Atmospheric carbon hits historic levels, raising
the stakes for adaptation

Jan. 31, 2014 |

Global emissions of carbon dioxide from the burning of fossil fuels rose to a record 40 billion tons in 2013, driving the atmospheric concentration of the greenhouse gas to a level not seen in human history.

“You have to go back three to five million years to find carbon dioxide concentrations this high,” says John Kutzbach, a member of the Wisconsin Initiative on Climate Change Impacts and former director of the Nelson Institute Center for Climatic Research (CCR) at UW-Madison.

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Since regular CO2 measurements began in the late 1950s, the average level of carbon dioxide in the atmosphere has gone from 315 to nearly 400 ppm.

The average carbon dioxide (CO2) level in the atmosphere has reached 396 parts per million and briefly topped 400 last spring. That’s up from 315 in the late 1950s, when regular atmospheric measurements of CO2 began. The pre-industrial level was about 280 parts per million.

Higher levels of CO2, methane and other greenhouse gas pollutants are driving up the Earth’s average temperature and causing an increase in powerful storms, droughts and other extreme weather events. The National Oceanic and Atmospheric Administration reports that 2013 tied for the fourth warmest year since 1880, continuing a long-term trend of rising global temperatures.

None of this surprises Kutzbach, an emeritus professor of atmospheric and oceanic sciences who has studied the relationship between carbon and climate throughout his career. He is a member of the National Academy of Sciences and has served on several of its expert panels on climate change since the late 1970s.

“An early Academy report said that carbon dioxide levels were rising, global temperatures were going up, and the connection between them was almost certain,” he explains. “The estimates we made then as to the amount of temperature increase (per additional unit of carbon) turn out to have been accurate.”

Subsequent reports have warned that global warming would cause melting of mountain glaciers, rising sea levels, changing rainfall patterns and other effects now being observed.

“It’s an accelerating trend, and one of the great challenges is for us to figure out how to slow and ultimately stabilize these emissions,” says current CCR director Jack Williams, a UW-Madison professor of geography and environmental studies.

In the meantime, he says, adaptation efforts such as the Wisconsin Initiative on Climate Change Impacts are critical.

“There’s a lot of work going on around adaptation planning right now,” says Williams. “But the faster things change with respect to CO2 levels and the climate change that will come out of that, the harder it is to adapt. That’s true for socioeconomic systems; it’s true for ecological systems. Faster changes are harder to adjust to than slower changes.”

Williams, who studies the historical impact of climate change on ecosystems, says the current rate of change poses unprecedented challenges for both nature and human society.

“Many of the species around us haven’t seen carbon dioxide at this level in their evolutionary lifetimes,” he explains. “If you combine that with rising temperatures, some parts of the world will be moving outside the range of what we’ve seen. We have this general challenge of novelty: How do we plan for and adapt to climates and an atmosphere that are outside of our current experience?”

Greenhouse gas emissions, climate change and the resulting impacts pose some of the most critical challenges facing scientists and decision makers, according to Williams.

“This is what we’ll be measured for by future generations,” he says. “What solutions did we come up with to tackle this problem?”