The connection to helicopters is becoming more vague with every post, but the discussion is interesting.
I think that deep within most reasonable people, you will find that they all agree that the net effect of carbon emissions is not a good thing, although perhaps some may think it is not a bad thing either.
By looking for evidence that it is bad, we are waiting for an unacceptable result. We could put known carcinogens into school lunches, and observe cancer rates amongst the students and former students for 20 years, and conclude that (within statistical accuracies) the data doesn't support removing the carcinogens. This is what is happening with the carbon emissions. We are looking for hard evidence that ill effects are occuring, but that hard evidence is going to be when we find ourselves with an unrecoverable atmosphere. I don't want that to happen.
Instead, we should acknowledge that the current evidence may not be 100% convincing, but take action on it anyway and see if we can cause a trend towards improving the atmosphere. If we see improvement (even improvement at a higher derivative), then that will greatly support the current evidence.
Any steps we can take to reduce the emissions make sense. At this point, taking every possible step will have too much impact on our way of life, but there are savings that could be had almost everywhere that have little impact. I.e. don't go with a low emission vehicle that is 3 times too big for your needs, go with a low emission vehicle that is the right size. Works for helicopters too.
Matthew Parsons.