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( William M. Connolley 17:35, 26 Nov 2004 (UTC)) The following very old comments archived 2004/11/26.
I do not think this is a reliable source:
Kaczynski, T., 1991: The Unabomber Manifesto. Lispelite Press (F15), 40 pp.
I added the word 'allegedly' to facts attributed to Kaczynski, rather than just removing them. The 'allegedly' can be removed if a non-psychopathic source is found to corroborate the statements. In two other places I just removed the citation.
Removed the following from list of sources:
Neunke, M., 2001: White Pride Worldwide!! [Taken from
http://www.whitepride.com/sorel.html]
I didn't see any information about albedo at that site... though I suppose white people may be proud of their higher than average albedo. (cough cough)
I also removed these, pending further investigation:
Walker, E., 1987: Pictures of Preschoolers Out in the Snow. Dishwasher Picture Publishing, Volume 26, 151-1103.
Thompson, S. I. U. A. M., 2001: Worldwide Monthly Climate Tables. [Taken from http://www.woolpit.com/]
Rocky, S., and E. Bullwinkle, 1970: The Climate of the North Polar Basin. World Survey of Climatology, Vol. 14, Elsevier Publishing Company, 373 pp.
These all look like hoaxes to me. Rocky and Bullwinkle? Pictures of children in the snow? -- Jimbo Wales
There are still several mentions of Rocky and Bullwinkle in the page itself. They weren't added recently. They're in the form of source notations; could they have replaced the real source notations long ago? Is there any way we can pull up the page from many moons ago to see whether those were real references?
Also, someone who knows this field should really review this whole page for other subtle munges. -- Rootbeer
Can anyone find a real source that suggests albedo influences surfact temperature here on earth? I looked at Google and the only links I found claiming such an influence were educational projects for K-12 graders. - Tim
An albedo calculation example For a lattitude of 52N on 4 january with fresh snow (albedo 0.8) the mid-day (clear sky) insolation is 68 W/m2
The albedo of a forest/town = 0.15
0% forest/town | winter albedo 0.8 | insolation 68 W/m2 10% forest/town | winter albedo 0.735 | insolation 90 W/m2 20% forest/town | winter albedo 0.67 | insolation 113 W/m2 30% forest/town | winter albedo 0.605 | insolation 135 W/m2 40% forest/town | winter albedo 0.54 | insolation 157 W/m2 50% forest/town | winter albedo 0.475 | insolation 179 W/m2 60% forest/town | winter albedo 0.41 | insolation 201 W/m2 70% forest/town | winter albedo 0.345 | insolation 223 W/m2 80% forest/town | winter albedo 0.28 | insolation 245 W/m2 90% forest/town | winter albedo 0.215 | insolation 268 W/m2
100% forest/town | winter albedo 0.15 | insolation 290 W/m2
Insolation data derived using the insolation calculator download excel 2000 version http://members.lycos.nl/ErrenWijlens/co2/insol.zip
download excel 95 version http://members.lycos.nl/ErrenWijlens/co2/insol95.zip
You see that change of landuse has a dramatic effect on the winter energy balance.
I write a quick perl script to convert all these Fs to C or K -- Tarquin 17:33 Mar 13, 2003 (UTC)
The reference given doesn’t work anymore ( http://jeff.medkeff.com/astro/lunar/obs_tech/albedo.htm), I also found a reference that gives a different value of lunar albedo, of 0.12 instead of 0.072 ( http://www.universetoday.com/guide-to-space/the-moon/moon-albedo/). —Preceding unsigned comment added by Firstmatekevin ( talk • contribs) 14:02, 4 July 2010 (UTC)
The last sentence of the first paragraph is unclear; in comparison to land, do oceans typically have a higher or lower albedo, and do clouds contribute to higher albedo or to lower albedo? —Preceding unsigned comment added by 75.85.89.204 ( talk) 11:23, 20 December 2009 (UTC)
"tropics" section is flawed. Many factors control surface temperature, particularly those associated with vegetation. I find fault with the statement "When Brazilian ranchers cut down dark, tropical rainforest trees to replace them with even darker soil in order to grow crops, the average temperature of the area appears to increase by an average of about 3 °C (5 °F) year-round, which is a significant amount" as the lack of evapo-transpiration after forest is removed may have far more control over surface temperature than a change in albedo. The statement should be supported with a reference or should be removed.23:47, 2 September 2006 (UTC)
This page looks weird to me. Some of it is definitely rubbish: the arctic ice stuff (there is no SW in winter...). Is anybody very fond of this page...? [WMC]
( William M. Connolley 19:55, 15 Sep 2003 (UTC)) OK, no-one spoke up, so I've started stripping out stuff that looks especially dodgy to me, and putting it here (note: stuff left is not necessarily OK, just less obviously not). If anyone thinks I've been unreasonably harsh, please feel free to revert, or perhaps better make comments on a per-para basis. I've put comments on what I've removed.
