- #1
Graeme M
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- TL;DR Summary
- Within the contect of the earth/atmosphere system and the greenhouse effect, what is meant by the term "surface temperature"? In reading about this I find the use of the term confusing as it seems to refer to different quantities at different times.
I have been reading about the "greenhouse effect" of Earth's atmosphere, having been conscious that while I generally understand it I had never really examined it more closely. A problem that bothers me is mention of "surface temperature" which seems to vary according to context.
In some articles I read about how the surface temperature would be -18C without an atmosphere, but is actually 14C with an atmosphere. However, when we talk about 14C, is that the average temperature of the air (atmosphere) as recorded by thermometers, is it an average of air temps AND sea surface temps, or is it a derived value from some measurement by satellites of outgoing radiation?
The reason I am confused by this is that IF the Earth's surface without an atmosphere were -18C, I am assuming we are talking about the actual surface temperature as derived mathematically given incoming insolation and surface emissivity (which I understand for the Earth is close enough to 1). I understand this may be derived using the Stefan-Boltzmann Law, though I have no idea how to do that, mind you.
This seems to be a different quantity from that of measuring an air temperature, so it's not clear to me why we say that the GHE causes the Earth's surface to be 32C warmer than it would be without an atmosphere.
Or is this temperature difference more of a sort of simplified statement for the general public and not necessarily exactly what's going on?
In some articles I read about how the surface temperature would be -18C without an atmosphere, but is actually 14C with an atmosphere. However, when we talk about 14C, is that the average temperature of the air (atmosphere) as recorded by thermometers, is it an average of air temps AND sea surface temps, or is it a derived value from some measurement by satellites of outgoing radiation?
The reason I am confused by this is that IF the Earth's surface without an atmosphere were -18C, I am assuming we are talking about the actual surface temperature as derived mathematically given incoming insolation and surface emissivity (which I understand for the Earth is close enough to 1). I understand this may be derived using the Stefan-Boltzmann Law, though I have no idea how to do that, mind you.
This seems to be a different quantity from that of measuring an air temperature, so it's not clear to me why we say that the GHE causes the Earth's surface to be 32C warmer than it would be without an atmosphere.
Or is this temperature difference more of a sort of simplified statement for the general public and not necessarily exactly what's going on?