TOMORROWLAND Inside this enclosure, scientists simulate the conditions of 2111. Photo by Chad Greene; imaging by catchlightdigital.com

It's a cold day to visit the future. The road that leads there is an unassuming gravel path that winds through the wooded hills of eastern Tennessee near the Oak Ridge National Laboratory, where Manhattan Project scientists helped develop the atomic bomb more than half a century ago. Past fenced-in fields and groves of tall trees, a strange, silvery structure appears in a grassy clearing.

"Right here it's 2011," says Stan Wullschleger, a plant biologist and 20-year veteran of environmental projects at Oak Ridge. "But you walk through that door and you're 100 years in the future." Ducking his head, Wullschleger steps into an octagonal chamber nearly 40 feet across and 26 feet tall. The walls are made of the sort of plastic panels used in commercial greenhouses. It's warm inside.

Electrical wires jut from the ground and connect to an array of gadgets and gauges that precisely monitor and control conditions in what appears to be merely a plot of tall grass. Only this is no ordinary plot of grass. This is one of the world's most advanced laboratories for studying the climatic conditions of tomorrow. The discoveries made here will help scientists refine global and regional climate models and predictions -- such as those used by the Intergovernmental Panel on Climate Change (IPCC) -- and eventually inform the policies that will allow us to mitigate and adapt to environmental change. Given the importance of all of this, Wullschleger and his colleagues have built special elevated walkways to avoid crushing their study subjects: the grass, of course, and the delicate soil-based ecosystem that lies beneath.

As time machines go, this one is less Dr. Who than souped-up weather station. Thermometers and other measuring devices are everywhere, suspended overhead and mounted on metal poles, capturing key bits of information about the ways in which the ecosystem is responding to the artificially warm conditions. In the past, scientists have tried to study how plants and animals will react to climate change by pumping carbon dioxide into a bell jar or wrapping potted plants in plastic and turning up the thermostat. But those small, artificial environments miss too many of the natural variables in a real-life forest, such as wind and rainfall. This endeavor puts those variables back in the mix, explains Paul Hanson, a forest ecophysiologist at Oak Ridge and principal investigator on the project, called SPRUCE, which stands for Spruce and Peatland Responses Under Climatic and Environmental Change.

The chamber's open top eliminates the need for simulated rainfall, and anemometers track wind speed, a measurement needed to maintain air temperature. Heaters are adjusted frequently to simulate daily and seasonal temperature fluctuations. Devices on the ground measure carbon dioxide escaping from the soil, which is warmed, in this case, by dozens of vertical heat pipes buried throughout the enclosure, to a depth of nearly 10 feet.

"The reality is that in the future, the deep soils will warm too," Hanson says. "We've developed a technique to allow us to heat this portion of the ecosystem."

Even though SPRUCE is still in its test phase, it has already begun to reveal new information about the role that soil organisms play in determining local and regional carbon dioxide concentrations. As the soil warms, subterranean roots, fungi, and bacteria become more active, their respiration rates increase, and carbon dioxide emissons rise.

In early 2009, Hanson and his colleagues used a similar chamber to test how this might play out in 2100, when the average global temperature is predicted to be 4 degrees warmer than it is today. In the late spring, carbon dioxide spiked and continued to climb. By midyear, the heated plot was producing more than twice as much carbon dioxide as the control plot. Hanson says the results indicate that "there's a deep soil carbon source that past studies haven't manipulated in the way future climates would." To figure out what that source is, the scientists will need to examine root respiration and the activity of resident microbes more closely, combining such work with their study of soil warming.

The SPRUCE team will set up shop in 2013 in northern Minnesota, where 24 identical chambers will be assembled in the Marcell Experimental Forest, which is managed by the U.S. Forest Service. Over the course of a decade, the researchers will use SPRUCE to simulate various warming scenarios, and they hope the responses they witness -- in plants, animals, and other organisms -- will both illuminate how the ecosystem will evolve and expose previously unknown phenomena that play a major but hidden role in the ecosystem.

Ultimately, SPRUCE may help to reveal what even the most advanced climate models are missing: the unexpected responses that often occur in a complex and chaotic system. Whereas climate models allow researchers to predict future conditions based on past observations, SPRUCE chambers allow researchers to test those predictions, teasing out the underlying causes for a particular observation. That's what makes SPRUCE valuable, explains Werner Kurz, a senior scientist at Natural Resources Canada and a lead author on four publications commissioned by the IPCC on forestry and land use.

The panel is planning to issue its fifth report in 2014, which means data from the Marcell Experimental Forest won't be available in time. But the sixth report is likely to include these data, says the ecologist Yiqi Luo, an IPCC contributing author who studies how ecosystems regulate carbon dioxide. In his lab at the University of Oklahoma, Luo and his team fuse data from global change experiments into larger models, and he says projects like SPRUCE are "urgently needed" to verify their work.