The only possible explanation is that on Kilimanjaro, a glacier built up when the climate was colder, and that this glacier never completely melted because its extremely high albedo reflected away enough heat to keep itself cold enough not to melt, and to keep the air temperature at the summit much lower than that atop Mauna Loa. This very wide gap in temperatures, of nearly 11°C (20°F), occurs despite the fact that the skies above both mountains are very cloudy and the climate of both is very wet, so not much solar radiation reaches either summit. If Mauna Loa were completely dry, it could be expected that its temperature would be even warmer, perhaps as warm as that of Tibet at 14,000 feet in summer.
Thus children, much skinnier than adults, need more clothes in the wintertime to keep them warm, even if they are dark-skinned.
Albedo and frequency. There seems to be little mention of the fact that albedo is frequency dependent and objects which are white in visible light, (i.e. reflective), can be black (i.e. not reflective) in infra red, and so on for other frequencies. Most of the sun's energy comes to us as infra red heat. This means that apparent large changes in visible reflection are not necessarily significant in the main part of the spectrum. Someone said above that a molucule (or atom) has albedo, but this is highly frequency selective and is misleading if gross energy balances are being inferred in relation to global warming. For example it is often said that snow and crystals of ice have very high albedo, which is true in visible light, but they absorb at lower frequencies, otherwise, why would all the snow melt in summer? ProfSWback 16:44, 30 December 2006 (UTC)
Please note that reference 13, http://lenah.freeshell.org/pp/01-ONW-St.Petersburg/Fresnel.pdf, seems no longer available. (9-nov-2007). —Preceding unsigned comment added by Jdekloe ( talk • contribs) 13:15, 9 November 2007 (UTC)
I removed "(refs???)" from the end of the following sentence. Perhaps someone could actually find a decent reference for it.
- Mark 05:25, 28 Jun 2004 (UTC)
Last bit, Kuwaiti Oil Fires: it seems contradictory, with the last sentence saying "impossible". Can someone who knows about this clear it up?
I don't know where this article got the 0.31 Albedo figure of Earth. Albedo 0.39 is what Kaufmann says; Pater and Lissauer say that Earth has a "bond albedo" of 0.29 and a "geometric albedo" of 0.37 source. I changed the page to quote the albedo 0.39 figure, since that seems to be a reasonable number (and a really good album to boot). Samboy 08:18, 22 December 2005 (UTC)
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I find the definition to be completely useless and unscientific. How are incident and reflected radiation to be measured, and how is albedo determined to 3-figure accuracy if the definition is given in essentially unquantifiable terms ? Are we talking about power here ? Power in a certain bandwidth ? Power weighted according to spectral distribution ? Get real ! Enough of this pseudo-scientific posturing and do the job properly, or not at all. Andrew Smith
I have removed the following text pending the supply of a source for the statement:
This was marked with a "fact" template, which I think simply isn't enough. We should rather remove unsourced statements of this level of significance and query them (as I do here) on the talk page. -- Tony Sidaway 15:39, 2 July 2006 (UTC)
The albedo values for clouds given here differ from those given at cloud albedo. 4.232.6.75 21:59, 12 August 2006 (UTC)
The first line (on 12 Feb 2010) states: "The albedo of an object is the extent to which it diffusely reflects light from light sources such as the Sun. It is therefore a more specific form of the term reflectivity. Albedo is defined as the ratio of diffusely reflected to incident electromagnetic radiation."
Restricting the description to "diffusely" implies that the specular reflection is ignored, which is not true. Rather, the albedo measures the total reflected light ("exitance", to be precise, ref 1 below) summed over all directions, including both the specular component (generally brightest in the glint direction) and the diffuse component (generally seen at all angles, but not constant). Unfortunately, there are multiple measures (definitions) of albedo, as described in the Astronomical Albedo section. But I don't think any of them exclude all of the specular (glint) component, except to perhaps avoid the peak of the glint.
I propose the following:
"The albedo of an object is a measure of how strongly it reflects light from light sources such as the Sun. It is therefore a more specific form of the term reflectivity. Albedo is defined as the ratio of total-reflected to incident electromagnetic radiation."
(1) Gutman, G.,"A Simple Method for Estimating Monthly Mean Albedo of Land Surfaces From AVHRR Data", Journal of Applied Meteorology, 1988, vol = 27, pp 973-988.
