A number of the chemicals that make our modern daily lives possible also heavily influence the environment in which we live. When some of these chemicals are released into the atmosphere as vapors, they can interact with complex natural cycles to have unforeseen consequences. One of these interactions leads us to a group commonly called the greenhouse gases. Greenhouse gases (GHG’s) are gases either natural or anthropogenic in source that have the ability to absorb and re-emit light of the infrared wavelength. The interesting part is that this infrared light would normally escape into space were it not for the absorption events of the GHG’s. If enough of this thermal energy is captured and re-emitted back down to the planets surface a rise in global temperatures will result. The phenomenon that these gases produce is called global warming. This effect is akin to how the glass panes of a greenhouse allow light of visible wavelength pass through but trap the infrared light inside, thereby eventually raising the temperature of the greenhouse.
We attempted to measure the global warming potential (GWP, a relative measure of how effective a particular gas is at trapping infrared light, with carbon dioxide having a GWP of 1) of several laboratory solvents and gases, including CH4, CHCl3, CCl4, CH2CL2, CO2, and a halon mixture. Analyzing trends across these different gases would hopefully allow us estimate the impact of these gases on global warming at the rates they are currently being released as well as to make predictions as to the GWP’s of related gases.
(Fig1: Static Dilution Setup, Seen from the side)


(Fig2: Flowing Dilution Close-up)




In order to accomplish this, we took dilutions of these gases and measured them using Fourier Transformed Infrared Spectroscopy (FTIR). Whenever a gas must first have been vaporized from a liquid, a static dilution system was used to allow us to obtain quantitative dilution. We used a much more simple flowing dilution system whenever a gaseous source was available for us to make our dilutions from. The absorbancies were then collected and measured using a salt crystal FTIR collection cell. At this point the treatment of the data became highly mathematical. The wavelengths and intensities at which each molecule would absorb infrared radiation were entered into an equation that would give us out the GWP of that particular gas.
When we compared the GWP’s that we experimentally derived to “standard” values that have been tabulated already, we found that our results were vastly (about 10x-20x) lower that the published values. A quick glance at fig. 3 shows this. If we had gotten experimentally reasonable data, the bar graphs for each particular gas would match or at least be reasonably close. One likely culprit was the dubious security of air locks on the FTIR cells. If these locks were in fact leaky, then we were measuring gas concentrations that were significantly lower than what we were expecting to measure. Placing the larger concentration into the equations instead of the correct but unknown smaller concentration caused by the leaky cell would have given us this deviation. Other possible causes were incorrect use/calibration of the FTIR specs or human mistakes that took place in the dilutions.



Even though most of our data points were less than accurate, we were still able to make connections between some of the chemicals we use on a daily basis in the lab and the global warming effects we see increasingly each year. At the very least we were able to see that in fact, yes, greenhouse gases do absorb thermal radiation as well as the fact fact that some gases are more efficient in this action than others. Since these gases only represent a very small portion (excluding methane) of the GHG’s, we in fact only studied a small portion of the global warming effect. More research is needed into the entire field is needed not so much to discover more of the chemistry involved but more so into effective education techniques, for each day an individual does not fully understand his or her impact on the environment, the closer we get to changing our planet in a way we can’t fix.