“Global warming” may or may not be caused, or exacerbated, by human use of fossil fuels. Evidence from recent centuries (the short-term view, you might say) appears to be conclusive. Carbon dioxide and temperature levels started to rise at almost exactly the same time that the Industrial Revolution began in Europe. But paleoclimatologists (taking the long-term view) seem less certain. Of the two measures, the former appears more significant, in that carbon dioxide is now at an all-time atmospheric high, where temperature is less easy to determine from proxies. There is good evidence that the so-called Holocene Climatic Optimum of around eight thousand years ago involved temperatures higher than those we have today, and it seems very likely that temperatures about 120 kya (thousand years ago), when tropical animals roamed southern England not long before the onset of the last Ice Age, were at least 2̊C higher than today. There is also the possibility that global warming has been caused by increased solar activity, which occurred during the same 150-year time period. That activity has now largely died away, giving us an excellent opportunity to see whether temperatures now fall, or whether (with carbon dioxide levels continuing high) they continue to rise at the same rate as before. Carbon dioxide levels in the atmosphere should, if the Gaia system of checks and balances were working properly, be lowered by the absorption of CO2 by the oceans, and the fact that the oceans are presently CO2 saturated may have something to do with the horrendous abuse of the marine environment that has occurred over much the same period as industrial pollution of the atmosphere and soil, so could be a factor too.
Until very recently (in historical terms – I mean, less than 50 years ago), scientists were convinced that long-term solar system rhythms meant that we would soon be faced with a renewed icy period comparable to the Pleistocene. Those rhythms still exist, and presumably would reinstate themselves if we managed to lower carbon dioxe levels sufficiently – so the question we should be asking ourselves is whether our (very short-term, in geological time terms) use of fossil fuels is likely to raise carbon dioxide levels sufficiently to offset the solar system rhythms and continue the upward movement in temperatures.
But that raises another question. If fossil fuel use raises carbon dioxide levels, and those levels prevent us entering another Ice Age, is this a good or a bad thing? On the one hand, burning fossil fuels might be all that is preventing the onset of another Pleistocene-type episode. In which case, perhaps we shouldn’t be quite so worried about it, because if we stop burning them, the Ice Age tendency may reassert itself. And whilst the prospect of warming, with rising sea levels and possibly more chaotic and extreme climatic conditions, is bad enough, it’s nothing to what we shall face if we are assailed by another Ice Age, in which drought as well as cold, and probably violently fluctuating weather conditions to boot, if the climatic proxy evidence from the Pleistocene is correct!