Weather For Everyone: AccuWeather.com - Climate Change | Greenhouse Gases continue to Steadily Increase

Mar 23, 2012; 12:24 PM ET

It's still business as usual..........

Greenhouse gas concentrations in the atmosphere continue to steadily increase, according to NOAA's Earth System Research Laboratory.

The latest readings from the Mauna Loa Observatory in Hawaii indicate that atmospheric carbon dioxide (CO2) concentrations have increased to 393.65 parts per million as of February 2012.

Here are two common questions that NOAA has answered from their FAQ section........

What is the greenhouse effect?

The Sun, which is the Earth's only external form of heat, emits solar radiation mainly in the form of shortwave visible and ultraviolet (UV) energy. As this radiation travels toward the Earth, the atmosphere absorbs about 25% of it, and about 25% is reflected by the clouds back into space. The remaining radiation travels unimpeded to the Earth and warms its surface. The Earth releases back to space the same amount of energy it has absorbed from the Sun. However, the Earth is much cooler than the Sun, so the energy re-emitted from the Earth's surface is much weaker, in the form of invisible longwave infrared (IR) radiation, sometimes called heat radiation. If you stand close to a hot object, but do not touch it, you can feel how the IR radiation heats your skin, although you cannot see the IR rays.

Gases that absorb and trap this IR radiation, such as water vapor (H2O), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are known as "greenhouse gases". The atmosphere acts like the glass in a greenhouse, allowing much of the shortwave solar radiation to travel through unimpeded, but trapping a lot of the longwave heat energy trying to escape back to space. This process makes the temperature rise in the atmosphere just as it does in the greenhouse. This is the Earth's natural greenhouse effect and keeps the Earth 33 °C warmer than it would be without an atmosphere, at an average 15 °C (59° F).

How can minor atmospheric gases have such a large impact on climate?

The major gases, nitrogen (N2), oxygen (O2), and argon (Ar), which together comprise about 99.8% of the atmosphere, do not absorb visible light, nor infrared light. If the atmosphere contained only those three gases, the radiation would go right through without any effect on the heating of the atmosphere or surface. That leaves it to the minor gases such as water vapor, carbon dioxide, methane, nitrous oxide, ozone, and others to absorb infrared light. The total mass of the atmosphere is very large, about 5 x 1021 grams, or 5 million times a billion metric ton. The amounts of the minor gases are therefore still very large, sufficient to cause the absorption of a major fraction of infrared light in the atmosphere.