Scientist made the startling announcement on Friday that worldwide levels of carbon dioxide, a chief greenhouse gas, have reached the highest atmospheric saturation level known to mankind.
The gas, CO2, is responsible for global warming as it creates a thick barrier and traps heat like a greenhouse.
It was first measured in 1958, when levels were at 315.7 parts per million. Pre-industrial levels were around 280 ppm and Ice Age levels were estimated at 200 ppm.
Now, CO2 is at 400 ppm.
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It has many scientists worried as Dr. Pieter Tans, of the National Oceanic and Atmospheric Administration, said the last time levels were around 400 ppm was two million years ago during the Pleistocene Era.
While there are natural up and down cycles of carbon levels, triggered by natural sources like volcanic outgassing, combustion of organic matter, wildfires and respiration processes of living aerobic animals, scientists are chalking up this recent spike to human activity.
Tans said the rise of CO2 is "100 percent due to human activity," including burning of fossil fuels like coal and oil.
They also found that the oceans are absorbing more gas.
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Resarchers recommend reducing carbon emissions by buying local products, being mindful of packaging, energy-proofed house, not drinking bottled water, unplugging items that are not in use, biking or walking instead of driving and recycling.