Greenhouse Gases and Climate Change

Everybody is talking about greenhouse gases and climate change. The scientists, the media and politicians are all telling us that climate change is caused by greenhouse gases. Energy efficiency and curbing air travel are high on people's agenda. Are they really linked?

There is a very strong correlation between CO2 (one of the greenhouse gases) and global temperate. Scientists can look back over large time scales, with the help of tree rings and ice samples from the polar regions. Nobody disputes that the graph for global temperature looks very similar to the graph of CO2. Does this mean there is a cause and effect? There are four possibilities

  1. CO2 causes global temperature changes
  2. Global temperature causes CO2
  3. They are both caused by another (unknown) process
  4. It is coincidence

Lets take (4) first. There is a similar correlation between global warming and pirate (yes those bearded sea goers). As pirate numbers have decreased, temperature has increased. The solution is simple, breed more pirates. Obviously this conclusion is nonsense, but the correlation between pirate decrease and temperature increase is good.

(3) There is a possibility that there is another process which causes both CO2 and global warming. Let us imagine that the sun has gets hotter occasionally. Obviously this could be the causes of the global warming, and its not implausible that it could also cause an increase in CO2 through some as yet unknown process.

(2) Here we have a direct cause and effect, but its the opposite way round to the one normally given. Here's one possible mechanism: As the temperature increases, the seas get warmer. As the seas get warmer, they release CO2 into the atmosphere. Water can hold gases trap gases, for example, fish breath oxygen which is trapped (dissolved) in the water. CO2 is similarly dissolved in water. The amount of gas that can be dissolved in water is dependent on the water temperature, if you heat the water, less gas can be dissolved, so more CO2 is emitted.

(1) This is what most people tell you: Global warming is caused by CO2. The mechanism for this cause and effect is the now famous "Greenhouse" effect. Light hitting the earth's surface is reflected, but the heat is trapped by greenhouse gases, just like the glass in a greenhouse. Its a one-way street, sunlight can get in, but the heat can't get out. If you increase greenhouse gases more heat is trapped.

Changing our behaviour to limit CO2 emissions is probably only useful if #1 is correct.

So which of the four possibilities is it? I hear a lot of people being sceptics. If you don't believe that you are causing homelessness, starvation and war by flying on planes, is it because you've thoroughly analysed the data, and found flaws in the scientists logic? Or is it because you don't want to change your cushy life style, and being a climate sceptic is an easy way to avoid responsibility.

See also Global Warming Links