Randall Munroe, the author of the webcomic XKCD, has a habit of making wonderfully lucid infographics on otherwise difficult scientific topics. Everyone should check his take on global warming. It’s a stunning graphic showing Earth’s recent climate history. Take some time with it. Stroll through the events like the domestication of dogs and the construction of Stonehenge. And then ponder the upshot here.

There’s a common line among climate skeptics that "[t]he climate has always changed, so why worry if it’s changing now?" The first half of that sentence is undeniably true. Due to orbital wobbles, volcanic activity, rock weathering, and changes in solar activity, the Earth’s temperature has waxed and waned over the past 4.5 billion years. During the Paleocene it was so warm that crocodiles swam above the Arctic Circle. And 20,000 years ago it was cold enough that multi-kilometer-thick glaciers covered Montreal.

But Munroe’s comic below hits at the "why worry." What’s most relevant to us humans, living in the present day, is that the climate has been remarkably stable for the past 12,000 years. That period encompasses all of human civilization — from the pyramids to the Industrial Revolution to Facebook and beyond. We’ve benefited greatly from that stability. It’s allowed us to build farms and coastal cities and thrive without worrying about overly wild fluctuations in the climate.

And now we’re losing that stable climate. Thanks to the burning of fossil fuels and land use changes, the Earth is heating up at the fastest rate in millions of years, a pace that could prove difficult to adapt to. Sea level rise, heat waves, droughts, and floods threaten to make many of our habitats and infrastructure obsolete. Given that, it’s hardly a comfort to know that things were much, much hotter when dinosaurs roamed the Earth.

(By the way, one of the more surprising things I learned from this was that mammoths were still around when the Pyramids were being built. Who knew?)

Further reading:

My colleagues Joss Fong and Estelle Castwell made a very similar point with this video. As they put it, climate change isn’t about “saving the planet.” The planet will be fine. It’s us who need to worry a bit.

The world set a goal of keeping global temperatures within 2°C of the optimum level seen above. So what happens now that we’re likely to go past that?

How do we know humans are causing global warming?

A visual tour of the world's CO2 emissions