Q: What happened to carbon dioxide levels during lockdown?
A: They reached an all time high despite a reduction of 80% output from China.
In fact, inspecting the graph, you just can’t see any sign of lockdown at all.
The reason is that atmospheric levels are hardly affected at all by human emissions.
The oceans contain 98% of all the CO2 in our biosphere so for every 100 tonnes of CO2 we pump out, 98 of them get dissolved in the sea and only 2 tonnes remain in the air.
Henry’s law of physics means that as the oceans around Mauna Loa warm slightly in the summer, some CO2 will come out of solution much the same way as if you were to heat some carbonated water in a pan you would see bubbles.
When the winter comes around again, the oceans cool slightly and CO2 near the surface of the water will be absorbed back into the sea.
This effect, together with seasonal absorption of CO2 by plants accounts for the cyclic nature of the chart.
The overall slight rise is from the gradual warming of surface water, possibly caused by deep water from a previous warm period rising to the top.
More CO2 means more plant growth particularly in drought areas.
Global Monitoring Laboratory
Henry’s Law – Wikipedia