It’s the final week of the semester, so it’s time for a little fun in the world of weather and climate visualizations. One of the toughest things that Geologists have to deal with is conveying a sense of time scales. It’s difficult for present-day humans to conceive of how long ago (or recent) the Roman Empire or Han Dynasty were, let alone 4.6 billion years of Earth history. We often use interesting comparisons, like how the time gap between Tyrannosaurus (68-66 million years ago) and humans is smaller than the gap between Tyrannosaurus and Stegosaurus (155-150 million years ago). Sometimes we use analogies, like how an average human lifespan is 0.00000204% of all Earth’s history, which is about the same percentage of your life you just spent reading this paragraph.
With climate change, scientists often are approached with the question: “Climate has changed before, so why is this time worse?” An important is that this time it’s changing very fast, and rapid change is more problematic than gradual change. The faster the change, the harder it is for plants and animals (and humans) to adjust. But conveying that sense of rapid change can be difficult when our time series are so long, stretching tens of thousands of years. It rarely looks good on a single powerpoint slide or a single 8 1/2″ by 11″ piece of paper. You either have to scrunch everything into a very condensed and crowded graph, use an inset box to zoom in on today, or use multiple slides/figures. Or… you could use the tendency for modern webpages to scroll indefinitely to convey a sense of time. This is the tactic of the webcomic xkcd.
No, seriously. The main reason for reading the comic is to laugh at the little bits of humor slipped in, but Randall Munroe at xkcd is diligent about scientific research. The temperature data for the visualization are based on a combination of HADCRUT4 (from the UK Meteorology Office), the Intergovernmental Panel on Climate Change (IPCC, funded by the UN), and peer-reviewed journal articles in the journals Nature (Shakun et al. 2012), Science (Marcott et al. 2013), and Climate of the Past (Annan and Hargreaves 2013). Those last three are all paleoclimate reconstructions.