Understanding Global Change... Definition: Global change refers to the consequences of natural processes and human activities biospheric, geospheric, atmospheric, oceanic and socioeconomic that affect the global environment directly and through the accumulation of local or regional impacts. Some global changes, such as deforestation, can be measured in days. Others, such as climate change and stratospheric ozone depletion, span decades, centuries and millennia. Imagine flying into the city of Toronto and finding it under several kilometres of ice. That is what you would have found had your plane approached Pearson International Airport 20,000 years ago. In fact, extreme minimum temperatures, associated with major global glaciations, have occurred at roughly 100,000 year intervals for the past 800,000 years. Each of these glacial periods has been followed by a dramatic 4 to 6 C warming, sufficient to create an interglacial state similar to the one which we are currently experiencing (see Figure 1). Figure 1 : Global temperature variations of the past one million years. Click here to view figure (show file size) - not available yet As you stand on the ice sheet, you might begin to realize that the planet you once thought of as fixed and unchanging is actually in a state of constant change. But this change is unlike anything to which we are normally accustomed because we operate within a shorter human time scale while the planet operates within a much longer geological one. In our twentieth century society of technological advances and engineering creativity, certain changes appear seemingly overnight. If you had left Calgary in 1970 and returned for a visit in 1979 at the peak of the oil boom, you would probably have needed a tour guide to find your way around. But in that space of time, natural conditions on the planet changed very little; so little in fact that the changes would have been imperceptible to the human senses. The contrast between the rate of human induced change and that of `natural' global change is so dramatic that it appears as though the planet is static and unchanging when it is not. When you compare the harsh environmental conditions that exist on other planets to the relatively narrow range of conditions that are necessary to support life on earth, you begin to realize how special the earth's ecosystems really are. For example, the amount of solar energy reaching our planet is, in theory, sufficient to produce an average surface temperature of only -18 C, a temperature that would not support life as we know it (remember, only 4 to 6 C differentiates our current conditions from the last ice age!). Yet we know from actual measurements that the earth's average temperature is more like 15 C, a difference of 33 C! The additional warming is due to the presence of greenhouse gases in the atmosphere (see Figure 2 comparing temperature change and atmospheric concentrations of greenhouse gases). Figure 2 : A comparison of local temperature change in Antarctica and concentrations in the atmosphere of two greenhouse gases --methane and carbon dioxide. xxx Click here to view figure (show file size) - not available yet Our planet is roughly 4.5 billion years old. Humans have been on this earth for less than two million years, but it is only in the past 200 years that we have had any significant and large-scale impact upon the global natural environment. Environmental conditions became degraded within human settlements and around the early factories of the industrial revolution, but away from these places, the ecosystem's capacity to purify and repair itself was sufficient to contain the extent of most human impact. However, since World War II this situation has changed dramatically. Exponential growth in human population, rapid technological advances, and significant increases in both material and energy consumption have put humans in a position where their daily activities are altering entire global systems such as the atmosphere and the oceans at a rate that has never before been experienced on this planet. It is the unprecedented rate of this change that is largely responsible for what we are calling global change. The global ecosystem is composed of an almost infinite number of interacting sub-systems ranging in scale from global to very local. These systems exist in a state of dynamic balance that is slowly but constantly changing at a rate that is consistent with the geologic time scale. Global change research examines the consequences of imposing rapid change on this balanced, or very slowly changing set of systems. It is concerned with how global systems such as climate, the atmosphere, and the oceans will adjust in response to these changes. It is also concerned with how large regional systems such as tropical rainforests, coastal areas, lakes and deserts will react both to rapid changes in global systems, and to the direct effect of human-induced change. Finally, the field of global change is concerned with how societies and economies will be affected by these changes. To clarify a potential area of confusion, global change differs from global climate change in that the former is much broader than the latter. In fact, global climate change is included as an issue within global change. The report begins by examining the importance of global change to Canadians. It will then attempt to explain the general concepts behind each of the major global problems facing our planet, along with the current best estimates regarding the expected consequences associated with these problems. Examples of global change include global warming, ozone depletion, deforestation and long-range transport of air pollutants. The report then discusses how global change might affect society and how society should attempt to react. Finally, the report will suggest how Canadians can respond to global change at the individual, corporate and government level. Note: The above passage is an excerpt from the publication Global Change and Canadians. xxx Click here if you want to view or download the entire report. (Link to publications section) - not available yet