Letter from Stephanie: Temperature & Albedo | AMNH
The long term trend from albedo is that of cooling. In recent years Each surface has a specific effect on the Earth's temperature. Snow and ice. These results reveal linkages between albedo and urban land cover The relationship between LST and near‐surface air temperature in the. The Albedo Effect, Urban Heat Islands, and Cooling Down Your Playground What is the relationship between color and the temperature.
And if clouds complicate matters, so too do the seasons. Every year, albedo peaks twice. The first peak occurs when the Antarctic sea-ice is at its winter maximum.
The second peak, which is larger, occurs when there is snow cover over much of the Northern Hemisphere. Albedo also changes due to human interaction. Forests have lower albedo than topsoil; deforestation increases albedo. Burning wood and fossil fuels adds black carbon to the atmosphere.
The albedo effect and global warming
Some black carbon settles on the surface of the ice, which reduces albedo. Albedo and Global Warming The most significant projected impact on albedo is through future global warming. As the white surfaces decrease in area, less energy is reflected into space, and the Earth will warm up even more.
The loss of Arctic ice is of particular concern. The ice is disappearing quite fast; not only is albedo decreasing, but the loss triggers a positive feedback. By exposing the ocean surface to sunlight, the water warms up.
Climate Science Glossary
This melts the ice from underneath, while man-made CO2 in the atmosphere warms the surface. Humidity also increases; water vapour is a powerful greenhouse gas. More ice therefore melts, which exposes more water, which melts more ice from underneath… This loop fuels itself, the effect getting more and more pronounced.
This is a good example of a positive feedback. Increased water vapour also has another effect, which is to increase the amount of cloud. As mentioned already, clouds can increase albedo a negative feedbackbut also warming a positive feedback.
Measuring Albedo The albedo of a surface is measured on a scale from 0 to 1, where 0 is a idealised black surface with no reflection, and 1 represents a white surface that has perfect reflection.
Taking measurements of something with so many variables and influences is clearly going to be a challenge. Satellite data is constrained by the orbit of the satellite. Clouds can be hard to distinguish from white surfaces.
Indirect measurement may also be problematic. The Earthshine project investigated a phenomenon where light reflected by Earth illuminates the dark side of the moon.
By measuring the brightness, the amount of albedo - reflectivity - could be estimated. The project reported a counter-intuitive finding. This seems contradictory, as Anthony Watts was quick to note when he voiced his sceptical argument in If higher albedo was having a cooling effect, how could global warming be taking place?
Tricky Business Science constantly seeks to improve itself. Just as fresh snow has a higher albedo than does dirty snow, the albedo of snow-covered sea ice is far higher than that of sea water.
Albedo Effect - Universe Today
Sea water absorbs more solar radiation than would the same surface covered with reflective snow. When sea ice melts, either due to a rise in sea temperature or in response to increased solar radiation from above, the snow-covered surface is reduced, and more surface of sea water is exposed, so the rate of energy absorption increases.
The extra absorbed energy heats the sea water, which in turn increases the rate at which sea ice melts. As with the preceding example of snowmelt, the process of melting of sea ice is thus another example of a positive feedback. Because of this, in order to reduce the error of energy estimates, it is important to measure the albedo of snow-covered areas through remote sensing techniques rather than applying a single value for albedo over broad regions.
In sunlight, dark clothes absorb more heat and light-coloured clothes reflect it better, thus allowing some control over body temperature by exploiting the albedo effect of the colour of external clothing. For example, the effects of a spectrally responsive albedo are illustrated by the differences between the spectrally weighted albedo of solar photovoltaic technology based on hydrogenated amorphous silicon a-Si: H and crystalline silicon c-Si -based compared to traditional spectral-integrated albedo predictions.
In the case of evergreen forests with seasonal snow cover albedo reduction may be great enough for deforestation to cause a net cooling effect.
Deciduous trees have an albedo value of about 0.
- Albedo Effect
- Letter from Stephanie: Temperature & Albedo
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They found that new forests in tropical and midlatitude areas tended to cool; new forests in high latitudes e. The reflectivity of a water surface is calculated using the Fresnel equations see graph. At the scale of the wavelength of light even wavy water is always smooth so the light is reflected in a locally specular manner not diffusely. The glint of light off water is a commonplace effect of this. At small angles of incident light, waviness results in reduced reflectivity because of the steepness of the reflectivity-vs.
However, as mentioned above, waviness causes an appreciable reduction. Because light specularly reflected from water does not usually reach the viewer, water is usually considered to have a very low albedo in spite of its high reflectivity at high angles of incident light.
Note that white caps on waves look white and have high albedo because the water is foamed up, so there are many superimposed bubble surfaces which reflect, adding up their reflectivities. Fresh 'black' ice exhibits Fresnel reflection. Snow on top of this sea ice increases the albedo to 0. Different types of clouds exhibit different reflectivity, theoretically ranging in albedo from a minimum of near 0 to a maximum approaching 0. Clouds keep Earth cool by reflecting sunlight, but they can also serve as blankets to trap warmth.