Its new report, the update of a volume published in 1990, was completed this month. This bespeaks the struggles of a community trapped between the orderly reasoning of scientists who must work with limited data, and the pragmatic demands of policy makers. But in comparison to the assessment made 5 years ago, the new IPCC report shifts toward implicating human activity. For the first time since the Antarctic ozone hole, human activity is a leading suspect in a global-scale climate change. The IPCC's increased concern is driven by recent improvements in computer models of Earth's climate.
Aerosols represent one more piece of the global warming picture that is fitting into place.
There is consensus among researchers about some aspects of the global warming issue. Scientists generally agree that the global average temperature rose about 1.5 degrees F over the past 100 years. If this increase were to continue, rainfall patterns and growing seasons would alter, polar ice would melt at a faster pace, and extreme weather could become commonplace. The disruption to water supplies, agriculture, coastal settlements, and natural habitats would be monumental. Circumstantial evidence for human involvement in global warming is easy to find.