UNDER THE MICROSCOPE:DAVID BELLAMY, well-known presenter of TV nature programmes over the years, was interviewed about climate change on The Late Late Showon January 23rd. Bellamy believes that current global warming and climate change is a natural phenomenon and not significantly affected by man-made emissions of greenhouse gases (anthropogenic climate change).
He made his case vigorously and was interviewed gently by Pat Kenny. The only reaction I saw to Bellamy’s performance came from the Greens, and this mostly confined itself to protesting that Bellamy was interviewed alone and unchallenged by an expert representing the majority side of the argument.
Little attempt was made to counter the scientific claims made by Bellamy. I believe that these claims should be answered on scientific grounds and that we should not simply rely on dogmatic assertion against them. In my opinion Bellamy’s arguments against anthropogenic climate change, although drawing on scientific evidence, are also heavily informed by intuition. Although I am not an expert in this area, I will attempt to refute Bellamy’s main claims in this article.
Bellamy's principal claims were, (a) carbon dioxide doesn't drive current global temperature rise because historical records show that global temperature increase is followed, not preceded, by a rise in carbon dioxide levels; (b) temperature patterns on earth are driven by the sun's activity. He also claimed that he has been shunned by the BBC since he criticised wind farms on the Blue Peterprogramme in 1996.
As I described in a recent article, over the long term scientists have detected cycles of ice ages separated by brief warm periods called interglacials. This pattern is triggered by Milankovitch cycles, regular changes in the earth’s orbit and axis of inclination that change the incoming pattern of sunlight received on earth. When the southern hemisphere starts to receive more springtime sunshine, temperatures rise there, melting Antarctic sea ice and glaciers. As the temperature rises, atmospheric carbon dioxide also rises but lags behind temperature rise by 800 to 1,000 years. The carbon dioxide is emitted from the oceans as they warm – carbon dioxide is less soluble in warmer than in colder water.
When carbon dioxide is emitted from the oceans into the atmosphere, it enhances the greenhouse effect and warms the earth. It mixes through the earth’s atmosphere and amplifies and spreads to northern latitudes the warming that began in the southern hemisphere. The temperature forcing effect of the Milankovitch cycle alone is relatively weak, but amplified by carbon dioxide release, the overall warming effect becomes strong enough to bring the entire earth out of an Ice Age.
It is well understood scientifically how carbon dioxide warms the world. Human activities have significantly increased carbon dioxide levels in the atmosphere since the industrial revolution. Science clearly tells us that this must contribute to world warming. To claim, based on the historical record, that carbon dioxide cannot drive world temperature change is like claiming that guns cannot increase murder rates now because historical studies show that knives were usually the cause.
Climate change sceptics frequently claim that the sun is the sole cause of global warming. They point out that the sun was more active over the past 60 years than during the previous 1,150 years and there has been a steady increase in sunspot numbers over the past few hundred years. All scientists, of course, agree that the sun strongly influences earth's climate and many studies have examined the connection between global temperature and solar variations. These studies generally conclude that the correlation between the sun and climate ended in the 1970s, whereas global warming continued. Even the study most cited by the sceptics (IG Usoskin and others, Proceedings 13th Cool Stars Workshop, Hamburg, July, 2004) , concludes that global warming over the past 30 years cannot be attributed to the sun. The great majority of scientists attribute this warming to a rise in atmospheric carbon dioxide.
It would be fantastic if mainstream science had overlooked the effect of the sun on global warming. The sun is the earth’s only external source of energy. Without the sun the earth would be a frozen, dark wasteland. The effect of the sun and variations in its output on earth’s climate has been extensively investigated by mainstream science.
Finally, David Bellamy claims that the BBC no longer commissions him to make TV programmes because of his sceptical views on anthropogenic global warming. This is, of course, entirely a matter between himself and the BBC. However, some commentators point to the apparently poor correlation between his parting of the ways with the BBC and his public pronouncements on anthropogenic climate change – he last worked for the BBC in 1994, but his public sceptical utterances on global warming don’t seem to have begun until 2004.
William Reville is UCC associate professor of biochemistry and public awareness of science officer; http://understandingscience.ucc.ie
