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Seeing is believing: Information visualization and the debate over global warming

When Roger Friedman of Fox News said in his review of Al Gore's recent film on global warming, “It doesn't matter if you’re Republican or Democrat, Liberal or Conservative, your mind will be changed in a nanosecond,” he wasn't referring to scenes of Gore reflecting on the meaning of life before a slow-flowing river or even the images of glaciers collapsing or polar bears swimming in the open ocean in search of vanished ice. He was talking about a particular graph shown in the film that depicts the variation in temperature compared to the levels of carbon dioxide in the atmosphere over the last thousand years. Whether or not you accept the claim put forward in “An Inconvenient Truth” that the earth is getting warmer as a result of human activities will rest in large part on how you respond to this one slide. Not surprisingly, the graph and the data it represents have been the subject of a great deal of controversy. In fact, the “hockey stick graph” as it has been nicknamed because of its characteristic shape, may be the most contested example of information visualization in the history of science.

hockey stick graph

Figure 1: The original “Hockey Stick” graph from the Intergovernmental Panel on Climate Change Third Assessment Report showing the relationship between temperature and levels of carbon dioxide over the last 1000 years.

Critics of the graph play rough. The researchers responsible for the original data have been brought before Congress to defend their findings, with one member of the House going so far as to demand to inspect their personal financial records for evidence of bribery. Not only has the data been under the microscope, but the way that the data is represented has been minutely dissected. An article published by the conservative think tank the Heartland Institute calls the slide in Gore’s film, “A triumph of data manipulation.” Among other criticisms, the article claims that you can’t tell whether warmer temperatures precede or follow the rises in levels of carbon dioxide and that the scale along the vertical “y” axis is not clearly labeled. Rarely has an example of design been subjected to such intense scrutiny at every level from so many sources.

image of a slide

Figure 2: An image of slide from Al Gore’s presentation.

But why should one graph matter so much? The scientific reports on climate change must run into the millions of pages and nevertheless news organizations and pundits continue to, as one BBC headline put it, “Row Over Climate Hockey Stick.” Nancy Duarte and Jill Martin of Duarte Design, the firm that has been working with Al Gore since 2003 to create and refine graphics for the presentation shown in the film, declined to comment on the hockey stick itself, but they did provide a clue to the continuing obsession with the image. “Your brain is hardwired to process visually first and then verbally,” Duarte said, when putting together graphics for a presentation, “the goal is to communicate instantly. You're looking for impact.” This, then, is the “nanosecond” that Roger Friedman referred to in his review. Images and graphs can communicate immediately and, given the choice between words and images, we look to the images first. A recent survey by the National Science Foundation indicates that Americans are getting the message: Over 90% of U.S. adults have heard of global warming, with the majority considering it a “serious or very serious” problem. This is particularly impressive given the low rate of scientific literacy generally: 50% of U.S. adults don’t know how long it takes for the earth to orbit the sun.

According to Duarte Design, the key to creating an effective slide is including a convincing amount of detail while not distracting from the main message. “In general, you want to keep the visuals minimal and eliminate background noise to emphasize your point.” Making your point too forcefully may compromise credibility.

alternate graph

Figure 3: Alternate graph showing temperature is cooler now than it was during the Medieval Warm Period. By John Daly.

The graph above was offered by critics of global warming in an attempt to show that temperatures are not, in fact, on the rise. Because it lacks the level of detail of the “hockey stick” graph, it seems less creditable and less “scientific,” regardless of the validity of the data on which it was based. The issue of global warming seems complicated, and so we expect the graphs that represent it to seem complicated also. As Edward Tufte has famously observed, less is often just less when it comes to visualizing information. So designers should think twice before sacrificing complexity for the sake of clarity. “Complex information graphics correlate many data points in a way that conveys the overall message without sacrificing the nuance of detail or oversimplifying the concept,” says Martin. “Rather, they strike a balance between ‘thesis’ and ‘data’ levels of an argument and thus present a more robust and interesting case.” Although critics of the hockey stick have offered alternative visualizations, few of them have been as visually compelling as the original. The simplified graph below, which charts the same data, would only be convincing to someone who already agreed with the claim that the current pattern of global warming is part of the natural cycle.

simplified graph

Figure 4: Simplified graph showing temperature is cooler now than it was during the Medieval Warm Period. By David Wojick, PhD.

