Taking the historical temperature

■ Cathal McMahon’s letter (Irish Independent, July 7) should be put in perspective when he writes that “this current heatwave, with the possibility of a nationwide drought, comes after the heaviest snowfall in March in more than 36 years”.

While it is certainly unusual that, for the last fortnight or so, Irish summer resembled a Polish summer made perfect by the absence of mosquitoes, this heatwave still pales in comparison with Irish summers in Roman times.

So warm the Romans grew grapes in northern England, and studies of semi-fossilised trees that give accurate climate reading back to 138BC indicate in the years 21 to 50AD, temperatures were 1C warmer than now (not to mention Hannibal crossing the Alps with elephants at the end of October).

Yes, we did get “the heaviest snowfall in March in more than 36 years” – that means three pleasant, dry days of mild snow, perfect for children (here, unlike in the rest of the world, exempt from school for that occasion).

But the River Tiber in Italy completely froze in 398BC, 396BC, 271BC and 177BC; and so did the River Thames during the so-called Maunder Minimum (1645-1715).

Mr McMahon writes about CFCs being on the rise again – would that not be a good argument against China’s ‘One Belt, One Road’ initiative, given that China’s CFC consumption is almost a hundred times bigger than that of the US – and our imports only fuel its environment-damaging production (China is by far the biggest greenhouse emitter in the world)? Grzegorz Kolodziej

Bray, Co Wicklow