Chonny ( talk) 20:49, 12 February 2010 (UTC)
Okay, the Fairbanks section says:
..but I read once that some climatologists said that if they plant about 10,000 trees in the ever-sunny steaming-hot San Fernando Valley of Los Angeles, that it could lower the average temperature of the Valley by several degrees, as the Valley's concrete sidewalks are reflecting the sunlight and heating up the air for several meters above the surface. So- which is right? or, is it that the trees will provide shade, heating up themselves to provide cooler air at the surface? I'm confused. - Eric 00:10, 25 December 2006 (UTC)
It's not albedo, Eric. While a small amount of the energy is used in photosynthesis, evapotranspiration would be the major cause of the cooling. Concrete and asphalt pavement reflect relatively little, the heating of the air is mainly due to conductive transfer. It takes about 600 calories of heat energy to change 1 gram of liquid water into a gas.(DW 20061231) 68.151.34.107 21:45, 31 December 2006 (UTC)
The first paragraph should be in plain English for the many non-scientists who will read it. I don't have the expertise to be sure I write it correctly, but here's a draft idea:
Now it says,
Albedo is the ratio of reflected to incident electromagnetic radiation power. It is a unitless measure indicative of a surface's or body's reflectivity.
I think most readers will not understand "incident", "electromagnetic radiation power", or "unitless", or the way these things tie together. Suggested revision:
Albedo is a measure of how much electromagnetic energy (e.g., light) a surface reflects. When electromagnetic energy, such as light, hits a surface, such as a window or a mirror, it must either pass into the surface or be reflected. For example, when light hits a typical mirror, almost all the light is reflected; thus the mirror's albedo is high. When light hits a typical window, almost all the light passes through; thus the window's albedo is low. Most surfaces both reflect and absorb; for example, there are two way mirrors, and a window both allows sunlight through and reflects it -- you can see the glare.
Guanxi 18:07, 4 February 2007 (UTC)
Albedo describes what proportion of electromagnetic energy (e.g., light) a surface reflects. When electromagnetic energy, such as light, hits a surface, such as a window or a mirror, it must either pass through the surface or be reflected. For example, when light hits a typical mirror, almost all the light is reflected; thus the mirror's albedo is high. When light hits a typical window head-on, almost all the light passes through; thus the window's albedo is low. Most surfaces both reflect and absorb; for example, there are two way mirrors, and a window both allows sunlight through and reflects it -- you can see the glare.
Deuar 17:13, 5 February 2007 (UTC)
- Albedo is a measure of what proportion of electromagnetic energy (e.g., light) a surface reflects. When electromagnetic energy, such as light, encounters a surface, such as a window or a mirror, the energy must either be absorbed, pass through the surface, or be reflected. For example, when light hits a mirror or white sheet of paper, almost all the light is reflected; thus their albedo is high. When light hits a dull black object or a cave entrance, it does not come out; hence their albedos are low. A window is interesting in that when light hits it head on, most light passes through and the window's albedo is low, but when light hits the same window at a grazing angle it acts partly like a mirror, and its albedo becomes high. Most common surfaces act as some combination of the above behaviours.
Deuar 16:27, 9 February 2007 (UTC)
I think our definition may not be technically correct. The following is from the
Reflectivity article:
That part of incident light that is reflected from a body of water is specular and is calculated by the Fresnel equations. Fresnel reflection is directional and therefore does not contribute significantly to albedo which is primarily diffuse reflection.
I am curious why specular reflection contributes less to albedo, but I don't think this is the forum. I'm more concerned with how to define albedo properly. The definition in the current Abledo article also seems wrong (assuming the Reflectivity article is correct), since it doesn't distinguish between different kinds of reflection. Guanxi 18:09, 11 February 2007 (UTC)
Where should the topic of Albedo Enhancement be best handled? here? Global warming? Global dimming? Kgrr 02:11, 26 March 2007 (UTC)
Sure the Albedo is highest if the light is reflected by objects that are white? -- pizza1512 Talk Autograph 06:28, 30 April 2007 (UTC)
I've searched the web for specific references to the albedo effects of large-scale deserts, e.g. Sahara, on a hunch that the high albedo effect of such deserts may be a significant balance of Earth's temperature control mechanism. Suspiciously, such references are unavailable - nobody seems to have addressed that point.
I read something years ago concerning Gaia Theory and "Daisyworld", and a search brought up http://www.schumachercollege.org.uk/articles/college-articles/stephan/fromgaiatheory.html
In place of bright daisies, think deserts.
As we increasingly burn more fossil fuels we are heating the environment, with such heat being transferred globally, increasing the size of those deserts. Desertification is seen as bad, but I wonder if it is the only mechanism that currently we have to prevent runaway global warming? Deserts may become increasingly important as reflectors of heat back to space, to maintain temperature balance. Those countries (typically economically poor) may be supported economically by the world community, in the same way as is being proposed through the "carbon cap and trade" idea.
Much is being made of the value of using solar power farms as a green way of obtaining heat for our use, but surely they are yet more "black daisies" that will add to global warming.
Basically, we are hungry for energy, and are releasing it from within the Earth as fossil fuel, and will be trapping it on its arrival from the Sun (as solar energy farms). After we've finished with it, every bit of that energy ends up in the environment at large. We need to find a way of gathering that waste energy for redistribution.
Fractain 17:43, 1 May 2007 (UTC)
this is my first wikipedia article edit, so don't mind the mess I make of formatting...
several places this article cites temperatures that are innaccurate in some sense, because 3 degrees Celsius is simply not the same as 5.4 degrees fahrenheit.
unless there is something I am completely missing.
who wrote this?
Raging thunder ( talk) 16:06, 11 December 2007 (UTC)
I wrote this article as a mock research paper in high school and then put it on Wikipedia in 2001 as a prank: [1] I'm sorry for letting it sit here this long; I really didn't think about it after I did it, and it took me five years to remember that I had ever even edited the Albedo article, much less created it. I remembered when I came here looking for information on albedo for a real research paper, and reading through the article I realized I was reading some of my own words. So I removed most of it, but apparently either i missed some or the edits were restored. So this time I'm really cleaning up. Note: the info I'm removing isn't necessarily wrong; it's just that the original paper was only a mock paper, to teach us how to write research papers, so the factual accuracy of the information wasn't really important. I remember myself just skimming through some books on the subject and jotting down various notes. Once again, I apologize for vandalizing Wikipedia and for taking seven years to confess to it and clean up after myself. If you look at my recent contributions, you can see that I have ~2000 good faith edits and no bad ones. Soap Talk/ Contributions 17:05, 19 September 2008 (UTC)
I think the geoengineering material should be removed. It is outside the scope of albedo as a physical concept and quantity, and while relevant geoengineering articles can link to this page, I don't think it warrants its own section here, and perhaps not even to be mentioned. Awickert ( talk) 17:30, 31 January 2009 (UTC)
I believe that the definition of albedo is the fraction of all sunlight reflected (all wavelengths not just visible wavelengths as stated in the article) Hke33ly ( talk) 22:48, 13 April 2009 (UTC)
A surface can have an albedo even if it has never been exposed to sunlight. So why mention the sun in its definition?-- Singularitarian ( talk) 10:08, 2 September 2009 (UTC)
This article seems to be written from the perspective of a climatologist or an astronomer. However, albedo is an important concept in computer graphics and computer vision as well. It seems the article should be revised to account for these perspectives.-- Singularitarian ( talk) 10:04, 12 September 2009 (UTC)
The current version of the article says that albedo is a specific case of reflectivity. However, Wikipedia distinguishes between reflectivity and reflectance, and by my understanding albedo is a specific case of reflectance, not reflectivity.-- Singularitarian ( talk) 22:44, 15 September 2009 (UTC)
Albedo units were reported in the article interchangeably as either proportions of 1 (i.e. the average albedo of the earth is approximately 0.3), or as percentages (i.e. the albedo of snow was reported as being 90%). In addition to this there are ambiguous statements where relative differences in reflectivity are given as percentages, in the same sentence as giving absolute albedo values, making the situation even more confusing. For example "winter albedos of treeless areas are 10% to 50% higher than nearby forested areas". Does this mean the albedo is 0.1 to 0.5 higher (in absolute terms) or 10-50% higher as a proportion of the albedo of forested areas? I have thus changed direct references to albedo values to be all expressed as a proportion of 1. I have left the above ambiguous statement in place because the original meaning of the author cannot be known with confidence. —Preceding unsigned comment added by 147.66.8.158 ( talk) 04:01, 15 January 2010 (UTC)
Key for understanding concept of green roofs to reduce urban heat islands and slow global warming is concept of high-albedo construction materials.
Need a section here to point to from roofing or a new section on high-albedo roofing & paving materials, etc.
Mitigation via high albedo materials: See, e.g., http://en.wikipedia.org/wiki/Urban_heat_island#Mitigation
Relation to Global Warming: http://en.wikipedia.org/wiki/Urban_heat_island#Relation_to_global_warming
Ocdcntx ( talk) 15:41, 16 February 2010 (UTC)
Do the values given refer to some "reference" spectrum of white light or to sunlight (which is 50% IR)? This needs to be clarified. According to the "Percentiles" section of our page Planck's Law, 50% of sunlight is infrared at wavelengths > 711 nm. Therefore, the difference between solar and visible albedos becomes very large. In the case of snow, the near-IR albedo is roughly 50% less than the visible [2], thus a visible albedo of 90% would be a total solar albedo of less than 70%, representing a 200% "increase" (!!!!) in absorbed energy. I wouldn't exactly call this negligible...
129.2.46.178 ( talk) 00:58, 4 June 2010 (UTC)Nightvid
Section 3.5, the article says there is higher albedo from water early and late in the day, but calls this a high angle. The highest angle is normally (no pun intended) when the sun is directly overhead. The high albedo is at low angles, when the sun is near the horizon. The article is very unclear on these points. Ladarzak ( talk) 05:57, 18 February 2012 (UTC)
What is it? — Preceding unsigned comment added by Goatbar ( talk • contribs) 18:25, 2 May 2016 (UTC)
![]() | This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
( William M. Connolley 17:35, 26 Nov 2004 (UTC)) The following very old comments archived 2004/11/26.
I do not think this is a reliable source:
Kaczynski, T., 1991: The Unabomber Manifesto. Lispelite Press (F15), 40 pp.
I added the word 'allegedly' to facts attributed to Kaczynski, rather than just removing them. The 'allegedly' can be removed if a non-psychopathic source is found to corroborate the statements. In two other places I just removed the citation.
Removed the following from list of sources:
Neunke, M., 2001: White Pride Worldwide!! [Taken from
http://www.whitepride.com/sorel.html]
I didn't see any information about albedo at that site... though I suppose white people may be proud of their higher than average albedo. (cough cough)
I also removed these, pending further investigation:
Walker, E., 1987: Pictures of Preschoolers Out in the Snow. Dishwasher Picture Publishing, Volume 26, 151-1103.
Thompson, S. I. U. A. M., 2001: Worldwide Monthly Climate Tables. [Taken from http://www.woolpit.com/]
Rocky, S., and E. Bullwinkle, 1970: The Climate of the North Polar Basin. World Survey of Climatology, Vol. 14, Elsevier Publishing Company, 373 pp.
These all look like hoaxes to me. Rocky and Bullwinkle? Pictures of children in the snow? -- Jimbo Wales
There are still several mentions of Rocky and Bullwinkle in the page itself. They weren't added recently. They're in the form of source notations; could they have replaced the real source notations long ago? Is there any way we can pull up the page from many moons ago to see whether those were real references?
Also, someone who knows this field should really review this whole page for other subtle munges. -- Rootbeer
Can anyone find a real source that suggests albedo influences surfact temperature here on earth? I looked at Google and the only links I found claiming such an influence were educational projects for K-12 graders. - Tim
An albedo calculation example For a lattitude of 52N on 4 january with fresh snow (albedo 0.8) the mid-day (clear sky) insolation is 68 W/m2
The albedo of a forest/town = 0.15
0% forest/town | winter albedo 0.8 | insolation 68 W/m2 10% forest/town | winter albedo 0.735 | insolation 90 W/m2 20% forest/town | winter albedo 0.67 | insolation 113 W/m2 30% forest/town | winter albedo 0.605 | insolation 135 W/m2 40% forest/town | winter albedo 0.54 | insolation 157 W/m2 50% forest/town | winter albedo 0.475 | insolation 179 W/m2 60% forest/town | winter albedo 0.41 | insolation 201 W/m2 70% forest/town | winter albedo 0.345 | insolation 223 W/m2 80% forest/town | winter albedo 0.28 | insolation 245 W/m2 90% forest/town | winter albedo 0.215 | insolation 268 W/m2
100% forest/town | winter albedo 0.15 | insolation 290 W/m2
Insolation data derived using the insolation calculator download excel 2000 version http://members.lycos.nl/ErrenWijlens/co2/insol.zip
download excel 95 version http://members.lycos.nl/ErrenWijlens/co2/insol95.zip
You see that change of landuse has a dramatic effect on the winter energy balance.
I write a quick perl script to convert all these Fs to C or K -- Tarquin 17:33 Mar 13, 2003 (UTC)
The reference given doesn’t work anymore ( http://jeff.medkeff.com/astro/lunar/obs_tech/albedo.htm), I also found a reference that gives a different value of lunar albedo, of 0.12 instead of 0.072 ( http://www.universetoday.com/guide-to-space/the-moon/moon-albedo/). —Preceding unsigned comment added by Firstmatekevin ( talk • contribs) 14:02, 4 July 2010 (UTC)
The last sentence of the first paragraph is unclear; in comparison to land, do oceans typically have a higher or lower albedo, and do clouds contribute to higher albedo or to lower albedo? —Preceding unsigned comment added by 75.85.89.204 ( talk) 11:23, 20 December 2009 (UTC)
"tropics" section is flawed. Many factors control surface temperature, particularly those associated with vegetation. I find fault with the statement "When Brazilian ranchers cut down dark, tropical rainforest trees to replace them with even darker soil in order to grow crops, the average temperature of the area appears to increase by an average of about 3 °C (5 °F) year-round, which is a significant amount" as the lack of evapo-transpiration after forest is removed may have far more control over surface temperature than a change in albedo. The statement should be supported with a reference or should be removed.23:47, 2 September 2006 (UTC)
This page looks weird to me. Some of it is definitely rubbish: the arctic ice stuff (there is no SW in winter...). Is anybody very fond of this page...? [WMC]
( William M. Connolley 19:55, 15 Sep 2003 (UTC)) OK, no-one spoke up, so I've started stripping out stuff that looks especially dodgy to me, and putting it here (note: stuff left is not necessarily OK, just less obviously not). If anyone thinks I've been unreasonably harsh, please feel free to revert, or perhaps better make comments on a per-para basis. I've put comments on what I've removed.
The only possible explanation is that on Kilimanjaro, a glacier built up when the climate was colder, and that this glacier never completely melted because its extremely high albedo reflected away enough heat to keep itself cold enough not to melt, and to keep the air temperature at the summit much lower than that atop Mauna Loa. This very wide gap in temperatures, of nearly 11°C (20°F), occurs despite the fact that the skies above both mountains are very cloudy and the climate of both is very wet, so not much solar radiation reaches either summit. If Mauna Loa were completely dry, it could be expected that its temperature would be even warmer, perhaps as warm as that of Tibet at 14,000 feet in summer.
Thus children, much skinnier than adults, need more clothes in the wintertime to keep them warm, even if they are dark-skinned.
Albedo and frequency. There seems to be little mention of the fact that albedo is frequency dependent and objects which are white in visible light, (i.e. reflective), can be black (i.e. not reflective) in infra red, and so on for other frequencies. Most of the sun's energy comes to us as infra red heat. This means that apparent large changes in visible reflection are not necessarily significant in the main part of the spectrum. Someone said above that a molucule (or atom) has albedo, but this is highly frequency selective and is misleading if gross energy balances are being inferred in relation to global warming. For example it is often said that snow and crystals of ice have very high albedo, which is true in visible light, but they absorb at lower frequencies, otherwise, why would all the snow melt in summer? ProfSWback 16:44, 30 December 2006 (UTC)
Please note that reference 13, http://lenah.freeshell.org/pp/01-ONW-St.Petersburg/Fresnel.pdf, seems no longer available. (9-nov-2007). —Preceding unsigned comment added by Jdekloe ( talk • contribs) 13:15, 9 November 2007 (UTC)
I removed "(refs???)" from the end of the following sentence. Perhaps someone could actually find a decent reference for it.
- Mark 05:25, 28 Jun 2004 (UTC)
Last bit, Kuwaiti Oil Fires: it seems contradictory, with the last sentence saying "impossible". Can someone who knows about this clear it up?
I don't know where this article got the 0.31 Albedo figure of Earth. Albedo 0.39 is what Kaufmann says; Pater and Lissauer say that Earth has a "bond albedo" of 0.29 and a "geometric albedo" of 0.37 source. I changed the page to quote the albedo 0.39 figure, since that seems to be a reasonable number (and a really good album to boot). Samboy 08:18, 22 December 2005 (UTC)
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I find the definition to be completely useless and unscientific. How are incident and reflected radiation to be measured, and how is albedo determined to 3-figure accuracy if the definition is given in essentially unquantifiable terms ? Are we talking about power here ? Power in a certain bandwidth ? Power weighted according to spectral distribution ? Get real ! Enough of this pseudo-scientific posturing and do the job properly, or not at all. Andrew Smith
I have removed the following text pending the supply of a source for the statement:
This was marked with a "fact" template, which I think simply isn't enough. We should rather remove unsourced statements of this level of significance and query them (as I do here) on the talk page. -- Tony Sidaway 15:39, 2 July 2006 (UTC)
The albedo values for clouds given here differ from those given at cloud albedo. 4.232.6.75 21:59, 12 August 2006 (UTC)
The first line (on 12 Feb 2010) states: "The albedo of an object is the extent to which it diffusely reflects light from light sources such as the Sun. It is therefore a more specific form of the term reflectivity. Albedo is defined as the ratio of diffusely reflected to incident electromagnetic radiation."
Restricting the description to "diffusely" implies that the specular reflection is ignored, which is not true. Rather, the albedo measures the total reflected light ("exitance", to be precise, ref 1 below) summed over all directions, including both the specular component (generally brightest in the glint direction) and the diffuse component (generally seen at all angles, but not constant). Unfortunately, there are multiple measures (definitions) of albedo, as described in the Astronomical Albedo section. But I don't think any of them exclude all of the specular (glint) component, except to perhaps avoid the peak of the glint.
I propose the following:
"The albedo of an object is a measure of how strongly it reflects light from light sources such as the Sun. It is therefore a more specific form of the term reflectivity. Albedo is defined as the ratio of total-reflected to incident electromagnetic radiation."
(1) Gutman, G.,"A Simple Method for Estimating Monthly Mean Albedo of Land Surfaces From AVHRR Data", Journal of Applied Meteorology, 1988, vol = 27, pp 973-988.
Chonny ( talk) 20:49, 12 February 2010 (UTC)
Okay, the Fairbanks section says:
..but I read once that some climatologists said that if they plant about 10,000 trees in the ever-sunny steaming-hot San Fernando Valley of Los Angeles, that it could lower the average temperature of the Valley by several degrees, as the Valley's concrete sidewalks are reflecting the sunlight and heating up the air for several meters above the surface. So- which is right? or, is it that the trees will provide shade, heating up themselves to provide cooler air at the surface? I'm confused. - Eric 00:10, 25 December 2006 (UTC)
It's not albedo, Eric. While a small amount of the energy is used in photosynthesis, evapotranspiration would be the major cause of the cooling. Concrete and asphalt pavement reflect relatively little, the heating of the air is mainly due to conductive transfer. It takes about 600 calories of heat energy to change 1 gram of liquid water into a gas.(DW 20061231) 68.151.34.107 21:45, 31 December 2006 (UTC)
The first paragraph should be in plain English for the many non-scientists who will read it. I don't have the expertise to be sure I write it correctly, but here's a draft idea:
Now it says,
Albedo is the ratio of reflected to incident electromagnetic radiation power. It is a unitless measure indicative of a surface's or body's reflectivity.
I think most readers will not understand "incident", "electromagnetic radiation power", or "unitless", or the way these things tie together. Suggested revision:
Albedo is a measure of how much electromagnetic energy (e.g., light) a surface reflects. When electromagnetic energy, such as light, hits a surface, such as a window or a mirror, it must either pass into the surface or be reflected. For example, when light hits a typical mirror, almost all the light is reflected; thus the mirror's albedo is high. When light hits a typical window, almost all the light passes through; thus the window's albedo is low. Most surfaces both reflect and absorb; for example, there are two way mirrors, and a window both allows sunlight through and reflects it -- you can see the glare.
Guanxi 18:07, 4 February 2007 (UTC)
Albedo describes what proportion of electromagnetic energy (e.g., light) a surface reflects. When electromagnetic energy, such as light, hits a surface, such as a window or a mirror, it must either pass through the surface or be reflected. For example, when light hits a typical mirror, almost all the light is reflected; thus the mirror's albedo is high. When light hits a typical window head-on, almost all the light passes through; thus the window's albedo is low. Most surfaces both reflect and absorb; for example, there are two way mirrors, and a window both allows sunlight through and reflects it -- you can see the glare.
Deuar 17:13, 5 February 2007 (UTC)
- Albedo is a measure of what proportion of electromagnetic energy (e.g., light) a surface reflects. When electromagnetic energy, such as light, encounters a surface, such as a window or a mirror, the energy must either be absorbed, pass through the surface, or be reflected. For example, when light hits a mirror or white sheet of paper, almost all the light is reflected; thus their albedo is high. When light hits a dull black object or a cave entrance, it does not come out; hence their albedos are low. A window is interesting in that when light hits it head on, most light passes through and the window's albedo is low, but when light hits the same window at a grazing angle it acts partly like a mirror, and its albedo becomes high. Most common surfaces act as some combination of the above behaviours.
Deuar 16:27, 9 February 2007 (UTC)
I think our definition may not be technically correct. The following is from the
Reflectivity article:
That part of incident light that is reflected from a body of water is specular and is calculated by the Fresnel equations. Fresnel reflection is directional and therefore does not contribute significantly to albedo which is primarily diffuse reflection.
I am curious why specular reflection contributes less to albedo, but I don't think this is the forum. I'm more concerned with how to define albedo properly. The definition in the current Abledo article also seems wrong (assuming the Reflectivity article is correct), since it doesn't distinguish between different kinds of reflection. Guanxi 18:09, 11 February 2007 (UTC)
Where should the topic of Albedo Enhancement be best handled? here? Global warming? Global dimming? Kgrr 02:11, 26 March 2007 (UTC)
Sure the Albedo is highest if the light is reflected by objects that are white? -- pizza1512 Talk Autograph 06:28, 30 April 2007 (UTC)
I've searched the web for specific references to the albedo effects of large-scale deserts, e.g. Sahara, on a hunch that the high albedo effect of such deserts may be a significant balance of Earth's temperature control mechanism. Suspiciously, such references are unavailable - nobody seems to have addressed that point.
I read something years ago concerning Gaia Theory and "Daisyworld", and a search brought up http://www.schumachercollege.org.uk/articles/college-articles/stephan/fromgaiatheory.html
In place of bright daisies, think deserts.
As we increasingly burn more fossil fuels we are heating the environment, with such heat being transferred globally, increasing the size of those deserts. Desertification is seen as bad, but I wonder if it is the only mechanism that currently we have to prevent runaway global warming? Deserts may become increasingly important as reflectors of heat back to space, to maintain temperature balance. Those countries (typically economically poor) may be supported economically by the world community, in the same way as is being proposed through the "carbon cap and trade" idea.
Much is being made of the value of using solar power farms as a green way of obtaining heat for our use, but surely they are yet more "black daisies" that will add to global warming.
Basically, we are hungry for energy, and are releasing it from within the Earth as fossil fuel, and will be trapping it on its arrival from the Sun (as solar energy farms). After we've finished with it, every bit of that energy ends up in the environment at large. We need to find a way of gathering that waste energy for redistribution.
