Discussion > Albedo questions.
Hi Rhoda
I once looked into albedo calculations and assumptions, going so far as to engage with two very polite climate scientists who are at the forefront of oceanic albedo work.
There is enormous complexity in calculating values for the oceans (which cover the majority of earth's surface, of course). The scientists I contacted had worked hard to gauge the effect of things like wave height, wind shear, sun angle and water depth: admirable work. But there did not appear to have been any calculation of albedo differential for shallow water with different bottom compositions. This struck me as an oversight because I know from much time on or above the water (I am a keen fisho), in various parts of the world, the difference it can make.
One blindingly (pun intended) obvious example: Sugar-white sands in tropical shallows will have a much higher albedo than the grey mud of the Humber estuary.
Okay, one could argue that the overall effect on global albedo is small. But so are many of the values that are being measured. There are large areas of shallow sea, mostly in the tropics where insolation is potentially greatest and its reflection all the more significant.
In the end, the whole subject became too big to grasp. I'm not a scientist, and while I do have an enquiring mind I also know my limits.
At a 'smell test' level, however it did leave me thinking that the assumptions underlying this part of the albedo calculation were somewhat inadequate.
Gixxerboy
rhoda
For years, I've been biennially conducting highly technical scientific research into tropical albedo. here's a result from Thailand, photo taken at dawn. Lots of albedo here.
Hector Pascal
Hector
I'm interested in that kind of field work myself. I have an integrated hypothesis I would like to explore, involving assessment of likely sub-surface albedo around tropical reef, that of large, shiny marine predators brought to the surface, and the albedo of beverages exposed to the tropical sun approaching dusk. Do you think I could get a grant for it?
Gixxerboy
I'm not a scientist and until a couple of years ago I thought albedo was something to do with a lack of pigmentation :o. I would expect that sattelite instruments could be used to measure albedo effects across the electromagnetic spectrum. Do such projects exist? Surely measurement is preferred to modelling/guessing? Clicking ont he first results of a Google search brought up papers dating from 8-10 years ago. This presentation from the Georgia Institute of Technology was particuarly useful in communicating the uncertainty. From the 3rd slide -
"For example, the change of albedo of 0.01 is comparable to
global energy balance change of 3.4 Wm-2 (average incident
solar radiative flux is 341 Wm-2) which is similar in magnitude to
the impacts of doubling carbon dioxide in the atmosphere"
http://irina.eas.gatech.edu/EAS_spring2006/Choi.pdf
Are they really saying that albedo forcing is massively more significant than CO2? And yet so little is known about it it would appear. My flabber is well and truly gasted.
FarleyR
I took a look at a few papers on albedo measurement. I found it interesting that they seemed anxious not to upset the AGW applecart.
When they reported increases in albedo, the authors clearly felt the necessity of including a line or two along the lines that "Of course, although increased cloud albedo reduces the energy arriving at the Earth's surface, increased cloud covering increases the greenhouse effect, trapping more heat, so the increased albedo does not mean global warming has been reduced".
Martin A
Jun 5, 2013 at 8:11 AM | FarleyR
The paper is an excellent find. I have searched in vain for papers on albedo measured from space (perhaps just looking in the wrong place). I would be grateful for any more references.
And I completely agree with your comment. Unless albedo, and its' dependency, can be understood to a high degree of accuracy, any CO2 signal will remain lost in the noise.
Roger Longstaff
So, that albedo thing, how does it work? Oh, I know how it works for the astronomers looking at a speck of a planet and gathering general information about its reflectance as a body. I don't see how that can be applied directly by climatologists working to within fractions of a watt/m^2 to finding the legendary missing heat. Again I suspect the use of averages by climate science in place of local values integrated. The albedo IS an average. It works fine for astronomy. In climate work if it varies from 30% to 35% (wikipedia) then it is crucial to know when it is reflecting which proportion of what incoming radiation. Does it work as the same number for all wavelengths? I reckon not. If the average albedo for a day is at 35% for the earth as a whole doesn't that mean a day of such reduced incoming radiation that ten days of 'missing heat' can disappear into space? Do warmists take that into account? Do they have actual measurements of anything?