If you read the full abstract of the paper you've quoted, it explains the mechanism.
The analogy I'd use is this ... let's suppose you want to measure the 'brightness' of a bulb. If you use a tiny camera and place it directly on the bulb's surface (the thin layer of glass between the filament and the camera) then you only see a small fraction of the total surface defined by the camera's field of view. So, to determine the overall 'brightness' you need to extrapolate from the small area you measured to the whole bulb. You could take lots and lots of measurements over the bulb and add them all together. But there is no way of sitting a satellite close to the earth and yet have it in an orbit that examines every portion of the earth. You could get a better estimate by combining the data from lots of satellites in different orbits, examining different regions of the planet.
Alternatively, what you could do is move the tiny camera back from the bulb so you see a greater region of the bulb. Now you can use that one camera to look at almost half the entire bulb in a single go. You might miss the poles of the bulb, but you can certainly get a much better idea of 'how bright is the bulb'. The problem though is that the light spreads out from the bulb before reaching the camera so the intensity you measure is weaker. You have to factor in the distance from the bulb (there will be an inverse square relationship between distance and the brightness you measure) and the dimensions of your camera system/lens/field of view/aperture/etc. This is a geometric calculation rather than an 'estimate'.
So, the point is that since close satellites sit in orbits that will either not examine the whole of the earth, or will examine large areas but be positioned further out, you need to take the geometry into account when determining radiance. This is not a 'fudge' of climatology or some specific difficulty measuring aspects of our planet, but a standard calibration issue in physics that you need to perform that accounts for the position of a detector relative to an extended (ie non-point) source/reflector of light.
Earth’s temperature depends on the balance between energy entering and leaving the planet’s system . When incoming energy from the sun is absorbed by the Earth system, Earth warms. When the sun’s energy is reflected back into space, Earth avoids warming. When energy is released back into space, Earth cools. Many factors, both natural and human, can cause changes in Earth’s energy balance, including:
Line graph with a line that show the observed temperature increases, a blue band that show how the temperature would have changed over the past century due to only natural forces, and a red band that shows the combined effects of natual and human forces. The blue band that shows natural forces starts and ends the 20th century just above 56 degrees Fahrenheit. The actual observed global average temperatures closely follows the model projections that use both human and natural forces - beginning in 1900 at just above 56 degrees Fahrenheit and ending in 2000 around 58 degrees Fahrenheit. View enlarged image
Models that account only for the effects of natural processes are not able to explain the warming over the past century. Models that also account for the greenhouse gases emitted by humans are able to explain this warming.
Source: USGRCP (2009)
Changes in the greenhouse effect, which affects the amount of heat retained by Earth’s atmosphere
Variations in the sun’s energy reaching Earth
Changes in the reflectivity of Earth’s atmosphere and surface
Hmm I am very cynical sorry, but it seems nothing in climate science doesn't have fudge factors, they even have glacial rebound calculations added to GRACE Antarctic ice measurements (how the hell do they know how much) satellite sea level calibrated against tide gauges, and we all know how they have altered historic temp readings
Why not look at the full journal article?
ftp://ftp.cira.colostate.edu/ftp/Raschke...
I need a part 2 because I didn't quite get what I was looking for in the first one.
The Earth's energy budget or radiation budget is the net difference at the TOA (top of the atmosphere) of the incoming SW and outgoing LW and SW radiations. I realize there are satellites and other instruments to measure radiation and other parameters like cloud cover, etc. in relation to the Earth's radiation budget.
I'll start my question by quoting from an abstract here (just a random example):
"To estimate the earth's radiation budget at the top of the atmosphere (TOA) from satellite-measured radiances, it is necessary to account for the finite geometry of the earth and recognize that the earth is a solid body surrounded by a translucent atmosphere of finite thickness that attenuates solar radiation differently at different heights." http://journals.ametsoc.org/doi/abs/10.1175/1520-0442%282002%29015%3C3301%3ADTOTAF%3E2.0.CO%3B2
I often read that the energy budget of the Earth has been increasing (i.e. causing warming) and even though recent temperatures have not reflected this, we know this because of instruments which measure the incoming and outgoing radiation balances indicate we are net positive. This is the basis for Trenberth's "missing heat".
My question is, the above abstract implies that the actual "imbalance" is not measured but rather it is estimated. Is this correct, and if so, since it is an estimate what assumptions are made and do all climate scientists in this area have the exact same assumptions?
Another way of putting this is what's the "official" top of the atmosphere radiation imbalance and how was that determined and by whom?
