When you think of Global Warming, do you imagine receding glaciers and ice-caps and nod gravely, or do you glance out your window at falling snow and laugh derisively? Either way, I’d like to speak with you.
Throughout my assorted travels around the vast web of irreverence that is the Internet, I’ve stumbled across and have participated in discussions revolving around the issue of Global Warming and Climate Change. A common thread that I have noticed running through these discussions is that many people – myself included – have difficulty explaining the whys and hows of Global Warming.
Well, through this short series of posts I will explore some of the basic principles behind Global Warming, Climate Change, Atmospheric Pollution and why these phenomena are bad news for our future.
Firstly, The Greenhouse Effect.
This phenomenon is named after the garden-variety greenhouses that many avid green-thumbs employ to grow their favourite plants out of season, or in a climate that would otherwise prevent their growth. The principle behind these gardening miracles is quite simple. The sun emits heat and light radiation, mostly in the form of infrared and visible light. The composition of the greenhouse structure permits short-wave infrared to pass through, but as infrared light is reflected back it becomes long-wave radiation, which the greenhouse does not allow to pass through. Therefore, heat and light radiation is trapped within the greenhouse. A perfect recipe for plant growth!
This basic principle holds true for the atmospheric greenhouse effect. Reflected sunlight is trapped within the Earths atmosphere by certain gases, which causes the planet to heat up. It is important to note that this effect is entirely natural and entirely necessary for complex life. Without the Greenhouse Effect, the average surface temperature on Earth would drop to approximately -15ºC!
Secondly, The Greenhouse Factor and Greenhouse Gases.
Everybody knows that carbon dioxide is a greenhouse gas, but did you know that water vapour is a greenhouse gas? Surprised? Well, so was I.
A greenhouse gas is defined as an element or compound present in the atmosphere that absorbs infrared radiation reflected from the Earth, trapping heat within the atmosphere. The main greenhouse gases are water vapour and carbon dioxide. Other significant greenhouse gases are methane, nitrous oxide, and various man-made CFC’s (chlorofluorocarbons).
The greenhouse factor is a measure of how much a gas affects the greenhouse effect relative to the same amount of carbon dioxide, when carbon dioxide is taken to be 1.
The Greenhouse Factor of Certain Gases
Gas Greenhouse Factor
Water Vapour 0.1
Carbon Dioxide 1
Nitrous Oxides 160
CFC’s 21,000 – 25,000
These greenhouse factors explain why the burning of fossil fuels, which release carbon dioxide, and the use of man-made chemicals affect the greenhouse effect so strongly. Higher concentrations of these compounds in the atmosphere result in an Enhanced Greenhouse Effect. This enhanced greenhouse effect then leads to a rise in the average surface temperature of the Earth because increased concentrations of these gases trap more heat.
So, Global Warming is a rise in the global average surface temperature, caused by an enhanced greenhouse effect, which is caused by the greenhouse factor of certain greenhouse gases, that are released into the atmosphere through human activities.
(Thanks for reading. In my next post, I hope to discuss Global Warming in more detail and to look into some of its effects.)
Feel free to correct any mistakes in this post and to criticise any aspect of it. I apologise if anything is wrong. I’m not an expert, merely an interested person.