Tranforming Earth's Air

1. Earth from Space
Thin atmosphere, fragile globe
2. Life-Saving Natural Greenhouse
Main ingredients of atmosphere = nitrogen (78%) oxygen (21%) = do nothing for heat
Trace ingredients of air trap heat near ground
= carbon dioxide, CO2
= water vapor, H2O

Without natural greenhouse ground = -16 degrees Celsius
with natural greenhouse
ground = +15 degrees Celsius

Water freezes at 0 degrees Celsius

Greenhouse warms like a bucket with a hole in it

More CO2
Smaller hole more heat kept

Reason why atmosphere does not explode is the hole that releases heat.

3. Sun brightens, atmosphere changes
As time goes on Sun gets slowly brighter.
Suggests greater terrestrial greenhouse ~ 4 billion years ago when life existed but
Sun was 30% fainter. (eg. 70% of present brightness)

Gaia hypothesis - plants and animals control environment - favorably for them.
Plants replenish oxygen.

Less CO2 in atmosphere over 4 billion years ago = less warming because Sun is brighter.
But mankind dumping more CO2 in air.

4. Our present layered atmosphere

                 |             hot ionosphere Sun's X-ray

                 |    cold  
 
height       |              hot stratosphere Sun's ultraviolet ozone

                 |    cold 
  
                 |_________________________
                                temperature ---->

5. Sun's Brightness Varies Over 11-year Activity Cycle

Solar constant = total Sun's irradiance over all wavelengths
= energy per unit time per unit area reaching Earth's air from Sun

Solar constant is not constant, but varies over time from 1 sec to 10 years
Sunspots = brief cooling of radiactive output
Maximum solar activity cycle, Sun brightens in total radiance by about 0.1 percent
X-ray and ultraviolet vary even more with activity cycle - 100 to 10 times
X-ray increase at maximum in solar activity cycle warms ionosphere more.

6. Ozone is made by Solar Ultraviolet
Good ozone = in stratosphere

Solar ultraviolet + oxygen molecules = oxygen atoms
Oxygen atom (O) + oxygen molecule (O2) = Ozone (O3)
More ozone when Sun is active
Bad ozone = man-made ground level smog