Visualizing a Greenhouse Gas
Stunning technologies provide dynamic images of carbon dioxide in the atmosphere
This essay was inspired by this image and the video from which it is captured. I hope you will take a minute to view the video, and then we can talk about what this piece of visual and scientific art represents and what it can tell us about the Earth system.
This image and the video are here:
There is an old adage that says “a picture is worth a thousand words.” Viewing this video suggests that a thousand words might not be nearly enough, but then video wasn’t an option in 1918 when the phrase first appeared in this form in an advertisement in the San Antonio Light newspaper. Since 2013, several modern renditions of this old expression have raised the bar for videos as high as 1.8 million words.
What this video depicts is a simulation of the dynamic distribution of carbon dioxide in the atmosphere over the course of a year. The most important of the several greenhouse gases driving increases in global temperatures, carbon dioxide is injected into the atmosphere primarily by the burning of fossil fuels, but is also impacted by seasonal changes in the carbon gain and loss by plants and ecosystems.
I’ve watched this video several times. Each enjoyable viewing reinforced some basic insights about our changing Earth system. Here are just a few:
· Northern hemisphere countries dominate the increase in carbon dioxide emissions - You can trace high rates of emissions from North America, Europe and China
· Seasonality of concentrations is driven by both reduced burning of fuels for heating and increased carbon dioxide uptake by plants (photosynthesis) in the summer
· Impacts of land use such as burning of fields in the tropics are reflected in increased carbon dioxide and also as carbon monoxide – the grey plumes in the video
· Dynamic shifts in concentrations are driven by, and map the movement of storms and weather patterns in general, especially in the winter when concentrations are elevated. Imagine how many words it would take to describe those patterns!
That rapid mixing of emitted carbon dioxide within the atmosphere of the northern hemisphere, and the relatively narrow range of concentrations, both support the accuracy and value of another image worth many thousands of words: the “Keeling Curve” of carbon dioxide concentrations measured at a single location atop Mauna Loa in Hawaii.
This icon of the global change era captures both the inter-annual dynamics visualized in the video (the saw-tooth pattern in the graph below), and the long-term increase over the last 60+ years. You might notice that the legend with the video captures a range of concentrations, in the year 2006, from 377 to 395 parts per million. Current concentrations exceed 410. While measurements at observatories in the southern hemisphere show the same decadal trend of increasing carbon dioxide as at Mauna Loa, the inter-annual fluctuations are much less pronounced, as would be predicted from the video.
You may see additional patterns in this piece of kinetic, scientific art. The accompanying narration, presented by Dr. William Putnam, lead scientist on the project that produced the video, offers others as well.
So how did this video come about? Although the nature of the video might suggest satellite remote sensing, this is, rather, the result of two intensive research efforts: mapping emissions globally, and developing models of circulation patterns in the atmosphere. Those circulation models, which give this video its dramatic visual impact, may be familiar to you, as they are similar to ones that websites and broadcasters use to predict the weather tomorrow and a couple of days beyond. They are the constantly evolving result of a continuous effort by a large community of researchers and technicians that gather the basic weather data needed to parameterize those models, as well as scientists and programmers that incrementally improve the realism and accuracy of the models.
Methods for estimating the emissions of carbon dioxide in space and time are evolving as rapidly as the climate models. In the U.S., an early, intense NASA-sponsored project called VULCAN compiled data from sources as disparate as power plants, automobiles and residential and commercial spaces.
Global emissions are more challenging, especially where detailed country-level data are not available. Current methods include an ingenious combination of population density, economic activity, large point sources like power plants, and images of nighttime lighting across urban-to-rural areas. These nighttime images are an intriguing visual summary of both population density and degree of economic development.
The effort to create data sets of carbon dioxide emissions based on written reports from public and private sources is time-consuming and perhaps subject to reporting errors. Why can’t we just measure carbon emissions directly?
Maybe we can. Estimates of carbon dioxide emissions can be inferred from high resolution satellite measurement of the distribution of this gas in a column of air. This is the goal of NASA’s relatively new Orbiting Carbon Observatory-2 (OCO-2).
Launched in 2014, OCO-2 determines the concentration of carbon dioxide in a column of air by measuring the absorption of sunlight reflected off the surface of the Earth. As with both lab and other remote sensing strategies, OCO-2 uses the “signature” of light absorbance at particular wavelengths to quantify the abundance of carbon dioxide.
Early results from these more detailed and repetitive measurement of carbon dioxide have been applied at scales ranging from the impact of size and density of cities up to a second global visualization, this time in three dimensions, of carbon dioxide concentrations in the atmosphere (see link under Sources).
Data, art, science; in a sense they all come together in that first video, conveying so much about the Earth system (more than 1.8 million words worth?). And this is just one in a series of complex and innovative technologies that allow us to visualize (or “see”) our world and how the global environment both works and is changing.
Sources
Earlier essays in this series have extolled the power of new technologies and networks that allow us to “see” our world. We’ve looked at the technologies revealing the radiational energy balance of the planet, changes in the massive ocean current known as the Gulf Stream and its connection to the global ocean circulation system, carbon balances of forests and preferential warming in the Arctic. Each of these matched a cutting edge technology with the kind of detailed, time-intensive field-based measurements that tie images from space to processes on the ground (or ocean).
The NASA image and video, with narration by Dr. William Putnam, lead scientist on the project, are here:
https://svs.gsfc.nasa.gov/11683
The “1000 words” expression has a long and interesting history. Here are a couple of references
https://en.wikipedia.org/wiki/A_picture_is_worth_a_thousand_words
from The Dictionary of Clichés by James Rogers (Ballantine Books, New York, 1985).
https://finance.yahoo.com/news/minute-video-worth-1-8-130000033.html
The Keeling Curve is here:
https://keelingcurve.ucsd.edu/
A good book on what goes into deriving the computer-generated predictions of weather is:
Andrew Blum. 2019. The Weather Machine: A Journey Inside the Forecast. Harper Collins Publishers.
Images of the Earth at night are here:
https://www.nasa.gov/sites/default/files/thumbnails/image/earthatnight-cover.jpg
An introduction to the VULCAN project is here:
https://vulcan.rc.nau.edu/About.html
https://vulcan.rc.nau.edu/assets/files/Gurney.ES&T.2009.pdf
One approach to summarizing global carbon emissions is here:
https://ourworldindata.org/co2-emissions
One example that uses nighttime lighting in estimating spatial patterns of carbon emissions is here:
https://essd.copernicus.org/articles/10/87/2018/
The OCO-2 satellite and mission are described here:
https://www.nasa.gov/mission_pages/oco2/index.html
The visualization of OCO-2 data over Los Angeles is here:
https://www.nasa.gov/feature/jpl/new-insights-from-oco-2-showcased-in-science
A second visualization of a year of carbon dioxide concentrations built on OCO-2 data is here: