Ever since global warming became a major issue, scientists have been discovering a blizzard of bewildering new data, feeding it into computer models, trying to frame the planet's present course and to project its future.
New facts _ and questions _ will be at hand for policymakers gathering in Bonn, Germany, beginning Monday to resume negotiations that collapsed last November on controlling the greenhouse gases blamed for the warming of the Earth.
Among the new research: Measurements collected since Cold War subs prowled under the arctic ice show the ice cap is getting thinner. But why? Is it global warming or a natural cycle _ or both?
In the Himalayas, the Andes and other middle latitude mountains, glaciers are receding, while others in high latitudes like Scandinavia are expanding. In the coming decades, parts of the Earth will get less rain, while some will get more. What does this mean for food production and freshwater supplies?
Also puzzling: As temperatures climb, the Earth's cloud cover will grow and reflect more sunlight, cooling in some places but perhaps warming others. No one is sure what effect this will have.
This week, at a conference of 1,500 scientists in Amsterdam, only a few basic assumptions were universally accepted: that Earth is indeed getting warmer because of human activity; that the warming already has begun to change our lives and the trend will increase; and that we ought to do something about it.
"Global change is real, and it is more serious than is perceived politically," said Berrien Moore III of the U.N. Intergovernmental Panel on Climate Change.
A report published by the panel this week documented evidence that the Earth is warming faster now than at any time in the previous 1,000 years and that the concentration of carbon dioxide in the air is higher than it has been in the past 400,000 years.
The Kyoto Protocol, set in 1997, outlined targets and timetables for industrialized countries to reduce emissions. Further negotiations on how to reach those targets have become embroiled in contention, pitting the United States against its European allies, and poor nations against the rich.
Since then, Washington has made prospects for an agreement dimmer. In March, President Bush renounced the U.S. commitment to Kyoto, calling it a flawed plan that would harm the U.S. economy.
The top U.N. climate official, Michael Zammit Cutajar, said parts of the treaty could be reconsidered if it would persuade Bush to retract his withdrawal from Kyoto _ but the basic concepts should remain.