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Greenhouse Gas Levels Approach ‘Worrisome’ Milestone

Photo by David McNew / Getty Images

Above: Warming temperatures are expected to cause sea levels to rise by as much as 3 feet over the next few decades.

Greenhouse gas carbon dioxide (CO2) is increasing at a steep rate in the Earth's atmosphere and approaching a troubling new milestone: The heat-trapping gas could reach sustained levels of 400 parts per million of carbon dioxide by next month.

Greenhouse gas carbon dioxide (CO2) is increasing at a steep rate in the Earth's atmosphere and approaching a troubling new milestone: The heat-trapping gas could reach sustained levels of 400 parts per million of carbon dioxide by next month.

Scripps Institution Of Oceanography

The Keeling Curve, a daily record of atmospheric carbon dioxide from Scripps Institution of Oceanography at UC San Diego.

Greenhouse gas is the main global warming pollutant caused by the burning of fossil fuels, such as coal for electricity and oil for gasoline.

Scripps Institution of Oceanography researcher Ralph Keeling is tracking daily CO2 measurements at remote locations throughout the Northern Hemisphere. The primary site is Mauna Loa, Hawaii. There, he's using the Keeling Curve founded by his late father, Charles David (Dave) Keeling, a world-leading authority on atmospheric greenhouse gas accumulation and Scripps climate science pioneer.

Measurements at Mauna Loa comprise the longest continuous record of CO2 in the world, starting from 316 ppm in March 1958.

Ralph Keeling said CO2 levels have never elevated beyond 300 parts per million in the last 800,000 years. He said the approaching 400 mark is expected, but "a bit worrisome."

"I think it will be a point that some people will look back on and say, 'Oh I remember when it crossed 400 back in the day,'” Keeling said.

When CO2 rises, the warming potential increases, Keeling added.

"It takes a while for the climate to catch up to the CO2 level," said Keeling. There’s a lot of lag in the climate system, so even if we could keep CO2 without rising beyond 400, we’d still have some significant additional climate changes in store."

Keeling said it’s increasingly doubtful that warming temperatures can be limited to the 2-degree Celsius threshold to avoid climate change’s catastrophic effects, like rising sea levels, droughts, floods and heatwaves.

"I think the opportunity to achieve that was more or less in the past decade and now it's probably not really realistic that we'll get there," said Keeling.

Scripps Institution of Oceanography is providing a website, keelingcurve.ucsd.edu, to offer daily updates on CO2 levels and to provide background information about how CO2 is measured, the history of the Keeling Curve, and resources from other organizations on the current state of climate. An accompanying Twitter feed, @keeling_curve, also provides followers with the most recent Keeling Curve CO2 reading in a daily tweet.

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