Up, up and away …
FRISCO — Atmospheric carbon dioxide levels are spiking earlier each year, scientists said last week, announcing that concentrations reached the 400 parts per million “milestone” two months earlier than last year.
CO2 levels peak each year in the spring as the Earth breathes in a great seasonal cycle. This year’s early 400 ppm reading is another clear sign that the heat-trapping gas is building up at an ever-increasing rate, according to data from the National Oceanic and Atmospheric Administration’s Mauna Loa Observatory in Hawaii.
According to Dr. James Butler, director of NOAA’s Global Monitoring Division, CO2 concentrations have increased every year since 1958.
“The rate of increase has accelerated from about 0.7 ppm per year in the late 1950s to 2.1 ppm per year during the last decade,” Butler said in a Q&A posted on this NOAA website.
The rate of increase in atmospheric concentrations is consistent with the emissions from fossil fuel combustion, Butler said, and the milestone serves as a reminder that, without drastic cuts in those emissions, the Earth’s temperature will continue climbing, and the world’s oceans will continue to become more acidic.
The concentration may hover at or above 400 ppm for several months, before planet’s seasonal respiration once again absorbs enough CO2 to drop the concentration back below that mark, but scientists expect that those peak levels will increase every year.
“The peak should occur again in May and this year may be over 402 ppm. Next year we expect it will be over 404 ppm,” Butler said.
Human activity has raised CO2 levels 120 ppm since pre-industrial times, with 90 percent of the increase in the past century.
Globally, CO2 levels can vary. With most sources in the northern hemisphere, concentrations have been highest in the Arctic, where the 400 ppm mark was topped about year before it first was measured at Mauna Loa. According to Butler concentrations will also reach that level in Antarctica in just a few years.
Slowing and stopping the buildup would require an 80 percent cut in emissions, but concentrations wouldn’t start falling for a long time without even more significant cuts.