The Greenhouse Gas Carbon Dioxide Reaches Another Dangerous Benchmark

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A daily record of atmospheric carbon dioxide from Scripps Institution of Oceanography at UC San Diego

The level of the most significant greenhouse gas in the atmosphere, carbon dioxide, passed a long-feared benchmark this week, reaching a concentration not seen on the earth for three million years, scientists reported Friday.

Carbon dioxide gauges atop Mauna Loa, the volcano on the big island of Hawaii that has long been ground zero for monitoring the global trend on carbon dioxide, or CO2, recorded an average daily level of carbon dioxide in the atmosphere above 400 parts per million. Carbon dioxide above 400 parts per million was first seen in the Arctic last year, and had also spiked above that level in hourly readings at Mauna Loa before.

While the reading is only one snapshot in time, and the level has been reached a few times in the past, it is a benchmark scientists have long feared and a grave reminder that efforts to bring greenhouse gases down to reduce human-induced global warming are more important than ever. The best available evidence shows the amount of CO2 in the air has not been this high for at least three million years, before humans evolved, and scientists believe the rise portends large changes in the climate and rising sea levels.

“It symbolizes that so far we have failed miserably in tackling this problem,” said Pieter P. Tans, who runs the monitoring program at the National Oceanic and Atmospheric Administration that reported the new reading.

Ralph Keeling, who runs another monitoring program at the Scripps Institution of Oceanography in San Diego, said a continuing rise could be catastrophic.

“It means we are quickly losing the possibility of keeping the climate below what people thought were possibly tolerable thresholds,” he said. “It takes a long time to melt ice, but we’re doing it. It’s scary.”

Virtually every automobile ride, plane trip and flip of a light switch adds carbon dioxide to the air, scientists say, and the amount of money being spent to find and deploy alternative technologies is deplorably low.

Data shows that China is now the largest emitter of CO2 on the planet, but Americans have been consuming fossil fuels extensively for far longer. Experts say the United States is more responsible than any other nation for the high levels of carbon dioxide in the atmosphere and the resulting rise in average global temperatures.

The average reading for an entire day at NOAA’s Mauna Loa station surpassed 400 parts per million for the first time in the 24 hours that ended at 8 p.m. Eastern Daylight Time on Thursday. This was confirmed by the Scripps monitoring station.

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co2_weekly_mlo_since1800

While the two monitoring programs use slightly different protocols, NOAA reported an average for the period of 400.03 parts per million and Scripps reported 400.08.

Carbon dioxide levels rise and fall on a seasonal cycle, of course, and the level will dip below 400 this summer as leaf growth in the Northern Hemisphere pulls about 10 billion tons of carbon out of the air. But experts say that will be a brief reprieve — the moment is approaching when no measurement of the ambient air anywhere on earth, in any season, will produce a reading below 400.

“It feels like the inevitable march toward disaster,” said Maureen E. Raymo, a scientist at the Lamont-Doherty Earth Observatory, a unit of Columbia University.

From studying air bubbles trapped in Antarctic ice, scientists know that going back 800,000 years, the carbon dioxide level oscillated in a tight band, from about 180 parts per million in the depths of ice ages to about 280 during the warm periods between. The evidence shows that global temperatures and CO2 levels are closely linked.

For the entire period of human civilization, roughly 8,000 years, the carbon dioxide level was relatively stable near that upper level. The burning of fossil fuels for energy, however, has caused a 41 percent increase in the heat-trapping gas since the Industrial Revolution, and scientists say the climate is beginning to react. Far larger changes are expected in the future unless policies can be put into place to reverse the trend.

Indirect measurements show that the last time the CO2 level was this high was at least three million years ago, during an epoch called the Pliocene period. Geological research shows that the climate then was far warmer than today, the world’s ice caps were smaller, and the sea level might have been as much as 60 to 80 feet higher.

Experts fear that human development activities are are leading to a return to those warm conditions and high sea levels. The difference this time is that billions of people are in harm’s way. The global population clock now shows there are more than 7 billion people alive on the planet, and the number is rising every second.

Dr. Keeling’s father, Charles David Keeling, began carbon dioxide measurements on Mauna Loa and at other locations in the late 1950s. He found a level in the air then of about 315 parts per million and demonstrated it by this comparison: If a person filled a million quart jars with air, about 315 quart jars of carbon dioxide be mixed in. His analysis revealed a relentless, long-term increase superimposed on the seasonal cycle, a trend that was dubbed the Keeling Curve.

Countries have adopted an official target to limit the damage from global warming, with 450 parts per million seen as the maximum level compatible with that goal.

“Unless things slow down, we’ll probably get there in well under 25 years,” Ralph Keeling said.

Yet many countries, including China and the United States, have refused to adopt binding national targets. Scientists say that unless far greater efforts are made soon, the goal of limiting the warming will become impossible without severe economic disruption.

“If you start turning the Titanic long before you hit the iceberg, you can go clear without even spilling a drink of a passenger on deck,” said Richard B. Alley, a climate scientist at Pennsylvania State University. “If you wait until you’re really close, spilling a lot of drinks is the best you can hope for.”

Climate scientists reject political arguments against the need to worry about carbon dioxide levels or global warming, which mostly come from Republicans in the U.S. Research shows that even at such low levels, carbon dioxide is potent at trapping heat near the surface of the earth.

“If you’re looking to stave off climate perturbations that I don’t believe our culture is ready to adapt to, then significant reductions in CO2 emissions have to occur right away,” said Mark Pagani, a Yale geochemist who studies climates of the past. “I feel like the time to do something was yesterday.”

© 2013, Glynn Wilson. All rights reserved.

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