Global Warming

            
            
             In 1990, the Intergovernmental Panel on Climate Change (IPCC), an international body established by the United Nations to provide scientific advise to global policy makers regarding such issues as the buildup of greenhouse gases, evidence and attribution of climate change, and predictions of global climate scenarios over the next century, issued its inagural report. That report concluded that human activity had been increasing the concentration of greenhouse gases in the atmosphere to the highest levels in recorded history. According to the IPCC, atmospheric carbon dioxide, the most common greenhouse gas, had increased from pre-industrial levels of about 280 parts per million by volume (ppmv) to a 1990 level of 370 ppmv, far greater than the concentrations found by scientists for any prior historical period. The report further concluded that global surface temperatures had increased about 0.5 degrees C since the late 19th century (within a range of 0.3 and 0.6 degrees C). The IPCC used this and other data gathered from fossil records, ice core drillings, tree ring analyses, marine sediment cores and the like to develop global weather models designed to account for past global temperature changes and predict future temperature scenarios. Prominent among those predictions was the report's conclusion that if no measures were taken to reduce human production of carbon dioxide - the "business as usual- scenario - CO2 concentrations would likely double by 2065. .
             According to the IPCC, increased CO2 concentrations are significant not only because atmospheric CO2 deflects infrared radiation back to earth (the greenhouse effect) but also because the retained heat from such deflection has an "amplifying- effect on climate patterns. For example, according to the IPCC's 1990 climate model, increased global surface temperatures resulting from the greenhouse effect of higher CO2 atmospheric concentrations "force- other climate changes that trampoline global temperature increases.