One of the research interests of Victoria Slonosky is the analysis of long-term variability from long instrumental records and climate reconstructions. She graduated at McGill University, worked for some time at CRU. She has sent me a very interesting text, which I am glad to post here on her behalf:
This is not a post to discuss the scientific case for or against anthropogenic climate change. The past few months (or years, for some people) have been interesting not so much for any specific revelations, but because they’ve led to a re-examining of many of the arguments. There is so much vigorous debate on almost every aspect of climate change theory that it seems as if every theory, every assumption, has to be considered and tested again from first principles..
As I do this, I can’t help reflecting that we are all products of our beliefs and times, and history has shown that nearly all of our scientific beliefs eventually get overturned. A century ago, until Einstein, most scientists believed in ether; two centuries ago, before Lavoisier, many believed in phlogiston. The nature of light has gone back and forth between waves and particles for centuries, until we’ve decided, with a certain degree of exhaustion, that it’s both. Unfortunately, as Kuhn has shown, neither consensus nor, I would add, good intentions, are a guarantee in science. We can never tell which of this year’s crazy ideas will become the next decade’s working hypothesis.
The idea of anthropogenic climate change is not new, and there exists literature on this theme through history. I recently came across an early Canadian version of this theory: that forests caused cold winters, so clearing forests would improve the climate. Oddly enough, considering current discussions on the Roman Warm Period, this theory came about from the writing of the Romans. Gibbon’s descriptions of the Roman campaigns in cold and snowy forests of northern Belgium and Germany, and of Julius Caesar's military exercises on the frozen Seine, struck the early settlers as being very similar to their Canadian conditions. Since Canada is actually further south than much of western Europe, the difference in climate between them couldn’t be due to latitude, so they attributed it instead to the presence of forests. The difference between the cold and snowy winters of Roman description and the contemporary mild European winters was the evidence.
Deforestation thus became a civic duty; every tree felled not only cleared land for agriculture, but also represented an infinitesimal increase in temperature. This theory of human-induced climate change persisted, with some controversy, until the late 19th century, when it was finally, and regretfully, abandoned. It was concluded (somewhat morosely) after looking through two and a half centuries of documentary data that while there considerable variability, there was no overall change whatsoever in the onset date of spring or winter. Making a virtue out of necessity, Canadians turned their attention instead to ice hockey and tobogganing.
How would we evaluate this theory today? On the one hand, deforestation is linked to carbon emissions, which should increase the temperature, but would probably not be noticeable on a regional scale. On the other hand, the albedo of forests is lower than that of fields of grain or snow, so deforestation should have lead to winter cooling. Then there's the effect of evapotranspiration, which should have led to summer warming, but decreased cloud cover, which would lead to...we don’t know. Maybe the most curious thing about this episode is that over several centuries, large-scale deforestation had no discernible long-term effect on the regional climate.
The debate over anthropogenic climate change touches off echoes that persist through the history of Western thought: determinism vs chaos theory; nurture vs nature; free will vs fate; Plato vs Aristotle. The idea that we are causing climate change can be frightening, but it also implies we are in control; that we can decide whether to let warming continue or whether to stop it. This is an idea has always been with us (Hans has a very good overview on the history of human attempts to control the climate), starting with prehistoric weather gods. It continues with countless examples through history, with priests attempting to save Alpine villages from advancing glaciers by throwing holy water on them during the Little Ice Age, to the Canadians diligently clearing the forest in an attempt to create Montreal-sur-Seine, and on through to today. Where is dividing line between anthropogenic causes of climate change and an anthropocentric view of the world? It was interesting (and a bit troubling) that the statement that came out of Copenhagen was not to limit greenhouse gas emissions, or to limit anthropogenic climate forcing, but to limit any global temperature increase to less than 2 degrees.
All this is not to say that I think anthropogenic climate change isn’t happening or isn’t scientifically possible. We should recognize, though, that these themes are not only from the realm of science, but also form part of our (Western) philosophical and sociological background; they are part of our intellectual history. We need to be vigilant, and to be aware that our cultural background may be influencing our thinking. The scientific method of observation, deduction and independent verification is the only way we have found so far to try to step out of ourselves, of our times and beliefs. This is why the Feynmanian ideals are so central to science, and why it ‘s so important to retain a level of skepticism, debate and reproducibility. It’s what stands between us pursing a lower-carbon lifestyle and priests throwing holy water on a glacier.