Graph shows concentrations of atmospheric Co2 for the last 800,000 years, with measurements, starting from 1958, made at Mauna Loa in Hawaii. - Image courtesy of World Meteorological Organization
Scientists monitoring atmospheric concentrations of CO2 from a mountaintop in Hawaii recently reported that the presence of this greenhouse gas exceeded 400 parts per million (ppm) for the first time in at least three million years – a period when temperatures were much warmer than today. The significance of this seemingly dry statistical trend is stunning as reported in the New York Times:
From studying air bubbles trapped in Antarctic ice, scientists know that going back 800,000 years, the carbon dioxide level oscillated in a tight band, from about 180 parts per million in the depths of ice ages to about 280 during the warm periods between. The evidence shows that global temperatures and CO2 levels are tightly linked.
In addition to the location in Hawaii, several other Global Atmosphere Watch stations from the Arctic to the Equator reported CO2 concentrations exceeding 400ppm.
Experts believe that in order to limit warming to 2°C – a goal based on expected impacts – concentrations should rise to no more than 450 ppm, a level we may reach in only about 25 years based on current trends.