Global Warming The surface temperature of the Earth is largely governed by the way in which sun's rays which are allowed to penetrate the atmosphere but are then trapped and cannot escape back to space. For millions of years carbon dioxide in the upper atmosphere has been present at about 280parts per million. Carbon dioxide, and other gasses, transmit the visible and Ultra Violet (UV) rays from the sun, but are not good at transmitting InfraRed (IR) rays. Since the higher energy rays from the sun are those in the visible and UV part of the spectrum, the filtering of IR is not a problem. Rays from the Earth are generally in the IR simply because the Earth is much colder than the sun. If all of the Earth's IR rays could escape then the Earth would cool down. The presence of the greenhouse gases, like carbon dioxide, inhibit the loss of IR rays and so keep our planet warm. This is the classical greenhouse effect, it is how a greenhouse works and is essential to the survival of life on Earth over millions of years. The increased atmospheric carbon dioxide levels from burning fossil fuels is further inhibiting IR ray transmission and is therefore leading to an enhanced greenhouse effect - that is to say that the Earth is getting warmer. The current concentration of carbon dioxide in the upper atmosphere is over 358 parts per million.