Long-Term Trends in Atmospheric CO2
Burning fossil fuels consumes oxygen and emits CO2. This is simple chemistry that we learned in middle school, using a candle and a glass jar. It is possible to calculate the quantity of CO2 released from the candle by the chemistry of the candle, and calculate the concentration of CO2 in the jar from the quantity of CO2 released by the candle.
We can also easily find the quantity of CO2 released into the atmosphere by the global consumption of coal, oil and natural gas. Some respected organizations (the International Energy Agency, and the British Petroleum Statistical Review of World Energy) have collected the data on fossil fuels, and done the math on the quantity of CO2 released.
In an earlier post, we explored the annual cycles of CO2 fluctuation, and how those cycles vary by latitude.
We can also take the annual average for CO2 concentration in the Northern Hemisphere, and compare those readings to the annual average CO2 concentration in the Southern Hemisphere. We can see a clear difference. The Southern Hemisphere lags behind the Northern Hemisphere in terms of increasing CO2 by about 2.6 ppm.
Fossil fuel emissions are concentrated in the Northern Hemisphere; as we noted in the previous post, 90% of the world's population lives in the Northern Hemisphere, including the most industrialized economies.
The excess CO2 concentration of the Northern Hemisphere is closely matched, and easily explained by annual fossil fuel emissions of the Northern Hemisphere. I allocated global CO2 emissions by hemisphere according to figures for national GDP. In earlier posts, we have seen the strong correlation between GDP and energy use. About 83% of global GDP, and by inference, CO2 emissions, occur in the Northern Hemisphere. The excess CO2 delivered to the atmosphere in the Northern Hemisphere accounts very well for the difference in CO2 between the Northern and Southern Hemispheres.
The use of fossil fuels has grown exponentially since the industrial revolution ( M.K. Hubbert, 1956; D.H. Meadows, et al 2004). Annual consumption has grown from essentially zero before the year 1800, to over 10.4 billion tonnes of oil equivalent in 2010.
A carbon dioxide concentration of 450 ppm is sometimes cited as a theoretical "tipping point", beyond which climate change becomes irreversible, due to positive feedback mechanisms (i.e., release of greenhouse gasses from permafrost, dissolution of carbonate sediments due to ocean acidification, release of methane from gas hydrates, etc.).
Based on the consistency of the exponential increase in atmospheric CO2, the growth of world population, and industrialization of the world economy, it seems likely that atmospheric CO2 levels will continue to rise and likely exceed the 450 ppm and 500 ppm thresholds within the next 35 years.
This is fourth of five posts in a series about global atmospheric CO2.
The Keeling Curve
Global CO2 data is available from Keeling et. al., on the Carbon Dioxide Information Analysis Center website. http://cdiac.ornl.gov/trends/co2/
Data for CO2 released by fossil fuels is available from EIA CO2 Emissions from Fuel Consumption,
And the BP Statistical Review of World Energy:
Historic CO2 levels: