Do you think that the USA attitude to global warming is responsible?

Greenhouse Gases

The greenhouse effect in greenhouses arises because the glass panes absorb most of the longwave infrared radiation emitted by plants, soil, etc. It is then emitted back into the greenhouse. (Note that in greenhouses, much of the higher temperature is not due to the greenhouse effect, but due to the fact that the warm air cannot rise, and cooler air is not drawn in). Longwave infrared radiation is the warmth that you can feel if you put your hand beside something that is hot but not glowing (do not put your hand above it, or you will feel convected heat as well). Try putting a glass jug safely between you and the source of heat and you should feel less heat as the glass absorbs the energy.

The Earth's atmosphere can act like the glass, and keep the warmth in. This is not a bad thing - the greenhouse effect is in fact a good thing as it keeps us warm, - but changes in the greenhouse can be bad for us if they mean that the Earth gets too hot or too cold.

Not all gases absorb longwave infrared radiation; only those that do are called greenhouse gases. In practice the molecules of these gases always have either more than 2 atoms, or 2 atoms of different elements. So, Argon (Ar) for example is not a greenhouse gas. Nitrogen (N₂) and Oxygen (O₂) between them make up almost 99% of the atmosphere, but are not greenhouse gases. Water (H₂O) (0.5% of the atmosphere) and carbon dioxide (CO₂) (0.036%) are the main greenhouse gases.

Human activity raised CO₂ from 285 p.p.m. in 1850 to 360 p.p.m. approximately between 1850 and 1996, and is thought to be the main cause of the rise in the global mean surface temperature (GMST) of the Earth during that time of about 0.7 °C .

There are a lot of other factors which climatologists consider when explaining or predicting changes in the Earth's temperature, including changes in:

• solar constant - the amount of solar radiation falling on an area, which is believed to fluctuate by about 0.5% (this depends on the solar luminosity and the distance between the Earth and the sun)
• solar luminosity - the total power of the electromagnetic radiation from the sun
• the Earth's orbit and tilt
• oceans and continents - these are not fixed
• atmospheric composition - this includes volcanic activity, major asteroid strikes, the gradual removal of early CO₂ from the atmosphere by the oceans
• amount of cloud cover - a variety of factors may have affected this
• dust in space - between the sun and the Earth

A lot of human activities affect the amount of greenhouse gases there are in the atmosphere, either directly or indirectly. Many scientists believe that our activities explain a significant proportion of global warming, and that we need to take strong action now to reduce them. The Kyoto Protocol was designed as a step in the right direction, but the USA has not ratified it.

Science Academies Urge Greenhouse Gas Cuts, World scientists say humans causing global warming

The Royal Society, the U.S. National Academy of Sciences and fellow societies are calling on G-8 countries to "identify cost-effective steps that can be taken now to contribute to substantial and long-term reductions in net global greenhouse gas emissions". The Bush administration's policy on climate change was called "misguided". Delay was said likely to be costly.

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