Those who want to raise awareness about the federal government's debt in the U.S. have long used the concept of a "debt clock", showing a more-or-less real-time view of how big the debt is at any moment. This site is an example of the concept. Regardless of how the actual concept has been used in various political fights (I don't want to get into that minefield...), from a marketing point of view, the idea is striking. It's almost something that Don Drapper might have come up with...
So if it's good enough for the debt warriors, why not use it for something else, another important issue... Like our ongoing mad-science-experiment with modifying the composition of our atmosphere by pumping billions and billions of tons of carbon dioxide into it. This is exactly what the media-savvy folks at Bloomberg have done. They have created a Carbon Clock that not only shows a real-time estimate of the current CO2 concentration in the Earth's atmosphere, but it's a whole integrated dynamic website that teaches a few things about climate science.
I strongly encourage you to check it out and forward it to friends & family who might learn a thing or two.
But if you want to get an idea, the image above shows one of the slides; in it you can see the clear trend of the past 50+ years, with the sawtooth seasonal pattern caused by the fact that the Northern hemisphere has more landmass and biomass than the southern one. That might seem striking, but it should wake up anyone when put into the context of the past 10,000 years:
Anyway, it's much better to see the animated version, with the clock climbing up relentlessly... See for yourself.
I'll leave you on this graph from the Mauna Loa Observatory, clearly showing how this year's CO2 readings went way above 400ppm for part of the year. A new sad milestone for humanity.