For the first time in human history, atmospheric concentrations of carbon dioxide could rise above 400 parts per million throughout much of the Northern Hemisphere as soon as May 2013.
The latest CO2 measurement was taken at the Mauna Loa Observatory in Hawaii and reported by the Scripps Institution of Oceanography, a research center at the University of San Diego that tracks increases in atmospheric CO2 levels.
Climatologists including former NASA scientist James Hansen have previously stated that 350 parts per million (ppm) was the "magic number," the level beyond which long term climatic changes will be unleashed with catastrophic consequences for human civilization.
"I wish it weren't true, but it looks like the world is going to blow through the 400-ppm level without losing a beat," said Scripps geochemist Ralph Keeling, whose father David's pioneering measurements at Mauna Loa, which have come to be called the "Keeling Curve," provide the longest continuous record of CO2 in the world.
The Keeling Curve begins from 316 ppm in March 1958, and approaches 400 ppm today. "At this pace we'll hit 450 ppm within a few decades," said the younger Keeling.
Scientists estimate that the last time CO2 was as high as 400 ppm was between 3.2 million and 5 million years ago, when Earth's climate was much warmer than today. Prior to the Industrial Revolution, when humans began to leave an indelible stamp on the atmosphere by burning fossil fuels, CO2 hovered around 280 ppm.
The dramatic rise in CO2 over the last century is unprecedented; there is no known period in geologic history characterized by such an increase. The scientific community generally agrees that the CO2 increases are a result of human activity and have caused dramatic climatic changes that threaten human civilization.
In the wake of Scripps's announcement, climate change groups across the world called for precipitous action from governments and businesses to reduce greenhouse gas emissions.
“This is one milestone no one should be happy about reaching,” said Mark Reynolds, Executive Director of Citizens Climate Lobby, a group calling for the United States Congress to pass legislation that would tax carbon dioxide emissions. “Our civilization has altered the balance that nature carefully maintained for hundreds of thousands of years. We risk tragic consequences if we fail to restore that balance.”
In order to reduce U.S. emissions and set an example for other nations, CCL has proposed passage of a steadily-increasing, revenue-neutral carbon tax that returns proceeds to taxpayers. The proposal has garnered widespread bipartisan support, including from conservatives who usually oppose both tax increases and environmental measure.
George Shultz, who served as Treasury Secretary for Richard Nixon and Secretary of State for Ronald Reagan, has endorsed the carbon tax as a way to employ the power of the free market to shift away from the use of fossil fuels.
"The globe is warming and we should be taking steps to do something about that,” Shultz said in March at a forum in Washington, D.C. Schultz added that the carbon tax should be “justified solely, and only, as a way of leveling the playing field. I don’t want it to be seen as a way of raising money for federal operations.”
Shultz has also endorsed heavy investments in alternative energy sources like solar and wind that are renewable and do not rely on burning fossil fuels.
Scripps maintains a Twitter account that provides regular readings of CO2 levels at Mauna Loa Observatory. The most recent reading, from April 30, was 399.50 ppm CO2 in the atmosphere. A week earlier, on April 23, Scripps reported 398.36 ppm.
Harry Stevens is a freelance reporter covering climate change, corporate social responsibility, social enterprise, and sustainable finance. Harry has contributed to several media outlets, including Justmeans, GreenBiz, TriplePundit, and Sustainablog. You can follow Harry on Twitter: @Harry_Stevens