The ozone layer in the stratosphere serves to filter harmful
UV radiation, enabling life on the surface of Earth to thrive. The depletion of the ozone layer in the
stratosphere caused great alarm in the scientific community when it was
discovered in the 1980s, as increased UV exposure poses a risk to organisms. The Montreal Protocol was enacted in
1987 as an international protocol intended to reduce the use of ozone depleting
substances, namely chloroflourocarbons (CFCs).1 The Montreal Protocol is largely
considered a success as the production of most CFCs has ceased and the ozone
layer is recovering.
An article published in the Huffington Post describes an
unexpected caveat to the general success of the Montreal Protocol.2 The article states that 39 kilotons of CCl4
(an ozone depleting chemical) are still being produced every year. The quantity of CCl4 is
unexpected given reports that the chemical stopped being emitted in 2007. Though the source of CCl4 is
unknown, the article concludes with the prediction that the ozone layer can
make a complete recovery if the levels of ozone depleting chemicals continue to
decline.
The Huffington Post article is discussing a study published
in Geophysical Research Letters,
which describes the slower than expected decline of CCl4 levels in
the atmosphere.3 The
authors use NASA’s 3-D GEOS Chemistry Climate Model to predict changes in
levels of CCl4 in the atmosphere accounting for the changing rate of
photolysis, soil and ocean sinks, and stratosphere-troposphere mixing. The results of the models show an
inter-hemispheric gradient of CCl4 more consistent with a mean
lifetime of 35-years (as opposed to the previously thought 25 year lifetime),
and an approximate global CCl4 emission of 39 kilotons/year.
The most important issue, and what both articles highlight
well, is the unexpected presence of CCl4 in the atmosphere, and the
threat this chemical poses to the ozone layer. One major shortcoming of the Huffington
Post article is the failure to mention explicitly that though there are
unexpected levels of CCl4, overall levels are still decreasing at a
rate of ~1%/year (as opposed to the predicted 4%/year.) Additionally, the article cites the lead
author, Qing Liang, in her conclusion that it is “apparent there are either
unidentified industrial leakages, large emissions from contaminated sites, or
unknown CCl4 sources."2
This statement is not included in the Geophysical Research Letters paper. The Huffington Post article also fails to reference the suspected lifespan of CCl4 of 35 years as opposed to 25 years. This is mentioned in the video that
accompanies the article, but I think it is a mistake to not include this in the
writing.
Overall, I think the Huffington Post article and Geophysical Research Letters agree
relatively well in that they both stress the unexpected levels of CCl4. However, because the Huffington Post
article doesn’t write about the fact that the levels of CCl4 are
still decreasing, the longer estimated lifespan of CCl4, and stresses
the unknown and possible “industrial” source of the unexpected emissions, I
believe the threat and potential malicious source of CCl4 emissions
are oversold.
1. Montreal Protocol on Substances that Deplete the Ozone
Layer. (n.d.). Australian Government (Department of the Environment). Retrieved September 19, 2015.
2. Boehrer, K. (2014, August 23). Ozone-Depleting Compound
Found In Unexpected Concentrations Despite Ban. Huffington Post. Retrieved
September 19, 2015.
3. Liang, Q., P. A. Newman, J. S. Daniel, S.
Reimann, B. D. Hall, G. Dutton, and L. J. M. Kuijpers (2014).
Constraining the carbon tetrachloride (CCl4) budget using its global trend and
inter-hemispheric gradient. Geophysical
Research Letters, 41, 5307–5315, doi:10.1002/2014GL060754.
I think that the fact the Huffington post article failed to mention the decrease in CCl4, suggests a potential bias of Boehrer. It is possible that Boehrer desires stricter restrictions than The Montreal Protocol provides.
ReplyDelete"There should be zero emissions of the compound under the international agreement, but NASA measurements show an average of 39 kilotons are still emitted every year. That's about 30 percent of what peak emissions were before the substance was regulated."
DeleteAs Alex mentioned it wouldn't be possible to have a stricter standard for regulation, but I agree that she might be hoping to see this standard become a reality. Firstly, by identifying the source of CCl4 emissions, and then by addressing the issue from there.
DeleteI agree with Taylor. If the general decrease in emissions continues over time, then the brief increase of CCl4 will not have been very significant.
