This animated chart from the Cooperative Institute for Research in Environmental Sciences shows the amount of carbon dioxide in our atmosphere. Note the spike?
Measuring CO2 in parts per million (ppm), the chart shows, first, how the amount of the gas in our atmosphere has increased year-by-year over the past few decades, and then, how dramatic those increases are relative to CO2 levels over the last 800,000 years. (For context, anthropologists believe Homo sapiens started acting like the humans we recognize today, with different languages and cultures and technologies, only about 50,000 years ago.)
Yes, the levels of CO2 in the atmosphere fluctuate naturally over time — but not by this much. Experts have concluded that, to keep the Earth’s climate from spinning out of control, the amount of CO2 in the atmosphere must be kept below 350 ppm. Because of our fossil fuel consumption, we’re now well beyond 400. And, as the National Climate Assessment recently illustrated, we’re starting to feel the effects.