Warming to the task

BOULDER — If there were no data on the changing levels of carbon dioxide in the atmosphere, deciding on the next steps in environmental protection would be based on a hunch.

Considering the broad nature of implications and the expense for addressing the impact humans have on the climate, the data must be objective, accurate and thorough.

For that reason, Pieter Tans, senior scientist with the Earth System Research Lab at the National Oceanic and Atmospheric Administration in Boulder, leads a team that collects, analyzes and maintains data on carbon dioxide levels as well as other greenhouse gases.

Tans’ decades of work in the field of global carbon cycles have earned him awards and continued to set the bar for air-quality comparisons from different locations and at different times.

The Carbon Cycle Greenhouse Gases Group in NOAA’s Global Monitoring Division measures carbon dioxide in the air that’s collected from about 70 different locations including the Middle East, Antarctica, Australia, Africa and the desert in Mongolia.

Independent measurements are made by both NOAA and the Scripps Institution of Oceanography in La Jolla, California.

“We compare information from different labs to document that it’s true,” Tans said.

Big news in May was that the daily mean concentration of carbon dioxide in the atmosphere of Mauna Loa, Hawaii, one of the primary air-quality test sites, surpassed the 400 parts-per-million, or ppm, level for the first time since measurements began in 1958.

Countries target an agreed-on 450 ppm as the maximum level acceptable in limiting the damage from global warming.

The average carbon dioxide level was about 280 ppm in the 19th century before the Industrial Revolution, Tans said. The rate of increase today is more than 100 times faster than the increase that occurred when the last Ice Age ended.

“This is higher now than it has been in the last 4 million years. We have measurements from air bubbles in ice that go back 800,000 years. The bubbles are a sample of the air quality then,” he added, explaining the method for attaining the information.

Ongoing measurements help researchers study where carbon dioxide, as well as other greenhouse gases, go, what natural processes release them and what human activities increase them.

Carbon dioxide is credited as the most significant greenhouse gas contributing to climate change. In addition to natural processes that cause release of the gas into the atmosphere, high levels are created by fossil-fuel burning, Tans said.

“CO2 and temperature are coupled,” he said. “We know from physics that more CO2 in the atmosphere will lead to higher earth-surface temperatures.

“The debate isn’t about the global warming hypothesis – the debate is how fast and how far it will go.”

That’s why accurately and consistently monitoring levels of greenhouse gases is so important.

The method Tans uses to measure carbon dioxide was originally developed by David Keeling of the Scripps Institution of Oceanography and first utilized in 1958 at Mauna Loa.

The slopes of the Hawaiian volcano were an ideal site because they were away from urban sources and vegetation – both seen as contributors to changes in carbon dioxide levels.

Mauna Loa’s location also allows for measurement of the air from most of the northern hemisphere because of wind patterns, Tans said.

When Keeling started studying carbon-dioxide measurements there and at other locations, he found a consistency in the numbers derived from air in a variety of locations – from forests to cities. This consistency was not detected prior to his work because the methods of collection were far less accurate than his.

The discovery led Keeling to see that the earth system might behave with more regularity than was previously believed and that it was necessary to continue to collect these accurate measurements to reveal the regularity.

Both factors lay the foundation for a solid study of air quality.

Keeling also discovered a regular shift in carbon dioxide levels because of seasonal cycles that caused growth and decay of land plants. The trend now is referred to as the Keeling Curve.

“Keeling started this and he did everything right from day one, including maintaining quality control by comparing two different samples,” Tans said.

“As the operation has grown, we’ve made sure we have a data management system that can keep up so we can store all the results and make them available to all of the world on our website.”

The data is a springboard for numerous studies worldwide.

Along with about 25 people on his team, Tans measures, analyzes and documents readings for about 50 greenhouse gases.

“We want to get an understanding of what the earth itself is doing with this excess of gases we’ve caused, and we want to quantify human-caused emissions because ultimately it has policy implications.”

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