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		Earth's climate has shifted dramatically over the millennia. Ice ages and warm periods have come and Ed Carmack says... gone. But those changes transpired over thousands or millions of years, in response to natural processes. With the aid of pollen records, fossils and ice cores, scientists have extended our record of climate back in history to show that the global average temperature has increased in the last thousand years, but almost all of that increase has occurred in the last hundred. Since the advent of the industrial revolution, Ken Denman says... higher and higher concentrations of greenhouse gases have been emitted into the atmosphere, primarily through the combustion of fossil fuels – coal, oil and gas. In 1896 the Swedish chemist Arrhenius theorized that carbon dioxide emissions from the burning of coal would amplify Earth's natural greenhouse and warm the planet. A little less than a hundred years later scientists came to the consensus that human beings were responsible, at least in part, for global warming. David Fischer says... Assigning blame for global warming is a tricky business. The U.N.-appointed Intergovernmental Panel on Climate Change agrees climate change is occurring, but the interactions between climate determinants – solar radiation, ocean currents, evaporation, wind, precipitation, clouds – are complex. Scientists are attempting to distinguish between ordinary climate variability and human-induced change.			John Fyfe says... Whatever the cause, the Earth certainly appears to be warming. Here in Canada, increases in average temperature have been observed in most regions, significantly more than the globally averaged increase, and more pronounced in northern latitudes. Glaciers are melting in the Canadian Rockies. * Extreme weather events may be occurring with increased frequency, although this issue is complex. * People in the Arctic are noticing profound changes unheard of in their oral history, the disappearance of stable multi-year ice for instance, or the slumping and melting of permafrost. Fritz Koerner says... Explaining these phenomena is difficult enough. Predicting future events, and what these will mean for human populations, is an even more daunting task. To this end, scientists have developed complex computer models, about 140 of them, running on supercomputers around the world. Humfrey Melling says... How extreme will climatic changes be? Can we prevent them from happening or at least mitigate their severity? Will we be able to tolerate them? How will they vary region to region? Will we be able to adapt? These are questions scientists are trying to answer, but they are also questions for all of us.

	The following voices (and more) are featured in Change, Episode Two of the ClimateWatch audio series
	ClimateWatch is a series of audio documentaries and public service messages about Earth's atmosphere, climate change and global warming. This five CD set is available to university, community, public and commercial radio stations, and to educational and academic users. Follow the Orders link. Home | Origins | Change | Impacts | Action | Voices | Lexicon | Orders | Links | Contact us Thursday, March 6, 2003 Copyright © 2003 ClimateWatch.net, Earth Chronicle Productions