Thirty years ago Charles F. Baes, Jr., a chemist at the U.S. Department of Energy’s Oak Ridge National Laboratory, wrote that the earth was undergoing a great “uncontrolled experiment,” one that would soon reveal the global consequences of rising greenhouse gas concentrations. Today scientists know that deforestation, land use and the burning of fossil fuels are warming our planet. We are less certain, however, about how climate change will alter forests and grasslands, as well as the goods and services these ecosystems provide society.
Much of the climate change news in the mass media comes not from experiments but observations. Scientists monitor Arctic sea ice, glaciers and natural events such as the timing of leaf appearance and inform the public when changes fall outside normal expectations. Recording this kind of information over time is important. But rather than waiting to see how an evolving climate slowly alters the biosphere, climate change biologists are conducting field experiments, often at large scales, to see how ecosystems will respond to more or less precipitation, rising concentrations of carbon dioxide (CO2) and warming temperatures. Experimental data are key to determining if and to what extent ecosystems will be affected by climate change in 10, 50 or 100 years and how those changes might feed back to further advance change. The results can help separate fact from fiction in the climate debate, which is charged with emotion.