean the actual Top of Atmosphere at 0 ATM. Let's tackle convection and then we can get to evaporation. Convection is caused by a combination of gravity and differences in fluid density. When the Earth's surface is heated, it not only radiates energy to cool, but it also conducts heat energy to the adjacent air above it. When this occurs the air expands and becomes less dense than the cooler air above it. At this point gravity comes into play and pulls more strongly on the cooler more dense air above, effectively dragging the cooler air underneath the warmer air. The Earth's surface warms that parcel of air and the process repeats. Convection only occurs up to the tropopause because at that point the temperature scale inverts and temps get higher with altitude. This is why you often see thunderstorms form anvils since the cooler upper troposphere stops where the stratosphere begins to warm. It is also worth mentioning that the atmosphere is elastic in nature where the tropopause varies in altitude depending upon the temperature. Lower at the poles, cooler more dense air, higher in the tropics, warmer less dense air. This is important because if the atmosphere was fixed in size the temp would rise faster with more heat added since it could not expand to reduce both pressure and temp. So in real terms, convection is only relevant to the TOA in that it transports most of the energy the Earth is cooling up to the tropopause where radiation finishes the job.
    0 0
  39. @235 yocta, Here's the claim. If you heat a body with radiation and it has both radiation and convection as a means to cool, it will cool more so via convection and as you increase the surface temp, you increase the convection rate more so than the radiation rate. You be the Peer. Is this correct or is it incorrect?
    0 0
  40. @236 Riccardo, In the IPCC reports their diagrams note that convection is only responsible for ~10% of cooling the Earth's surface. This is plainly false, see #239. Are you suggesting that radiation is more efficient at transferring energy than convection because moist convection was included in a 1964 model? How about dry convection? While GHG's may slow the rate of Radiation cooling, the increase in temps will only cause the radiation and convection rates to increase, where the convection rate of cooling increases more than the radiation. Again, since convection is not impeded, no greenhouse, the cooling rate is free to increase as temps rise. Now assume that this is new data and you are the Peer reviewing. Are you qualified to answer or must you have a document to refer to?
    0 0
  41. theendisfar, I take as a form of due respect to listen to what people say regardless their degree, not even scientific journals ask for the degree. I do have a physics degree but i'm not interested in discussing it.
    0 0
  42. @241 Riccardo, I meant no disrespect, please allow me to clarify. Without knowing your background, reply @236 seemed as though you were parroting someone else's understanding rather than having the understanding yourself. I have no issue with taking your word that you are a physicist, no need to discuss that. From @233, have I made any false statements? Can you see where I'm going? If not, I am pleased to clarify my position or arguments.
    0 0
  43. theendisfar, there's an excellent paper by Kiehl and Trenberth showing measured values for radiation, convection, evaporation, etc. at the Earths surface. I understand this was updated recently - values haven't changed more than 2%, mostly in a higher average thermal radiation value for the surface due to the 4th order dependence of radiation to temperature. Sorry I don't have a link to the most recent update. They explicitly include convection and evaporation in their models. Thermals (convection) account for ~24 W/m^2, evaporation is 78, and radiation is 390 W/m^2 (updated if I recall to 396 in the most recent writeup). Thermals therefore account for ~5.7% of energy leaving the Earths surface, thermals and evaporation for ~21% - significant, if not dominant, energy flows. They are of course not at all involved in TOA energy exchanges. As to credentials and the like, theendisfar, I personally don't have the resources to recreate all lines of evidence for any scientific assertion made - that seems to be what you're asking for. I read the papers, I examine the methods, and look for well supported conclusions. If the evidence is weak or the conclusions unwarranted I'll ignore that source in the future. If you feel the consensus view is incorrect, collect your evidence and publish it. That's how reputations are made in science; proving something different! Peer review isn't perfect, but it's pretty d**m good - and if you manage to slip something through peer review that is WRONG it will be gladly pointed out by other scientists interested in correcting the record (and getting something published :) ). On the other hand, if what you want is to butt heads while waving credentials - have fun, but I'm going to decline to participate.
    0 0
  44. @243 KR, I have little use for credentials as I have little use for taking 'peer review' at face value. Citing Peer Review without a complete understanding is little different than waving someone else's credentials. I was just asking that anything presented in this conversation be understood completely by the presenter. This way we will not be using someone else's credibility, or lack there of, as a crutch or deficit. "Thermals (convection) account for ~24 W/m^2, evaporation is 78, and radiation is 390 W/m^2 " If convection is more efficient than radiation, then the above statement is false. For example, think of a Thermos. If convection were less efficient than radiation, then they would not use a vacuum to reduce cooling. I will take the time to read the article, but can you respond to my reply? Perhaps another way is to pose a question. When is Convection not more efficient than Radiation?
    0 0
  45. Is convection more efficient than radiation? Don't assert - take a measurement! I have little (read that "no") use for assertions that aren't driven by real-world observations. Those are beliefs, not evidence, and beliefs cannot falsify observations. The actual measurements of convection and thermal radiation show that in this case it is not more efficient. These are measured values observed in nature. What are your measurements (not thought experiments) of surface heat transfer that indicate otherwise? If you have different measurements, you can argue over observed efficiency. However, current measurements indicate that thermal radiation is ~16x more efficient under these conditions than convection, and that evaporation/latent heat is >3x as efficient as convection. I'll note that the rate of change for these pathways will likely be very different - as temperatures shift, they will increase/decrease by various amounts. But under current conditions convection is a minor contributor to surface/atmosphere energy transfer.