ReplyDeleteAs with many sources of popular media, the Huffington post exaggerates and simplifies the science to tell a better story. I agree with Taylor that the threat of carbon tetrachloride emissions are "oversold". It is also interesting to note what carbon tetrachloride is used for today. It is used to evaluate hepatoprotective agents in research, and it is used in chemistry as a solvent and as a source of chlorine.
ReplyDeleteI agree with Taylor's summation that the Huffington Post article contains a slant of sensationalism. As noted in the original article, the original and unreconciled 25 year lifetime estimate of CCl4 and the need for new estimates to better re-evaluate and measure the partial lifetimes of Tocean and Tsoil are all important pieces of information that seem to have been conveniently disregarded. This information along with the Huffington Post article's failure to note the (albeit slow) ~1% decline, creates the impression to the reader that CCl4 emissions are actually on the rise. All in all, leaving out some of this factual information does make for a better story.
ReplyDeleteThe Huffington Post may exaggerates and intentionally ignores some facts, but it's not wrong to raise people's awareness. I've read an article about the possible sources of the unexpected emissions. Besides what Rebecca mentioned above, there is another potential source know as brown fields (some old chemical waste disposal sites) .
ReplyDeleteThis comment has been removed by the author.
DeleteYes, I agree that it in the case of environmental precautions, it is better to have an audience that overcorrects a perceived problem as opposed to ignoring one.
DeleteWhile I agree in this case there's probably little harm in increasing public awareness through exaggerate I would caution against using such tactics repeatedly. If everything is the next "worst thing ever" it's likely to drown out issues that are actually very important. If every other title is "X will destroy us all if we don't stop it now!" the audience is going to become desensitized and assume an actual threat is simply an exaggeration.
DeleteI'd argue that such a sweeping statement is an overgeneralization for complex issues. In this NY Times Op-Ed, http://www.nytimes.com/2014/11/10/opinion/making-chemistry-green.html, the authors propose a blanket ban on commercial organohalogen compounds. An overcorrection, could imply an even larger ban of all organohalogen compounds which include numerous pharmaceuticals (http://pubs.acs.org/doi/abs/10.1021/cr4002879). This enters a gray area of whether the health risks of individuals in need of treatment are of more important than the limiting the introduction of potential PBT into the environment.
DeleteDoes anybody know what industry specifically emits CCl4?
ReplyDeleteThe above comment is mine. I forgot to edit my profile before posting.
DeleteRight now, the emission source is unknown. CCl4 was used to make refrigerants, but that was largely phased out with the Montreal Protocol. Today, I think the uses are mostly research, but it has pretty severe health effects so it's becoming less frequently used.
DeleteIt was also used as a cleaning agent.
DeleteIn general, the Huffington Post article is too short to give enough information regarding what type of contaminated sites might be emitting CCl4.
ReplyDeleteI agree that the article does sensationalize the issue (what would a HuffPo article be without a little fear-mongering though?), but I think part of the reason for that lies with the NASA press release. Similar to the article, the press release over-emphasizes the presence of unknown sources and only references the atmospheric lifetime of CCl14 in a single sentence near the end of the release. Maybe they were pandering for more news hits?
ReplyDeleteVery possible, and I agree. While the video did provide more information, I don't think it reflected the paper very well.
DeleteThis comment has been removed by the author.
ReplyDeleteI agree that the Huffington Post article 'oversells' the emission of carbon tetrachloride. As we've mentioned in class, discussion of scientific studies by the media tends to omit key evidence and factors that may influence how the research should be interpreted. In this case, the HuffPost article omits the ~1% reduction in carbon tetrachloride levels. The reader, without accessing another source, is left to think that the carbon tetrachloride level is not reducing at all, and that because emissions continue, they level may in fact be rising. This is a critical misinterpretation, and while both sources highlight the need to understand carbon tetrachloride better, the HuffPost article introduces an element of sensationalism. However, it is important to note that the HuffPost article is immediately engaging and accessible by a varied and large audience. The general public is drawn to sound bites, infographics, and short articles, as suggested by the brevity of the HuffPost article and the embedded video. While these are not necessarily appropriate for scientific papers, it should serve as a challenge to scientists to try to connect with the general public in ways they find relatable and to incorporate multimedia elements when possible.
ReplyDelete