Private investigator Dean Krell steps down from a trailer onto a dirt road in central Kansas, looks at his watch, and at exactly 1400 Greenwich mean time releases a four-foot weather balloon.
As the balloon disappears into a cloudless sky, expensive instruments inside the air-conditioned trailer beep and hum. Mr. Krell returns to the trailer to monitor the flight, jotting down data on a clipboard.
Krell, a retired undersheriff, admits he isn't 100 percent sure why the federal government is collecting 24-hour-a-day readings of atmospheric conditions from the rural station outside Hillsboro, Kan.
"I tell people that if they notice some strange equipment, it's because [the government] is really trying to make contact with flying saucers," says Krell. "I don't mind if they are, as long as they pay me."
In fact, Krell, along with the farmers, housewives, and others who help man the station, is engaged in a vital experiment - the Atmospheric Radiation Measurement Program (ARM) - aimed at providing the missing link in scientists' knowledge of global warming.
The 10-year, $450-million project began in 1992 and now ranks first in priority among the more than 150 projects overseen by the multiagency US Global Change Research Program (GCRP), officials say.
More immediately, ARM data are being used by several other US agencies, including the National Aeronautic and Space Administration (NASA), the Department of Defense, the Central Intelligence Agency (CIA), and the National Weather Service, in offshoot projects that range from improving missile defense and guidance systems to providing better forecasting of droughts, severe thunderstorms, and tornadoes.
"No other facility can provide this type of data," says Gerald Romick, a Johns Hopkins University scientist under contract with the Ballistic Missile Defense Organization to improve the accuracy of the MSX satellite launched last April.
The focus of the project, however, is global warming. Scientists broadly agree that warming is occurring, according to a report issued last December by the intergovernmental panel on climate change, a group of about 2,000 scientists from around the world. Greenhouse gas pollution (from burning of fossil fuels) contributes to some degree to the warming trend, the report concluded.
Among the uncertainties, however, is how clouds will affect the warming. Some think clouds will trap warmth around the earth, thus amplifying the trend.
But others believe clouds act as natural thermostats that can slow the warming, both by producing rain and by reflecting sunlight back into space.
"We do not have a really solid understanding of the impact of clouds on long-term climate variability, and that is where the ARM program fits in," says Tom Baerwald, deputy assistant director for Geosciences at the National Science Foundation (NSF).
"[ARM] is extremely important because it focuses directly on the crucial uncertainty in global climatology."
ARM data will allow scientists to devise more sophisticated weather models that take into account the complex interplay of clouds and solar radiation.
The models, in turn, will help generate predictions of how global warming will affect the earth's environment in the coming century.
"We want to find out what will be the effect of climate change on the United States in the next 50 to 100 years," says Jim Teske, an ARM site operations manager.
"If the answer is that all the food production for the world moves north to Canada and Russia and we end up growing cactus, that would be a big impact."
To answer that question, ARM is taking the largest continuous set of readings on the earth's atmosphere ever made. Driving the experiment is a novel, cost-effective philosophy of scientific research.
Instead of sending a group of highly paid scientists into the field to spend two weeks at a time gathering data, ARM uses sophisticated new instruments to collect years of continuous information with routine maintenance by local hires such as Krell and others from the Hillsboro area.
At its primary research site - a 55,000-square-mile swath of Kansas and Oklahoma in the southern Great Plains - ARM has installed the world's biggest collection of advanced remote sensing devices to record temperature, wind speed and direction, humidity, and atmospheric pressure.
From the Midwest, data are sent via the Internet to the Energy Department's Pacific Northwest National Laboratory in Richland, Wash.
There, it is packaged daily for 100 scientists around the world who are creating more sophisticated weather models.
Two other sites, in the tropical western Pacific and on the North Slope of Alaska, are under way. All three ARM sites are located in areas of intense weather conditions to better test theories about global warming.
For example, the tropical western Pacific site - a 5,000-mile-long stretch along the equator from Indonesia to Christmas Island - covers an area with the warmest sea temperatures on the planet.
Cloud systems formed over this "warm pool" help regulate the amount of solar energy reaching Earth and how much heat escapes from Earth to space.
The Alaska site will allow researchers to study the impact of global warming on an icy, snowy area, as well as on the major "pumps" for global ocean currents located nearby.
Similarly, scientists set up the main ARM site in the Great Plains storm corridor known as "tornado alley" to test a prediction that warming will increase the number of tornadoes and hurricanes - the earth's climatological safety valves.
The region's pristine air quality also better approximates natural weather patterns without the distorting effect of man-made greenhouse gases.
"We should see more intense thunderstorms, more flooding, and more severe hurricanes in coming years," predicts Douglas Sisterson, a program manager at Argonne National Laboratory near Lemont, Ill. The Argonne laboratory operates the ARM Great Plains site for the US Energy Department.
Such momentous predictions don't concern Krell, who worries more about the minute-to-minute logistics of the weather balloon launches at the Hillsboro station.
"We don't want to even lose one flight, each one is so expensive," says Krell, as crickets chirp in the grass around him.