The National Oceanic and Atmospheric Administration (NOAA) reported May 9 that the daily mean concentration of carbon dioxide in the atmosphere of Mauna Loa, Hawaii, surpassed 400 parts per million (ppm) for the first time since measurements began in 1958. The best available evidence implies that levels have not been this high for at least 3 million years.
This marks an important and long-feared milestone. Because Mauna Loa is the oldest continuous carbon dioxide (CO2) measurement station in the world, it is the primary benchmark site for tracking the increase of this powerful heat-trapping gas across the globe.
Scientific research shows carbon dioxide (CO2) pumped into the atmosphere by human activities—such as burning fossil fuels—is the most significant greenhouse gas (GHG) contributing to climate change. Its concentration has increased every year since scientists first started taking measurements at Mauna Loa more than five decades ago. The rate of increase has increased since then, from about 0.7 ppm per year in the late 1950s to 2.1 ppm per year during the last 10 years.
“That increase is not a surprise to scientists,” said NOAA senior scientist Pieter Tans, with the Global Monitoring Division of NOAA’s Earth System Research Laboratory in Boulder, CO. “The evidence is conclusive that the strong growth of global CO2 emissions from the burning of coal, oil, and natural gas is driving the acceleration.”
“There’s no stopping CO2 from reaching 400 ppm,” said Ralph Keeling, a geochemist at the Scripps Institution of Oceanography. “That’s now a done deal. But what happens from here on still matters to climate, and it’s still under our control. It mainly comes down to how much we continue to rely on fossil fuels for energy.”
For more information, visit www.noaa.gov.
