Global CO2 nears troubling benchmark

By Scott Waldman, E&E News, May 7, 2019

Researchers at the Mauna Loa Observatory recently observed record-high levels of atmospheric CO2.

The world has surpassed a level of carbon dioxide not seen in about 3 million years, and levels are accelerating an unprecedented pace.

Atmospheric carbon dioxide almost topped 415 parts per million on May 1 at the Mauna Loa Observatory in Hawaii, according to the University of California, San Diego's Scripps Institution of Oceanography. On that day, the observatory measured a CO2 level of 414.94 ppm. Levels could go even higher and surpass the 415 ppm mark before the end of spring.

Every year, carbon dioxide tends to spike in the spring before plant life reemerges in a large part of the world to begin the uptake of the greenhouse gas.

But the rate of carbon emissions has accelerated in recent years, said Gernot Wagner, author of "Climate Shock: The Economic Consequences of a Hotter Planet" and a researcher at Harvard University's Center for the Environment. The jump from 410 ppm to 415 ppm happened more quickly than the jump from 400 ppm to 405 ppm, which happened faster than the previous 5-ppm jump, and so on, he said.

That accelerating rate of increase is one of the more alarming, and less covered, aspects of the rising CO2 levels, he said.

"It's what matters most for all these climate damages; it's the increase in those concentrations that is still increasing at an increasing rate," he said. "We are going in the wrong direction at an increasing speed."

The newest benchmark brings current CO2 levels in line with the Pliocene Epoch, which occurred between 2.58 million and 5.33 million years ago. At that time, global average temperatures were 5.4 to 7.2 degrees Fahrenheit hotter than today and 18 degrees warmer at the poles, according to Scripps. Sea levels were 16 to 131 feet higher than today, Scripps has found.

During ancient climate change events, an increase of 10 ppm of atmospheric carbon dioxide might have taken 1,000 years. It has taken just six years to go from 400 ppm to 415 ppm. When the late Charles David Keeling started measuring carbon dioxide at Mauna Loa in 1958, levels stood at 316 ppm, a slight increase from the 280 ppm before the Industrial Revolution.

At the current rate, CO2 levels will top 1,000 ppm in about a century. That level will profoundly alter life on the planet and render wide swaths of Earth uninhabitable, scientists have found.

Keeling's data set — it's now maintained by his son Ralph — is regarded as one of the key measurements that demonstrate how human-caused climate change is affecting the planet. The elder Keeling developed the Keeling curve, which shows annual fluctuations in CO2 levels and links them to fossil fuel consumption.

As carbon dioxide levels rise, so, too, do global temperatures. The last five years have been the hottest on record. And while nothing happens as the 415 ppm benchmark is surpassed, it's another significant step into a warmer world, Wagner said.

"We've never had this global experiment. It's an amazingly fast increase," he said. "Three million years ago, when we did have CO2 levels as high as they are today, those changes happened very, very slowly, and the world was a very different place. We had crocodiles in the Arctic Circle; we had sea levels 30 to 90 feet higher than today."