New perspectives on climate change

Not only is information visualization being used to communicate information to the public, but it is also being used by scientists as a primary tool for understanding environmental trends on the global scale. When dealing with many different data points, sometimes the only way to understand the “big picture” is to make a picture. The visualizations that are created in the process overlay colors and patterns onto the familiar image of the globe, creating an image that is both strange and familiar. Many environmental systems move too slowly or involve too many interrelated variables to be comprehensible without the aid of visualization tools. “Scientific visualization of simulation data allows one to zoom around at will, run forwards or backwards in time at any rate, and transform and filter the data arbitrarily (for example, light up regions in bright green where the divergence of some vector field exceeds a threshold),” Chris Henze explains.

ECCO Project

Figure 5: Image from NASA’s Estimating the Climate and Circulation of the Ocean (ECCO) project. Click here to see animation.

Chris Henze is the technical lead of the visualization group in the Advanced Supercomputing Division at NASA’s Ames Research Center. He works with scientists and engineers to turn what, in some cases, represents years worth of data collected by hundreds or thousands of instruments positioned all over the world into an image or sequence of images that can be viewed in a matter of minutes. When dealing with complex trends such as climate change, the ability to compress space and time is crucial. This is not unlike the type of compression that occurs when you try to represent a thousand years worth of information along an x and y axis—as seen in the hockey-stick graph. The difference between data mapping and information visualization is that the former retains the appearance of the systems it represents while the latter imposes a spatial relationship that does not exist “in the wild.”

Led by Dr. Robert Atlas of the Laboratory for Atmospheres at Goddard Space Flight Center, members of the Finite Volume Circulation Modeling group are using visualizations to predict the landfall of hurricanes up to five days in advance. The team has achieved accuracy in predicting landfall within approximately 100 kilometers and also predicting storm intensity, with an advance warning of three to five days based on simulation results for hurricanes Frances, Ivan, and Jeanne. The five-day forecast for hurricane Ivan accurately predicted intensity to be a strong Category Four hurricane on the Saffir-Simpson scale, making landfall on the Gulf coast of Alabama as an intense Category Three storm.

cloud patterns

Figure 6: Image from NASA’s Finite-volume General Circulation Model (fvGCM) project showing cloud patterns. Click here to view animation.

Even the most sophisticated visualization, however, can be ineffective on its own. As Edward Tufte observes in his book Visual Explanations, showing multiple images side by side helps us to “monitor and analyze multi-variable processes. By providing a quick, simultaneous look at a continuing flow of different measurements, multiples help sort out the relevant substance…” One visualization tool used at NASA is the “hyperwall,” a seven-by-seven cluster of flat panel screens, each driven by its own dual-processor computer with a high-end graphics card. This tool helps researchers display, analyze, and study high-dimensional datasets using different tools, viewpoints, and parameters to display the same data. Displaying multiple perspectives on the data simultaneously lessens the risk that any one visualization method will lead to mistaken assumptions. But, if you want to see it really big, each of the 49 computers can display, process, and share data, so that a single image can be displayed across all screens.

ocean temperatures

Figure 7: Image from ECCO project showing different ocean temperatures on the surface and at a depth of 160 meters, respectively. Click here to view the animation.

One of the key concerns of those who study climate change is that an influx of warm water into the arctic regions will disrupt the ocean currents that help to regulate temperature globally. A disruption in these currents could greatly accelerate the melting of the polar ice caps, which would, in turn, cause sea levels to rise dramatically. “A recent project involved visualizing multiple physical fields (temperature, salinity, wind stress, heat flux, etc.) at 5-minute intervals from a global model simulating a year of ocean dynamics. The extremely high spatial and temporal resolution of the visualizations are allowing the scientists to investigate detailed mechanisms of formation of the subtropical water in the North Atlantic,” says Henze. To give a sense of the amount of data that is necessary in order to accurately model a system such as ocean dynamics, consider this: For this project, Henze sent over 70 terabytes of data to the graphics machines. That is approximately 3.5 times the amount of text contained in Library of Congress.

If that sounds like a lot, just wait. According to Henze, “Graphics chips are evolving at ‘Moore's Law cubed’—doubling every 6 months—so 5 years is 10 doublings or a 1000-fold increase. Our biggest machine in 2001 was 1.2 TFLOPs, today it is 62 TFLOPs.”

Whatever conclusions NASA scientists may come to about global warming as a result of new imaging technology, it is inevitable that other scientists will reach different conclusions. Scientists often disagree, offering different data to support alternative claims on an issue, or subjecting the same data to different interpretations with different conclusions. Understandably, this causes confusion in the mind of the general public, who don’t know how to evaluate conflicting claims or which side, in the end, to believe. For an issue such as global warming, which requires millions of people to take action based not on observable phenomenon, but on scientific projections, this lack of certainty might be disastrous. After all, you don’t have to believe the scientists that dispute global warming in order to do nothing—you just have to be confused enough to be complacent.

Visualizing consensus

Because it is possible to find at least one scientist willing to dispute almost any claim, it is important not just to know what some scientists think, but to know what most scientists think. But how does one measure consensus in the scientific community? The traditional method is to send out a poll and then publish the results. This method has several drawbacks: it can take a long time; the results can be skewed depending on which scientists were polled; and, even if you know what most scientists think, you still don’t necessarily know why they think it. There’s no way to know what data they are relying on to support their claims.

interactive map

Figure 8: Interactive map based on a search of articles published between 1981-2003 that relate to the topic “mass extinction.” The image shows the connections between articles as well as the relative importance of particular articles. By Chaomei Chen.

Dr. Chaomei Chen, professor at Drexel University and editor of the journal Information Visualization, is trying to map science—or at least scientific literature—in order to understand what scientists are thinking about and why. Using articles that appear in peer-reviewed journals as his source, Dr. Chen has developed software that maps the relationships between scientific articles and the sources they cite. Every article not only presents new material, but also cites previous articles that dealt with the same or a similar subject or that the author feels are influential or relevant.  And, because the journals are peer reviewed, at least a few other scientists must think that the article is worth publishing. Chen’s software maps the relationships between of articles that address that topic and displays those relationships as lines of different colors. For instance, if an article about global warming cites another article that studies carbon dioxide emissions, both articles will appear as dots on the screen with a green line connecting them. The more often an article is cited by other articles, the larger the dot that represents it. This makes it easy to see which articles are most often cited. This interactive map allows you to click on the dot and pull up a bibliographic reference so you can look up the article.

Articles on similar subjects are also clustered together, so that you might see, for example, that hundreds of articles have been written on global warming but only a few have been written about the idea that the earth is getting cooler. “You can think of this like a voting system,” says Chen. “Each citation is a vote for that article. When you start to put them together you can see a network begin to emerge and you can see which contribution or piece of knowledge is most often cited and therefore considered most important. This network you can think of this as a snapshot of the scientific communities thinking on that subject at that particular time as recorded in the scientific literature.”

If you map these articles to a timeline, you can start to see patterns in the way that science in general progresses. Not only can you see where the scientific community is focusing its attentions—what Chen calls a “research front”—but you can also see what areas are receiving less attention, and what areas were once popular but have now fizzled out. Depending on the x and y axis the user selects, science resembles a staircase—progressing through a series of breakthroughs—rather than the slow, steady accumulation of knowledge one might expect. Sometimes this shift in interest occurs because new data becomes available, sometimes it is due to external events. The destructive fury of hurricane Katrina, for example, inspired a flurry of articles about the relationship between rising temperatures and extreme weather. These articles may cite recent studies on hurricanes or they may pull up an article that was written years ago but whose findings have gained new importance in light of the event.

climate change articles map

Figure 9: Map based on articles published between 2000-2006 that relate to the term “climate change.” By Chaomei Chen.

Most articles are published and then soon superceded by other research or methodologies. A few, however, become classics and are cited over and over again, which, in the graph above, is what causes the long strands looping back into the past.

