Today, 21st June, is #ShowYourStripes day. These stripes, which show a colour for the average temperature of each year, blue for a cool year, red for a warm year, were invented by Ed Hawkins, climate scientist at the University of Reading, and though they’ve been around for a while, they’ve recently taken off on Twitter.

The trend is clearer when you look at the stripes for the whole world, since the local variability is ironed out. There’s still variability though, as our climate system is a complicated thing. There’s plenty of places in it for the additional heat to go, into warming the deep oceans or melting ice for instance, whereas what these stripes are showing is the recorded surface temperatures.

With local temperatures being so variable, and memory so unreliable, it can be hard for people to get a clear sense of what’s happening to our planet. These stripes show that whilst you get cool years and warm years, there is a quite unmistakable warming trend, a trend that’s particularly pronounced in the last few decades.

Of course, we all know that and we’ve known it for a while, but there’s knowing and there’s KNOWING. Some things we know, if someone asks us, but it’s knowledge that gets filed away into a neglected back room of our memory bank as we go about our day to day lives. An image they say can speak a thousand words, or in this case, several thousands or millions of data points.