The
article I chose was published online (September 26, 2016) on the National Geographic magazine and is
titled "Global Warming Is Real -
But 13 Degrees? Not So Fast." (1) This article highlights a Nature report (2) that was published on
the same day, in which the author predicts an alarming 13 degrees Fahrenheit (7
degrees Celsius) rise in global temperatures over the next few millennia. That is, if current atmospheric levels of CO2
were to remain constant.
In
her Nature paper, the author Carolyn
Snyder employed data from ocean sediment cores and various climate models to estimate the evolution of global surface temperatures over the past two million
years. In order to study past climates
(paleoclimates), scientists typically use climate proxies (ex: ice cores, tree
rings, and ocean sediment cores) as indirect pieces of evidence to determine ancient
climatic patterns (3). These proxy indicators can provide useful paleoclimatic
information, as their character of deposition or rate of growth is strongly
influenced by the climatic conditions of the time in which they were deposited
or grew (4). As such, chemical traces
(ex: isotopic ratios) induced by climatic changes can frequently be recovered
from proxies.
In
her study, Snyder utilized an extensive database of proxies derived from 59
ocean sediment cores to estimate sea surface temperatures. These methods included measuring the Mg/Ca
ratios in planktonic formation, using alkenone unsaturation indices, and
comparing microfossil abundances. Most
notably, these studies have allowed Snyder to construct the longest
comprehensive historic temperature record to date. Specifically, Snyder demonstrated the first
use of a multi-proxy database in providing a spatially weighted proxy
reconstruction of global average surface temperatures over the past two million
years. While previous temperature
reconstructions have extended further back (up to 3 million years), they were
either significantly less comprehensive or focused primarily on certain time
periods. In fact, the longest
comprehensive temperature record published before this study went back to only
22,000 years.
Snyder's
study provides key insights into several important paleoclimate topics,
including the magnitude and stabilization of polar amplification, the role of
global temperature in the mid-Pleistocene transition, and the dependence of
Earth system sensitivity (the Earth's long-term temperature response to a doubling of CO2 levels) on radiative
forcing (the difference between sunlight absorbed by the earth and energy
radiated back to space). Upon comparing
her new temperature record with radiative forcing from greenhouse gases (Figure 1), Snyder
estimates a 7-13 degrees Celsius change in global average surface temperature per
doubling of atomspheric carbon dioxide, in millennia timescales. This result suggests that, even if current CO2
levels were to remain constant, the Earth could potentially experience a
total warming of 3-7 degrees Celsius over the next few millennia.
In
his National Geographic article, the
author Craig Welch introduced the broader implications of Snyder's research
through a critical lens, citing the perspectives of several prominent climate scientists
who have expressed skepticism towards Snyder's controversial conclusion. In particular, Welch highlights the critiques
made by Gavin Schmidt, chief of NASA's Goddard Institute for Space
Studies. Schmidt pointed out that
Snyder's study had failed to account for changes in Earth's orbit that
affected global temperatures and drove the expansion and retreat of glaciers
throughout the time period covered in her analysis. Schmidt's own research into Earth's long-term
sensitivity to CO2 has suggested that a 4.5 degrees Celsius increase
in global temperatures would be expected (on a millennia scale) from a doubling
of pre-industrial CO2 levels. To allow readers to learn more about Schmidt's
views, the National Geographic
article also provided a link to a blog post (5) written by Schimdt ("Why
correlations of CO2 and temperature over ice age cycles don't define
climate sensitivity").
Overall, I would give the National Geographic article a rating of
9/10. It was interesting to see that the
National Geographic article explained
the key findings of Snyder's Nature
report in the context of an ensuing debate that arose in the scientific community,
regarding the accuracy and validity of Snyder's conclusions. In addition to including strong quotes that
highlight both the merit and potential flaws of Snyder's study, the author
employed an engaging and informative narrative (along with an educational
video) to help readers gain a greater appreciation for each scientist's arguments through
better understanding the science behind global warming/natural fluctuations in atomspheric CO2. Ultimately, the author finished the article on a diplomatic note - Snyder's efforts deserve applause, yet her method may not be the best way to measure Earth's long-term sensitivity to CO2 emissions. All in all, I appreciated how the National Geographic article not only informed the general public
about a major research finding, but also opened the doors for general readers
to gain insight into the scientific community's diverging responses and active discussion towards a study of significant impact.
References:
(1) Welch,
Craig. "Global Warming Is Real - But 13 Degrees? Not So Fast."
http://news.nationalgeographic.com/2016/09/global-warming-study-13-degrees-is-wrong-climate-change/
(2) Snyder, C. Nature, 2016, 538, 226.
http://www.nature.com/nature/journal/v538/n7624/full/nature19798.html
(3) "Past Climates on Earth -
Paleoclimatology"
http://www.globalchange.umich.edu/globalchange1/current/lectures/kling/paleoclimate/
(4) "Paleoclimatology: Climate
Proxies"
http://serc.carleton.edu/microbelife/topics/proxies/paleoclimate.html
(5) Schmidt, Gavin. "Why
correlations of CO2 and temperature over ice age cycles don't define
climate sensitivity."
http://www.realclimate.org/index.php/archives/2016/09/why-correlations-of-co2-and-temperature-over-ice-age-cycles-dont-define-climate-sensitivity
This was an extremely well written blog Alex! I also thought the National Geographic article did an excellent job highlighting the key findings of the Nature publication, as well as discussing the flaws in the work. I like the quotes from various personal that state their disbelief of Snyder's conclusions. I also liked that Welch sectioned the material by informative headings: "Bad deduction from a good record" and "An open question". I believe these contribute to the easy read Welch's article. The video was informative and easy to understand as well. Again, a great post!
ReplyDeleteThanks Josh! I also agree that Welch's headings in each section effectively breaks up his text and summarizes his key points.