These visualizations tell us what scientists are talking about, but they don’t necessarily indicate what they are saying. We can’t yet tell whether most scientists think global warming is real just by looking at the images—we would have to drill down by clicking on the dots and then actually read the significant articles.  “We don’t know that everyone necessarily agrees with the paper they are citing, but just that it has value as a reference or discussion point,” says Chen.

Chen’s current research involves the analysis of conflicting opinions. His goal is to find a way to map what a specific piece of research has to say on an issue—for example, which papers support the idea that humans are responsible for climate change and which hold that climate change is part of the natural fluctuation. “You will be able to see the substructure of the whole matter of debate. In addition to knowing how many articles support an opinion, you can see what kind of evidence your opponent consistently draws on to make their argument.” Scientists tend to be cagey sorts and rarely come right out and bluntly state their conclusions. Even after reading an entire article it can be difficult to figure out just where a scientist stands on the issue. For this reason, Chen decided to work with issue that people clearly have strong positive or negative opinions about. He decided to start with the debate over the bestselling book, The Da Vinci Code, using the comments posted to Amazon.com.

There main reasons he made this surprising decision is that the book drew unusually polarized responses: the 3000 people who reviewed the book tended to either love it or hate it with very few in between. Just as importantly, Amazon.com not only allows people to provide a written review of the book, but also to rank the book by assigning it a certain number of stars. Five stars means they loved the book and one star means they hated it. This ranking is important because it gave Chen and his team a means of correlating the opinions expressed in the text. Chen set out to discover which terms people who assigned the book one or five stars most often included in their descriptions.

da Vinci cluster

Figure 10: A view of the cluster “Leonardo da Vinci art” and surrounding clusters in positive reviews. By Chaomei Chen.

This research is significant because eventually it will allow Chen to be able to map not just the topics of scientific articles, but also whether those articles support or refute a specific claim. We will be able to compare the number of scientists that support a particular theory at a single glance and be able to access the research they use to support their opinion with just a click. With luck, this software should effectively end the debate over whether or not the majority of scientists support a theory, making it much more difficult for opponents of scientific theories to keep the public confused and, therefore, inert.

Pictures and stories

Information visualization is able to communicate the intricacies of global warming in a way no other discipline can. Its messages can be immediate and powerful, without sacrificing the level of detail necessary to represent the complex subject accurately. Not only is information visualization helping scientists and politicians communicate with the public, it is a primary tool for scientific study, and for the study of science itself. It is particularly telling that even the medium of film could not compete with the power of these visualizations. According to “An Inconvenient Truth” director Davis Guggenheim, “I thought, a film about a slide show? A filmed lecture? I don’t get it. And then I saw his slide show. The information in it is so powerful, and we all just felt like, what if we could give people a front-row seat to this.”

“An Inconvenient Truth” is the first popular film to make such prominent use of a live presentation to communicate about a complex issue, but it may not be the last. Presentations that combine information visualizations and live narrative are quickly becoming the most common way of presenting information for businesses, academics, and the military. After all, there are no tedious reports to read and the audience can provide immediate feedback. As technologies that allow simultaneous transmissions and real-time interactions become more sophisticated, the popularity of live presentations will only increase.

So, for designers interested in information visualization, it is important to keep in mind the context in which these images will be displayed. Al Gore does not just slap the hockey stick up on the screen; the slide is carefully introduced and then deftly romanced. “The best way to tell a story is to show progress over time. There has to be a transformation,” says Nancy Duarte. The most memorable moment in “An Inconvenient Truth” is when Gore goes off the edge of the graph, rising up in a cherrypicker high above the stage to show what will happen if the present trends continue unabated. It’s a nice bit of theater—the message is dramatized as well as shown through the graph and described verbally. It’s also a crucial moment in the story Gore is telling. After all, it’s difficult to know with absolute certainty if CO2 levels will continue to rise at the rate that is indicated on (or, in this case, off) the chart and, if they do, whether temperatures will rise accordingly. But, because of the detailed graph that accompanies the predictions and the dramatic effect of Gore’s performance, the audience is carried effortlessly along from the past into the future. The transformation is complete: lifeless data becomes a wake up call to a crisis.

Where to go from here

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