The science from the skeptics point of view is not often reported in the mainstream media, so I have compiled a summary of this as an informed layman. I will focus on the central issue, the impact that carbon dioxide has on the climate rather than refuting the supposed effects as they tell us nothing about why the climate in changing.
Firstly, some theory on the greenhouse effect. Heat radiation from the sun would hit the earth’s surface and rebound into the infinite expanse of space were it not for greenhouse gases. These trap heat in the atmosphere making life on earth possible. When we add more greenhouse gases to the atmosphere, like CO2 from the burning of fossil fuels, they trap more heat. Warmists say this will keep happening as long as we add greenhouse gases with a whole range of nasty consequences.
So why is this not the case? Well, carbon dioxide has a diminishing effect, each unit of carbon dioxide you add to the atmosphere will have less of a warming effect than the one that preceded it. This is because carbon dioxide absorbs only certain wavelengths of light and these are approaching their saturation point (although given the nature of a logarithmic curve, it will never be fully saturated) and so they cannot absorb much more. History has demonstrated this property during times when carbon dioxide levels were considerably higher than today. Half a billion years ago (around the time organisms more complex than bacteria began to evolve), its concentration was 7000 parts per million as opposed to 380ppm today. Temperatures did not reach the ridiculously high levels you would expect without the diminishing effect.
Another reason that carbon dioxide warming is not as significant as we are led to believe is the feedback involved. Feedback is basically when a change in a system leads to a further change. It can be positive; the secondary effect leads to amplification of the original change, or negative which counteracts it. Climate models have exaggerated warming predictions because they factor in positive feedback (and a number of other assumptions). As a result, they overestimate warming by a factor of between three and six. The data however actually implies negative feedback. Professor Richard Lindzen points to data obtained from satellites which suggest that the heat absorbed by greenhouse gases is not what would be expected. An example of a negative feedback mechanism is the albedo effect of clouds identified by Roy Spencer which leads to a net cooling effect, and Lindzen’s iris hypothesis.
We have now discussed a couple of reasons why carbon dioxide warming is not what is would be expected to be, now the evidence to show that it is not. Greenhouse warming is expected to be more obvious at a latitude of between 30N and 30S and an altitude of between 8 and 12km. This so-called ‘hotspot’ is simply not there, indicating that the any warming we have witnessed could not have been caused by greenhouse gases. We would also expect a net accumulation of heat in the oceans, however work by David Douglass and Bob Knox shows that there has been none for 68 years.
Ice core data from Vostok in Antarctica shows a correlation between temperature and carbon dioxide concentrations, which Al Gore implies proves carbon dioxide has driven climate for the history of our planet. He suggests it is important above all other factors. However, Gore has completely distorted the concept of causality, it is in fact temperature that effects CO2. We can observe an 800 year time lag to testify to this. This is because higher temperatures impair the ability of oceans to hold CO2 (this relates to change in Gibbs free energy with temperature for a decrease in entropy). No substantial positive feedback is evident that we would see if carbon dioxide had a significant impact.
Alarmists say that the current warming trend is unprecedented and unmatched, but this is simply not true. For one, it was warmer in medieval times, a time known to climatologists as the Medieval Warm Period. We then entered a cooler phase in our planet’s history around the 1600s known as the Little Ice Age. The current warming trend started after this time. So warming for the past century is to be expected. In fact, most of it occurred before 1940, before most of our emissions and world temperatures actually declined after the second world war when fossil fuel consumption accelerated during the post-war economic boom. Even today as we continue to burn fossil fuels at an unprecedented rate, temperatures have simply refused to rise in line with the prediction of the alarmists. They peaked during the 1998 El Nino phenomenon and have actually fallen.