With seemingly unprecedented storms and floods afflicting almost everywhere, there is a temptation to assume, without calling further evidence, that the nemesis of climate change must be upon us, and so it well may be.
However, we must avoid falling into that classical error of logic called "coincidental correlation", better known by its Latin exposition post hoc, ergo propter hoc, which means "after this, therefore because of this".
It describes the logical fallacy where it is assumed that because one thing follows another, the second event must have the first one as its cause. For example, if I have a cold and take a dose of Ezicure, and all my symptoms promptly disappear, a fallacious conclusion could be that Ezicure must be effective.
More to the point, perhaps, we have had several storms of unusual severity, and the world is growing warmer; the storms, therefore, must have been caused or exacerbated by the global warming.
There are two possible ways to expose a fallacious post hoc, ergo propter hoc conclusion.
One may show that the effect was caused by something other than the suggested cause, or alternatively, demonstrate that the correlation is coincidental by evidence that the effect would have occurred anyway, even if the suspected cause did not occur. In the case of storms and global warming, the first possibility is not available to meteorologists; but let me suggest a version of the latter.
November's aggressive tendencies have been in evidence throughout the centuries. As long ago as 1316, the belfry of Christ Church cathedral was blown down, and many other Dublin buildings destroyed, in a severe gale on November 19th that year.
In another November gale, that of 1637, "in one night ten or twelve barks" were blown from their anchorage in Dublin Bay, "of the most part whereof never no news hath ever been heard since". On November 10th, 1696, the packet-boat William was wrecked near Sutton with the loss of more than 80 lives.
Just over 200 years ago, in November 1797, severe flooding caused many houses in Patrick Street in Dublin to be under several feet of water, and rowing-boats were used to negotiate the Castle Yard. In November 1807, severe blizzards affected the whole country, and great loss of life occurred when the Rochdale and the Prince of Wales were wrecked.
So severe storms, floods and even blizzards have occurred in many previous Novembers - quod erat demonstrandum, but then, as the philosopher John Locke remarked, "It is one thing to show a man that he is in error, and another to put him in possession of the truth."