Atmospheric CO2 Levels and An Introduction to Ocean Acidification

 Dear readers,

As mentioned before, the second most common greenhouse gas is carbon dioxide, making up 9-26% of atmospheric greenhouse gases. There is hard data available from a myriad of sources that confirms that CO2 levels have been rising over the last century, primarily as a result of the increased burning of fossil fuels during and after the Industrial Revolution. According to a report by the Intergovernmental Panel on Climate Change (IPCC), since 1750, the concentration of CO2 has increased by 108ppm (parts per million), an increase of 38.6%, bringing us to a current concentration of 388ppm. While several other greenhouse gases have increased during this time period, such as methane (CH4), nitrous oxide (N2O), and CFCs (chlorofluorocarbons, chemical compounds that deplete the ozone), we will focus on CO2 levels because they have the greatest impact on the oceans.

CO2 levels are extremely important from the oceanic perspective because the oceans play a key role in the planet's carbon cycle. In fact, the oceans tend to act like a carbon sink for both bound carbon (in living and dead materials) and for CO2. This means that the oceans can actually buffer global CO2 concentrations, but this can only go on for so long before the ocean's chemistry gets profoundly changed as a result of the increased CO2 being taken up. The ocean is able to buffer gaseous CO2 by chemically converting it to carbonic acid (H2CO3). Unfortunately, an increase in carbonic acid in the oceans results in a lowering of the pH level and an increase in acidity. In future entries, we will talk about the importance of rising ocean acidity on the marine flora and fauna that call the oceans home.

As you can see by the graph, since pre-industrial times the average oceanic sea surface pH has decreased from between 0.06 to 0.11 pH units, with the greatest pH changes in the Atlantic. Since pH is calculated on a logarithmic scale, this translates into a substantial change in pH levels. (photo credit: http://images-mediawiki-sites.thefullwiki.org/02/2/6/4/88391784058062717.png)

Getting a Bad Rep. Frequently, when greenhouse gases are discussed, they are discussed negatively as climate change indicators, and overall, get a bad reputation. But everything is needed in moderation, and the greenhouse gases in our atmosphere play an extremely important role in determining our planet's climate. Do you know what temperature our planet would be right now if we had absolutely no greenhouse gases?