A new and unsettling benchmark for global climate change occurred May 9 as carbon dioxide measurements across most of the Northern Hemisphere exceeded 400 parts per million, as measured by the Mauna Loa Observatory in Hawaii. The observatory, located two miles up the famous Hawaiian volcano, has been taking hourly readings of carbon dioxide concentrations for the past 55 years.
Many climate scientists and activists have said 350 parts per million is the safe upper limit for carbon dioxide in the atmosphere.
Carbon dioxide levels at Mauna Loa were at 317 parts per million in 1958, when the observatory began its monitoring.
Announcing the first-ever 400 ppm reading, Pieter Tans, senior scientist with the Global Monitoring Division of National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, said, “That increase is not a surprise to scientists. 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.”
The statement from the NOAA went on to note:
“Before the Industrial Revolution in the 19th century, global average CO2 was about 280 ppm. During the last 800,000 years, CO2 fluctuated between about 180 ppm during ice ages and 280 ppm during interglacial warm periods. Today’s rate of increase is more than 100 times faster than the increase that occurred when the last ice age ended.”
The 400 mark is not a tipping point, according to an article on the Inside Climate News website, but “an important symbolic milestone that underscores government inaction on global warming.”
Quoted in the article, Jim Butler, director of global monitoring at the NOAA, said, “This is another global emissions target that we’ve blown past without doing anything.
“Stronger storms, droughts, rising seas. We are already seeing the impacts of increased CO2 in the atmosphere,” he said. “How much further can we really go?”