“
Climate change alarmism is a belief system, and needs to be evaluated as such. There is, indeed, an accepted scientific theory which I do not dispute and which, the alarmists claim, justifies their belief and their alarm. This is the so-called greenhouse effect: the fact that the earth’s atmosphere contains so-called greenhouse gases (of which water vapour is overwhelmingly the most important, but CO2 is another) which, in effect, trap some of the heat we receive from the sun and prevent it from bouncing back into space. Without the greenhouse effect, the planet would be so cold as to be uninhabitable. But, by burning fossil fuels—coal, oil and gas—we are increasing the amount of CO2 in the atmosphere and thus, other things being equal, increasing the earth’s temperature. But four questions immediately arise, all of which need to be addressed, coolly and rationally. First, other things being equal, how much can increased atmospheric CO2 be expected to warm the earth? (This is known to scientists as climate sensitivity, or sometimes the climate sensitivity of carbon.) This is highly uncertain, not least because clouds have an important role to play, and the science of clouds is little understood. Until recently, the majority opinion among climate scientists had been that clouds greatly amplify the basic greenhouse effect. But there is a significant minority, including some of the most eminent climate scientists, who strongly dispute this. Second, are other things equal, anyway? We know that over millennia, the temperature of the earth has varied a great deal, long before the arrival of fossil fuels. To take only the past thousand years, a thousand years ago we were benefiting from the so-called medieval warm period, when temperatures are thought to have been at least as warm, if not warmer, than they are today. And during the Baroque era we were grimly suffering the cold of the so-called Little Ice Age, when the Thames frequently froze in winter and substantial ice fairs were held on it, which have been immortalised in contemporary prints. Third, even if the earth were to warm, so far from this necessarily being a cause for alarm, does it matter? It would, after all, be surprising if the planet were on a happy but precarious temperature knife-edge, from which any change in either direction would be a major disaster. In fact, we know that, if there were to be any future warming (and for the reasons already given, ‘if’ is correct) there would be both benefits and what the economists call disbenefits. I shall discuss later where the balance might lie. And fourth, to the extent that there is a problem, what should we, calmly and rationally, do about it?
”
”