Measurements made by the Scripps Institution of Oceanography reveal that average CO2 levels in the first few days of 2015 are already above 400 parts per million. Experts say this could lead to a series of consecutive months above this worrying threshold.

As reported by Andrea Thompson in Climate Central, daily averages since New Years Day have continued at this level through to January 9. Even with daily fluctuations, the current year "will likely see many months above 400 ppm, possibly starting with the very first month of the year." The 400 ppm mark, says Thompson, is a symptom of the larger story of humans altering Earth's climate. She explains:

While the 400 ppm mark is somewhat symbolic (as the increase in warming between 399 ppm and 400 ppm is small), it is a large increase from pre-industrial CO2 concentrations, which were around 280 ppm. The progressively earlier occurrence of these high CO2 levels ‚ÄĒ not seen in somewhere between 800,000 and 15 million years ‚ÄĒ points to the inexorable buildup of heat-trapping gas in the atmosphere as human emissions continue unabated. That increase in CO2 and other greenhouse gases has raised Earth's average temperature by 1.6¬įF since the beginning of the 20th century. Some scientists say that to avoid the worst consequences of climate change, that warming needs to stay under 2¬įC, or 3.6¬įF.

CO2 concentrations wax and wane with the seasonal plant cycle. Carbon dioxide levels begin to rise in late fall as the death of Northern Hemisphere vegetation releases it into the atmosphere, reaching a peak in May, after which the spring and summer plant growth causes it to decline once again. NASA's new OCO-2 satellite mission has recently taken the most detailed snapshot of atmospheric CO2 to date, in the hopes of learning exactly where CO2 sources and sinks are, said mission scientist Christopher O'Dell, of Colorado State University.

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This recent NASA simulation shows how CO2 levels ebb and flow over the course of the year. The northern and southern regions feature wild swings in concentrations as the growth cycle of plants and trees changes:

Because plants can only pull so much CO2 out of the atmosphere in a given season, and because human emissions keep rising, we can expect to reach the 400 PPM mark earlier and earlier. Thompson quotes the NOAA's Pieter Tans as saying, "I am not surprised that we are seeing daily means greater than 400 already popping up regularly. Next year that should start happening in November."

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Yikes.

Read the entire Climate Central article here.

Image: Scripps Institution of Oceanography

[ via Think Progress ]

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