Talk:Albedo

Talk:Albedo/archive

Contents

1 WMC removing old stuff 2 Brazillian Ranchers 3 Kuwait oil fires 4 Suggest 9 possible wiki links for Albedo.

WMC removing old stuff

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 albedo of an object can be used to help determine its chemical composition. Every molecule of every substance has its own albedo, but albedo can also refer to a collection of very many objects, and can even be applied to objects of a very large scale, such as the planet

Composition by albedo? Really?

Since albedo can greatly affect the temperature of an area, it is advantageous for people, especially in cold climates, to settle in areas where the albedo is very low, so that they can get as much warmth as possible from the sun. The reverse is true in desert and tropical climates; people want to live in areas where as much solar radiation as possible will be emitted back into space.

Apart from local stuff, like painting houses white (not mentioned here) I can't see any evidence for that.

The difference would most likely be more than 17°C (30°F) if the landscape of the rainforest was white instead of dark green. As evidence for this theory, scientists have climbed to the top of Mount Kilimanjaro in Tanzania, which is located in an area well described as "steaming jungle". But Kilimanjaro's temperatures remain well below freezing all year round, despite the fact that its summit is only about 20,000 feet above sea level. Assuming that the average temperature at sea level around Kilimanjaro is about 27°C (81°F) (this is the GHCN's record of the average temperature at Dar Es Salaam, a nearby sea-level weather station), and that the temperature up the mountain slope decreases only 1°C (2°F) per 1,000 feet because of the semi-moist environment, it seems that the temperature at the summit should be about 5°C (41°F), which is much warmer than the approximately -7°C (20°F) that it has been estimated that Kilimanjaro actually receives. By comparison, the Hawaiian volcano Mauna Loa, which peaks at about 14,000 feet, has an annual average temperature in the GHCN of approximately 4°C (40°F), despite the fact that Hawaii is a cooler and drier environment than northern Tanzania and thus the lapse rate there would be expected to be higher, thus resulting in a colder temperature at the summit of Mauna Loa.

Here we have a long chain of unsupported assumptions.

But there is no snow at the top of Mauna Loa to reflect back incoming solar radiation, and although the climate at the summit is very rainy, snow is relatively rare and the coldest recorded temperature is -10°C (14°F), which reduced to sea level at a rate of 1°C (2°F) gives 6°C (42°F), which is not much higher than the lowest temperatures recorded at other sea-level stations in Hawaii. And the average annual temperature at sea level in Hawaii is only about 23°C (74°F), and it is during the dry season a dry 25°C (77°F), so it can be seen that the lapse rate along the slope of Mauna Loa is not significantly higher than 1°C (2°F) per 1000 feet, whereas on Kilimanjaro the lapse rate is almost doubled, for no logical reason.

Err?

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.

Err, both are very wet, but above it sez that Hawaii is drier.

Another good example of albedo in action is Greenland. Greenland is an island covered almost completely with ice. In the winter, very little sunlight reaches Greenland, so albedo is not as important. But in the summertime, it makes a very big difference, making summertime temperatures even colder than they would normally be for a given latitude and elevation. For example, Eismitte is a weather station situated a bit south of the geographical center of the island (near 70°N) at an altitude of 9843 feet. The average temperature inland at 0 feet at 70°N in Eurasia and North America in July is about 13°C (55°F). Given a lapse rate of 1°C (2°F) per 1000 feet, we could expect the July average at Eismitte to be 2°C (35°F). In fact, 1°C (2°F) per 1000 feet is often an overestimate near the poles because of the unusual convective activity that causes inversions to arise there. But the actual average July temperature at Eismitte is only -12°C (10°F), and furthermore, the next warmest month is June, at only -17°C (2°F). June being warmer than August is a clear sign that there are some outside influences on the climate, in particular that sunlight plays an unusually large role in regulating temperature, because June is the sunniest month of the year in most of the northern part of the Northern Hemisphere. But we cannot ignore the fact that the temperatures in all summer months are much colder than the predicted values using the 1°C (2°F) lapse rate. This is obviously due to the very high albedo that Greenland's ice cap provides. Further evidence for this theory can be seen in the fact that other stations in Greenland have very low summer temperatures as well, and in fact are relatively consistent all year round with a 1°C (2°F) per 1000 feet lapse rate.

More imaginary lapse rates. Or am I being too harsh?

Some parts of the Arctic Ocean are frozen over with ice all year round. These areas have the unusual distinction of experiencing heat convection coming from the ocean below as well as the air above. The temperature of the purest Arctic Ocean water is roughly -2°C (28°F) at all depths, in all seasons. The temperature of the ice above, however, is much colder because it reflects away some of the heat of the water below it. During the summertime, the upward face of the ice reflects away solar heat and prevents itself from melting completely. The ice that does melt helps keep the average July temperatures at the North Pole at about -1°C (31°F).

This is confused.

Thus children, much skinnier than adults, need more clothes in the wintertime to keep them warm, even if they are dark-skinned.

Not albedo

There is a simple relationship between the albedo of an area of the earth's surface and its color. The lighter the color, the higher the albedo. A white substance would have an albedo of 1.00, or 100%, while a black substance would have an albedo of 0.00 or 0%. The human eye perceives green light especially well, so green substances have albedos somewhat lower than one might think.

