1 Relevant Issues and Current Dimensions in Global Environmental Change
Global environmental change (GEC) includes both systemic changes that operate globally through the major systems of the geosphere biosphere, and cumulative changes that represent the global accumulation of localized changes. The importance and awareness of GEC has greatly increased since the second UN Conference on Environment and Development (UNCED) in 1992. During the last two decades, GEC research programs around the world have advanced our understanding of the Earth's ever changing physical, chemical, and biological systems and the growing human influences on these systems. On the basis of current knowledge attention is now focused on the critical unanswered scientific questions that must be resolved to fully understand and usefully predict future's GEC. It is hoped that measurable significant progress would be made in the forthcoming Earth Summit 2012, formerly known as United Nations Conference on Sustainable Development (UNCSD) or Rio+20 scheduled for Rio de Janeiro in June 2012. Generally, the earth's climate system varies naturally across a range of temporal scales, including seasonal cycles, inter annual patterns such as the El Nino/La Nina Southern OscillationENSO, inter decadal cycles such as the North Atlantic and Pacific Decadal oscillations, and multimillenial scale changes such as glacial to inter glacial transitions (Harley et al. 2006) This natural variability is reflected in the evolutionary adaptations of species and large scale patterns of biogeography. In all, human activities play an important part in virtually all natural systems and are forces for change in the environment at local, regional, and even global scales. Human drivers of GEC include consumption of energy and natural resources, technological and economic choices, culture, and institutions. The effects of these drivers are seen in population growth and movement, changes in consumption, deor reforestation, land use change, and toleration or regulation of pollution, and other issues highlighted in section two of this chapter. For instance, the Intergovernmental Panel on Climate Change (IPCC) reports that, if global average temperatures exceed 2degC there will be irreversible impacts on water, ecosystems, food, coastal zones and human health. We have a 50% chance of avoiding a 2degC warming if we stabilize greenhouse gases at 450 ppm CO2 eq (parts per million carbon dioxide equivalents) Recent evidence suggests even more rapid