For as long as I can remember I have enjoyed reading books about history. Not only are history books interesting in their own right, but they can also shed light on the climate in earlier times. Because most historians are solely concerned with their subject, and not with supporting one side or the other in “climate wars”, detais of extreme weather events in the past are often narrated with apparent objectivity. All the more is this the case, if the history book in question was written half a century or more ago, before the climate crisis cult had even come into existence.

Currently I am reading “Hannibal – the Struggle for Power in the Mediterranean” by Sir Gavin Rylands de Beer. His foremost claim to fame is as an evolutionary embryologist, but he developed an interest in the Alps specifically and in history generally, which interests synthesised in his fascination with Hannibal and his journey across the Alps with elephants. He was the first (by detailed analysis of the historical sources – primarily Polybius and Livy – together with a study of how the landscape fitted their narrative) to propose the Col de la Traversette as the probable route taken by Hannibal. His theory received support a decade ago when a churned-up mass of sediment in a 1m-thick mire at Col de Traversette was discovered, that could be directly dated to the time of Hannibal’s invasion. Perhaps, then, Sir Gavin’s observations regarding history should be taken seriously.

We’re well used to scaremongering articles in the Guardian (“It has not been as hot as this for at least 125,000 years, prior to the last ice age, and most likely longer, potentially going back at least 1m years”), but what if they’re simply not true? Which brings me back to Sir Gavin’s book. It was first published in 1969, and I am reading a 1974 version, published a couple of years after Sir Gavin’s death. Back then, the main climate scaremongering was with regard to a possible return to an ice age rather than “global boiling”, but in any event discussion of the climate then lacked today’s hysteria and constant drumbeat of propaganda. And so Sir Gavin could calmly note that temperatures during Hannibal’s march could not be lower than they are today and may have been higher (or least that was the case in the late 1960s, when he wrote those words). He relied on four “independent methods” to assess the climate in Hannibal’s day.

The study of glaciers

He noted that the advance down valleys of glaciers depends on temperatures and on precipitation levels. We can see the limit of former glacial extension as shown by their terminal moraines. From the 16^th to the 19^th centuries CE (as we now say) he says that glaciers advanced much further than at any other time since the end of the last ice age. Thus the “present” condition of Alpine glaciers is not a diminished relic of their extension in the last ice age but rather of their extension during their recent (“Little Ice Age”) maximum.

He observed that as glaciers retreat, they are constantly leaving uncovered tree trunks from forests which were overrun during their more recent advance. Some such tree trunks have been found at an altitude of more than 2,250m. Classical authors also offer clues regarding the earlier climate – Strabo quoted Polybius as saying that in the Noric Alps there were gold mines that were worked profitably. This is today the region of the High Tauern in Austria. The Goldberg mines there were worked extensively in the Middle Ages, but in the 17^th century CE the adits to some of the mines were covered as the ice once more advanced.

His conclusion: “It follows, therefore, from the evidence of glaciology that the temperature in 218BC[E] was at any rate not lower than it is at present.”

Studying the Height of the Tree Line

Here he is referring to places where the absence of trees is not attributable to the advance of glaciers or to the activities of humankind, such as pasturing of animals or felling trees for fuel use. He states that in northern Italy the tree line is at least 300m lower than it was. He was, of course, writing more than half a century ago, but I would be astonished if the tree line has risen there by as much as 300m in the intervening years. He references Virgil talking of pine-clad Monte Viso, and notes that it bears no pine forests today, and that Hannibal’s route passed close by.

Conclusion: “The inference is that the climate was then warmer”.

Pollen analysis

“These studies indicate that there were temperature maxima in 550BC[E] and in 1200 [CE], and between these periods a temperature similar to that in the present day.” From which I extrapolate that he concluded that it was warmer at the bookend dates he refer to than it was when he was writing.

Study of cores taken from the ocean bed

Here he refers to the quantity of calcium carbonate deposited being dependent on the temperature at the ocean surface at the time of deposition. The time of deposition is ascertained from the level in the core of the specimen being studied. He says that at the level corresponding to 550BC[E] the annual rate of calcium carbonate deposit was 1mm per square cm, whereas when he was writing it was 0.9mm. The values for 218BC[E] were intermediate between those of 550BCE and 1969[CE].

Conclusion: “the world temperature in 550BC[E] was 1 or 2 degrees higher than at present”. Sadly he didn’t say whther he was referring to degrees Celsius, but even if (as seems distinctly possible, given when he was writing) he was referring to degrees Fahrenheit, the point remains – it was warmer in 550BCE than half a century ago.

What to make of it all? Well, we must apply caveats. First, it might well be argued that science has moved on and the findings would now be different, given modern scientific methods (although it’s hard to argue away hard evidence such as the altitude of tree lines and retreating glaciers exposing previous forests that had been submerged when the glaciers advanced). Secondly, we will be told that if Sir Gavin was working in degrees Fahrenheit, then we have seen temperatures rise by at least his 1 or 2 degrees since 1850, and much of that warming has occurred since 1970. Nevertheless, even allowing for such caveats, there is a strong case for arguing that 2,250 or so years ago, the temperature was at least as high as it is now. We don’t hear talk of climate tipping points then, nor are we given to understand that the world was then facing a climate crisis.

We can learn a lot from history. Perhaps the main thing we should learn is that today’s temperatures are not unprecedented, there is no climate crisis, and we really should focus instead on the other issues jeapardising humankind and environmental well-being. There is, after all, no shortage of candidates.