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