well I don't know about you, but while covid may have stopped flights and restricted car travel,  I reckon the use of home heating and electricity consumption probably increased, and those readings are from Mona Loa - its a fairly smoothed rolling average of many months.

And of course the lockdowns were all over the place in that sort of timescale and far from simultaneous over the planet.  In the UK for example we had the first stay home orders in March, but then schools and shops re-opened in June with eat out to help out in August etc. And then we re-locked and did it all again in time for Christmas

https://www.instituteforgovernment.org.uk/data-visualisation/timeline-coronavirus-lockdowns

incredibly disruptive, incredibly expensive, but when seem in the context of an annual timeline, a short duration, and things were up and running for at least six months of the year.

I'm not too sure that we'd expect much of a dip, more of a wobble. - the total oil consumption figures do show not a lot of a dip either though the fuel prices went all over the place with panic buying and then overstocking.

For the UK the drop in fuel consumption in lockdown  is noticeable but not a total collapse by any means, and you have to see that against the trend that consumption of things like coal and gas use was already dropping.

total UK energy use dropped from 200 megatonnes of oil equivalents in 2018 to about 160-170 megatonnes in 2019 and 2020. to put that drop in perspective in 2018 it was already on the way down from about 220 in 2010-11 and higher still before that. And we don't have a pandemic now, and its still around the same levels, gently drifting down.

"lowest natural gas use since 2015" is not exactly a huge change either, as there was no pandemic in 2015, just a milder winter.

https://assets.publishing.service.gov.uk/media/622a228ed3bf7f1581a6eb22/DUKES_2021_Chapters_1_to_7.pdf for 2010- 2021 figures.

https://assets.publishing.service.gov.uk/media/66f420f1080bdf716392e8c1/Energy_Trends_September_2024.pdf for the more up to date stuff.

Mike.

Equally you could look at that graph and ask what changed in the UK in 1980 as before that it is a wobbly flat, after that it is a steady rise with a modest wobble superimposed. Maybe the dust and dirt of coal actually did us some favours by blacking out the peak of the sun ?
Mike.

We have warm and cold spells for all sorts of reasons.  There's a corresponding cold spell in the 1600's.  None of that explains the sudden massive spike in CO2 that started at the time of the industrial revolution.

Plants mostly absorb CO2 and let out O2.  So more plants should lead to falling CO2.  It's plants absorbing CO2 that explains how you can have a pot plant that's bigger than the pot it grew in - most of the plant is made from CO2.

Yeast isn't plants.  Yeast eats sugars and lets out CO2.  Pretty much the opposite of what plants do.

From the ice cores, CO2 wiggles from about 180 to 280 ppm for 800 000 years, with one spike to 300 ppm.  Then in the 20th century, it suddenly shot up through 300 ppm and is now 420 ppm and still rising.  There's nothing natural that's changed so fast.

But it corresponds entirely with the industrial revolution.

If humans are changing the atmosphere so rapidly, in a way that's never been seen before, then looking back at previous natural climate changes that took millennia to happen doesn't help.

Interestingly the rate of temperature rise between  1700 and 1725 is almost identical to the rise between 1980 and 2000. What are the mechanisms for two similar rises almost 300 years apart?

Plants respire all the time emitting CO2. They only photosynthisise in daytime or under artificial light.

What is respiration and photosynthesis in plants? - BBC Bitesize

Is it realistic

It's surprising what we can achieve when we want to. Send a man to the moon within a decade.  Or the 1944 Normandy landings - not just getting a couple of hundred thousand men across the channel despite determined opposition, but constructing two entire shipping ports (Mulberries), in the UK, out of concrete and steel despite severe wartime material and manpower shortages, and then moving the entire lot to France. Oh, and a cross-channel fuel pipeline. And that was on top of building in effect a new army and most of an air force in the previous few years, not to mention having lots of our facilities (and workforce) being bombed to smithereens by the Luftwaffe. Our ancestors wouldn't be impressed if with access to global resources, and far more advanced technology, we can't sort out a relatively simple power system in less time that it took them to win an entire world war.

   - Andy.

Yes, plants do letout a bit of CO2 at night, because there's no sunlight.  But primarily plants build themselves by taking in water and CO2, gathering energy from sunlight, and producing sugars and oxygen.  The sugars can be converted to complex hydrocarbons (such as cellulose), and they spit out the oxygen because it's nasty corrosive stuff.

indeed -most of the carbon in the cellulose of the plant fibres comes from the air, only the water and a few trace elements come up via the roots, but more than half of the weight of a tree is taken from the atmosphere while it grows.

Mike.