According to the Scripps Institute of Oceanography, atmospheric carbon dioxide levels will surpass 400 parts per million (ppm) for the first time in human history.
Scientists guess that CO2 levels have surpassed 400 ppm at several points in the past, such as during the Pliocene Epoch. However, scientists estimate during that period global average temperatures climbed 3 or 4 degrees C (5.4-7.2 degrees F) higher than today’s and as much as 10 degrees C (18 degrees F) warmer at the poles. Sea level ranged between five and 40 meters (16 to 131 feet) higher than today.
Activists across the country are campaigning to reduce carbon dioxide levels to 350 ppm–what many scientists consider to be the safe level of atmospheric carbon dioxide.