Fractain 17:43, 1 May 2007 (UTC)
this is my first wikipedia article edit, so don't mind the mess I make of formatting...
several places this article cites temperatures that are innaccurate in some sense, because 3 degrees Celsius is simply not the same as 5.4 degrees fahrenheit.
unless there is something I am completely missing.
who wrote this?
Raging thunder ( talk) 16:06, 11 December 2007 (UTC)
I wrote this article as a mock research paper in high school and then put it on Wikipedia in 2001 as a prank: [1] I'm sorry for letting it sit here this long; I really didn't think about it after I did it, and it took me five years to remember that I had ever even edited the Albedo article, much less created it. I remembered when I came here looking for information on albedo for a real research paper, and reading through the article I realized I was reading some of my own words. So I removed most of it, but apparently either i missed some or the edits were restored. So this time I'm really cleaning up. Note: the info I'm removing isn't necessarily wrong; it's just that the original paper was only a mock paper, to teach us how to write research papers, so the factual accuracy of the information wasn't really important. I remember myself just skimming through some books on the subject and jotting down various notes. Once again, I apologize for vandalizing Wikipedia and for taking seven years to confess to it and clean up after myself. If you look at my recent contributions, you can see that I have ~2000 good faith edits and no bad ones. Soap Talk/ Contributions 17:05, 19 September 2008 (UTC)
I think the geoengineering material should be removed. It is outside the scope of albedo as a physical concept and quantity, and while relevant geoengineering articles can link to this page, I don't think it warrants its own section here, and perhaps not even to be mentioned. Awickert ( talk) 17:30, 31 January 2009 (UTC)
I believe that the definition of albedo is the fraction of all sunlight reflected (all wavelengths not just visible wavelengths as stated in the article) Hke33ly ( talk) 22:48, 13 April 2009 (UTC)
A surface can have an albedo even if it has never been exposed to sunlight. So why mention the sun in its definition?-- Singularitarian ( talk) 10:08, 2 September 2009 (UTC)
This article seems to be written from the perspective of a climatologist or an astronomer. However, albedo is an important concept in computer graphics and computer vision as well. It seems the article should be revised to account for these perspectives.-- Singularitarian ( talk) 10:04, 12 September 2009 (UTC)
The current version of the article says that albedo is a specific case of reflectivity. However, Wikipedia distinguishes between reflectivity and reflectance, and by my understanding albedo is a specific case of reflectance, not reflectivity.-- Singularitarian ( talk) 22:44, 15 September 2009 (UTC)
Albedo units were reported in the article interchangeably as either proportions of 1 (i.e. the average albedo of the earth is approximately 0.3), or as percentages (i.e. the albedo of snow was reported as being 90%). In addition to this there are ambiguous statements where relative differences in reflectivity are given as percentages, in the same sentence as giving absolute albedo values, making the situation even more confusing. For example "winter albedos of treeless areas are 10% to 50% higher than nearby forested areas". Does this mean the albedo is 0.1 to 0.5 higher (in absolute terms) or 10-50% higher as a proportion of the albedo of forested areas? I have thus changed direct references to albedo values to be all expressed as a proportion of 1. I have left the above ambiguous statement in place because the original meaning of the author cannot be known with confidence. —Preceding unsigned comment added by 147.66.8.158 ( talk) 04:01, 15 January 2010 (UTC)
Key for understanding concept of green roofs to reduce urban heat islands and slow global warming is concept of high-albedo construction materials.
Need a section here to point to from roofing or a new section on high-albedo roofing & paving materials, etc.
Mitigation via high albedo materials: See, e.g., http://en.wikipedia.org/wiki/Urban_heat_island#Mitigation
Relation to Global Warming: http://en.wikipedia.org/wiki/Urban_heat_island#Relation_to_global_warming
Ocdcntx ( talk) 15:41, 16 February 2010 (UTC)
Do the values given refer to some "reference" spectrum of white light or to sunlight (which is 50% IR)? This needs to be clarified. According to the "Percentiles" section of our page Planck's Law, 50% of sunlight is infrared at wavelengths > 711 nm. Therefore, the difference between solar and visible albedos becomes very large. In the case of snow, the near-IR albedo is roughly 50% less than the visible [2], thus a visible albedo of 90% would be a total solar albedo of less than 70%, representing a 200% "increase" (!!!!) in absorbed energy. I wouldn't exactly call this negligible...
129.2.46.178 ( talk) 00:58, 4 June 2010 (UTC)Nightvid
Section 3.5, the article says there is higher albedo from water early and late in the day, but calls this a high angle. The highest angle is normally (no pun intended) when the sun is directly overhead. The high albedo is at low angles, when the sun is near the horizon. The article is very unclear on these points. Ladarzak ( talk) 05:57, 18 February 2012 (UTC)
What is it? — Preceding unsigned comment added by Goatbar ( talk • contribs) 18:25, 2 May 2016 (UTC)