Summing up

The extremely complex interrelations between human activity and natural forces—air masses, winds, ocean currents, evaporation, and precipitation—means that researchers from many fields pool their efforts in an attempt to understand how the climate is reacting to changes. But this complexity also means that knowing what the climate will be like in fifty or one hundred years is among the most challenging problems in science. Some of the changes researchers in all these areas are exploring may seem small, especially in relation to the typical temperature changes associated with daily and seasonal cycles. But although regional and short-term temperatures do fluctuate over a wide range, global temperatures are generally very stable. Indeed, during the last Ice Age (about 20,000 years ago), the average global temperature was only about 5°C cooler than it is today. The fact that seemingly small changes can have dramatic effects is one reason why an understanding of the data, techniques, and controversies of global climate research is so fundamental to understanding the phenomenon itself. We’ve collected and discussed some of the data on the following pages to give you a sense of how the problem is being studied—and what all that research may be telling us.

more sites on the scientific debate about global climate change • Intergovernmental Panel on Climate Change (IPCC) - A comprehensive assessment of policy-relevant scientific, technical, and socioeconomic dimensions of climate change by a UN-established scientific panel. • Climate Science and Policy: Making the Connection - A review of the IPCC report on climate change by a panel of distinguished scientists, who disagree with the IPCC findings. • Climate Change Science: An Analysis of Some Key Questions - A 2001 report from the National Research Council with discussions of natural climate variation, human effects on climate, and estimates of future climate change.