In the news lately has been a New Zealand climatologist who has been looking askance at received opinions regarding anthropogenic global warming. His name is Chris de Freitas, and he is a member of the faculty of the University of Auckland. I recently ran across an article of his, in which I read the following:
There is little doubt that average annual global temperature has been generally trending upwards in line with the expectations of many climate scientists. The cause, however, is debatable since the trend started before modern industrialisation began pumping millions of tonnes of carbon dioxide into Earth’s atmosphere.
From 1940 to 1980 during the post World War II industrial boom when carbon dioxide increased rapidly, there were 40 years of global cooling.
On the other hand, there was a distinct global warm period in mediaeval times when carbon dioxide levels were much lower than they are now.
Carbon dioxide concentration in the atmosphere is currently higher than at any time in the past 600,000 years, yet global temperatures were much higher during all the major warm interglacial periods that occurred during this time, despite much lower levels of carbon dioxide.
His point, of course, is that if human activity is not the cause of climatic variations, we might want to reconsider putting the world’s economy on a carbon-crisis footing.
The greenhouse effect of carbon dioxide in the atmosphere is almost saturated, so that the effect of carbon dioxide on global temperature is already close to its maximum. Adding more has an ever decreasing effect.
To illustrate the process, compare painting over a glass window with thin paint. The first coat of paint reduces some light shining through; the second coat cuts out a little more. Beyond this additional coats have an ever decreasing effect.
In the light of the latest evidence, a new question is being asked: What is the basis for the claim that carbon dioxide is a major driver of global climate?
If it turns out that there is no basis, or that the evidence for it is weak, a new and perhaps more important question arises: Are carbon dioxide emissions unwelcome?
It’s a well-known fact that carbon dioxide is food for plants, and that at current concentrations they are carbon dioxide-starved. Increased carbon dioxide has a pronounced fertiliser effect on plant growth. Plants convert the carbon dioxide into food and fuel. It keeps our forests and pastures healthy.
No one knows for sure what the future holds, but there are some good clues as to what’s going on. It hinges on growing evidence that natural influences on climate are in fact stronger than any man-made greenhouse effect.
It may be premature to discard our anxiety over the threat of possible human-caused global warming, but this anxiety should not be based on ignorance of what science can tell us.
Now Dr. Frietas et al. have published a paper casting further doubt on the notion that anthropogenic carbon emissions are the principal driver of climatic variation. Learn more here.