The Past and Future Keeling Curve

With all the present-tense climate f&%kery going on in the world, it’s easy to lose track of the fact that it’s CO₂ that’s primarily driving these events (with methane in second place for now). Okay, for the purists, it’s overshoot that’s causing the f&%kery. But we’re going to stick to CO₂ for the purpose of this article. Meanwhile, as civilization crashes and burns, as our fellow humans murder each other over who believes in which invisible friend, as Net-Zero pledges are made and broken, it’s physics that’s telling us the bottom line reality: 1.5°C will be effectively shattered by the end of this year.

Ah, but there’s still “hope.” The latest data shows that real progress is apparently being made on the rate of growth of CO₂.

That last sentence requires some explanation. CO₂ itself continues to rise. The latest data from NOAA  shows September, 2023 CO₂ at 418.51 parts per million (ppm), up 2.60 ppm from a year ago. There’s no question that CO₂ is going to blast through 430 ppm and 440 ppm over the next ten years. And the most up-to-date Keeling curve does not appear to show any progress at all:

In this post I want to dig deeper into the NOAA data and explore what it predicts about the timing of Net-Zero and the future of the Keeling curve. I’m going to focus here on the rate of growth of CO₂, not on the quantitative amount of CO₂ in the atmosphere. The rate of growth is what Net-Zero is all about. When will the pure, raw, physical amount of CO₂ in the atmosphere stop growing?

A small caveat. Net-Zero is not actually about getting to Zero growth in CO₂. It’s about getting to “implied zero growth” — planting a tree today that will offset some amount of CO₂ over the future lifespan of that tree. That kind of thing. Here is the Wikipedia definition:

Global net zero emissions, or simply net zero, is a state in which human-caused emissions are balanced by human-caused carbon dioxide removals over a specified time period. In some contexts, “emissions” refers to emissions of all greenhouse gases, and in other contexts it refers only to emissions of carbon dioxide.

Net-Zero is a lame metric. What I’m discussing here is simply “Zero.” When will the amount of atmospheric CO₂ stop growing?

Okay, back to the main topic. As mentioned above, the last 12 months showed a growth in CO₂ of 2.60 ppm. But ENSO cycles, sun cycles, volcanic eruptions, economic crashes, global industrial shutdowns and other things can greatly impact the rate of CO₂ growth. Twelve months is too short a period to get a good sense of where things are going. For that reason, I am going to focus on the 36-month running mean of the Keeling curve. That is, each month’s CO₂ will be that month’s current reading averaged with the preceding 35 months. I will use this 36-month running mean to compute the growth of CO₂.

[Math moment. For those who like calculus, I am taking the “time derivative” of the 36-month running mean of the Keeling curve.]

So, for example, in September, 2020, the 36-month running mean for CO₂ was at 410.90 ppm.  The 36-month running mean for CO₂ for September, 2023, was 418.06 ppm. Together, this shows a “36-month mean rate of growth” of 7.16 ppm over the last 3 years.

Here is a graph of the 36-month mean rate of atmospheric CO₂ growth from March, 1964 to September, 2023:

As you may be able to tell from the graph, the maximum rate of growth in CO₂ happened in February, 2019. The 36-month period from February, 2016 to February, 2019 saw a gain of 7.83 ppm. It’s been mostly downhill ever since.

As an aside, many people notice that huge dip in the early/mid 1990’s. That was the aftermath of the Mount Pinatubo eruption. The multi-year impact of this eruption on the rate of increase of CO₂ was staggering. Here is an article on the topic, if you want to read more about it. But things got right back on track after the start of the millennium.

Okay, back to the graph above. The rate of growth of CO₂ has been declining steadily since 2019. That’s a fact. A hopium-soaked optimist might look at that decline and say that we’re making progress towards Net-Zero. They might say that wind, solar, EVs and every other green energy source are doing their thing. They might even block me on Twitter for disagreeing. Nevertheless, let’s assume the optimist is 100% right and look at the implications for the future.

Here is the same graph, with a linear interpolation showing the future growth of  CO₂ assuming these declines continue at their current rate:

This graph even shows when Net-Zero will be reached. If you squint, you will see it. At the current rate of decline in the growth of CO₂, we should see Net-Zero sometime in mid-October, 2076.  That’s 53 years from now.

From this extrapolation we can use a little mathematical trickery and work backwards to predict the future of the Keeling curve. And so, I offer you the “Past-and-Future Keeling Curve”:

In particular, we now have a prediction for the future maximum CO₂. That maximum? 484.60 ppm, happening in April, 2075.

Of course, none of this is going to happen. Long before much of this comes to pass, global industrial civilization will have collapsed and billions of humans will likely have perished under the weight of our collective planetary f&%kery. The climate casino’s over/under is for the maximum to be reached sometime in the 2040’s at about 450 ppm.