This is a guest post from John Russell. I won’t describe what it says as it speaks for itself, but it is quite remarkable that our basic understanding of how CO2 will influence our climate has changed little in the last 100 years or so. I won’t say anymore. John’s post starts now.
Every so often, usually to do with some form of household maintenance, I find myself up in the loft. There, surrounded by the boys’ old and broken Star Wars toys; remnants of Amigas and Sinclair Spectrums; piles of tattered school exercise books with scrawled handwriting; my dad’s paintings and mother’s German lessons on audio cassette; and my collection of hippy-era LPs, I come across something that stops me doing what I went up there to do and I spend the next half an hour sitting on a box, reminiscing.
So it was that today I, literally, stumbled across ‘PHYSIOGRAPHY’, ‘by Huxley and Gregory’. As I picked it from the floor where it had fallen from a box I’d knocked over, I remembered it from my childhood: tatty olive-green cover, yellow-edged pages, and that musty smell that anyone who goes in old book shops knows so well. Although it had my name inside the cover—scrawled in the days when my signature was still spidery and yet to evolve into its adult form—it had belonged to my dad. Nostalgia flooded me: I couldn’t remember a time before it had been around, though I doubt I’d seen it for the best part of 50 years.
I turned its pages: ‘AN INTRODUCTION TO THE STUDY OF NATURE’. ‘Copyright’. …’First edition 1904.’ ‘…Reprinted 1919’. ‘Contents… Chapter I, Maps and Map Reading; Chapter II, Springs and Rivers; Chapter III, Clouds and Rain…’.
I stopped in my tracks: ‘Chapter V, Composition of the Atmosphere’. I wonder… I flicked the pages, skip reading until I finally arrived at page 88. There it was: ‘Carbon Dioxide and Climate’.
At this point I’ll stop waffling and leave Huxley and Gregory to tell you the state of climate knowledge more than 100 years ago.
Carbon Dioxide and Climate.—The atmosphere surrounding the earth may be compared with the glass of a greenhouse, which permits the bright rays of the sun to pass through, but prevents the escape of the dull radiations from the heated surfaces below it. This action is due to the carbon dioxide and water vapour in the air; but as the proportion of the latter varies very considerably, while the quantity of the former is almost the same in the open air everywhere at all seasons, evidently the protective action of carbon dioxide gas is of prime importance. If the proportion of this gas in the atmosphere could be increased, the temperature of the ground and of the air surrounding us would be raised, and if it were to be diminished all parts of the earth would become cooler. This conclusion appears astonishing when the small concentration of the gas in the atmosphere is borne in mind. In ten thousand cubic feet of pure air there are only three or four cubic feet of carbon dioxide; that is to say, only one third per cent. of air consists of the gas to the protective qualities of which we are so much indebted. Tyndall suggested long ago that the intensely cold periods of the earth’s history—Ice Ages—could be caused by variations in the proportion of carbon dioxide in the atmosphere, and more recent investigations have given support to this theory. It has been shown that a diminution of carbon dioxide to two-thirds of its present amount would probably lower the average temperature of the northern regions of the earth by at least 99°F., and hence produce the climate of the Great Ice Age. On the other hand, and increase to triple the present amount, that is, to about one per cent. in the air, would probably produce a rise in temperature amounting to thirty to forty degrees, and thus convert the deserts of polar ice into regions warm enough for the development of a rich and flourishing flora as they were in former ages. There is thus substantial reason for believing that variations of climate in the past could have been caused by slight variations in the proportion of carbon dioxide in the earth’s atmosphere.