DeleteNice post Alex! Not only did the National Geographic article explain Snyder's findings clearly & thoroughly, but you did as well! One thing that I found interesting was a criticism that mentioned Snyder's failure to account for how Earth's orbit affects global temperature. Schmidt's estimate of 4.5C is quite a bit smaller than Snyder's estimate of 7C. While Schmidt's blog post was helpful in expanding on the topic, I am now curious about the relevance of Snyder's study. Can Snyder's results be ignored due to lack of orbit consideration? Does this deem Schmidt's results as a more accurate estimate of global warming? Just some general thoughts I had about what you called the "scientific community's diverging responses."
ReplyDeleteThanks Shannon! I think that Snyder's conclusion brought up significant debate, partly because her numbers are significantly higher than other reported values (which tend to be around Schmidt's estimate of 4.5 C). Also, many are skeptical towards Snyder's simplistic approach of making direct comparisons between CO2-driven global temperature changes in the modern era vs. during the past ice age. This is mainly because global temperature changes during these glacial cycles were not mainly CO2-driven. They were also driven by changes in the Earth's orbit. It's tough to say if Schmidt's predictions are more accurate than Snyder's, but since he studied warmer eras before the ice ages, he doesn't encounter Snyder's challenge of having to take into account orbital variations. But I presume that his predictions have their own minor set of shortcomings too. I think that ultimately, it's important for everyone to take these long-term climate predictions with a grain of salt.
DeleteGreat blog post and article find. I really liked the article talked about feedback loops and how they contribute to warmer and cooling of the Earth, since we are learning about them in class. I'm curious how Synder's paper made it through a peer review if so many scientists disagree with her findings. I would think that someone would have caught her errors earlier. Overall I think the Nature article did a great job of explaining CO2 effects on warming the Earth especially for people who do not know much about how this happens.
ReplyDeleteThanks Stacey. I am also surprised that Snyder's reviewers overlooked these shortcomings during the review process. It would have even been appropriate for Snyder to add in a brief comment about how these predictions could be improved upon with more studies that take into account orbital variations.
DeleteI really enjoyed reading your post, Alex! I, too, think the Nat. Geo. article did a really great job reviewing Synder's publication. Specifically, I think the news article was very diplomatic in the way they criticized Snyder. I appreciated how they pointed out both the successes and shortcomings of her work, especially considering how easy it would have been for the Nat. Geo. article to emphasize Synder's overestimates and improper handling of data.
ReplyDeleteThanks Liz! I also really appreciated the author's efforts to praise and recognize the significance of Snyder's work, in terms archiving global climate evolution.
DeleteGreat post, Alex! I liked the way the National Geographic article used direct quotes numerous time and how they highlighted the key findings from the journal. I agree with some of the previous posts wondering how this article ever got published and through peer review. I wonder if Snyder has reviewed the report after getting these negative comments. The article does a good job of helping people understand this subject who aren't in the field. I am also a little reluctant that they found this error and that our world will not be warming up this much this fast.
ReplyDeleteThanks Lindsey! Snyder herself has stated that she isn't convinced that orbital effects are that important in this case. She claims her study provides a single measure of the relationship between CO2 levels and historic temperatures. But I still think that she could have chosen her wording more carefully in her paper as to sound less definitive.
DeleteNice find Alex! It’s interesting to see a popular media article that contradicts the findings in a study, and doesn’t just take them at face value (or even overestimate them). We have mostly seen articles thus far that carry the results too far, rather than looking critically at the data. It’s a refreshing change. The only fault I found with the National Geographic article was the last sentence. While the whole article the author did a great job of citing and backing up his claims, he fails to do so at the end. He ends with the statement that the large sea-level rise and fast warming, “appears preventable”. I think, although this is a catchy way to end a media article, it needed to be supported, especially if we do want to prevent this potential disaster.
ReplyDeleteThanks Annabel! I agree with your ideas on the last sentence of the National Geographic article. Even though Snyder's numbers might be a bit inflated, the majority of studies have still shown that global temperatures are trending upward. And like you said, the author never mentions any measures to prevent further rises in global temperatures.
DeleteNice job, Alex! I agree that the author helped readers gain a greater appreciation for each scientist's arguments. And I also think that Snyder did an excellent job reconstruction of global average surface temperatures over the past two million years. But what she utilized are mostly some indirect evidences, maybe her research can be a more convincing and comprehensive one if she would apply some direct methods in discovering. Anyway, a refreshing report!
ReplyDeleteReally nice post, Alex! You did a great job in covering this topic. I also thought that the Nat. Geo. article did a good job on focusing on the science behind the study, and leaving the issue more of an open topic, rather than one that is closed and definitive. Snyder's work really is impressive, tracking the global temperature averages back that far is no mean feat, and the credit she received is just, but there might be a better or more conclusive way to track this data, just through some of the inconsistencies tree or ice data may provide about the CO2 content in the atmosphere. But overall, this article was a good read.
ReplyDeleteWith a publication like National Geographic, I would expect the quality of the scientific discussion to be greater than the average news source. Including not only the Nature paper, but also several other scientists who've done research and/or disagree with Snyder's conclusion. Not often enough do news sources give opposing arguments and the information to inform readers of important context. Also, the Nat Geo article does a good job explaining the science of the research to their audience. Nice job.
ReplyDeleteThis really is an interesting article ALex. It is fascinating new technique to be able to predict the amount if CO2 in the future and how it relates to the past CO2 levels. I enjoyed reading the National Geographic article and how they interviewed that NASA expert. His comment was interesting that the tilt and position of earth can effect the measurements used in the Nature paper. It is nice to see that there are such high amounts of research into CO2 emissions and predicative\ve models since it will effect us all.
ReplyDelete