Carbon Dioxide
What is CO₂, and why does it matter?
Carbon dioxide (CO₂) is a greenhouse gas — it traps heat in Earth’s atmosphere.
Think of it like a blanket around the planet: a little keeps us warm, but too much makes things overheat.
As we burn fossil fuels, we add more CO₂ to the air. This thickens the blanket and warms the planet — a key driver of climate change.
Let’s look at how CO₂ levels have changed over time.
The Keeling Curve
A clear signal of human impact
This chart shows the Keeling Curve — a long-term record of atmospheric CO₂ measured at Mauna Loa Observatory in Hawaii since 1958. Named after scientist Charles David Keeling, it reveals a steady rise in CO₂ levels from about 330 parts per million (ppm) in 1974 to over 420 ppm today — a more than 20% increase.
This sharp rise, largely due to burning fossil fuels like coal, oil, and gas, is a key indicator of human-driven climate change.
Over 100 ppm added in 50 years - faster than any time in human history.
👁️ Look Closer
If you zoom in on the Keeling Curve, you'll notice something strange.
Those little zigzags? They’re not mistakes. They're part of the story.
What you're seeing is the Earth breathing — a pattern that repeats every single year.
Let’s take a closer look.
The Earth's Breathing Pattern
CO₂ rises and falls with the seasons
This chart shows daily atmospheric CO₂ levels (white) and a red smoothed curve highlighting seasonal variation. Each year, CO₂ rises and falls as plants absorb and release carbon — a natural rhythm often called the Earth’s breath.
But over time, even this cycle can’t keep up. The baseline continues to climb, revealing that natural processes alone can no longer absorb the excess CO₂ from human activity. Recognizing this cycle helps us understand what’s normal — and just how far we’ve pushed beyond it.
The Earth’s carbon cycle still follows its ancient rhythm — inhale, exhale, year after year.
But something else is happening beneath the surface.
The rhythm hasn’t changed — but the pace has.
CO₂ isn’t just rising. It’s rising faster than it ever has in human history.
The Rate of CO₂ Rise Is Accelerating
Each year we wait, the challenge grows harder to reverse.
This chart shows annual average CO₂ levels as bars, colored from blue to red to reflect rising concentrations over time.
The smooth line above represents the year-to-year percentage change. It shows how CO₂ isn’t just increasing — it’s increasing faster. Small percentage gains today add much more carbon than in the past, making the climate challenge more urgent.
Some CO₂ spikes stand out from the background noise.
When we apply a long-term average to the Mauna Loa record, a few years rise sharply above the rest — beyond what’s expected from seasonal cycles.
These anomalies reflect moments when the Earth’s systems were overwhelmed: massive wildfires, warming oceans, global energy surges, or widespread drought.
Each of these events left a statistically significant footprint in the atmosphere — and a warning in the data.
Wildfires
Industrial Growth
Drought
Signals in the Noise
Every spike is a signal. Every delay makes it harder to respond.
This graph highlights moments when CO₂ levels spike far above normal — signals that something unusual is happening on Earth.
Anomalies are detected using a rolling z-score over a 1000-day window; values exceeding two standard deviations from the norm are flagged.
Many spikes align with major global events like wildfires, economic disruptions, or shifts in energy use.
Over time, these anomalies have become more frequent and erratic — a sign that the atmosphere is growing increasingly unstable and responding more loudly to human impact.
We’ve seen how CO₂ levels have changed — and how anomalies reveal a restless atmosphere. But where are we headed from here?
Every Increase Is a Warning. Every Year Counts.
CO₂ is rising faster than ever — the choices we make now will shape the climate we inherit.
This graph shows projected atmospheric CO₂ levels calculated using Prophet, a forecasting tool in Python that analyzes historical trends to predict future values.
According to this model, by 2040 we could reach around 470 parts per million (ppm) — a level comparable to the increase from the 1970s to today, but occurring in just 15 years instead of 50.
This rapid rise highlights the accelerating pace of emissions and underscores the urgency of climate action.