Greenhouse effect, global warming?

IU team participating in data collection to monitor a fragile environment

By Susan Williams

Sue Grimmond (right), IUB associate professor of geography, shows the IU tower in Morgan Monroe State Forest to a group of international visitors who were participants in a meeting of one of the working groups of the InterGovernmental Panel on Climate Change (IPCC). The IPCC was established by the World Meteorological Organization (WMO) and the United Nations Environmental Program in 1988 to assess information on climate change and its impacts, and to formulate response strategies.

The global importance of atmospheric science research is represented by an IU team working in Morgan Monroe forest. Team members, with the tower distantly behind them, include (from left): Hans Peter Schmidt (Switzerland), assistant professor of geography; J. C. Randolph (Texas), professor of public and environmental affairs; Ford Cropley (England) and Hong-Bing Su (China), post-doctoral fellows in geography; Jeff Ehman (Indiana), a doctoral candidate in SPEA; and Sue Grimmond (New Zealand), associate professor of geography.
Hong-Bing Su, a post-doctoral fellow working on the IU Morgan Monroe State Forest Project, stands at the foot of the 150-foot tower to explain the tower's function, instrumentation and results to IPCC visitors.
Photos by Heather Hill

Eagles reintroduced as part of a program for the protection of endangered species fly high above the canopy of foliage in Morgan Monroe State Forest. Sharing the birds' air space, a sentinel-like tower "keeps watch," taking measurements designed to contribute to the bank of knowledge on exchanges of carbon dioxide between a mixed deciduous forest and the atmosphere. Hopefully, this data will further the understanding of environmental issues such as global warming and the greenhouse effect.

The IU tower is one of a number of North American data collection sites in a global research network (FLUXNET) funded in part by the Department of Energy's National Institute of Global and Environmental Change (NIGEC). North American sites are part of Ameriflux, while European sites are known as Euroflux. About half of the North American towers, including IU's, are located in forested areas while the rest are in grasslands, crops, wetlands or arid sites.

"The basic rationale of the research is driven by a need to better understand increasing concentrations of carbon dioxide in the atmosphere," explained Sue Grimmond, IUB associate professor of geography in the Atmospheric Science program and director of the IU site, who says those values have increased from 280 ppm to more than 360 ppm over the past century.

"Such increases, it is believed, will result in an enhanced greenhouse effect and global warming."

The tower, which is 150 feet tall, supports equipment that measures very rapid fluctuations in wind, and the exchange of carbon dioxide, water and heat between the forest canopy and the atmosphere. Thus, it is equipped to measure not only the concentration of CO2 in the atmosphere, but also the "flux," the actual exchange processes between the Earth's surface and the atmosphere.

Instruments mounted on the tower then pump air down to gas analyzers in an instrument shelter at ground level. Grimmond said that measurements are taken above the canopy so that the integrated response of the forest can be measured, not just the behavior of individual trees.

According to Grimmond, while it is well established that the concentration of carbon dioxide in the atmosphere is rising, the potential and actual role of terrestrial and marine ecosystems in offsetting the increase is open to debate.

"Current estimates of CO2 exchange between the oceanic, terrestrial and atmospheric carbon reservoirs and the source (anthropogenic carbon derived from burning fossil fuels and deforestation) leaves a considerable amount of carbon unaccounted for. This has resulted in the so-called 'missing sink' problem.

"Put simply, estimates suggest that more carbon is being released into the atmosphere than is being measured in the atmosphere. Where is this carbon going? What systems are taking it up? How long can they continue to do so? What potential exists, if any, to increase this uptake?"

Hans Peter Schmid, IUB assistant professor of geography, is principal investigator along with Grimmond in undertaking carbon dioxide measurements. Other collaborators are: ecologist J.C. Randoph, IUB professor of public and environmental affairs; and atmospheric scientists Sara Pryor, assistant professor, and Rebecca Barthelmie, associate professor, both in geology.