Credit: XKCD

If I had a nickel for every time I’ve heard ‘but the climate has and always will be changing,’ I’d be filthy rich. That would actually be convenient since I’d be wealthy enough to surround myself in a bubble that renders me immune to the perils of man-made climate change like rising sea levels, droughts, floods, and the food shortages that will come with it, cataclysmic freak weather and so on.

The gist of man-made climate change is simple. Since the industrial revolution in the mid-19th century, humans have been spewing carbon dioxide, methane and other greenhouse gases into the atmosphere at an accelerated rate. Today, the average CO2 concentration in the atmosphere is above 400 parts per million (ppm), up from 315 ppm in 1954 and 276 ppm in 9,000 BCE. All of this carbon traps heat and warms the planet. This warming happens at a global scale and at a rate that is unprecedented unless you count mass extinction events.

Yes, the climate is changing due to the natural variations in the planet’s weather patterns or the sun’s activity, but the effects aren’t nearly as far-reaching and intense as what we’re seeing today. In other words, it’s enough to take a few steps back to see the bigger picture, preferably on a geological timeline. Then, the net output between the contribution of human activities and the planet’s natural variability becomes clear.

The ever witty and resourceful Randall Munroe from XKCD has a nice comic that explains climate change very neatly. What’s interesting about the comic is how Munroe plotted his timeline, choosing to graph time on the vertical axis and temperature on the horizontal axis. Typically, you’ll see the plot in the reverse in most science papers, but Munroe’s framework allows him to draw some cool comics while making the temperature variation the center of the reader’s attention. Very crafty!

The timeline starts around 22,000 BCE when humans barely became dispersed all over the planet and more than 10,000 years before agriculture was invented. Since then, humans have gone through various periods of significant climate change, including a big and little ice age, as well as multiple volcanic eruptions. We’ve survived and even flourished despite these events, but as the timeline shows the climate never swung so abruptly from one extreme to the other. It’s always a smooth transition which at least gives species some time to adapt. What we’re living through is anything but smooth. I’ll leave you to the comic.