The Creation Of The Greenhouse Effect

The greenhouse effect is brought about by the ability of the atmosphere to be selective in its response to different types of radiation. The atmosphere readily transmits solar radiation— which is mainly short-wave energy from the ultraviolet end of the energy spectrum—allowing it to pass through unaltered to heat the earth's surface. The energy absorbed by the earth is reradiated into the atmosphere, but this terrestrial radiation is long-wave infrared, and instead of being transmitted it is absorbed, causing the temperature of the atmosphere to rise. Some of the energy absorbed in the atmosphere is returned to the earth's surface, causing its temperature to rise also (see Chapter 2). This is considered similar to the way in which a greenhouse works— allowing sunlight in, but trapping the resulting heat inside—hence the use of the name 'greenhouse effect'. In reality it is the glass in the greenhouse which allows the temperature to be maintained, by preventing the mixing of the warm air inside with the cold air outside. There is no such barrier to mixing in the real atmosphere, and some scientists have suggested that the processes are sufficiently different to preclude the use of the term 'greenhouse effect'. Anthes et al. (1980) for example, prefer to use 'atmospheric effect'. However, the use of the term 'greenhouse effect' to describe the ability of the atmosphere to absorb infrared energy is so well established that any change would cause needless confusion. The demand for change is not strong, and 'greenhouse effect' will continue to be used widely for descriptive purposes, although the analogy is not perfect.

Without the greenhouse effect, global temperatures would be much lower than they are—perhaps averaging only -17°C compared to the existing average of +15°C. This, then, is a very important characteristic of the atmosphere, yet it is made possible by a group of gases which together make up less than 1 per cent of the total volume of the atmosphere. There are about twenty of these greenhouse gases. Carbon dioxide is the most abundant, but methane, nitrous oxide, the chlorofluorocarbons and tropospheric ozone are potentially significant, although the impact of the ozone is limited by its variability and short life span. Water vapour also exhibits greenhouse properties, but it has received less attention in the greenhouse debate than the other gases since the very efficient natural recycling of water through the hydrologic cycle ensures that its atmospheric concentration is little affected by human activities. Any change in the volume of the greenhouse gases will disrupt the energy flow in the earth/atmosphere system, and this will be reflected in changing world temperatures. This is nothing new. Although the media sometimes seem to suggest that the greenhouse effect is a modern phenomenon, it is not. It has been a characteristic of the atmosphere for millions of years, sometimes more intense than it is now, sometimes less.

The Basic Survival Guide

The Basic Survival Guide

Disasters: Why No ones Really 100 Safe. This is common knowledgethat disaster is everywhere. Its in the streets, its inside your campuses, and it can even be found inside your home. The question is not whether we are safe because no one is really THAT secure anymore but whether we can do something to lessen the odds of ever becoming a victim.

Get My Free Ebook

Post a comment