My official title is Research Ecologist with the United States Geological Survey. But more and more I find myself having common cause with distilleries and those who engage in that craft. To explain the complexity of changes wrought by humans on their environment and Earth’s climate system requires careful distillation of a complex and often chaotic literature into something understandable, digestible, and hopefully insightful. But the quality of the scientific information matters, just as the quality of the water and grains would matter to a distiller. So I often find myself on missions of discovery, where I seek those myriad acts of minor genius that have resulted in exquisite visual explanations. These are the finely crafted scientific artifacts that can declutter and focus the mind, expanding our understanding of the causes and consequences of our actions as a species.
This is why, when discussing the basics of human-caused climate change with the public, I am so fond of the graphic on the preceding page, produced by the National Oceanic and Atmospheric Administration’s Global Monitoring Laboratory. The original graphic is an animated tour de force. What’s shown here is a static version, but the information content for purposes of visualizing climate is just as striking. The figure shows trends in atmospheric carbon dioxide (CO2) from the present (at far right) back through several ice age cycles, to eight hundred thousand years ago (eight hundred kyBCE, or thousands of years before the Common Era). On this longer timescale, the carbon that humans have added to the atmosphere from burning fossil fuels is seen to be more akin to an instantaneous shock than a gradual, inexorable increase that is observed over a person’s lifetime. This is the source of human-caused climate change.
For hundreds of thousands of years, carbon dioxide levels in the atmosphere cycled up and down as ice ages ebbed and flowed. These changes affected and were affected by shifts in global temperature, and CO2 concentrations ranged between about 185 and at most 300 parts per million (ppm), or about 0.03 percent of the earth’s atmosphere. But since the beginning of the Industrial Revolution, carbon dioxide concentrations in the atmosphere have risen to levels unseen on Earth in the last three million years: about 69 ppm in the first 235 years, to 347 ppm, and another 69 ppm in just the last thirty-five years. The response of our planet’s climate system to this shock is an imbalance in incoming versus outgoing energy (or a radiative forcing in the technical parlance), and a resulting increase in Earth’s temperature and attendant changes in the climate system. According to the latest report issued by the Intergovernmental Panel on Climate Change, “Human influence has warmed the climate at a rate that is unprecedented in at least the last two thousand years.
To view the visualization shown here in its original animated form, visit gml.noaa.gov/ccgg/trends/history.html.
For more from the IPCC report referenced above, see: IPCC, 2021: Summary for Policymakers. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Eds. Masson-Delmotte, V., P. Zhai, A. Pirani et al. Cambridge University Press. In press.
Data sources for the visualization include the following:
Bereiter, B., Eggleston, S., Schmitt, J., et al. 2015. “Revision of the EPICA Dome C CO2 record from 800 to 600 kyr before present.” Geophysical Research Letters 42.2: 542–549. doi.org/10.1002/2014GL061957
Scripps CO2 program, Scripps Institution of Oceanography. Keeling curve data, 1959-2021 CE. scrippsco2.ucsd.edu
Rubino, M., Etheridge, D. M., Trudinger, C. M., et al. 2013. “A revised 1000 -year atmospheric δ13C-CO2 record from Law Dome and South Pole, Antarctica.” Journal of Geophysical Research: Atmospheres 118.15: 8482–8499. doi.org/10.1002/JGRD.50668