ECONOMIC SLOWDOWN NOT NOTICED ON ATMOSPHERIC CO2 LEVELS

Not Even The Global Covid-19 Disaster  Will Make A Big Difference To  Atmospheric  CO2 Levels Roy Spencer, 15 May 2020 Why the current economic slowdown  won’t show up in the atmospheric CO2  record Summary: Atmospheric levels of carbon  dioxide  (CO2) continue to increase with no  sign of the  global economic slowdown in  response to the spread of COVID-19. This is  because the estimated reductions in CO2  emissions (around -11% globally  during 2020) is too small a reduction to be noticed  against  a background of large natural variability.  The reduction in economic activity would have to be  4 times larger than 11% to halt the rise in atmospheric  CO2. Changes in the atmospheric reservoir of CO2 occur  when there is an imbalance between surface sources and sinks of CO2. While the global land and ocean areas  emit approximately 30 times as much CO2 into the atmosphere as humans produce from burning of fossil  fuels, they also absorb about an equal amount of CO2.  This is the global carbon cycle, driven mostly by biological activity. There are variations in the natural carbon cycle, such as  during El Nino (more CO2 accumulation in the  atmosphere) and La Nina (more CO2 removed from the atmosphere). Greater wildfire activity releases more CO2, while major volcanic eruptions (paradoxically) lead to greater  photosynthesis from more diffuse sunlight and  extra removal of CO2 from the air. The most dramatic variations are seasonal, as the land- dominated Northern Hemisphere experiences an annual cycle of vegetation growth (CO2 removal) and decay (CO2 release). The increase in atmospheric CO2 observed since the 1950s  is most likely dominated by anthro- pogenic CO2 emissions,  which are twice as large as that needed to explain the observed rise. As I have shown before, a simple CO2 budget model driven by (1) estimates of global yearly anthro- pogenic CO2 emissions, (2) El Nino and La Nina activity, and (3) a CO2 removal rate that is proportional to how much “extra” CO2 is in the atmosphere compared to a “preferred baseline”  CO2 level, yields an excellent fit to yearly CO2 observations at Mauna Loa, Hawaii. Fig. 1. Yearly Mauna Loa, HI CO2 observations since 1959  (red) versus a simple CO2 budget model (blue). But those are yearly measurements, and we are now  interested in whether the recent global economic  slowdown is showing up in the monthly Mauna Loa CO2  data. If we remove the large seasonal  variations (driven by the seasonal growth and decay of Northern Hemisphere vegetation), we see no evidence of the economic slowdown through April, 2020. Fig. 2. Monthly CO2 data since 2015 from Mauna Loa, HI after the average seasonal cycle is statistically removed. As can be seen in Fig. 2, there are some pretty large month -to-month jumps and dips around the long-term increase (represented by the dotted line). These are probably natural variations due to fluctuations in the average seasonal variations in vegetation growth and decay, wildfire activity, and El Nino and La Nina activity (which are imperfectly  removed in the solid blue line in Fig. 2). Variations in economic activity might also be involved in these fluctuations. The point is that given the large month-to-month variations in natural CO2 sources and sinks seen in Fig. 2, it would be difficult to see a downturn in the anthropogenic source of CO2 unless it was very large (say, over 50%) and prolonged (say over a year or longer). Instead, the U.S. Energy Information Administration (EIA) estimates that the global economic slowdown this year  due to the spread of the novel coronavirus will amount to only about an 11% reduction in global CO2 emissions. This is simply too small of a decrease in CO2 emissions to show up against a background of considerable monthly and yearly natural variability in the atmospheric CO2 budget. Full post & comments