In Part 1 of my review of the MOOC, Data Exploration and Storytelling: Finding Stories in Data with Exploratory Analysis and Visualization, I provided some background on the course framework, including what a MOOC was. Also, I provided the biographies of Albert Cairo and Heather Krause that were from the course web site.
In Part 2 of this review, I am going to share some of the content that was taught in Module 1. I am also going to expand on one of the topics Professor Cairo addressed, The Hockey Stick Chart.
Again, I hope you find this review helpful and I highly encourage you to take courses not only from them, but other offerings in the MOOC space.
Module 1 – Finding and Understanding Data
In the first video of this module, Professor Cairo provides us a definition of visualization. This is the same definition he discusses in his two seminal books, The Functional Art (2012) and The Truthful Art (2016).
Per Professor Cairo,
A visualization is a graphic representation designed to enable exploration, analysis, or communication.
He then provides two interesting stories related to data encoding. The first story deals with course grades provided by an instructor. When the instructor uses a 0 to 100 scale, where 0 would be an F and 100 being an A or A+, the average score was 72. When it came time for the students to write reviews of this instructor, his students provided that instructor less than favorable reviews. So, the professor decided to perform an experiment. He changed his scale from 0 to 137 where 137 would be an A or A+. This change had the average score now at 96. Now, in the next series of reviews, the students started giving him glaring reviews.
The question to raise here is if a score of 96 over 137 is a better average score than 72 over 100? After hearing Professor Cairo tell the story, you may be tempted to think 96 is a better average than 72 as it is a larger number and most of us associate a score of 96 with being close to a very high A. Professor Cairo pointed out we as humans are very bad at dealing with numbers as they are “abstract representations of quantities.” 
He then shows the participants the data visualization below where these numbers are mapped onto spatial properties. As you can now visually see, an average of 96 on a scale of 0 to 137 is not as good an average as 72 is on a scale of 0 to 100.
This example fit in with the primary goal of the course to show the participants ways to use data as a source to tell stories. As the course progresses, we will see more tools and techniques from Alberto and Heather that they use to interrogate data for answers – gathering, cleaning, organizing, analyzing, visualizing and publishing data to find and tell stories. 
The Hockey Stick Chart
The next story Professor Cairo told us had to deal with a very famous (and controversial) chart related to climate change. This chart is known as The Hockey Stick Chart.
Professor Cairo first shows us records of global temperatures from the year 1000 up to the year 2001. He presented these numbers as a data set in a numerical table (think of an Excel spreadsheet). Alberto points out that viewing the numbers as a data set, it is almost impossible to see trends and patterns in the data unless you are a
very good statistician or a very good data scientist who is very good at extracting
meaning for this data.
Again, Professor Cairo maps and transforms the data onto a time
series lag chart. He points out that this is one of the most famous and one of the most persuasive data visualizations created. It is commonly called The Hockey Stick Chart that was designed by several environmental scientists in 1988 and 1989. The story
that it tells is very, very persuasive. 
At this point, I want to expand on Professor Cairo’s story and delve into more detail about The Hockey Stick Chart.
In 1998, a yet unknown climate scientist named Michael Mann (photo, right) and two of his colleagues published a paper that sought to reconstruct the Earth’s past temperatures going back 500 years before the era of thermometers to show how out of whack recent warming has been.
The finding: Recent northern hemisphere temperatures had been “warmer than any other year since (at least) AD 1400.” The graph above depicting this result looked rather like a hockey stick: After a long period of relatively minor temperature variations (the “shaft”), it showed a sharp mercury upswing during the last century or so (“the blade”). 
The report disseminated quickly through climate science circles. Mann and another colleague soon lengthened the shaft of the hockey stick back to the year 1000 AD. In 2001, the UN’s Intergovernmental Panel on Climate Change featured the hockey stick in its Third Assessment Report. Based on this evidence, the IPCC proclaimed that “the increase in temperature in the 20th century is likely to have been the largest of any century during the past 1,000 years.”
Smoothed reconstructions of large-scale (Northern Hemisphere mean or global mean) surface temperature variations from six different research teams are shown along with the instrumental record of global mean surface temperature. Each curve portrays a somewhat different history of temperature variations and is subject to a somewhat different set of uncertainties that generally increase going backward in time (as indicated by the gray shading). This set of reconstructions conveys a qualitatively consistent picture of temperature changes over the last 1,100 years and especially over the last 400.
Then the National Academy of Sciences weighed in in 2006, vindicating the hockey stick as good science and noting:
The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators, such as melting on ice caps and the retreat of glaciers around the world.
All Hell Breaks Loose
Mann was now facing a myriad of scientific and political attacks on his work. The Hockey Stick Chart was repeatedly attacked, and so was Mann himself. Congress got involved, with demands for Mann’s data and other information, including a computer code used in his research.
This report did not change the minds of climate deniers, in fact, it emboldened them more. Mann and his colleagues were drawn into the 2009 “Climategate” pseudo-scandal, which purported to reveal internal emails that (among other things) seemingly undermined The Hockey Stick Chart. Only, they didn’t.
In the meantime, climate scientists continued to work to prove (or disprove) Mann’s theories. Over the years, other researchers were able to test Mann’s work using “more extensive datasets, and more sophisticated methods. And the bottom line conclusion doesn’t change.” Mann’s single hockey stick chart soon became several dozen variations created by different groups of scientists. Mann referred to them as a “hockey team.”
Recent studies support the hockey stick more powerfully than ever. One report, from Nature Geoscience, featured more than 80 authors, showed with extensive global data on past temperatures that the hockey stick’s shaft seems to extend back reliably for at least 1,400 years. In Science, Shaun Marcott of Oregon State University and his colleagues extended the original hockey stick shaft back 11,000 years. “There’s now at least tentative evidence that the warming is unprecedented over the entire period of the Holocene, the entire period since the last ice age,” says Mann.
Scientists at the 2014 People’s Climate March in New York.
Credit: Joe Brusky/flickr
“Climate deniers like to make it seem like the entire weight of evidence for climate change rests on the hockey stick,” explains Mann. “And that’s not the case. We could get rid of all these reconstructions, and we could still know that climate change is a threat, and that we’re causing it.” The basic case for global warming caused by humans rests on basic physics–and, basic thermometer readings from around the globe. The hockey stick, in contrast, is the result of a field of research called paleoclimatology (the study of past climates) that, while fascinating, only provides one thread of evidence among many for what we’re doing to the planet. 
Next Blog Post: Continuation of the Review of Module 1 – Finding and Understanding Data
 Alberto Cairo and Heather Krause, Course Video: Module 1: Visualization for Discovery, Data Exploration and Storytelling: Finding Stories in Data with Exploratory Analysis and Visualization, Knight Center for Journalism in the Americas, The University of Texas – Austin, January 16–February 26, 2017.
 Chris Mooney, The Hockey Stick: The Most Controversial Chart in Science, Explained, The Atlantic.com, May 10, 2013, https://www.theatlantic.com/technology/archive/2013/05/the-hockey-stick-the-most-controversial-chart-in-science-explained/275753/?utm_source=eb.