Some Summary Comments on Global Warming
Review of the processes:
- Radiation comes from the Sun to earth. The Sun looks very much like a black body
radiating at a temperature of around 5,700 K. There is a spectrum of wavelengths
in this black body distribution.
- Here is a link to some solar and geo data.
- This light is reflected by cloud cover around earth, by the polar ice caps and
by the earth itself. The efficiency of these processes is important to the magnetude
of greenhouse warming.
- The radiation, of appropriate wavelengths, is absorbed by molecules in the atmosphere.This
helps to cause many chemical reactions creating dissociations of oxygen, for example,
producing atomic oxygen. These reactive species are responsible for the creation
of ozone, and hydroxyl radicals among others and heat the atmosphere by enthalpy
changes in chemical reactions.The absorption of sunlight by molecules (greenhouse
gases) also heats the atmosphere by collisional energy transfer.
- The solar radiation that is not absorbed by the molecules in the atmosphere is
absorbed by the earth-the land mass, vegetation, the oceans, etc. That portion not
reflected directly is emitted after warming the earth as "heat" radiation.
- That heat radiation, 1 to 50 micrometers from the near infrared to the far infrared,
radiates into the atmosphere where those wavelengths that correspond to molecular
energy levels are absorbed by the molecules.
- The molecules re-radiate that energy in all directions, quite a bit back towards
earth. If there are molecular collisions in the atmosphere the excitation energy
may be transformed to kinetic energy, or heat.