20  The Story of a Warming World

20.1 Part 1: The Invisible Engine

Climate change begins with the atmosphere’s chemistry. To understand why the Earth is warming, we must first look at the “Keeling Curve,” the most famous graph in Earth Science.

In 1958, Charles Keeling began measuring CO2 at the Mauna Loa Observatory in Hawaii.

At the start of the record, CO2 levels were around 315 parts per million (ppm). This was already higher than the pre-industrial average, but the curve was just beginning its climb.

If you look closely at the line, you see a zig-zag pattern. This is the “breathing of the Earth.”

When the Northern Hemisphere tilts toward the sun (spring/summer), plants bloom and inhale CO2, dropping the levels. In the fall, leaves decay and release it back.

However, the “breathing” is overwhelmed by a much stronger force.

As we scroll to the present day, the trend accelerates upward. We have now passed 420 ppm, a level not seen on Earth for millions of years. This vertical ascent is the direct result of burning fossil fuels.

20.2 Part 2: The Consequence

Rising CO2 is not just a number; it traps heat. We can see the direct correlation when we look at global temperature anomalies over the last century.

This chart shows the global temperature deviation from the 20th-century average.

Between 1880 and 1940, years were often cooler than average (shown in blue). The climate fluctuated naturally, but remained relatively stable.

By the 1980s and 1990s, a shift occurs. The blue bars disappear, replaced almost entirely by red. The “greenhouse effect” predicted by physics is now visible in the data.

In the last 20 years, the warming has intensified.

The bars are not just red; they are growing taller. This shows that the rate of warming is increasing, driven by the CO2 accumulation we saw in the previous chart.

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