Is Atmospheric CO2 Declining from the Covid Economic Collapse?

I have had a number of people ask me:  with CO2 emissions collapsing from the economic downturn, are CO2 levels no longer going up or declining?   In fact, a brief search on the web reveals some headlines that seem to be suggesting this:

The bottom line of this blog is this:  CO2 levels are not falling, and it is difficult to see much impact on the rate of rise.  And it will be a good opportunity to talk about some aspects of the variation of CO2 in the atmosphere.

Let's start by looking at the concentrations of CO2 in the atmosphere as measured by NOAA at its Mauna Loa observatory on the Big Island (below).  This is an excellent place to measure CO2--away from any localized sources.  CO2 is relatively well mixed in the lower atmosphere (both spatially and in the vertical) so the measurements at this observatory are highly reflective of global variations over time.

You will note that CO2 has risen from around 317 parts per million (ppm) in 1960 to around 413 ppm today and the rate of increase is accelerating.  Mankind is not doing much to slow the increase, that is quite clear.  If you look closely, you will notice CO2 levels going up and down each year, like clockwork.

To get a view of this annual variability, here is a plot of the month values (red dash lines), with the black lines showing the impact of averaging designed to take out the seasonal variations (the plot goes through March).  CO2 levels tend to peak in mid-spring and the decline until they reach bottom in October.  Buy why?

It has to do with the cycle of plant growth in the northern hemisphere, where most of the planet's vegetated land area is found.   During the late spring and summer, plants grow and pull CO2 out of the atmosphere for their use in photosynthesis. But during the late autumn and winter, plants shut down, with many losing their leaves.  Their consumption of CO2 drops enormously, while CO2 is released as microbes feast on dead material, releasing CO2.  And, of course, we contribute to this increase with greater heating using fossil fuels.

But let's get back to the impact of mankind using less fossil fuels because of the coronavirus.  China put on the brakes in January and February, followed by Europe, the U.S. and most of the remainder of the world.  The numbers are still coming in, but the declines are substantial, with U.S. petroleum sales down by roughly 30% (see below).

To get a better idea of the recent changes in CO2, here are the weekly Mauna Loa CO2 numbers (green lines) for the past two years (below).   Monthly averages are shown by the red lines.   No obvious slowing of CO2 increases.  Note, there is often a flat period from February through March.

I downloaded the CO2 data and plotted it in all kinds of way, such as one year changes, one month and three month changes, and more.  Nothing suggested a major shift in the upward trends in CO2, so stories suggesting otherwise are not supported by observations.

 In some ways, the lack of  change in the upward trend in CO2 is not particularly surprising.    There is a lot of natural variability that obscures the signal.   CO2 emissions have only declined for a few months and China is already coming back online.  And there is still plenty of fossil fuels being used for heating, air conditioning, and basic transportation systems (including trucks and trains).    CO2 has a long lifetime in the atmosphere, so decreasing emissions would only slow the rise a bit, never causing a decline.

In short, with the world coming back online during the next few months, the long-term influence of this drop in emissions will be very small.  It is also provides notice that only really huge declines in CO2 emissions, far greater that what is occurring during this lockdown period, will be necessary to really move the needle on global warming.

A sobering thought.