Carbon dioxide in air breaks million-year-old record in Arctic, subtropics

Atmospheric testing has taken place at the Mauna Loa observatory in Hawaii for more than 50 years. (HANDOUT PHOTO)

The United States’ National Oceanic and Atmospheric Administration says the world’s atmosphere has passed a milestone in climate change: on May 9, carbon dioxide concentrations in the atmosphere of Mauna Loa, Hawaii, surpassed 400 parts per million for the first time since measurements began there in 1958.

All Arctic sites in NOAA’s sampling network reached 400 ppm for the first time last year, NOAA said.

The parts-per-million or ppm measurement of carbon dioxide provides a way of measuring the traces of this gas in the atmosphere.

And the level of 400 ppm for carbon dioxide in the atmosphere is alarming because for the past 800,000 years the levels of carbon dioxide have never exceeded 300 ppm.

Scientists estimate that the last time that carbon dioxide levels remained as high as 400 ppm was probably between 3.2 million and five million years ago.

Then, Arctic was as much as 14 C to 22 C warmer than today, trees like larch, birch, alder and cedar, covered the land, and giant beavers and eight-foot-tall camels roamed the High Arctic.

High levels of carbon dioxide in the Arctic were a prelude to what is now being observed at Mauna Loa, a site in the subtropics, this year, NOAA said May 10.

The concentration of carbon dioxide, the most significant greenhouse gas contributing to climate change, has increased every year since scientists started making measurements on the slopes of the Mauna Loa volcano more than 50 years ago, NOAA said.

But the rate of increase has increased since the measurements started, from about 0.7 ppm per year in the late 1950s to 2.1 ppm per year during the last 10 years.

Today’s rate of increase is more than 100 times faster than the increase that occurred when the last ice age ended.

The problem: carbon dioxide added to the atmosphere and oceans remains for thousands of years, making it more and more difficult to avoid even more substantial climate change, NOAA said.