Global Warming

Greenhouse Effect

Shown above is an Infrared Map of the Earth. Red areas represent regions of high heat retention in the atmosphere. This is an equatorial band because that is where the atmosphere has the most water vapor.

The earth has a natural greenhouse effect due to trace amounts of H20 and CO2 that naturally occur. The enhanced greenhouse effect refers to the augmentation of these natural gases by human activities.

What's the evidence?

The energy balance in the atmosphere is shown here:

The main components in this diagram are the following:

What Happens to the 69% of the incoming radiation that doesn't get reflected back:

Achieving Thermal Equilibrium:

This short wavelength radiation is absorbed by the earth which heats the earth to a finite temperature. Since the earth wants to stay in thermal equilibrium, it must re-radiate this energy.

The earth has an equilibrium temperature of about 300 Kelvins . At this temperature, the wavelength of the emitted radiation is in the infrared.

What happens to the outgoing infrared radiation?

So clearly, if human activities increase the ability for the earth's atmosphere to absorb IR radiation, this produces a net warming of the atmosphere over time. This is the Enhanced Greenhouse effect:

Concentration increases since 1750:

Data showing the increasing concentration of Greenhouse Gases:


CO2 is steadily increasing at the rate of about 1 ppm per year


NOx is leveling off due to pollution abatement on vehicles


CH4 is only recently been measured. Rate of increase is about 10 ppb per year. However, since 1 CH4 molecule is worth 25 CO2 molecules, the equivalent growth rate in terms of CO2 is 2.5 ppm. Thus methane will eventually be the dominant enhanced greenhouse gas in our atmosphere. What can we do about this?

Proceed on to Global Warming

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