This Letter to the Editor, written by CO2 Coalition Member Euan Mearns, was published in The Press and Journal, January 10, 2024:

Sir, Regarding the four P&J letters of Jan 3, three mention me by name. I fully respect the right of the public to challenge what I say. I will try to keep my replies concise.

John Morrison makes unsubstantiated claims of unparalleled and unprecedented environmental circumstances. It is normally unwise to make such sweeping statements. Mr Morrison cites a NOAA graph of temperature over the last 12,000 years or so. My guess is that this will be the temperature record from the GISP 2 ice core from the Greenland summit. The problem here is that the ice cores provide a temperature proxy record while the recent temperature history comes from thermometers. The ice core proxies tend to smooth out short time-scale fluctuations, such as those recorded by thermometers at all geographic scales. The extreme highs and lows and rates of change are lost in the proxies. It is erroneous (although standard practice) to compare proxies with thermometers.

Lesley Ellis simply mis-represents what I said. “His analysis makes fundamental errors in the treatment of the data, talking about a range when it should be a trend analysis”. What I in fact said “There are gradual trends of increasing annual temperature and rainfall that begin mid 19^th century, as the UK emerged from The Little Ice Age and continue to this day”.

And “He equates ecosystems with agricultural production and the two are entirely different”. And what I in fact wrote: “”We are now in the midst of a climate breakdown – our ecosystems that regulate the climate and enable food production are degrading and are at risk of collapse.”” Note the double quotes since here I am quoting what James Hutton Institute said, these are not my words!

Lesley Ellis goes on to say “Ecosystems support agriculture and if they collapse, all agriculture is affected.” My experience of modern agri-business in rural Perthshire is that they have turned whole farms that existed in the 1960s into single fields, they are sprayed with pesticide, herbicide and ammonium nitrate fertilizers, and as a result produce vast crop yields in otherwise biologically barren mono-cultures. There is normally no natural ecosystem in sight.

Alastair Ballantyne challenges my assertion that CO₂ during the Jurassic was 2000 ppm while at the same time conceding it might have been 1800 ppm, this is within rounding errors. The main point he wants to make is that high CO₂ levels (920 ppm) may be a risk to human health – more scaremongering. When we breathe in, the air contains 21% oxygen and 0.043% CO₂. When we breath out, it contains 16.4% oxygen and 4.4% CO₂ (that is 44,000 ppm). It’s hard to see how breathing in 920 ppm could somehow be dangerous. There are two factors at play here and one of them is oxygen depletion in poorly ventilated space like class rooms and lecture theatres.

A consensus view from UK and USA authorities is that prolonged exposure above 5000 ppm CO₂ is undesirable. 30,000 ppm CO₂, beyond short periods, is dangerous and 40,000 ppm results in death. Luckily, Earth’s atmosphere has moved from 280 ppm pre-industrial to just 420 ppm today. Just another 4580 ppm to go before things turn undesirable for human health compared with the 140ppm increase we have experienced since the beginning of the industrial revolution.

Have a Happy New Year and sleep easy.

Dr. Euan Mearns

Aberdeen