Not only is the amount of CO2 in the atmosphere on the rise, the rise itself has been getting faster — so CO2 concentration has been accelerating. A reader recently asked whether or not there’s any sign of its increase flattening out, or even stopping its acceleration.
Here’s the CO2 data from Mauna Loa:
I transformed this to anomaly, in fact I computed adaptive anomaly because the annual cycle itself has changed over time. The anomalies are clearly accelerating, so I fit a quadratic curve and plotted it (in red) along with the adapative anomalies (in black):
The CO2 growth follows the quadratic curve so closely, it’s a bit hard at times to tell them apart.
If this pattern has changed, we should see the change in the residuals from that quadratic fit. Here they are:
There’s lots of fluctuation, some of it related to known factors like the strong el Niño events of 1998 and 2016, but there’s no sign of a downturn recently.
I tested for any change in the acceleration in several ways. For instance, I computed the acceleration of each 10-year span and plotted the result: no sign that acceleration has stopped. I also tried 5-year time spans, which is too brief to show non-zero acceleration (the uncertainty is too big) but also shows no sign of any change in the acceleration.
What might be the clearest illustration comes from computing annual average CO2 concentration and using it to estimate the year-on-year change, which is the velocity of CO2 concentration. Acceleration will show as a trend in the velocity. Here are the estimates, together with a trend line which illustrates the overall rise in velocity (i.e. acceleration of CO2):
This makes it obvious just how much the “noise” in the system can make it harder to detect acceleration and its changes. But I’ve tested this time series for a change in its trend, and found no reliable evidence. Not even close.
Bottom line: CO2 is on the rise, the rise itself (velocity) has been getting faster (acceleration), and there’s no evidence at all that has changed recently.
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