Why This CO2 Chart Doesn’t Scare Me

Someone sent me a chart because it was giving them anxiety, and I want to explain why I look at the exact same data and feel no anxiety about climate change.

Someone sent me this chart recently because it was giving them anxiety, and I want to explain why I look at the increase in CO2 and feel no anxiety about climate change.

The chart shows global atmospheric CO2 concentrations going back 800,000 years. Before we started burning oil, coal, and natural gas about 200 years ago, CO2 stayed somewhere between 180 and 300 parts per million for that time period. Today we’re at 426 ppm. Zoomed in on that 800,000-year window, the recent spike looks extreme. And I get why that’s nerve-wracking at first glance.

But zoom out further—to hundreds of millions of years—and the picture changes completely. CO2 levels were far higher in Earth’s history: around the time of the dinosaurs they hovered near 2,000–3,000 ppm, and at earlier points they were even higher than that. Over the past hundred million years, atmospheric CO2 has been getting pulled out of the air and sequestered by the planet’s natural carbon cycle.

The carbon cycle

There’s a constant flow of carbon through the planet’s systems—the ocean, the atmosphere, and living things. Humans are about 18% carbon; CO2 itself is just one carbon atom bonded to two oxygen atoms. When algae bloom, they pull huge amounts of CO2 out of the atmosphere. Over millions of years, that algae sinks to the ocean floor, gets buried in layers, and eventually—compressed and moved by tectonic activity—becomes the fossil fuels we burn today. So today we are simply burning carbon based life from millions of years ago.

Another way to think about it: we’re taking carbon that was sequestered by natural processes millions of years ago and returning it to the atmosphere. At any given moment, roughly 95% of the CO2 cycling through the atmosphere is naturally occurring—I’m exhaling it right now (at 38,000 ppm!), and plants are absorbing it constantly. CO2 is a fundamental building block of life. It’s not a foreign substance we’ve introduced; it’s something the planet has been moving around for eons, and we’re just returning some of it to the atmosphere where it came from.

The planet is greening

One unexpected positive consequence of that added CO2 is more plant growth. NASA’s own data shows significant global greening since 1980—an increase in leaf coverage equivalent to roughly two times the area of the continental United States. Plants are growing bigger and faster because they have more of what they need to photosynthesize.

Here’s a ninth-grade biology refresher: plants take in CO2 through pores on their leaves called stomata. When CO2 is scarce, they need more stomata, held open longer, which costs the plant more water and time. More atmospheric CO2 means plants can be more efficient. They have fewer stomata, lose less water, and grow faster. By the burning of fossil fuels we’ve essentially doubled the available “food” for most plant life, and current levels are still below what’s ideal for many plant species.

Most of the plants we grow and eat—wheat, rice, most vegetables— are what’s called C3 plants, and they aren’t even at their optimal photosynthesis level yet. That would take roughly 800 ppm; we’re at 426. For context: greenhouse growers deliberately pump CO2 up to 1,200–1,500 ppm because of how much it benefits plant growth. And on the other end, if CO2 drops below 150 ppm, photosynthesis stops working and plant life dies off. If anything, lower CO2 levels would be something to be concerned about.

What about the warming?

This is the part that actually drives the anxiety, so let’s unpack it. What I didn’t understand when I was still in the climate movement is that CO2’s warming effect is logarithmic, not linear or exponential—each additional molecule of CO2 added to the atmosphere has a smaller incremental warming effect than the one before it.

Think of it like putting stickers on a window to block light. The first few stickers block a lot of light. But as the window fills up, each additional sticker blocks less and less, because there’s less exposed glass left to cover. CO2 works the same way: the first 100 ppm did most of the work of keeping the planet out of a deep freeze. Every increment since then—200 ppm, 300 ppm, 400 ppm—has caused less and less warming.

The calculation for CO2’s warming effect (known as climate sensitivity) says that doubling atmospheric CO2 produces roughly 1°C of warming. So going from today’s 426 ppm to 850 ppm would add about 1°C—not runaway warming, just another single degree. And because we’re currently adding roughly 2.5 ppm of CO2 per year (out of about 5 ppm emitted because half gets naturally reabsorbed), reaching 850 ppm would take about 175 years. Getting another degree beyond that would require doubling again, to over 1,600 ppm—which, at the same emission rate, would take even longer.

A Calming Conclusion

Zoomed out over Earth’s real history, today’s CO2 levels aren’t unprecedented—they’re actually historically low. What we’ve done is return some previously sequestered carbon to the atmosphere, which is fueling more efficient plant growth around the planet and producing modest, diminishing warming over long period of time. That’s the full picture behind the scary-looking chart.

Watch my Instagram video where I go through my logic: