The Sun generates the energy that warms the Earth. The Sun’s extreme surface temperature (In the range of 9900 F (5500 C) results in the emission of electromagnetic radiation. (ER) The ER most obvious to us is sunlight. But in addition, gamma rays, X-rays, and Ultraviolet are emitted and reach the Earth. This ER is called short wave because the wave length (crest to crest) is in meters 0.0000007 or shorter.
The above illustration shows the range of ER. All the way from Gamma rays to Radio waves. The most energetic are those from the Sun. In one second, light can travel 299,792kms (186,000 miles). All ER travel that same distance in a second. The difference between x-rays and radio waves is the amount of energy each contains. The shorter the wave length, the more energetic it is.
The energy of the radiation at the top of the Earth’s atmosphere is about 1350 watts/meter². When the radiation strikes the Earth it heats. Not all the of the Sun’s energy reaches the Earth as some of it is reflected back into space or is absorbed in the stratosphere. At noon on a clear day the energy you might feel could be as high as 1000 watts/meter². But it is necessary to account for the fact that the Sun shines , on average, 12 hours per day and is only directly over head a noon. The accepted standard for the average energy at the top of the Earth’s atmosphere is 343 watts/meter².
Of the 343 watts/meter², about 77 watts/meter² are reflected back into space by clouds and the atmosphere. The surface of the Earth reflects another 23 watts/meter² into space. Thus on average about 240 watts/meter² of the Sun’s radiation heats the Earth’s surface.
Obviously the Earth must rebalance this by rejecting some of the 240 watts/meter² or the Earth would soon be too hot to support life. Most of the heat sent back into space is done through “evapotranspiration and latent heat fluxes or conduction/convection processes” according to Wikipedia. These processes are part of a water cycle. An example for this kind of heat sent back into space, when a pound of water vapor (steam) condenses in the upper atmosphere, the latent heat released is 970 Btus (1,023 kJoule).
When the Earth’s surface air temperature is cooler than the objects heated by the Sun, for example at day’s end, the objects begin emitting infrared (IR). These thermal IR waves are called long waves as they have wave lengths greater than 0.0001 meters. The length of the wave is dependant on the temperature of the object emitting the ER. Thus many frequencies of IR occur. The hotter the object, the shorter the waves Exactly how the” greenhouse” works is subject of a number of different views. Read the comment section of “How the climate system works (for dummies)” ****by Dr Spencer to get a feel for the many opinions on how the Greenhouse Effect works. One thing is clear, the name “greenhouse” is probably a misnomer. A greenhouse is a closed system with glass ceilings. But greenhouse is a familiar term so we will stay with this term although it is technically an incorrect name.
The thermal IR emitted into the atmosphere wants to go back into space. On its way it encounters molecules of various gases. The predominate gases in the atmosphere, nitrogen (N2) and oxygen (O2) have almost no effect on the outgoing thermal IR. H2O and CO2 however, do have the capability of capturing some IR, The illustration that follows shows the “greenhouse gases” and their absorption bands. it is clear that water vapor is far and away the predominate molecule—–not CO2. This may surprise some people because the warmer’s focus is on CO2.
The molecules that absorb the thermal IR reradiate this heat in all directions. That means some of the heat is directed back to Earth . The reradiated heat does warm the Earth. The Earth’s temperature will increase causing more IR to be sent back into space. The temperature will continue to increase until incoming and outgoing energies are balanced.
What the warmers do not tell you, unless you know enough to ask, is why should we worry about CO2 when it is H2O that intercepts thermal IR on its way back into space. For starters, they have no control over the water vapor in the atmosphere. Secondly, If elimination of the use of fossil fuels is your goal, CO2 is your stand-in of choice. They have another concept and it is positive feedback . More about this in the next posting.
Part 4 is next, The weakness of the CAGW theory.
*** web address for Dr Spencer’s posting which you will have to copy and paste in your address bar. whhttp://www.drroyspencer.com/2015/01/how-the-climate-system-works-for-dummies/