An Atmospheric Milestone

By Kolby Hoagland | May 16, 2013

On May 9, scientist at the Mauna Loa Observatory in Hawaii recorded an average daily atmospheric CO2 concentration greater than 400 ppm. This milestone is strictly symbolic as it emphasizes the high rate that CO2 emissions have been released to the atmosphere since the beginning of the Industrial Revolution. Global atmospheric concentrations were around 280 ppm before the Industrial Revolution, but with population growth and industrialization atmospheric CO2 concentrations have grown by 70% and led to last week’s milestone reading for a daily average of CO2 at Mauna Loa.

Scientists believe that CO2 concentrations have not been this high in the atmosphere for the last 2.5 million years. When concentrations were that high, during the Pliocene, the roughly four million year epoch was characterized by an average annual global temperature 3 C° warmer than the current average, sea levels 9 feet higher than current levels, and forests in areas of Canada that are covered today with ice. The measuring of atmospheric CO2 at Mauna Loa began with Charles David Keeling in 1958. He plotted what is known as the Keeling Curve (see Chart 1), which shows the seasonal fluctuation of CO2 with an overall increase from year to year. For atmospheric concentrations measurements before 1958, tiny bubbles trapped in artic ice sheets gives scientists the means to calculate prehistoric levels of atmospheric CO2. Combining Keeling’s Curve with ice core sample data, Chart 2 shows the correlation between average global temperature, CO concentrations, and sea levels over the last 400,000 years. For the bioenergy industry the 400 ppm milestone should emphasize the importance and continued work with life cycle analysis (LCA) to prove lower carbon intensities than fossil energy sources.

A recent paper by Roger Sedjo from Resources for the Future, Comparative Life Cycle Assessments: Carbon Neutrality and Wood Biomass Energy, delves into the variability in results among LCAs from the varied scope and parameters that LCAs might or might not include. Sedjo explains that depending on the breadth of what is included in an LCA, the results can drastically vary, such as with the Manomet Study of Wood Biomass Energy where one forest was analyzed on even terms with fossil carbon. Though not stated in Sedjo’s study, a greater understanding of the parameters and scope behind LCAs needs to be apprehended by stakeholders and policy makers so that realistic solutions to mitigating climate change are put into practice.


Keeling Curve Global Temp Correlation