This December, world leaders will meet in Kyoto, Japan to sign an amendment to the Rio Treaty that will establish strict targets and timetables for reducing carbon dioxide and other "greenhouse" gas emissions. The central premise of the amendment and of the treaty itself is that atmospheric concentrations of these gases are growing at an alarming rate, increasing global temperatures, threatening our environment and our very lives.

President Clinton is likely to sign the amendment even though U.S. compliance costs are expected to run into the hundreds of billions of dollars each year, arguing that the threat to the environment justifies these costs.

The media should be skeptical. As they prepare to cover the Kyoto summit, journalists need to ask four crucial questions.

Is global warming occurring and, if so, how much?

Since the end of the last Ice Age, the planet has warmed by roughly 1.5 degrees Celsius, but there is little evidence that this warming trend has continued over the past 50 years.

According to Intergovernmental Panel on Climate Change (IPCC) climate models, by now global mean temperatures were supposed to be rising at a rate of 0.3 degrees Celsius per decade. But satellite and weather balloon measurements show a slight cooling trend while ground level measurements indicate warming of about half the projected amount. In either event, the temperature fluctuations are modest.

Would life be better with or without global warming?

Evidence suggests that even if global warming does occur, it could be beneficial.

While the scientific community is divided over many aspects of the global warming theory, the effect of global warming on precipitation levels is not one of them: Global warming would mean more condensation and more evaporation, producing more and/or heavier rains. With one-third of the world's population currently suffering chronic water shortages, global warming could save billions of people from malnutrition, economic despair, or even death.

If history is any indication, greater precipitation may be only one of many benefits of global warming. For example, between the 10th and the 12th centuries, when the planet's temperature was roughly 0.5 degrees Celsius warmer than it is today, agriculture in North America and Europe flourished and the southern regions of Greenland were free of ice, allowing cultivation by Norse settlers. Prior to the onset of this Little Ice Age, temperatures were comparable to those forecast by the U.N.-sponsored IPCC, the international body which monitors temperature change, for 2030-2050.

Global warming could also mean greater agricultural productivity and greater water conservation as CO2 acts as a fertilizer on plant life while reducing plant transpiration (the passage of water from the roots through the plant's vascular system to the atmosphere).

Is global warming the result of natural phenomena or human activity?

Scientists don't fully understand the role of natural CO2 emissions on climate, much less the role of human emissions. Earth was in the grip of an ice age 440 million years ago, despite the fact that CO2 concentrations were up to ten times current levels.

There is similarly little evidence of a link between human CO2 emissions and climate change. Two-thirds of the rise in global temperatures since the mid-19th century occurred before 1940, when carbon dioxide emissions from human activities were still minimal. Further, despite a more than 19 percent rise in such emissions since 1979, the planet temperature has cooled slightly over the past 18 years by 0.9 degrees Celsius.

Is the cure worse than the disease?

The initial objective of international negotiators is to reduce CO2 emissions to their 1990 levels by the year 2000, with further reductions slated for 2010 and 2020. Just stabilizing these gases at 1990 levels could cost one to three million jobs in the U.S., according to CONSAD Research Corporation.

The economies of developing nations would pay an even higher price. Over the next two decades as much as 60 percent of all carbon emissions will come from the developing world, meaning that strict emission controls on these nations will be required.

World leaders are thus preparing to impose enormous costs on the world's people to stop a phenomenon that may not exist, could be a net plus if it does, and may be impossible for human beings to control in any event. The media can contribute to a more thoughtful, rational policy debate by asking these four questions.

David A. Ridenour is vice president of The National Center for Public Policy Research ( Reliefrprt@aol.com or 202/543-1286)

— Rich Noyes