One of the most common problems I encounter in discussions with people regarding climate change is the confusion of âÄúclimateâÄù with âÄúweather.âÄù âÄúWeatherâÄù is a word used to describe the atmospheric conditions such as wind, temperature, humidity and precipitation âÄî conditions that occur in the short term and on a limited spatial scale. Not surprisingly, weather is highly variable; in 2007 Chicago had 60 inches of snow, while in 2006 it received a little over half that amount. âÄúClimate,âÄù on the other hand, is used to describe long-term patterns in these parameters. To return to the Chicago example, average snowfall has varied by almost an entire order of magnitude (from a minimum of 10 inches to a maximum of 90 inches) since 1885, but the average has changed fairly little. Another major issue is the mistaken interchangeable use of âÄúglobal warmingâÄù and âÄúglobal climate change.âÄù âÄúGlobal warming,âÄù by definition, is merely an increase in the average temperature of the entire planet. It does not mean that every day this year will be warmer than last year or that all parts of the globe will warm equally. Indeed, most models predict that higher latitudes will experience more dramatic increases of temperature than lower latitudes, and there may also be regions that experience a cooling trend. It is important to remember, however, that an increase in average global temperature is more a harbinger of greater problems to come than a problem in and of itself. What is more worrisome is the impact that minute changes in temperature might have on atmospheric processes that either benefit or threaten human civilization. One commonly used example of a change in climate associated with global warming is the predicted increase in the severity and/or frequency of tropical storms. These systems draw energy from warm tropical waters, so even a slight increase could dramatically enhance the destructive potential of winds and storm surges. A much graver problem may be changes in precipitation patterns that increase the rate of desertification, particularly in developing countries where agriculture is critical for economic development as well as subsistence. It must be stressed that many of these predictions exist largely in model or theoretical forms, but that does not mean that such results should be ignored. In a democratic society such as ours, open debate is essential for sharing ideas and developing policies and social norms that are conducive to our economic and cultural development. However, such debate requires a more complete understanding of the matters at hand, especially the language used, than many citizens receive through mass media outlets. I hope I have clarified some of the semantic issues encountered in such conversations. Jacob Osborne, University graduate student