Since the beginning of human civilization, our atmosphere contained about 275 ppm of carbon dioxide. That is the planet “on which civilization developed and to which life on earth is adapted.” Beginning in the 18th century, humans began to burn coal, gas, and oil to produce energy and goods. The amount of carbon in the atmosphere began to rise, at first slowly and now more quickly. Many of the activities we do every day like turning the lights on, cooking food, or heating our homes rely on energy sources that emit carbon dioxide and other heat-trapping gases. We’re taking millions of years worth of carbon, once stored beneath the earth as fossil fuels, and releasing it into the atmosphere.
Right now we’re at 400 ppm, and we’re adding 2 ppm of carbon dioxide to the atmosphere every year. Unless we are able to rapidly turn that around and return to below 350 ppm this century, we risk triggering tipping points and irreversible impacts that could send climate change spinning truly beyond our control. [Source: 350.org]
How Fast Can We Transition to a Low-Carbon Energy System? (Not fast enough)