By: Chris Burke
The Earth has reached a milestone, and not one worth celebrating. Rather than a moment in history where humanity can raise a glass in celebration of its’ achievements, we find ourselves sitting here wondering where things went wrong: Carbon in the atmosphere has hit 400 parts per million (ppm).
Why is this fact cause for the bleak opening of this post? For starters, many scientists argue that we need to maintain a level of 350ppm of carbon in the atmosphere to avoid runaway climate change. The UN provides a higher threshold, somewhere around 420ppm, but with the current path we are on that threshold is likely to be broken. Second, as the National Geographic puts it:
“The last time the concentration of Earth’s main greenhouse gas reached this mark, horses and camels lived in the high Arctic. Seas were at least 30 feet higher—at a level that today would inundate major cities around the world.
“The planet was about 2 to 3 degrees Celsius (3.6 to 5.4 degrees Fahrenheit) warmer. But the Earth then was in the final stage of a prolonged greenhouse epoch, and CO2 concentrations were on their way down. This time, 400 ppm is a milepost on a far more rapid uphill climb toward an uncertain climate future” (Source)