Climate change, models, recent long-term temperature data and energy policy: is Covid-19 affecting our leading minds?

Before climate change activism, people would argue passionately about the cricket, footy and whether Fords were better than Holdens. Having an opinion about climate change, let alone declaring it, is now the centre of personal, political and international disputes. After 40 plus years' as an earth scientist, I will retain the right and indeed enjoy questioning any theory put forward by other scientists, its is the scientific method and why so many of us remain scientists (it's certainly not for the money or respect!).

Climatology was until the late 1980s the domain of earth scientists, meteorologists and academics studying both current and historic climate using signals locked onto the records of sediments, ice cores and tree rings. In the late 1980s, things changed with the explosive growth of computing power and the development of global circulation models (GCMs) that allowed simulations of the global climate using crude 500km square grids. Two other elements blossomed at this time. Firstly, the software that enabled dramatic global images/videos 'demonstrating' the outputs of these GCMs in simple videos that could be used to engage stakeholders with easy to understand story-telling graphics. Secondly, political activists' gained the ability to promote their environmental holocaust views in the blossoming globalisation movement and its associated international government quangos. The IPCC is the ultimate pinnacle of this well-funded movement.

Having been intimately involved in this area at the time, I was sceptical as to the voracity of this new movement, choosing seek solutions to practical, achievable and realistic issues, such as water supply and pollution issues. These were real issues in need of urgent attention in the real world. Most of my colleagues continued in academia and have reaped the benefits of a 100-fold increase in the funding available to their new careers as "climate warming/change/adaptation" experts.

For three decades the GCM models have increasingly influenced global politics, while real datasets have been "homogenized" to match their unstable models forecasts. Climate models are now treated more like "Moses's tablets of stone", rather than the still simplistic, fallible modelling tools that have difficulty predicting past climate, let alone predicating future climate. Indeed, the last 20 years has demonstrated a continued need to reassess, adjust, homogenize (filter) data and add additional computing complexity to these inaccessible GCMs. Political activists and GCM proponents declare "97% consensus", smear opponents with "sceptical/denialist" labels and blatantly fiddle with the data to make the data match the GCM predications (see climate gate, Hockey Stick CSIRO Rutherglen-gate).

In the background, many thousands of scientists/academics/ researchers around the world carried on investigating, measuring and analysing paleo-records of temperature contained in the proxies of tree rings, ice cores, peat bogs and sediment records around the globe. This tedious/hard work is offering few rewards other than satisfaction One recent study reported via Nature's Science Reports (Margerelli et al 2020) caught my attention. Interestingly the tenet of their paper is to demonstrate that the Roman Empire may have been broken by natural climate change. The paper, while being scientific, is quite readable and worth a full read over a coffee or glass of wine. They use Mediterranean Sea sediment cores to detect temperature of the Sea and hence infer the trends in climate over the last 5000 years.

I have extracted the key element from their Figure 2 and added some clarificatory comments to assist.

The 5000 year temperature record align with the rise'n'fall of the Roman Empire, although I am sure the historians may say the corruption, disease, political/religious unrest and economic over-reliance on foreign conquests may have also had a significant impact. More interesting is the actual temperature record and the perspective it gives to the current debate of post-industrial temperature rises and the whole C02 argument promoted by GCM modellers and climate change activists.

Their temperature data shows several trends in temperature:

• Today's temperatures are much lower than the Roman Empire peak
• The maunder maximum warm period did occur (this data has been massaged to remove as per Mann et al in the infamous Hockey stick debacle).
• The current warm period is a result of us coming out of the Little Ice Age.
• Most significantly, Roman Empire growth occurred during a period when the climate was 2-3 degrees warmer than today.

The last point is probably the most significant and raises many questions. A warmer climate was certainly good for the Roman Empire. More significantly, it was warmer by 2-3 degrees and remained so for centuries. Further examination also shows that many other advances in civilisation occurred during periods of warming (Bronze Ages, Ancient Greece, European Renaissance). Climate change activists/politicians/GCM modellers have aggressively told us that 2'C warming would put us beyond the "climate tipping point" and lead to global catastrophe, our generation's "greatest existential threat".

In simple terms, if a warming climate aided the rise of the Roman Empire, why should it harm our far more advanced and 'intelligent' world today?