Smit, a member of the Scientific Advisory Committee to the UN Environment Program and a contributor to the Intergovernmental Panel on Climate Change, says low water levels in bodies of water as large as the Great Lakes can be expected even without global climate change and shouldn't come as a surprise. But they may become more frequent and severe with a changing climate.

  "Water is extremely sensitive to climate change," he says. "The lower rainfall in the past few years combined with high evaporation inevitably results in lower lake levels."

  But according to Smit, reports that the average temperature has risen and that Canada is seeing less precipitation in general must be interpreted with caution. Climate is naturally variable, he says, and temperatures and precipitation levels are expected to fluctuate from year to year. That's why a period of at least 30 years must be examined to identify patterns and to determine if fluxes in temperature and precipitation are meaningful.

  Smit agrees there have been frequent dry spells in Canada in recent years and that the low water levels of the Great Lakes are a serious concern. He says these conditions could be associated with climate change and shouldn't be ignored. But he notes that in two years, water levels could be way up again, and he encourages people to look at the other side of the story - how humans deal with variations in water supplies.

  Growing populations and the high quality of life that much of society enjoys contributes to climate-related problems such as water shortages and water-use restrictions. For example, more people drawing from drinking-water reserves to wash their cars and water their lawns - combined with dry spells - places stress on water supplies. Smit suggests that people start thinking more seriously about water management and the way they use water.

  "Very few people think we are having a water supply problem," he says, "but water is a crucial resource, and we need to manage it efficiently to avoid serious complications."

  Humans are also part of the equation because of the way they respond to - and cope with - climate variation, says Smit. Coping ability and methods are greatly influenced by social, economic and political conditions. Western societies are fortunate in that technological advancement and economic stability have provided early warning systems, insurance policies and relief programs to help deal with climate-related risks, he says.

  But in many developing countries, it's a different story. In Ethiopia, for example, a severe dry spell can lead to malnourishment and starvation; in Canada, it may be little more than an inconvenience.

  In the end, it remains an issue of society managing its resources effectively, says Smit. "Decision-making must ultimately be based on the knowledge that climate is inherently variable. When people make foreign investments or plan a vacation, they count on currency being changeable. We must remember that climate is unpredictable, too, and incorporate that knowledge in our plans."

  This research is sponsored by the Ontario Ministry of Agriculture, Food and Rural Affairs and the Canadian Meteorological Service.