Last month, carbon dioxide levels in the atmosphere were measured at 410 parts per million (ppm), the highest measurement in the past 800,000 years, according to the Scripps Institute of Oceanography.
"We keep burning fossil fuels. Carbon dioxide keeps building up in the air," stated Scripps scientist Ralph Keeling, adding, "It's essentially as simple as that," cited by USA Today.
Keeling has been recording carbon dioxide levels at the Mauna Loa Observatory in Hawaii since 1958.
In April, the average concentration of carbon dioxide in the atmosphere was around 410.31 ppm, the first time a Mauna Loa record has been greater than 410 ppm.
"At the recent pace, we'll hit 450 ppm in a mere 16 years, and 500 ppm 20 years after that. That's well within dangerous territory for the climate system," Keeling pointed out.
"As a scientist, what concerns me the most is not that we have passed yet another round-number threshold, but what this continued rise actually means: that we are continuing full speed ahead with an unprecedented experiment with our planet, the only home we have," tweeted Katharine Hayhoe, a climate scientist at Texas Tech University.
Marshall Shepherd, climate scientist and director of the Atmospheric Sciences program at the University of Georgia, noted that "our activities keep pumping a steroid into the naturally-varying atmosphere."
"Yes, climate has always changed and CO2 has varied but this as an experiment we have not seen, because humans are the new kid on Earth's block," Shepherd added, according to CNN.