    0 0
  46. @245 KR, Ponder this scenario for a moment. Heat an object to a given temp in a vacuum chamber and record the rate of cooling. Repeat but now flood the vacuum chamber with dry air at sea level (or close). Record the rate of cooling. Say the Radiation cooling Rate is R and the Convection rate is C. If it turns out that there is ever a case that 2R > C+R, then the laws of physics must be rewritten. In any event, ponder the statement and I'll elaborate tomorrow. Note that in zero gravity convection does not take place so the test would be invalid.
    0 0
  47. KR at 02:38 AM on 4 June, 2010, better than vacuum chambers and thermos bottles for a real world observation is perhaps ones own home. Our sole form of heating over winter is a large slow combustion wood heater in a large room at one end of the house. The heater has a fan to distribute heat out of vents at the front. Without the fan going the heater can quickly become unbearably hot when standing next to it and it takes considerable time before any warmth at all is felt at the extremities of the room. With the fan going the warmth is better distributed, but there is still some warmth differential within the room, but not as much as without the fan. However we also have a ceiling fan near the heater, and when this is switched on, running only on slow, the warmth is distributed much faster and more evenly. Not only that, with the ceiling fan the warmth gradually works it way through all the doorways to other rooms right to the further extremities of the house whilst reducing the high temperatures next to the heater. In summer time, an evaporative cooler with it's inbuilt fan is much more effective way of cooling than sitting an open ice box in the middle of the room hoping that the heat from the warmer room will radiate to the colder ice in order to cool the room.
    0 0
  48. Again - what are the actual measurements? Thought experiments and small scale analogies only take you so far, and do NOT trump actual data. Sunlight spectra at surface (multiple measurements, global averaging based on planetary geometry): 168 W/m^2 Thermal back-radiation spectra from atmosphere (REALLY well measured with spectroscopes): 324 W/m^2 Measured spectra of surface thermal radiation (multiple measurements in agreement with blackbody estimates): ~390 W/m^2 (396 as of the latest estimate, due to 4th power dependence on temperature and surface variations). Calculated evaporative cooling, based upon rainfall figures (what comes down must have gone up, known energy for evaporation and rainfall amounts): 78 W/m^2. Convection estimates, based on over the ocean bulk convection measurements, over the land measurements and calculations (multiple references in K&T): ~24 W/m^2, although there's actually some grounds to consider that an overestimate. 18 to 19 W/m^2 +/- 5 is rather more likely, as discussed in Kiehl and Trenberth, and in better agreement with the most recent radiative estimates. This is covered in section 4 - they generously attribute anything left over after the evaporative and radiation measurements to convection. This is still <6% of the total energy exchange. As to the small scale observations and thought experiments - the atmosphere is a heck of a lot bigger than a vacuum box, or even a house. It's important to take that into account. The measured values show that convection isn't the primary form of energy transfer. Unless you can produce different measurements, I'm going to consider these assertions contradicted by evidence to be unsupportable. Otherwise my belief in my own importance to the world would lead me to stand around in the middle of heavy traffic...
    0 0
  49. theendisfar, When you add air to the chamber it is conduction that becomes the dominant source of heat transfer, not natural convenction. The scenario would work pretty much identically in a zero-gravity environment. Also measuring the rate of cooling in the vacuum scenario would not be a direct proxy for calculating the thermal radiation of the object. Remember that all objects emit thermal radiation, so the energy the object is losing to its own radiation is somewhat offset by the radiation emitted by the walls of the chamber. If you want to make the same comparison to the atmosphere's rate of heat exchange, you have to subtract the radiation reflecting back down from the atmosphere (324 Wm^-2). In any case, there is no rule of physics that says for any given system where natural convection applies, the energy transfer from convection will exceed that of radiation. I think you are getting thrown off by trying to visualize it as an engineering problem, where improved conduction and forced convection can often significantly increase the rate of heat transfer. This rule of thumb does not mean that any given system where convection exists must by necessity have more heat transfer from convection than thermal radiation. The comparison is further complicated by the fact that scenarios like the ones you've provided deal with objects much smaller than the atmosphere, whereas with climate science you're dealing with the dynamics of the atmosphere itself. This scale and complexity does not lend itself to simple visualizations. Also, do not confuse conduction with natural convection as you did with your vacuum chamber and Thermos examples. In order to actually visualize the contribution of natural convection, the appropriate scenario would be something like this: place an object at the bottom of a chamber filled with air, measure the rate of heat loss from the object. Repeat the test in a zero gravity environment and compare the rates. Since humans rarely deal with zero-gravity situations, trying to solve this via visualization of common scenarios is probably not a good approach. I suggest you take KR's advice and rely more on actual measured values. Photons hitting a detector will be much more reliable than grossly oversimplified thought experiments. johnd, You are confusing forced convection with natural convection. The earth's atmosphere doesn't have any mechanical fans, it relies mainly on the force of gravity and the earth's rotation to generate convection currents. These same forces exist in your fireplace whether the fans are turned on or not.
    0 0
  50. KR at 04:37 AM, if convection is not the primary form of energy transfer, then what role does weather play which is primarily all about the redistribution of uneven heat energy. Storms are the mechanism that moves large amounts of heat in a hurry when the system has become unbalanced, some so violent they punch straight through injecting water straight into the stratosphere.
    0 0

Prev  1  2  3  4  5  6  Next

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


The Consensus Project Website

THE ESCALATOR

(free to republish)


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