Wednesday, November 21, 2018

The Story of (IR) Infrared Radiation and the Greenhouse Effect

In order to better appreciate the energy from the sun that sustains life on Earth, it behooves us to understand that:

Infrared radiation (IR) is popularly known as ‘heat radiation’. It and all electromagnetic waves (including light) of any frequency will heat surfaces that absorb them. Infrared light from the Sun accounts for 49% of the heating of Earth, with the rest being caused by light that passes through the atmosphere. The light energy that is converted to heat is absorbed and then re-radiated as IR at longer wavelengths.

“...the Sun does ‘not only’ produce IR, visible light, and UV. Fusion in the core actually gives off high energy gamma rays. However, as the gamma ray photons make their arduous journey to the surface of the Sun, they are continuously absorbed by the solar plasma and re-emitted to lower frequencies. By the time they get to the surface, their frequencies are mostly only within the IR/visible light/UV spectrum... then, when electromagnetic radiation from the Sun strikes the Earth’s atmosphere, some of it is absorbed while the rest proceed to the Earth’s surface. In particular, UV is absorbed by the ozone layer and re-emitted as heat, eventually heating up the stratosphere. Some of this heat is re-radiated to outer space while some is sent to the Earth’s surface.

In the meantime, the electromagnetic radiation that wasn’t absorbed by the atmosphere proceeds to the Earth’s surface and heats it up. Some of this heat stays there while the rest is re-emitted. Upon reaching the atmosphere, part of it gets absorbed and part of it passes through. Naturally, the ones that get absorbed add to the heat already there.
The presence of greenhouse gases make the atmosphere absorb more heat, reducing the fraction of outbound EM waves that pass through. Known as the greenhouse effect, this is the reason why heat can build up some more.”

Radiation from the sun:

Earth’s Atmosphere, Electromagnetic Radiation and the Greenhouse Effect: