I've been invited to a debate on Carbon Offsetting. It won't cost me anything to attend, since it's at the University where I work - so I won't have to worry about offsetting my travel!
It seems to me that the issue of carbon offsetting is actually two issues:
1. Should those that can afford it be helping those that can't to invest in CO2 reducing technologies? Perhaps, through charitable donations. To my mind, the answer is clearly yes, especially where the return on investment is good.
2. Should such investments be used to salve our conscience where we're failing to make our own CO2 savings? This is where charitable donations become offsetting.
Here, the answer is less clear cut, and probably depends on whether the offsetting tends to sustain the activity that is being offset. For strictly essential activities, which would continue under any circumstances, there's no danger of this.
Let's take two examples:
First, imagine that you have £10,000 to spend on a new, low energy, heating system for your house. You might save a ton of CO2 per year. If, instead, you spent it on efficient wood stoves in Africa, you might save 100 tons per year. Unless they would have bought the stoves anyway, you might well be justified in doing this, and regarding the savings as offsetting your heating emissions. This seems sensible to me.
Second, suppose you're planning an Australian holiday for your family, and lets imagine that no special circumstances apply - you've no relatives or business there, for example. This isn't a necessity, and it would cost you less to holiday nearer to home. If offsetting makes you less likely to change your destination, then it's probably a bad thing.