Carbon dioxide levels hit troubling milestone, scientists say
Brian Vastag and Jason Samenow,
Friday, May 10, 3:09 PM
Human influence on the Earth’s atmosphere touched what climate scientists called a dire milestone Friday as concentrations of heat-trapping carbon dioxide nudged up to a level unseen in about 3 million to 5 million years — long before modern humans.
A monitoring station in Hawaii recorded carbon dioxide concentrations of 400 parts per million Friday, dramatically up from the 316 parts per million recorded when the station made its first measurements in 1958. The monitor, high atop the Mauna Loa volcano, offers the longest-running record of atmospheric carbon dioxide measured directly from the air.
Carbon dioxide is a primary greenhouse gas, efficient at trapping heat from the sun. The colorless gas is released from power plants and vehicles as they burn coal, oil and gas.
“[The] increase is not a surprise to scientists,” said Pieter Tans, a senior scientist at the National Oceanic and Atmospheric Administration. “The evidence is conclusive that the strong growth of global [carbon dioxide] emissions from the burning of coal, oil and natural gas is driving the acceleration.”
Climate scientist Joanna Haigh of Imperial College London said the particular figure reached Friday — 400 parts per million — holds no particular significance except as a milestone. “It gives us the chance to mark the ongoing increase in [carbon dioxide] concentration and talk about why it’s a problem for the climate.”
Scientists have firmly linked rising atmospheric carbon dioxide to higher global temperatures, which have increased nearly a degree Fahrenheit, on average, since 1950.
Larger temperature increases have occurred in the Arctic. In 2009, an international agreement sought to limit temperature increases to 3.6 degrees Fahrenheit (2 degrees Celsius) by...