The Roman Warm Period

25 Jul 2020

Benny Peiser's newsletter on 24th July 2020 has the following post - ... which is telling us all something that was very well known 50 years ago, let alone in more recent research. See for example page 156-8 of HH Lamb, 'Climate, History and the Modern World', Routledge:1982 and HH Lamb, 'Climate: Present, Past and Future' (1972). One is left a bit flummoxed when they suggest this is something new, or are they saying something slightly different to earlier researchers. The Roman Warm Period was 2 degrees Celsius warmer than it is today, which is different in that it actually puts a figure on the warmth - and 2 degrees Celsius is quite a big difference. It is in fact the temperature rise chosen by the IPCC as the boundary prior to catastrophic global warming. We are nowhere near that at the moment which is why this new study hit the headlines. Apparently, nobody fried during the Roman Warm Period but we are all going to fry in the heat according to the doom mongers when we get past that threshold in the modern world. At other sites the emphasis is on 3.5 degrees warmer - but this is Fahrenheit. The empire, we are told, coincided with a 500 year period that is dated from AD1-500. This appears to be a misnomer as the Warm Period has previously been dated from 200BC-300AD. Several points of interest here, and from an SIS perspective we had a couple of articles published recently in Review, concerning a roughly 200 year gap that might exist in AD chronology. The AD1-500 would fit in with proxy data such as tree rings if 200 years was taken out of late Iron Age. Having said that I have to immediately knock the idea on the head as this study involves taking the temperature of sea water in the Mediterranean basin. Hence, a period of warmth on land could, and should, very well have preceded warmth in the sea - or  what we might call thermal expansion. In the 2nd century AD there is evidence of rising sea levels (in London for example) which became more problematic over the next two or three centuries. Warmth causes water to expand and seas should rise in tandem. This probably doesn't happen immediately but after a period of time. There is a lot of water in the Mediterranean and that must take time to heat up - particularly to a temperature as high as 2 degrees C. Hence, the science is not contradictory as a shallow reading of the headlines and a skimming of the article might suggest. The authors of the study, from Italy and Spain, are not looking at the Roman Warm Period in a parochial fashion, but are telling us what their data has shown (which is how science works). What might be parochial is the further suggestion in the press release that the warming may have begun contemporary with the fall of the Republic on the death of Julius Caeser, and the rise of the emperor Augustine. When surface temperature is taken into account the warmth clearly preceded 27BC - and there were plenty of other reasons for the changes in the political system inaugurated by Augustine. See for example Kyle Harper, 'The Fate of Rome; Climate, Disease and the End of an Empire', Princetown University Press: 2017.

At ... which is American, hence the use of Fahrenheit. The researchers say the warm period coincided with the fall of the Republic (as noted earlier). What I thought interesting here is they associate the warmth with a rise in sea levels (which are clearly documented in the Mediterranean). Was this why the global warmers anticipated a rise in sea levels during the warm 1990s and 2000s? They may have miscalculated how long it takes for the seas and oceans to warm after the warmth has been set in motion at the land surface, or in the atmosphere. The fact that sea levels have refused to significantly budge may be due to the amount of manipulation of temperature data (it was and is not as hot as they claim) or it could be that it takes a long time for water to expand thermally in a huge basin. Having said that the study makes the point that the warmth in Roman times was probably a result of solar activity. Of course this is also probably the cause of 20th century warming, in the 1920 and 1930s (see HH Lamb), as well as the 1990s and 2000s.

At ... we have a piece on alarmism. The journalist appears to object, reading between the lines, to the idea we should all convert to vegetarianism. However, it is also another take on the recently published ideas of Michael shellenberger and his book, 'Apocalypse Never' - which is now in the company of a new book on the same theme by Lomberg. Shellenberger (and Lomberg before him) were activists on the environmentalist front. Now they are backsliders, having 'seen the light', having got fed up with the lies and exaggeration of the alarmists, as they are described. As a former activist Shellenberger knows very well how it all works - but how do you convince the true believers. He wrote a piece on his views for Forbes magazine but it was pulled as a result of influence exerted by powerful people. He targeted in particular Extinction Rebellion and attacked the Green Blob over and over again in a couple of pages, for their hyprocrisy and exaggeration of the facts. Too strong on vibes for Forbes it would seem.