Rewrites near this bit

, but with different values for latitude and day, they would be different. The reason for this is not because of the amount of sunlight coming in, which does not change a substance's albedo, but because the actual environments would be different in summer. For example, a cultivated field may come in as high as the low 20s, depending on the crop being cultivated. Because of increased photosynthesis, all of the values for the forests and swamp lands are nearly doubled in the summer. The grassy field, however, remains at 20% regardless of season or latitude. Near the equator, particularly in rainforest areas, the soil is very black, and its albedo is very close to 0. Some shallow lakes may have albedos as high as 45% during times when the sun is striking the lake from a very acute angle, and more of its light is reflected. Alpine areas often have strange albedo values because of the unusual land formations.

More kind of wurbly stuff removed.

In the real world, the maximum albedo depends on the environment. Thus, even in the middle of winter with a heavy snow cover, the albedo of weather stations in the pine-forested areas from Europe to Siberia and in the Americas rarely goes above 40%, and many stations in this area have averages around 25%. Deciduous trees lose their leaves, and their albedos may rise to the mid-50's in winter. Open prairie climates will average around 73%, and barren tundra averages about 80%.

Keep to the subject...

If the theory of global warming is true, and the polar regions of the planet are going to be rapidly warming up, then the magnitude and path of the warming trend will depend largely on the albedo of the earth's polar regions, and to a lesser extent on the albedo of the whole planet. Because warm days in the Arctic mean heavier snowfalls, the extra snow will have a negative feedback, tending to bring temperatures down, masking the warming effect. But if the temperature rises year-round, then summers in some areas will be warm enough to melt the snow and ice completely, and thus the feedback effect in the summer will become strongly positive. For example, currently the most northern part of the Davis Strait between Canada and Greenland is blocked with ice year-round, and summer temperatures are very cold even for its latitude because of the albedo. If the ice were to melt, the very high-albedo ice would be replaced with some very low-albedo water, and temperatures would rise enormously, perhaps as much as 8°C (15°F), which would make the area warmer than any other area at that latitude. (This is what accounts for the unusually warm summers on the islands of Svalbard, in Norway. But Svalbard is surrounded by ocean, whereas the Davis Strait is surrounded by land, and thus has the potential to become even warmer than Svalbard.

This wanders of into GW, which doesn't fit here. I've added a much simplified and shorter version to the page.

If the ice melted, then there would be a way for the warm waters of the Gulf Stream to penetrate deep into the Arctic, and warm spells would become increasingly frequent. This could accelerate the melting of the Arctic Ocean, a process which would feed on itself. A melted Arctic would help many people living in Arctic areas, but could possibly hurt many others living in other parts of the globe.

Perhaps, but not very albedo-relevant.

Brazillian Ranchers

I removed "(refs???)" from the end of the following sentence. Perhaps someone could actually find a decent reference for it.

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 allegedly increases by an average of about 3°C (5°F) year-round (refs???).

- Mark 05:25, 28 Jun 2004 (UTC)

Kuwait oil fires

Last bit, Kuwaiti Oil Fires: it seems contradictory, with the last sentence saying "impossible". Can someone who knows about this clear it up?

(William M. Connolley 17:36, 26 Nov 2004 (UTC)) Looking, the KOF stuff seems of rather dubious relevance to albedo. It was probably a confusion with BC or aerosol, so I've added sections for both.

Suggest 9 possible wiki links for Albedo.

An automated Wikipedia link suggester has some possible wiki link suggestions for the Albedo article:

• Can link electromagnetic radiation: ...re of reflectivity of a surface or body. It is the ratio of electromagnetic radiation reflected to the amount incident upon it. The fraction, usu...
• Can link angle of incidence: ...s the spectrum of [[visible light]]. It also depends on the angle of incidence of the radiation: unqualified, normal incidence. Fresh snow...
• Can link weather station: ...thousands of weather stations across the world, the college weather station at [[Fairbanks]], [[Alaska]], is about 3°C (5°F) warmer tha... (link to section)
• Can link solar radiation: ...s especially marked during the late [[winter]] months, when solar radiation is greater. ... (link to section)
• Can link natural environment: ...itional zones. Part of the reason for this is the different natural environment of cities in tropical regions, e.g., there are more very da... (link to section)
• Can link carbon sequestration: ...ly warming) effect of albedo change and (cooling) effect of carbon sequestration on planting forests. They found that new forests in tropica... (link to section)
• Can link Climate models: ...ing from a minimum of near 0% to a maximum in the high 70s. Climate models have shown that if the whole earth were to be suddenly cove... (link to section)
• Can link greenhouse effect: ...mperature change due to an increase in the magnitude of the greenhouse effect, "all" we would need to do is increase the earth's overall ... (link to section)
• Can link indirect effect: ...direct (albedo) effect is generally to cool the planet; the indirect effect (the particles act as [[CCN]]s and thereby change cloud pro... (link to section)

Notes: The article text has not been changed in any way; Some of these suggestions may be wrong, some may be right.
Feedback: I like it, I hate it, Please don't link to — LinkBot 11:14, 1 Dec 2004 (UTC)