Thanks to Robin Barclay for his contribution (“Still a rising trend, SN, 31 July 2012).
Robin is right. It is, of course, still a rising trend. The climate continues to change, as it has done for about five billion years, under many influences including the level of atmospheric carbon dioxide.
None of the studies or people I quote denies that; if they did, I would only quote them in order to disagree.
Without going too far back there was the Medieval Warm Period during which Vikings cultivated Greenland, followed by the Little Ice Age when they were forced to leave there, starvation across Europe and ultimately, “ice fairs” on the River Thames before warming resumed.
We are currently still recovering from the Little Ice Age and many factors are involved such as ocean oscillations, cloud effects due to interaction of solar wind and cosmic rays (Dr Svensmark), planetary orbital and orientation effects and variations in ocean chemistry, to name but a few.
None of the scientists whose work I follow denies that an increase in carbon dioxide level, on its own, has a tendency to warm the planet. Neither do I deny that.
The argument is between those who hold the Intergovernmental Panel on Climate Change (IPCC) view that the only significant influence on climate is the level of atmospheric carbon dioxide and those who hold that many climatic influences exist and that the effects of varying carbon dioxide level are, consequently, not yet properly understood and in the final analysis, may even be insignificant.
Other influences arising from a small rise in temperature (feedbacks) will determine whether global temperatures rise higher (positive feedback) – or lower (negative feedback) – than the widely accepted average of 1C predicted to arise from a doubling of carbon dioxide level on its own.
For example, snow and ice melting reduces reflection of sunlight back to space and so adds to the initial warming i.e. “positive” feedback. A corresponding increase in low cloud cover, conversely, would be “negative” feedback
Sceptical climate scientists say too little is known about “feedbacks,” partly because the IPCC focus on carbon dioxide has led to a shortfall of research in other related fields.
Of the 20 or so computerised climate models referred to by the IPCC every single one assumes the overall feedback resulting from a small rise in temperature is positive and consequently, all models automatically predict temperature rises greater than 1C for doubling carbon dioxide – some excessively so – giving rise to alarm over rising sea levels.
But cloud effects are complex and poorly understood and Svensmark’s cosmic rays theory is currently being researched by none other than CERN in Geneva, hardly a bunch of cranky right-wing “fossil fuel shills.”
Cloud feedbacks could easily be “negative” and if strongly so, could render carbon dioxide effects insignificant; climate stability would be enhanced. We must wait and see.
If by 2100 it turns out that carbon dioxide effects really are significant, other energy sources such as thorium nuclear reactors will have – long since – largely replaced fossil fuels and “Peak Thorium” isn’t in the offing in the next several thousand years.
So, apart from the egg all over the faces of the temperature measuring fraternity yet again, the point about the halving of the trend is that, at 1.55 C per century, even if it were ALL due to carbon dioxide, it is within the aspiration to limit global temperature rise to 2C.
In 100 years will our great-great-grand-kids curse us for saddling them with a one foot rise in average sea level [University of Colorado, Boulder: current trend = +3.1mm/yr]?
Does anyone care now that the top of the high tide was two feet lower when Nelson was killed at Trafalgar in 1805? Or one foot lower than now during the Battle of Jutland?
Of course they don’t. Did anyone even notice?
John Tulloch Lyndon Arrochar email@example.com