This is a follow up to the previous post on a debate with Will Happer concerning satellite measurement of Earth atmosphere: What is directly measured at distance: temperature or radiation? My view is that temperature is directly measured and so can be reliable, while radiation is computed using some complex software for radiative heat transfer and so is unreliable. It seems that Happer is not perfectly happy with such a clear statement but does not give a clear alternative.
Let us see take a look at the most advanced system, which is the AIRS Atmospheric Infrared Sounder monitored by NASA presented as follows:
- AIRS is the first instrument ever to produce a three dimensional map of temperature and water vapour in the atmosphere directly measured from satellites:
We understand AIRS directly measures temperature at distance and that this can be very useful information!
We recall that there are several instruments like bolometers, pyrgeometers and infrared cameras which read temperature at distance typically using a thermopile sensor taking on source temperature at one end by radiative equilibrium at distance (like a thermometer in contact) and instrument reference temperature at the other end thereby reporting a voltage depending on temperature difference, thus reporting source temperature.
Why is then Happer speaking about measuring radiation? It is because global warming alarmism is based on an idea that the Earth absorbs more energy from the Sun than it emits to outer space as Outgoing Longwave Radiation OLR. Evidence is then presented as measured incoming and outgoing radiation, of size around 340 W/m2, from which a difference of less 1% is obtained and reported as alarming. That requires high precision measurement outgoing radiation from direct measurement and so it must be tempting to believe that this is what AIRS offers. But it does not.
Happer is not a climate alarmist, but he seems to be stuck with the alarmist dream of measuring OLR to a very high precision. Strange.
PS We may compare reading temperature vs radiation with determining a persons bank net vs determining the power of the person. The bank net can be directly read which is not possible for power.
Similarly, all lake side properties around the lake share the level of the lake, while their value is more difficult to decide.
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