Because there’s a natural annual cycle to the CO2 in the atmosphere in the northern hemisphere as measured at the Mauna Loa observatory, coupled with the underlying background increase that never seems to slow, it’s very difficult to detect if there has been in decline in daily CO2 levels since the start of the Coronavirus pandemic. As you can see the blue area graph of daily CO2 levels peaks each year in May, before falling back in September, as far as I know this has to do with the decomposition of leaves that have fallen from trees in the previous Autumn, but feel free to correct me if I’m wrong. The orange area graph which I’ve overlaid on top, shows the difference between the CO2 level this year and at the same date last year. If there had been any decline in the amount of CO2 in the atmosphere these numbers would be below zero, and as you can see on the 6th of May 2020 they are still close to 3 ppm higher than they were on the 6th of May 2019. So as far as I can tell the Coronavirus lockdown has had no discernible effect on global CO2 levels as yet – perhaps if all 7,782,849,416 of us on planet earth (less those on the ISS) breathed a little more slowly in the future that might do the trick.
Anyhow the reason I published that is because of the this blog from the Met Office news team:-
So the Met Office team, lead by a professor with an MBE no less, reckon that the May maximum will be 0.4 ppm lower because of Coronavirus and the September minimum 0.5 ppm lower too. At the moment the linear trend on the annual rise in CO2 since 1958 is around 2.45 ppm so 0.5 ppm represents not much more than 20% – or bugger all in real terms as CO2 levels continue to relentlessly power upwards. Predicting what the May maximum CO2 level will be when it’s already the seventh of May doesn’t see much of a forecast to me, I’ll have to remember to look back in the autumn to see how well they did with their September prediction, the figure for which I notice they haven’t included in the article.