It is strange that some folk readily accept authority backed by scientism and other folk (like me) despite some scientific credentials are quite comfortable to reject it all!

Firstly, let me say, I believe in science and the scientific method. After all, that is why we can build aeroplanes that fly and computers that process huge amounts of data.

The scientific method is essentially experimental. Scientists produce a theory, or logical model, for how something works and then they test it repeatedly. If it keeps working and reflecting reality accurately you stick with the theory. If you find situations where the theory doesn't fit reality, you improve the theory or sometimes reject the old theory entirely.

The majority opinion counts for nothing and the length of time a theory has been accepted means little.

So, let's consider anthropogenic changes in the climate and predictions for global disaster, and why I comfortably use common sense to reject it.

1. The theory and computer models for this make long term predictions. Those predictions have not been tested and the experiment cannot easily be repeated. Existing predictions do not match measurements well and as a result they produce many models trying to show they all agree with a trend but the evidence is very flimsy. It also isn't too hard to see that extrapolations of simple theoretical knowledge regarding the greenhouse effect are not directly applicable, since the real situation is hugely complicated by a whole raft of positive and negative feedback effects which are very hard to predict, or model accurately.

2. Then, there are the historical considerations. When human beings first evolved 2 million years ago, it was a time when the earth was abundant with many kinds of life and we understand CO2 concentrations were around 2000ppm. Ever since, atmospheric CO2 has been consistently falling due to the effect of other life forms on earth and in the last ice age that is thought to be under 200ppm. That has since doubled to around 400ppm due to human activity and expected to rise further. We know that trees and much vegetation stops growing when CO2 falls below 150ppm. That would certainly be an ecological disaster. It seems more likely to me that humans have just averted that disaster, rather than created one!

It is very easy to think that you can't apply common sense to science when these scientists are so well educated. But, sadly often they can be persuaded to lose sight of common sense when there are research papers to be published and research grants to be claimed. Hence, it is all too easy for the politically powerful to manipulate the situation as they prefer! And many of those politicians that control the funding most certainly have an agenda.

Thanks to Martyn Riley for this guest post.